Anesthetic Considerations Flashcards
How is a patient classified by ASA status?
What is the most common medication allergy among children presenting for operation?
Allergies to certain antibiotics (especially penicillin, ampicillin, and cephalosporins) are the most common medication allergies in children presenting for an operation.
Anaphylactic allergic reactions are rare, but can be life threatening if not diagnosed and treated promptly.
What is the most common etiology for anaphylactic reactions among children for operation?
Latex allergy is the most common etiology for an anaphylactic reaction, and children with spina bifida (myelomeningocele), bladder exstrophy, or those who have undergone multiple surgical procedures are at greatest risk for such reactions.
In 1991, the FDA recommended that all patients should be questioned about symptoms of latex allergy prior to surgery.
The general consensus among the pediatric anesthesia community is that children in the high-risk groups noted above should not be exposed to latex-containing products (e.g., gloves, adhesive tape, catheters) and latex-free alternatives should be used instead.
Since 1997, the FDA has mandated that all latex-containing medical products should be labeled as such.
Many pediatric hospitals have elected to remove all latex-containing products from their supply chain because of the high risk to these identified patient populations as well as the increasing prevalence of latex allergy in health care workers.
It has been well documented that prophylactic medications (steroids, H1 and H2 blockers) are ineffective in preventing anaphylaxis in susceptible patients.
How do you manage anaphylaxis?
If a phylaxis occurs (hypotension, urticaria or flushing, bronchospasm), the mainstays of treatment are:
(1) stopping the latex exposure: stopping the operation, changing to nonlatex gloves, and removing any other sources of latex; and
(2) resuscitation: fluids, intravenous (IV) epinephrine (bolus and infusion), steroids, diphenhydramine, and ranitidine.
If anaphylaxis is suspected, blood should be drawn within 4 hours of the episode for tryptase determination, which can confirm the occurrence of an anaphylactic event but not the inciting agent.
Patients should be referred to an allergist for definitive testing to identify the antigen.
Such testing should occur at least 4–6 weeks after the episode of anaphylaxis to allow for reconstitution of the mediators, the depletion of which could cause a false-negative skin test.
In general, parents should be instructed to continue routine administration of anticonvulsant medications, cardiac medications, and pulmonary medications even while the child is fasting.
What aspects of a child’s family history must be elicited during preoperative evaluation for anesthesia?
Family history should be reviewed for pseudocholinesterase deficiency (prolonged paralysis after succinylcholine) or any first-degree relative who experienced malignant hyperthermia (MH).
A complete review of systems is important and should focus on those areas in which abnormalities may increase the risk of adverse events in the perioperative period.
How is malignant hyperthermia diagnosed and managed?
The incidence of an MH crisis is 1:15,000 general anesthetics in children, and 50% of patients who have an MH episode have undergone a prior general anesthetic without complication.
MH is an inherited disorder of skeletal muscle calcium channels, triggered in affected individuals by exposure to either inhalational anesthetic agents (e.g., isoflurane, desflurane, sevoflurane), succinylcholine, or both in combination, resulting in an elevation of intracellular calcium.
The resulting MH crisis is characterized by hypermetabolism (fever, hypercarbia, acidosis), electrolyte derangement (hyperkalemia), arrhythmias, and skeletal muscle damage (elevated creatine phosphokinase [CPK]).
This constellation of events may lead to death if unrecognized and/or untreated.
Dantrolene, which reduces the release of calcium from muscle sarcoplasmic reticulum, when given early in the course of an MH crisis, has significantly improved patient outcomes.
With early and appropriate treatment, the mortality is now less than 10%.
Current suggested therapy can be remembered using the mnemonic “Some Hot Dude Better GIve Iced Fluids Fast”.
Experts are available for consultation concerning suspected MH at the 24-hour MH hotline administered by the Malignant Hyperthermia Association of the United States (MHAUS).
Recommendations for treatment of an acute MH episode are available at the MHAUS website.
It should be noted that dantrolene must be prepared at the time of use by dissolving in sterile water. It is notoriously difficult to get into solution, and the surgeon may be asked to help with this process.
Recently an alternative to dantrolene, dantrium, has become available. It is more soluble at higher concentration and therefore more quickly and easily prepared, allowing administration of a lower volume of drug for effective treatment.
What muscle diseases are associated with malignant hyperthermia?
Patients traditionally thought to be MH susceptible include those with the following spectrum of muscle diseases:
Central core myopathy
Becker muscular dystrophy
Duchenne muscular dystrophy
Myotonic dystrophy
King–Denborough syndrome
However, many patients who develop MH have a normal history and physical examination.
In the past, patients with mitochondrial disorders were thought to be at risk. Recent evidence suggests that the use of inhaled anesthetic agents appears safe in this population, but succinylcholine should still be avoided, as some patients may have rhabdomyolysis (elevated CPK, hyperkalemia, myoglobinuria) with hyperkalemia without having MH.
Patients with myopathies of unknown origin, often presenting for diagnostic muscle biopsy, pose a unique dilemma, and anesthetics should be planned in consultation with genetic and metabolic teams if possible.
What perioperative complications should be anticipated for a patient with Trisomy 21?
Perioperative complications occur in 10% of patients with trisomy 21 who undergo noncardiac surgery and include severe bradycardia, airway obstruction, difficult intubation, post-intubation croup, and bronchospasm.
Patients may experience airway obstruction due to a large tongue and mid-face hypoplasia.
The incidence of obstructive sleep apnea (OSA) may exceed 50% in these patients and may worsen after anesthesia and operation.
Airway obstruction may persist even after adenotonsillectomy.
Many patients with trisomy 21 have a smaller caliber trachea than children of similar age and size; therefore, a smaller endotracheal tube (ETT) may be required.
Some trisomy 21 patients may have a longer segment of tracheal stenosis due to complete tracheal rings below the level of the cricoid.
Congenital heart disease (CHD) is encountered in 40–50% of patients with trisomy 21.
The most common defects are atrial and ventricular septal defects, tetralogy of Fallot, and atrioventricular (AV) canal defects.
For children with a cardiac history, records from their most recent cardiology consultation and echocardiogram should be available for review at the time of preoperative evaluation.
Recent clinical changes in their condition may warrant reassessment by their cardiologist prior to operation.
Patients with trisomy 21 have laxity of the ligament holding the odontoid process of C2 against the posterior arch of C1, leading to atlanto-axial instability in about 15% of these patients.
Cervical spine instability can potentially lead to spinal cord injury in the perianesthetic period.
The need for and utility of preoperative screening for this condition is controversial.
Even if the radiographic exam is normal, care should be taken perioperatively to keep the neck in as neutral a position as possible, avoiding extreme flexion, extension, or rotation, especially during tracheal intubation and patient transfer.
Any patient with trisomy 21 who has neurologic symptoms such as sensory or motor changes, or loss of bladder or bowel control should undergo preoperative neurosurgical consultation to exclude cervical cord compression.
What are current preoperative fasting guidelines?
Fasting violations are one of the most common causes for cancellation or delay of operations. Preoperative fasting is required to minimize the risk of vomiting and aspiration of particulate matter and gastric acid during anesthesia induction. Although the risk of aspiration is generally small, it is a real risk that may be associated with severe morbidity or death.
Research performed at our institution has demonstrated that intake of clear liquids (i.e., liquids that print can be read through, such as clear apple juice or Pedialyte) up until 2 hours prior to the induction of anesthesia does not increase the volume or acidity of gastric contents.
Our policy is to recommend clear liquids until 2 hours prior to the patient’s scheduled arrival time.
Breast milk is allowed up to 3 hours before arrival for infants up to 12 months of age.
Infant formula is allowed until 4 hours before arrival in infants <6 months old, and until 6 hours before arrival in babies 6–12 months old.
All other liquids (including milk), solid food, candy, and gum are not allowed <8 hours before induction of anesthesia.
Although these are the guidelines for our institution, the surgeon should be aware that NPO (nil per os) guidelines are variable and institutionally dependent.
Mitigating circumstances for NPO rules are limited to emergency operations, in which steps are taken to protect the airway from aspiration through the use of rapid sequence intubation.
Elective patients at particular risk for dehydration should be scheduled as the first case of the day when possible, and administration of clear liquids by mouth until 2 hours prior to arrival at the surgical facility should be encouraged.
Insulin-dependent diabetics, infants, and patients with cyanotic or single ventricle (SV) cardiac disease are among those requiring careful planning to avoid prolonged fasting times.
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The patient’s stomach must be empty to prevent aspiration of stomach contents into the lungs during anesthesia induction. However, the patient should also be optimally hydrated. These two goals are compatible and are not difficult to achieve. Patients who are fed at the usual mealtimes and sleep through the night present no particular problems if procedures are scheduled for the early morning hours.
Numerous studies have failed to document an increased pulmonary aspiration risk when fasting guidelines are relaxed. 49,50 The perioperative fasting guidelines developed by the ASA are listed in Table 13-2. 51 These guidelines allow children to ingest clear liquids up to 2 hours before scheduled surgery. Infants and toddlers can be fed breast milk up until 4 hours before surgery, and infants and young children can be fed formula up until 6 hours before surgery.
If these details are not clearly stated in an itemized fashion with specific times, fluids may inadvertently be withheld from some children, particularly infants, for excessively long periods. Procedures should be scheduled according to age, with the youngest patient being the first on the operating schedule. Both the surgeon and the anesthesiologist must be alert to delays and ensure that the infant’s fluid restriction is revised accordingly.
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What preoperative laboratories are required for anesthetic evaluation?
At the time of consultation, selected laboratory studies may be ordered, but routine laboratory work is usually not indicated. Policies vary among institutions regarding the need for preoperative hemoglobin testing.
In general, for any patient undergoing a procedure with the potential for significant blood loss and need for transfusion a complete blood count (CBC) should be performed in the preoperative period.
Certain medications, particularly anticonvulsants (tegretol, depakote), may be associated with abnormalities in blood components (white blood cells, red blood cells, platelets), making a preoperative CBC desirable.
Although serum electrolytes are not routinely screened, electrolytes may be helpful in patients on diuretics.
Preoperative glucose should be monitored in neonates, insulin-dependent diabetic patients, and also in any patient who has been receiving parenteral nutrition or IV fluids with a dextrose concentration >5% prior to surgery.
Routine pregnancy screening in all females who have passed menarche is strongly recommended. An age-based guideline (at our institution, any female >11 years of age) may be preferable.
Although it is easiest to perform a urine test for human chorionic gonadotropin (hCG), if a patient cannot provide a urine sample, blood can be drawn for serum hCG testing. Institutional policy may allow the attending anesthesiologist to waive pregnancy testing at their discretion.
Certain medications, particularly anticonvulsants, should be individually assessed regarding the need for preoperative blood levels.
The nature of the planned operation may also require additional studies, such as coagulation screening (prothrombin time [PT], partial thromboplastin time [PTT], international normalized ratio [INR]) prior to craniotomy, tonsillectomy, or surgeries with anticipated large blood loss.
When should a procedure be rescheduled in the event of an upper respiratory tract infection?
Because perioperative respiratory adverse events are the most common cause of significant adverse events in infants and children, one of the most common questions confronting an anesthesiologist is whether to cancel a procedure in a child with an upper respiratory infection (URI).
It is not uncommon for some patients to spend much of their childhood catching, suffering from, or recovering from a URI, with the highest frequency occurring in children under age 6 who attend day care or preschool.
Patients with a current or recent URI undergoing general anesthesia are theoretically at increased risk for adverse perioperative respiratory complications, including laryngospasm, bronchospasm, and hypoxia, with the youngest patients (<2 years) being at greatest risk.
However, anesthetic management may also be tailored to reduce stimulation of a potentially hyper-reactive airway.
Cancellation of a procedure imposes emotional and/ or economic burdens on patients and families, physicians, and operating rooms. Unless the patient is acutely ill, it is usually appropriate to proceed with the anesthetic.
Patients with high fever, wheezing, or productive cough may actually have a lower respiratory tract infection, and the planned procedure is more likely to be cancelled.
Our approach is to discuss the urgency of the scheduled operation with the surgeon, and then to review the risks and benefits of proceeding versus rescheduling with the parents, taking into consideration the possibility that the child may have another URI at the time of the rescheduled procedure.
Allowing the parents to participate in the decision-making process (when appropriate) usually leads to mutual satisfaction among all involved parties.
The decision to cancel or postpone a procedure (usually a delay of 4–6 weeks due to concern for prolonged hyperreactivity of the bronchi) should not be made lightly. Families have often sacrificed time away from work, taken children out of school, arranged childcare for other children, or have planned a vacation around the scheduled operation, and these considerations deserve respectful attention.
Symptoms tipping the scales toward cancellation include the severity of illness, as measured by an intractable or productive cough, bronchospasm, malaise, fever, or hypoxia on pulse oximetry.
A recent analysis of perioperative adverse respiratory events in children <18 years of age attempted to develop a risk prediction tool, and found age <3 years, greater ASA PS, morbid obesity, preexisting pulmonary disorder, and a surgical (vs radiological) procedure to be significant predictors for such events.
Clear rhinorrhea with a simple dry cough is usually not sufficient grounds for cancellation, provided the family understands the very small chance of needing postoperative supplemental oxygen and bronchodilator therapy.
What are some respiratory and airway considerations for ex-premature infants?
Infants born prematurely (<37 weeks gestation) may exhibit sequelae such as bronchopulmonary dysplasia (BPD), gastroesophageal reflux, intraventricular hemorrhage/hypoxic–ischemic encephalopathy (IVH/HIE), reactive airways disease (RAD), and airway issues including laryngo/tracheomalacia or tracheal stenosis. Preterm infants are also at increased risk for postoperative apnea after exposure to anesthetic and analgesic agents.
Although the incidence of BPD has fallen over the past two decades with the use of surfactant and new ventilation strategies, it remains the most common form of chronic lung disease in infants, and significantly complicates the perioperative management of ex-premature infants. BPD is associated with airway hyper-reactivity, bronchoconstriction, airway inflammation, pulmonary edema, and chronic parenchymal lung injury.
Several effects of anesthesia, together or separately, may have life-threatening consequences. After anesthetic induction, pulmonary vasoconstriction can aggravate ventilation–perfusion mismatch and lead to profound hypoxemia. Anesthetic effects on myocardial contractility can result in impaired right ventricular (RV) function, reduced cardiac output, decreased pulmonary blood flow, and profound cardiovascular compromise with hypoxemia. Increased airway reactivity during anesthetic induction or emergence from anesthesia can result in severe exacerbation of bronchoconstriction, impairing ventilation and pulmonary blood flow. Increased oral and bronchial secretions induced by the anesthetic can compromise airflow and lead to airway or ETT plugging. Because of diminished respiratory reserves in these patients, such plugging can quickly cause profound hypoxia and acute right-sided heart strain, arrhythmias, and possibly death. Preoperative optimization of the child’s pulmonary status using inhaled bronchodilators and inhaled steroids may be needed.
Preoperative measurement of electrolytes is warranted in children taking diuretics on a chronic basis such as furosemide and spironolactone. In addition, in patients who have required oral steroids for exacerbation of RAD in the prior 6 months, 48–72 hours of steroid administration may provide anti-inflammatory coverage, which may reduce the risk of perioperative bronchospasm. If the child has received large doses of or continuous treatment with steroids, perioperative stress doses may be necessary as recommended by the patient’s primary care provider, pulmonologist, or endocrinologist.
How can you manage postanesthetic apnea?
Former preterm infants receiving general anesthesia are at risk for postoperative apnea. Regardless of whether they have a history of apnea, premature infants and full-term infants less than 44 weeks’ postconceptual age may develop apnea in the postoperative period.
Postoperative apnea is defined as cessation of breathing or no detectable air flow for 15 seconds or longer, or less than 15 seconds with bradycardia.
The cause of this phenomenon is unknown. Recovery from general anesthesia may unmask immature central respiratory regulation or decrease upper airway tone; both factors are believed to be responsible for postoperative apnea.
Although postoperative apnea usually develops in the first 2 hours after the anesthesia, it may present as long as 12 hours after anesthesia.
Several investigators have tried to establish a postconceptual age after which healthy premature infants with no history of neonatal apnea can be discharged on the day of surgery. Unfortunately, the recommendations vary from 44 weeks to 60 weeks.
The variance of recommendations are based in part on the sophistication of monitoring. The more sophisticated the monitoring, the higher the rate of identified apneic spells. Because considerable controversy exists, each hospital must develop its own policy. It is reasonable to monitor former premature infants for 24 hours if their postconceptual age is 55 weeks or less.
Obviously, children with serious medical or neurologic problems or a history of significant and recurrent neonatal apnea are exceptions to this recommendation.
So far, anemia is the only independent risk factor identified that increases the likelihood of postoperative apnea in this at-risk population.
It has been recommended that anemic preterm infants with hematocrit values less than 30% have elective surgery delayed and receive iron supplementation until the hematocrit is greater than 30%.
If surgery cannot be deferred, anemic infants must be observed and monitored very carefully for postoperative apnea.
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Even without the additional burden of anesthetic/opioid-induced respiratory depression, the risk of apnea is increased in ex-premature infants due to the immaturity of the central and peripheral chemoreceptors, with blunted responses to hypoxia and hypercapnia.
In addition, anesthetic agents decrease upper airway, chest wall, and diaphragmatic muscle tone, thereby further depressing the ventilatory response to hypoxia and hypercapnia.
In the immediate neonatal period, immaturity of the diaphragmatic musculature causes early fatigability, which may also contribute to apnea.
Although postanesthetic apnea may be brief and resolve either spontaneously or with minor stimulation, even brief apnea in ex-premature infants may result in significant hypoxia.
Also, although most apneic episodes occur within the first 2 hours after anesthesia, apnea can be seen up to 18 hours postoperatively.
The increased risk of apnea impacts postanesthetic care of infants born prematurely, mandating that those at high risk be admitted for cardiorespiratory monitoring.
Despite numerous studies on this issue, the postnatal age at which this increased risk of apnea disappears is still being debated. The results of a meta-analysis of pertinent studies indicated that a significant reduction in the incidence of apneic episodes occurred at 52–54 weeks’ postconceptual age.
A hematocrit <30% was identified as an independent risk factor, with the recommendation that ex-premature infants with this degree of anemia be hospitalized postoperatively for observation regardless of postconceptual age.
However, conclusions drawn from this meta-analysis have been challenged, and the sample size of this study may not have been large enough to draw valid conclusions.
Until more patients are systematically studied, determining when a former preterm infant can most safely undergo an outpatient operation is up to the discretion and personal bias of the anesthesiologist and surgeon.
Institutional policies most commonly mention ages of 44 weeks for term infants (≥37 weeks), and from 52–60 weeks postconceptual age for infants born at <37 weeks.
Medicolegal concerns direct these practices in many institutions, but regardless of the postconceptual age at the time of operation, an infant should be hospitalized if any safety concerns arise during the operative or recovery period.
Although the risk of apnea can be decreased with regional anesthesia (spinal or caudal without general anesthesia or sedatives) and/or caffeine, our practice is to admit all at-risk patients with a postconceptual age of ≤60 weeks, to monitored, high-surveillance inpatient units for 23 hours after the anesthesia and operation regardless of the anesthetic technique used.
Similarly, infants born at term must be at least 1 month of age to be candidates for outpatient surgery as postanesthetic apnea has been reported in full-term infants up to 44 weeks postconceptual age. Fig. 3.1 shows an algorithm useful for determining day surgery eligibility in young infants.
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What are some considerations for patients with anterior mediastinal masses?
Patients presenting with AMMs (e.g., lymphoma) are at particularly high risk of airway compromise and cardiovascular collapse with the induction of general anesthesia due to compression of the trachea, great vessels, or right-sided cardiac chambers when intrinsic muscle tone is lost and spontaneous respiration ceases. When this occurs, obstruction of vascular inflow to the right atrium and/or outflow tract obstruction from the right or left ventricle can also occur.
Signs and symptoms of positional airway compression and cardiovascular dysfunction may, or may not, be present preoperatively, but importantly, the absence of signs and symptoms of airway compression and cardiovascular compromise does not preclude the possibility of life-threatening airway collapse or cardiovascular obstruction upon induction of anesthesia.
The preoperative evaluation should begin with a careful history to elicit any respiratory symptoms that could indicate the presence of tracheal compression and/or tracheomalacia, including cough, dyspnea, wheezing, chest pain, dysphagia, orthopnea, and recurrent pulmonary infections.
Symptoms may be positional, occurring when supine and improving when sitting.
Cardiovascular symptoms may result from tumor infiltration of the pericardium and myocardium, or compression of the pulmonary artery, pulmonary veins, superior vena cava (SVC), or right-sided cardiac chambers, resulting in decreased left ventricular preload and cardiac output.
Diagnostic evaluation includes chest radiographs and/or CT scans.
Chest CT is helpful in planning the anesthetic technique and in evaluating the potential for airway compromise during anesthesia.
Echocardiography is useful to assess the pericardial status, myocardial contractility, and compression of the cardiac chambers and major vessels, and should be performed in as supine a position as possible.
Unlike CT scans, echocardiography provides dynamic images that are often helpful.
Flow-volume loops and fluoroscopy can also provide a dynamic assessment of airway compression that other tests cannot assess.
Tumor-associated SVC syndrome may develop rapidly and is poorly tolerated.
Premedication is inadvisable in most patients with an AMM, as any loss of airway muscle tone may upset the balance between negative intrathoracic pressure and gravity, resulting in airway collapse.
Once the decision is made to sedate or anesthetize the child, maintenance of spontaneous respiration, regardless of induction technique, is paramount, as the decrease in intrathoracic pressure during inspiration can lessen the compressive effect of the mass and thus aid in maintaining airway patency.
It is essential to avoid the use of muscle relaxants because the subsequent airway collapse can be fatal if it proves difficult or impossible to ventilate the child despite successful endotracheal intubation.
Positioning the child is an important part of the anesthetic plan for these patients. The sitting position favors gravitational pull of the tumor toward the abdomen rather than allowing the tumor to fall posteriorly onto the airway and major vessels as occurs in the supine position, but the sitting position makes intubation challenging. Thus, positioning the symptomatic child in the lateral decubitus position is recommended.
Turning the child lateral or prone, or lifting the sternum, has been shown to alleviate acute deterioration in ventilation or cardiovascular collapse secondary to tumor compression.
In any patient with an increased potential for such obstruction, provision should be made for the availability of a rigid bronchoscope, the ability to move the operating room (OR) table to effect position changes, and the ability to institute cardiopulmonary bypass or extracorporeal membrane oxygenation (ECMO).
Compression of the cross-sectional area of the trachea on CT imaging to <30% of normal, or <70% normal with concomitant bronchial compression, has been associated with both intraoperative and postoperative complications.
When possible, percutaneous biopsy of the mass using local anesthesia with or without judicious doses of sedative medication is often ideal and poses the least risk to the patient.
In patients who have additional tissue sites from which a biopsy can be obtained (e.g., cervical, axillary, or inguinal lymph nodes), it may be safer to proceed with the patient in a semi-sitting position using local anesthesia and carefully titrating sedation so that spontaneous ventilation is preserved.
Recently, ketamine and dexmedetomidine have been shown to provide good sedation with preservation of airway patency and spontaneous respiration in this setting.
If progression to general anesthesia is required and airway and/or vascular compression exists, standby ECMO capability is strongly recommended.
Which cardiac conditions are at highest risk for anesthesia-related mortality?
Patients at highest risk for anesthesia-related mortality include those infants with SV lesions and patients with left ventricular outflow tract obstruction (LVOTO), cardiomyopathy, or pulmonary hypertension.
What are important considerations in the preoperative preparation and evaluation of cardiac patients?
Children with unrepaired or palliated heart disease, children requiring an operation as a result of their cardiac disease, and children undergoing emergency surgery tend to be more critically ill and require more intensive preoperative preparation and assessment.
In patients who have significant cardiopulmonary limitations or are not well compensated, screening in a preanesthetic clinic is useful for evaluating the patient’s current PS as well as gathering recent cardiology records and reviewing imaging results. For poorly compensated patients, this also allows time for selection of the most appropriate anesthesia providers and appropriate recovery venue as well.
With few exceptions, all cardiac medications should be continued perioperatively.
Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are occasionally held preoperatively due to the incidence of hypotension on anesthetic induction.
Patients receiving antithrombotic therapy (those with systemic-topulmonary shunts, mechanical or biological prosthetic heart valves, a history of thrombosis involving a conduit or a shunt, recent transcatheter interventions or device placement, treatment of Kawasaki disease, and the presence of risk factors for thromboembolic events including Fontan physiology) should have a perioperative plan for the appropriate discontinuation and resumption of these medications.
No specific pediatric guidelines exist for the discontinuation of antithrombotic medications prior to an elective operation, and management strategies ideally should be coordinated among the child’s cardiologist, surgeon, and anesthesiologist.
An emergency operation presents additional management issues and often adds risk in several areas. There may be little time preoperatively to optimize the patient’s cardiac condition, along with difficulty in quickly obtaining complete cardiology and surgical records. In such cases, the anesthetic preoperative evaluation is distilled to the most important factors, including the nature and duration of the present illness, the child’s underlying cardiac disease, baseline status, and medications.
Based on the child’s condition and the nature of the emergency, a decision can be made as to whether to proceed with the case with no further workup or a review of available old records, or whether new consultations and studies should be obtained prior to surgery.
It should also be recognized that certain patients tolerate hypovolemia poorly, including those with single ventricle physiology, LVOTO (Williams syndrome, hypertrophic obstructive cardiomyopathy, subaortic stenosis, aortic stenosis, and supravalvar aortic stenosis), systemic-pulmonary artery shunts, and polycythemic, cyanotic patients. Efforts should be made to appropriately hydrate these patients prior to induction of anesthesia.
What are the latest AHA recommendations for perioperative endocarditis prophylaxis?
The most recent American Heart Association (AHA) guidelines for perioperative endocarditis prophylaxis emphasize evidence-based practice, with current opinion reflecting the view that endocarditis is generally more likely to result from bacteremias occurring as a consequence of activities of daily living than those due to dental, gastrointestinal, or genitourinary tract procedures that do not incise/injure the mucosa.
Lesions associated with increased risk of infective endocarditis (IE) in children include cyanotic CHD, endocardial cushion defects, and left-sided lesions, with the relative risk of developing IE highest in the 6 months following cardiac surgery and in patients <3 years of age.
Except for the conditions listed in Box 3.4, the AHA no longer recommends routine IE prophylaxis.
What are special considerations for patients with pulmonary hypertension?
In children with CHD, prolonged exposure of the pulmonary vascular bed to high flows secondary to left-to-right shunting, pulmonary venous obstruction, or high left atrial pressures can lead to elevated pulmonary artery (PA) pressures and the development of pulmonary hypertension (PH).
Other pediatric populations at risk for the development of PH include an increasing population of premature infants with BPD, and children with chemotherapy-induced PH, genetic conditions such as glycogen storage diseases and heritable PH, certain connective tissue diseases, and portopulmonary hypertension.
The pathophysiology and anesthetic implications of PH have been well reviewed, and there is no ideal sedative/ anesthetic agent for these patients, nor is there consensus on how long after an anesthetic a child remains at higher risk for adverse events.
One study has identified that inpatients with suprasystemic PH, young age, and home oxygen use are significant risk factors for complications.
A frank discussion of the high risk of anesthesia in these patients, particularly those with systemic or suprasystemic PA pressures, should be held with the patient’s family when the consent for anesthesia is obtained.
Anesthetic management strategies are guided by three considerations:
(1) appropriate manipulation of factors affecting pulmonary vascular resistance (PVR);
(2) the effect of anesthetic agents on PVR; and
(3) maintenance of cardiac output (CO) and coronary perfusion pressures.
Increases in PVR can potentially culminate in RV failure if excessive.
Ventilator strategies can profoundly alter cardiovascular pathophysiology via complex interactions influencing cardiac function and output due to alterations in RV preload and afterload.
Given the propensity for desaturation and increases in PCO2 with spontaneous ventilation, controlled ventilation is recommended intraoperatively with maintenance of lung volumes at or around functional residual capacity (FRC) with minimal positive end expiratory pressure (PEEP), and avoidance of high inspiratory pressures, hypercarbia, or hypoxemia.
Normal preload should be maintained and hypotension avoided in these patients in order to optimize CO, coronary artery flow, and oxygen supply to the RV.
Dopamine, epinephrine, and milrinone should be available to improve cardiac function if necessary, and inhaled nitric oxide should also be available intraoperatively.
What are special considerations for CHD patients with cyanosis and polycythemia?
Cyanosis in patients with CHD can be the result of either right-to-left shunting with inadequate pulmonary blood flow (PBF) or admixture of oxygenated and deoxygenated blood in the systemic circulation.
Severe, longstanding cyanosis causes a variety of systemic derangements including hematologic, neurologic, vascular, respiratory, and coagulation abnormalities.
During preoperative evaluation, the child’s baseline range of hemoglobin–oxygen saturation, heart rate, and blood pressure should be noted along with any history of stroke, seizure, or preexisting neurologic defects.
Care should be taken intraoperatively to maintain normal fluid balance and cardiac function.
The use of air filters in the IV lines and meticulous attention to air in volume lines without filters is essential to avoid the occurrence of paradoxical emboli in children with right-to-left shunts.
Controlled ventilation is recommended for all but the shortest procedures due to the ventilatory abnormalities in these patients.
One of the initial responses to cyanosis is an increase in erythropoietin levels with a subsequent increase in hemoglobin and hematocrit.
At hematocrit levels ≥65%, the increased blood viscosity can result in a decrease in the delivery of oxygen to the tissues.
Preoperative phlebotomy is recommended only in patients who have hematocrit ≥65%, are experiencing symptoms of hyperviscosity, and are not dehydrated.
The acute onset of symptomatic hyperviscosity syndrome can be seen in cyanotic patients whose hematocrit abruptly increases due to dehydration.
In these patients, rehydration is recommended rather than phlebotomy.
Increased bleeding tendencies, and a variety of associated laboratory abnormalities, have long been noted in cyanotic patients.
When compared with acyanotic children, a disproportionate number of cyanotic children are thrombocytopenic, with the degree of thrombocytopenia directly related to the severity of polycythemia.
Abnormalities in prothrombin time, partial thromboplastin time, and individual factor deficiencies have also been described and defy simple classification.
Although these deficiencies may cause no symptoms other than bruising, severely cyanotic patients should have clotting studies prior to operation.
What are special considerations for patients with pacemakers/implantable cardioverter-defibrillators?
Indications for pacemakers in patients with CHD include congenital or postsurgical (acquired) complete heart block, and sinus node or AV node dysfunction, while in recent years increasing numbers of children have had ICDs placed for prevention of sudden cardiac death due to congenital or acquired long QT syndrome.
Necessary preoperative information for these patients includes the type of device, indication for device placement, location of the generator, date of last device check and remaining battery life, and the degree of reliance on the pacemaker for maintenance of CO (none, partial, complete).
Monitoring the patient for a perfusing rhythm throughout the procedure is essential, and invasive arterial monitoring should be considered for patients who are dependent on the device to maintain adequate cardiac output.
The American College of Cardiology/American Heart Association (ACC/AHA) guidelines advocate pre- and postoperative interrogation of permanent pacemakers.
All patients with an ICD should undergo preoperative device interrogation with disabling of defibrillation capability intraoperatively and resumption in the postoperative period.
Bipolar electrocautery should be utilized whenever possible in the patient with a pacemaker or ICD.
If monopolar electrocautery is used, the electrocautery return pad should be placed as far away from the pacing generator as possible, and the pacemaker generator/leads axis should not be located between the operative site and the grounding pad.
If the pacemaker cannot be placed in an asynchronous mode and electrocautery adversely affects it, cautery current should be applied for not more than 1 second at a time, with 10 seconds between bursts of current, to allow for maintenance of CO.
What are special considerations for patients with single ventricle physiology?
The anatomy of patients classified as having single ventricle (SV) physiology includes any lesion or group of lesions in which a two-ventricle cardiac repair is not feasible. Generally, either both AV valves enter a single ventricular chamber, or there is atresia of an AV or semilunar valve. Intracardiac mixing of systemic and pulmonary venous blood flow occurs, and the SV output is shared, or balanced, between the pulmonary and systemic circulations. Patients with relative hypoplasia of one ventricle, such as an unbalanced AV canal defect or severe Ebstein anomaly, may also undergo SV palliative operations.
An increased propensity to hemodynamic instability can be seen in SV patients at any stage of palliation, and the use of vasopressors, inotropes, and invasive monitoring may be warranted. Maintenance of a higher hematocrit is recommended (40–45%) for patients who are cyanotic.
A series of three separate staged palliative cardiac operations are generally performed for most children with SV physiology. After initial stage I palliation for hypoplastic left heart syndrome, patients are dependent on either a modified systemic-to-pulmonary shunt or an RV to PA conduit to provide PBF. The ratio of pulmonary to systemic blood flow is then dependent on the balance between systemic vascular resistance (SVR) and PVR, with patients extremely vulnerable to perturbations in PO2 , PCO2 , acid–base status, temperature, and volume status. Oxygen saturations >85% indicate pulmonary overcirculation, and patients may exhibit symptoms of congestive heart failure (CHF). Once the patient is anesthetized and mechanically ventilated, their oxygen saturation often increases, requiring readjustment of the FiO2 and PCO 2 to maintain target oxygen saturations between 75% and 85%. An acute drop in oxygen saturation along with the absence of a murmur indicates loss of shunt flow and is catastrophic. Immediate echocardiographic confirmation of shunt flow is crucial, with rapid institution of ECMO if necessary.
Patients usually undergo a second-stage procedure, or bidirectional cavopulmonary anastomosis, at 3–6 months of age, with the anastomosis of the SVC to the pulmonary circulation replacing the systemic-to-pulmonary shunt created during the first stage surgery. Oxygen saturations will continue to range between 75% and 85%, as patients are still mixing oxygenated and deoxygenated blood for ejection from the SV, but ventricular function is generally improved, as the volume load has been removed from the heart. However, systemic hypertension is frequently seen in these children.
At 18 months to 3 years of age, a total cavopulmonary anastomosis, or Fontan procedure, is performed. Surgeons may choose to place a fenestration in the atrial baffle, allowing right-to-left shunting to occur, and consequently these patients may have hemoglobin–oxygen saturations of ≥100%. The presence of aorto-pulmonary collaterals or baffle leaks may also result in decreased systemic oxygen saturation. As PBF is now passive, adequate preload and normal PVR are necessary to maintain cardiac output. An abrupt decrease in CO may be observed with the initiation of positive pressure ventilation in the patient with Fontan physiology.
Maintenance of euvolemia is critical in patients with SV physiology. Dehydrated patients should have an IV placed and adequate hydration restored prior to induction of anesthesia. Care should be taken to avoid hypovolemia, as PBF is dependent on preload. Normal sinus rhythm should be maintained if possible. Controlled ventilation is appropriate for most procedures as long as excessive airway pressures are avoided, and physiologic levels of PEEP may be used to avoid atelectasis without impairing PBF.
Although many children with SV physiology may appear well, they are uniquely susceptible to physiologic perturbations, especially hypovolemia. Laparoscopic procedures, although presenting many advantages, should be carefully undertaken in these patients, particularly infants.
In which conditions/syndromes should a difficult airway be anticipated?
The patient with a “difficult airway” may require advanced airway management techniques in order to secure his or her airway including the lighted stylet, videolaryngoscope, flexible fiberoptic bronchoscope, direct laryngoscopy with intubating stylet, fiberoptic rigid laryngoscopy, an anterior commissure scope, laryngeal mask airway (LMA) facilitated fiberoptic intubation, cricothyrotomy, and tracheostomy.
Anesthesiologists and facilities do not need availability of all of the listed techniques. However, when a difficult airway is anticipated, it is important to communicate the difficult airway potential to all members of the operating team and to have all necessary airway equipment present in the OR before induction of anesthesia.
Indirect intubation methods should be utilized rather than repeated attempts at direct laryngoscopy, as airway edema and bleeding increase with each intubation attempt, decreasing the likelihood of success with subsequent indirect methods.
Patients that require additional approaches to obtain an airway require additional OR time and, in certain cases, may remain intubated postoperatively, mandating ICU admission.
Unlike in adults, it is rare to encounter an unanticipated difficult airway in a normal-appearing child. Some congenital syndromes associated with difficult airway management are listed in Table 3.2.
The ASA has developed practice guidelines and an algorithm for management of the difficult airway in adults. These guidelines and algorithm are continually updated and well known to anesthesiologists. Although the guidelines and algorithm are intended for use in adult patients, their emphasis on the importance of having a clear primary plan with multiple back-up contingency plans is equally applicable to infants and children.
How do you approach a patient with a difficult airway?
Weiss and Engelhardt have proposed an algorithm for management of difficult ventilation and/or intubation in pediatric patients that was modeled on the adult algorithm (Fig. 3.3).
The multicenter pediatric difficult airway registry has recently published data indicating that early use of videolaryngoscopy or fiberoptic intubation (FOI) through a supraglottic airway such as a LMA (fiberoptic intubation through a supraglottic airway [FOI-SGA]) reduces the number of intubation attempts.
In the registry, there was higher rate of first attempt success using FOI-SGA in infants ≥1 year of age.
What are components of monitoring and vascular access by ASA standards?
Standard monitoring in pediatric anesthesia follows the ASA Standards for Basic Anesthetic Monitoring and includes pulse oximetry, noninvasive automated blood pressure measurement, electrocardiography, capnography, and temperature monitoring.
Temperature monitoring is indicated in most pediatric anesthetics because of the increased prevalence of both MH and, more commonly, hypothermia in infants and children exposed to ambient OR temperatures.
Oxygenation is measured indirectly by pulse oximetry with an audible and variable pitch tone and low threshold alarm. Measurement of inspired oxygen concentration is standard with the use of an anesthesia machine. Depending on the duration and magnitude of the planned operation, as well as the child’s preoperative condition, more invasive monitoring with placement of an arterial or central venous line may be necessary. The surgeon should communicate his or her expectations regarding the expected duration of surgery; the potential for blood loss; and the need for invasive monitoring preoperatively, intraoperatively, and/or postoperatively.
In cases in which large fluid shifts or blood loss are expected, or when length of surgery is prolonged (>4 h), placement of a urinary catheter aids in accurate assessment of urine output and fluid balance.
What are special anesthetic considerations for laparoscopy?
Anesthetic concerns center around the effects of abdominal insufflation on ventilation and hemodynamics.
Two features of laparoscopic intervention create concern in the anesthetic management of infants and children:
(1) creation of a pneumoperitoneum with the concomitant increase in intra-abdominal pressure and resultant changes in ventilator parameters; and
(2) extremes of patient positioning that may be required for optimal exposure of intra-abdominal structures.
An appreciation of the physiologic, hemodynamic, and ventilatory consequences during and after a laparoscopic operation is an important part of careful patient selection.
Carbon dioxide is the gas of choice for insufflation, as it is noncombustible and is cleared more rapidly from the circulation than the other options.
The cardiovascular consequences of intravascular gas embolism present less risk with CO2 than with an insoluble gas such as helium or air.
However, cardiovascular collapse has been reported in several infants following insufflation, with end-tidal gas monitoring implicating gas embolism as the cause of these events.
Neonates and very young infants may be uniquely at risk for such events because of possible patency and large caliber of the ductus venosus.
Carbon dioxide uptake may be significantly greater in children, owing to the greater absorptive area of the peritoneum in relation to body weight, and the smaller distance between capillaries and peritoneum.
A greater degree of hypercarbia has been demonstrated in younger children during CO2 insufflation.
Increases in minute ventilation by as much as 60% may be required to maintain baseline ETCO2 , but the goal for an appropriate CO2 level need not be the baseline value. Rather, ETCO2 can safely be allowed to rise into the 50s.
Patients with hydrocephalus warrant special mention in regard to CO2 insufflation. Although patients with VP shunts have been shown to have intracranial pressure increases associated with a modest decrease in cerebral perfusion pressure at an intra-abdominal pressure of 10 mmHg or less, a recent review of laparoscopic compared with open abdominal surgery in children with shunts showed no pneumocephalus or increase in the incidence of shunt infection in the laparoscopic group. This is due to the fact that most VP shunts now have a one-way valve that will not allow gas entry. Interestingly, one group recently reported a case of pneumocephalus that occurred in a patient with such a shunt and valve that was inserted 20 years earlier.
The increase in intra-abdominal pressure seen with laparoscopy is associated with well-documented cardiorespiratory changes. Changes in ventilatory dynamics occur due to cephalad displacement of the diaphragm. This results in a reduction in lung volume, ventilation–perfusion mismatch, and altered gas exchange.
Bozkurt and coworkers demonstrated statistically significant decreases in pH and PaO2, and increased PaCO2 after 30 minutes of pneumoperitoneum.
These changes are additive to the 20% reduction in FRC that occurs with induction of general anesthesia.
The magnitude of the pulmonary effects correlates directly with intraperitoneal pressures and may be further exacerbated by steep Trendelenburg positioning.
Significant cardiovascular changes have been demonstrated in response to increased intra-abdominal pressure and patient position. In the supine or Trendelenburg position, the venous return is less impaired when the intraabdominal pressure is kept below 15 mmHg.
The position preferred for upper abdominal procedures is reverse Trendelenburg or supine. The head-up position reduces venous return and CO.
Several pediatric studies have utilized echocardiography (supine), impedance cardiography (15° head-down), and continuous esophageal aortic blood flow echo-Doppler (supine) to assess hemodynamic changes during laparoscopic surgery.
These studies demonstrated significant reductions in stroke volume and cardiac index (CI), along with a significant increase in SVR.
Pneumoperitoneum was found to be associated with significant increases in left ventricular end-diastolic volume, left ventricular end-systolic volume, and left ventricular end-systolic wall stress.
All three studies demonstrated a decrease in cardiac performance and an increase in vascular resistance in healthy patients undergoing laparoscopy for lower abdominal procedures.
The cardiovascular changes seen with pneumoperitoneum (Box 3.5) occur immediately with creation of the pneumoperitoneum and resolve on desufflation.
What are special anesthetic considerations for thoracoscopy?
Thoracoscopy has advantages over open thoracotomy, including reduced postoperative pain, decreased duration of hospitalization, improved cosmetic results, and decreased incidence of chest wall deformity.
An optimal anesthetic plan considers potential respiratory derangements including ventilation–perfusion mismatch that may result from positioning, CO2 insufflation into the pleural cavity, and single-lung ventilation.
In addition, much like insufflation during laparoscopy, hemodynamic changes during chest insufflation can compromise preload, stroke volume, CI, and blood pressure.
In a study of 50 pediatric patients undergoing thoracoscopy for a variety of operations, systolic and diastolic blood pressures were significantly lower, and ETCO2 was significantly higher during thoracoscopy.
After intrapleural CO2 insufflation, there was a statistically significant increase in ETCO 2 during one-lung ventilation (OLV) compared with two-lung ventilation.
On the other hand, two-lung ventilation with CO 2 insufflation was associated with a lower systolic and diastolic pressure than OLV.
The increase in ETCO 2 correlated with the duration of the insufflation.
These factors should be considered along with any preexisting preoperative respiratory or cardiovascular compromise in planning the operation and anesthetic management.
The magnitude of the physiologic changes induced by either one-lung or two-lung ventilation with insufflation is impacted by the patient’s age, underlying comorbid conditions, and anesthetic agents utilized.
Many thoracic procedures require lung deflation and minimal lung excursion on the operative side while ventilating the contralateral lung.
OLV is useful if the surgeon requires additional exposure.
In the pediatric patient, there are several options for attaining unilateral lung isolation.
Complications related to anesthetic management are usually related to mechanical factors such as airway injury and malposition of the ETT. Additional problems related to physiologic alterations include hypoxemia and hypercapnia.
An unusual complication was reported during attempted thoracoscopic resection of a congenital cystic adenomatoid malformation in a 3.5-kg infant.
During CO2 insufflation, there was a sharp rise in ETCO2 accompanied by severe hypoxemia and bradycardia. This was due to occlusion of the ETT by blood. After conversion to open thoracotomy, it was discovered that there had been direct insufflation into the cyst and that the cyst communicated directly with the tracheobronchial tree.
Blood obstructing the ETT is a common occurrence during thoracic procedures involving structures with tracheobronchial connections, whether open or thoracoscopic, especially in infants in whom the ETT inner diameter is small and therefore at high risk for obstruction.
Change in ventilatory parameters, such as increasing airway pressure during volume ventilation or decreasing tidal volume during pressure ventilation, may precede desaturation and an increase in ETCO2 due to compromised ventilation associated with ETT obstruction.
ETT suctioning, and if necessary ETT lavage, may be required during the procedure to remove blood and/or secretions.
It is important to try to maintain a reasonable range of elevated CO2 in neonates undergoing thoracoscopic procedures. Mukhtar and colleagues reported that permissive hypercapnia with ETCO2 50–70 mmHg was associated with improved CO and arterial oxygen tension in neonates undergoing thoracoscopic ligation of patent ductus arteriosus.
A case series in which high-frequency oscillatory ventilation (HFOV) was used in neonates undergoing thoracoscopic procedures has been reported. HFOV enables better CO2 elimination while optimizing the visualization for the surgeons.
What are the most common complications in the postoperative period among infants and children?
The recovery period for infants and children may be more crucial than for adult patients, with 3–4% of infants and children developing major complications in the recovery period, compared with only 0.5% of adults.
Most of these complications occur in the youngest children (<2 years of age) and are most commonly respiratory in nature.
What is the most common cause of delayed discharge from the PACU?
Postoperative Nausea and Vomiting
PONV is the most common cause of delayed discharge from the postanesthesia care unit (PACU) and the most common reason for unanticipated hospitalization following outpatient operations.
Certain procedures, such as strabismus surgery, middle ear surgery, orchiopexy, and umbilical hernia repair, are associated with a >50% incidence of postoperative vomiting.
Similarly, the perioperative use of any opioid is associated with a very high incidence of PONV, even when general anesthetic drugs associated with a lower incidence of nausea, such as propofol, are used.
Common approaches to treat or prevent PONV include alteration of the anesthetic technique, perioperative administration of an antiemetic (either prophylactically or as treatment), and limitation of postoperative oral intake.
What is the most serious of the most common problems seen postoperatively among infants and children?
Respiratory complications are the most serious of the common problems seen postoperatively in infants and children. All respiratory complications are more common in children with a recent history of respiratory tract infection.
Post-intubation croup (or post-extubation subglottic edema) has been a well-recognized entity since airways were first secured with endotracheal tubes. Children are more prone to develop croup following intubation than adults due to their narrower laryngeal and tracheal lumens that are more easily compromised by mucosal edema. Children with trisomy 21 may be at increased risk for this complication due to the increased incidence of occult subglottic narrowing. Other contributing factors to the development of croup include traumatic or repeated intubation attempts, coughing (“bucking”) on the ETT, changes in patient position after intubation, and general anesthesia in children with a current or recent upper respiratory tract infection.
The incidence of post-intubation croup has decreased from 6% to 1% of all intubated children. This reduction has occurred because of the development and use of sterile, implant-tested ETTs, routine humidification of anesthetic gases, and the use of an appropriately sized (air leak pressure of <25 cm water) ETT.
With careful attention to appropriate cuff inflation and leak assessment, the increasingly common used cuffed ETTs in young children and infants has not been associated with an increased incidence of postoperative stridor.
Laryngospasm, while potentially life threatening, is almost always transient and treatable by early application of continuous positive airway pressure (CPAP) by mask combined, if necessary, with a small dose of propofol (1–2 mg/ kg).
Rescue with succinylcholine is indicated if oxygen desaturation persists despite CPAP and propofol.
Laryngospasm can also occur in the OR during anesthetic induction or emergence from anesthesia. Patients at an increased risk of laryngospasm include those with a recent history of a URI.
Effective maneuvers for management of laryngospasm have recently been outlined in a helpful algorithm accompanying a case scenario publication.
Bronchospasm is more common in children with poorly controlled asthma and those exposed to secondhand smoke. It is most often managed with administration of nebulized β-agonists such as albuterol.
What is intraoperative awareness?
Intraoperative awareness is a rare but disturbing condition in which patients undergoing an operation and anesthesia can recall surroundings, sounds, events, and sometimes even pain.
The definition of intraoperative awareness is: becoming conscious during a procedure performed under general anesthesia, with subsequent explicit memory of specific events that took place during that time.
A Sentinel Event Alert was issued by the Joint Commission (JC) regarding the prevention and management of intraoperative awareness in October 2004.
The ASA published a Practice Advisory for Intraoperative Awareness and Brain Functioning Monitoring in 2006. The incidence of intraoperative awareness in adults has been reported to be 0.1–0.9% in older studies, and 0.0068% or 1 per 14,560 patients in a 2007 report of 87,361 patients.
Most experts estimate the true incidence in adults to be 0.1–0.2%.
There is a dearth of literature about intraoperative awareness in infants and children, but there is a 2005 study of 864 children in which the incidence was reported as 0.8%. Some of these data may be confounded by the memory of entering the OR after administration of preoperative sedation or a memory of events and sensations during emergence.
Certainly, the likelihood of a clear memory of a painful event during surgery is a much rarer event than the other events more commonly reported.
However, there are multiple adverse consequences of intraoperative awareness, including post-traumatic stress disorder and medical-legal implications.
What are reasons for undertreatment of pain among children?
The goal of postoperative pain management should be to achieve good pain relief with minimal adverse effects. Effective pain management is associated with early mobilization, more rapid recovery, and faster return to work, school, and play.
The incidence of postoperative pain in the pediatric population, although difficult to evaluate objectively, is probably similar to that in the adult population. It is reasonable, therefore, to assume that about 75% of children will report significant pain on the first postoperative day.
Many studies looking at pain in hospitalized children report under-treatment in both medical and surgical patients. This under-treatment may be related to
(1) inadequate analgesia provided intraoperatively;
(2) underestimation of an infant’s ability to experience pain (primarily in neonates who have been erroneously believed to be incapable of experiencing or remembering painful experiences);
(3) fear of analgesic (primarily opioid) side effects;
(4) fear of addiction by both caregivers and parents;
(5) inadequate knowledge or utilization of pain assessment scales in children who are either pre-verbal or unable to use numerical rating scales;
(6) failure to appreciate the benefit of nonopioid analgesics in provision of effective pain relief while reducing total opioid dose and attendant adverse effects; and
(7) failure to utilize basic regional analgesic techniques that are easily applied even in the ambulatory setting.
How do you address undertreatment of pain among infants and children?
The management of pain in infants and children is hampered by the difficulty that exists in assessing pain. Many children may respond to pain by emotionally withdrawing from their surroundings, and this may be misinterpreted by the medical and nursing staff as evidence that they have no pain.
In addition, when questioned as to their degree of pain, children may not volunteer useful information for fear of painful interventions (e.g., “shots”).
To circumvent these difficulties, pain assessment scales have been developed for use in infants and children that are more objective and depend on caregiver assessment of body positions, facial expression, and physiologic variables.
Although there are many scales available, an institution should adopt one scale for each stage of development and ensure that caregivers are trained so that they are used reproducibly in settings where pain is treated.
Examples of these pain scales include:
Crying, Requires O2, Increased vital signs, Expression, Sleepless (CRIES) for neonates (until 1 month of age),
Face, Legs, Activity, Cry, Consolability (FLACC) from 1 month to age 4 years,
FACES for ages 5–9 years and in children who are developmentally appropriate,
and a numerical scale for those older than 10 years of age.
What is the current mainstay for postoperative pain control?
Opioids remain the mainstay in pain control postoperatively, although regional analgesic techniques (epidural or peripheral nerve block) are being increasingly used in infants and children, resulting in a decrease in perioperative opioid requirements.
There are many opioids available for both IV and oral administration, but they all have common adverse effects.
These include dose-dependent respiratory depression as mentioned above, which may be more prominent in neonates and young infants and in patients with OSA.
Other side effects that vary in prevalence among drugs and patients are dysphoria, somnolence, nausea and vomiting, pruritus, constipation, and urinary retention.
[H&A]
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Reluctance to use opioids in children is a common excuse for inadequate pain management in the pediatric population. Opioids are the mainstay of pharmacologic therapy for moderate to severe pain, however, and have established roles in procedural and perioperative pain management for children.
Acting on various subtypes of opioid receptors throughout the CNS, opioids cause dose-dependent pain relief and respiratory depression; other side effects include somnolence, miosis, decreased gastrointestinal motility, nausea, and urinary retention.
Many opioids induce histamine release, causing urticaria, pruritus, nausea, bronchospasm, and occasionally hypotension.
Pruritus is more common, and typically more intense, with neuraxial administration, likely owing to the CNS opioid effect rather than histamine release.
Opioid side effects can be managed with a variety of agents.
The opioid receptor antagonist naloxone rapidly reverses opioid effects. Mild respiratory depression or somnolence can be treated with IV naloxone 1.0 mg/kg titrated every 1 to 2 minutes as needed; doses of 10 to 100 mg/kg should be reserved for apnea or coma secondary to opioid overdose. Higher or repeated doses may be necessary.
Naloxone may precipitate withdrawal in opioid-dependent patients, and pulmonary edema has been reported with higher doses.
A low-dose naloxone infusion (0.25 mg/kg/min) may reduce the incidence of unwanted opioid side effects without significantly affecting analgesia for patients on patient-controlled opioid analgesic regimens.
Opioid analgesics do not generally have maximum effective doses.
Recommended doses are for initial administration in opioid-naive patients; titration to clinical effect is required, and higher doses may be necessary.
Increased dosage requirements (tolerance, tachyphylaxis) are often observed with prolonged administration or persistent pain.
Opioid therapy longer than 7 to 10 days may result in physical dependence, requiring weaning before discontinuation to avoid withdrawal.
Tolerance and dependence may occur independently. Addiction, a psychopathologic condition of volitional drug-seeking behavior, rarely develops in children receiving appropriately dosed opioids for analgesia and is not a valid reason to withhold therapy.
Opioids are commonly administered in conjunction with sedative-hypnotic agents, particularly benzodiazepines, increasing the risk of respiratory depression and desaturation.
Careful titration of doses, appropriate monitoring, and full capability to manage complications, including respiratory depression and apnea, are essential. Appropriate reversal agents should be available.
Opioid use in neonates and young infants has been the subject of much investigation and controversy. Historical studies in rats and humans suggested increased permeability of the neonatal blood-brain barrier to opioids, particularly morphine, and greater clinical respiratory depression.
It has more recently and more accurately been realized that the pharmacologic properties and clinical effects of morphine, fentanyl, and indeed all opioids in human neonates are subject to great individual variability.
In general, opioid clearance is decreased and elimination is more prolonged in neonates than in older children, with values approaching adult levels by several months of age.
There is no intrinsic reason to withhold opioid therapy from children of any age provided that doses are individualized to each patient and titrated to clinical effect.
[Coran]
Which opioid is the standard by which the potency of other opioids is measured?
Morphine remains the standard by which the potency of other opioids is measured.
Equipotent analgesic doses of commonly used IV opioids are listed in Table 3.3.
As the plasma concentration of morphine correlates poorly with its desired analgesic effect—a fourfold variation has been measured in the plasma concentration of morphine at which patients express the need for additional pain medicationmany clinicians believe that morphine is best administered in a patient-controlled device (patient-controlled analgesia [PCA]) to allow self-titration of medication according to the level of pain experienced.
A discussion of patient selection and dosing for PCA is beyond the scope of this chapter, but can be found in many textbooks of pediatric anesthesiology and pain management.
Patients receiving PCA should be continuously monitored for cardiorespiratory depression by monitoring the echocardiogram, respiratory rate, and pulse oximetry.
There is increasing safe and effective use of nurse- or parent-controlled PCA in many pediatric hospitals.
When PCA devices are not used, the intermittent bolus administration of morphine to opioid-naive children should be started at 0.05–0.1 mg/kg every 2–4 hours.
If the treatment of pain is initiated in the PACU or intensive care setting, similar doses may be administered every 5–10 minutes until the child is comfortable.
Which commonly-used opioid has a relatively short duration of action, and is 100 times more potent than Morphine?
Fentanyl is a synthetic opioid that usually has a relatively short duration of action as a result of its rapid distribution into fat and muscle due to its high lipid solubility.
With repeated dosing, the duration of action appears to increase.
When compared with morphine, fentanyl is about 100 times more potent. (Fentanyl dosages are calculated in micrograms rather than milligrams.)
In controlled comparisons with equipotent dosages, morphine is generally found to provide better, more long-lasting analgesia than fentanyl, but with more side effects such as pruritus, nausea, and vomiting.
The more rapid development of tolerance to analgesic effects is often seen in opioids having shorter half-lives (i.e., fentanyl) when compared with morphine or hydromorphone.
Which opioid is a well-tolerated alternative to morphine and fentanyl?
Hydromorphone is a well-tolerated alternative to morphine and fentanyl, and is thought to cause less pruritus and sedation than morphine, with the few adult studies that exist suggesting equivalence rather than superiority.
It is five to seven times more potent than morphine, and its duration of action is similar to that of morphine and longer than that of fentanyl.
What are criteria for discharge of children post-anesthesia/post-surgery?
In general, children should be comfortable, awake, and stable, on room air or back to baseline oxygen supplementation, have age-appropriate vital signs, and be well hydrated before discharge from outpatient surgery.
These variables have been quantified with the modified Aldrete score (Table 3.4), which lists the important factors taken into consideration for discharge.
Most institutions require a modified Aldrete score of 9 or greater for discharge to floor, but criteria for discharge home should be stricter, comprising the following elements:
Return to preoperative level of consciousness
Normothermia (≥35.5°C)
No oxygen requirement (or return to baseline oxygen requirement)
Return to preoperative level of motor function (excepting expected effects of nerve block)
Acceptable pain control
No ongoing vomiting, minimal nausea
Absence of surgical bleeding
At least 30 minutes after last administration of opioid
Discharge acceptable to surgeon
Oral intake (if required by surgeon)
What are indications for replacement with specific blood products?
Blood component therapy depends on the clinical setting and the availability of various blood products.
Fresh whole blood (i.e., blood that was obtained less than 4 hours previously) has limited availability.
Thus treatment with component therapy rather than fresh whole blood is the rule rather than the exception.
Packed red blood cells (RBCs) have a hematocrit value between 55% and 75% and are relatively hyperkalemic (K +/-15 to 20 mEq/L) and acidotic (pH <7.0).
The estimated rise in hematocrit for every 10 mL/kg of packed RBCs (assuming a hematocrit of 70%) depends on the patient’s age, size, and estimated blood volume.
The need for platelets during surgery can be predicted from the preoperative platelet count.
Platelets are mobilized from the spleen and bone marrow as bleeding occurs. An infant with a high preoperative platelet count (>250,000/mm3 ) may not need a platelet transfusion until two to three blood volumes are lost, whereas an infant who has a low count (<150,000/mm3 ) may need platelets after only one blood volume is lost.
Two platelet packs/10 kg increases the platelet count by 50,000 to 100,000/mm3 .
Fresh frozen plasma (FFP) is indicated for emergency reversal of warfarin, for correction of microvascular bleeding in the presence of elevated prothrombin time and partial thromboplastin time, and as part of a massive transfusion protocol.
Ten to 20 ml/kg of FFP usually raises the level of coagulation factors by 20%. FFP contains the highest concentration of citrate per unit volume of any blood product; thus rapid FFP causes the greatest change in ionized calcium.
Under most circumstances, mobilization of calcium and hepatic metabolism of citrate are sufficiently rapid to prevent precipitous decreases in ionized calcium. However, because infants’ calcium stores are small, rapid infusion of FFP can acutely decrease ionized calcium and cause significant decreases in arterial blood pressure.
Treatment of acute hypocalcemia includes IV calcium chloride (10 mg/kg) or calcium gluconate (30 to 60 mg/kg), which effectively increases ionized calcium and ameliorates hemodynamic changes.
When blood loss approaches one blood volume many centers have established massive transfusion protocols. These protocols help prevent the acidosis, hypothermia, and coagulopathy seen when only packed RBCs are infused during massive hemorrhage.
The goals of these protocols are to improve communication between the surgeon, anesthesiologist, and blood bank to expedite delivery of appropriate quantities of blood products to the patient care team. Although the transfusion and coagulation management in children experiencing severe hemorrhage is not well studied, it is prudent to develop a massive transfusion protocol. The goal of transfusion is to deliver blood products that resemble whole blood. Current data support the use of plasma-to-RBCto-platelet at 1:1:1.
[Coran]
What are the risks of inhalational anesthetics?
Several inhalation agents are available for induction and maintenance of anesthesia. The choice of agent depends on the age of the child and the disease process. Each agent has general and specific advantages and disadvantages (Table 13-4).
None ensures hemodynamic stability.
In patients with significant cardiac depression or hemodynamic instability, inhalation agents are generally avoided or used in markedly reduced concentrations.
In healthy children, most inhalation agents can be used safely and successfully regardless of age.
To spare children an awake placement of an IV catheter, anesthesia is often induced by inhalation.
However, inhalation anesthesia in children has some risk and is associated with an increased incidence of bradycardia, hypotension, and even cardiac arrest.
These risks have been reduced with the use of sevoflurane rather than halothane.
In premature or critically ill infants, the incidence of untoward effects from potent inhalation agents is attributed to age-related differences in uptake, anesthesia requirements, and cardiovascular system sensitivity.
The uptake of inhalation anesthetics is more rapid in infants and small children than in adults because of major differences in blood-gas solubility coefficients, blood-tissue solubility coefficients, body composition, ratio of alveolar ventilation to functional residual capacity, and distribution of cardiac output.
Thus, early in the course of anesthesia induction, infants have higher tissue concentrations of the drug in the brain, heart, and muscle than do adults.
[Coran]
What is the minimum alveolar concentration?
The minimum alveolar concentration (MAC) is the minimum concentration of an inhaled anesthetic at 1 atm of pressure that prevents skeletal muscle movement in response to a surgical incision in 50% of patients.
The MAC of a volatile anesthetic changes with the patient’s age (see Table 13-1).
LeDez and Lerman showed that premature infants younger than 32 weeks’ gestation have a lower MAC for isoflurane than do neonates of longer gestation.
For all anesthetic agents, the MAC is highest at 6 to 12 months of age.
The increased MAC requirement in conjunction with the rapid uptake of anesthetic makes infants and children very susceptible to anesthetic overdose.
What is the role of neuromuscular blocking agents in Pediatric surgery?
Neuromuscular blocking agents (i.e., muscle relaxants) are used to facilitate endotracheal intubation, to provide surgical relaxation, and to facilitate controlled mechanical ventilation.
This is accomplished through blockade of the nicotinic acetylcholine receptor site on the neuromuscular junction.
The use of neuromuscular blocking agents reduces the need for potent inhaled anesthetics or IV sedative-hypnotics.
Throughout infancy, the neuromuscular junction matures physically and biochemically.
The contractile properties of skeletal muscle change, and the amount of muscle in proportion to body weight increases.
As a result, the neuromuscular junction is variably sensitive to relaxants.
In addition, age-related changes in the volume of distribution of relaxants, their redistribution and clearance, and possibly their rate of metabolism occur. These factors influence the dose-response relationships of relaxants and the duration of neuromuscular blockade.
When allowances are made for differences in the volume of distribution and for the type and concentration of anesthetic, infants seem to be relatively resistant to succinylcholine and relatively sensitive to nondepolarizing relaxants.
The degree of neuromuscular blockade should be monitored with a nerve stimulator during the course of the operation, and the patient should be treated with a dose of the selected agent sufficient to achieve the desired degree of block.
The paralysis caused by nondepolarizing relaxants should be reversed at the end of each operation unless postoperative mechanical ventilation is planned.
Anticholinesterase drugs, such as neostigmine and edrophonium, combined with anticholinergics are given to prevent muscarinic side effects.
The effectiveness of reversal is judged by muscle strength, adequacy of ventilation, and response to nerve stimulation.
Minimum criteria for withdrawing assisted ventilation should include good muscle tone, flexing of the arms and legs, and adequate respiratory effort.
Neuromuscular blocking agents have no sedative, hypnotic, or analgesic effects, but they may indirectly decrease metabolic demand, prevent shivering, decrease nonsynchronous ventilation, decrease intracranial pressure, and improve chest wall compliance.
Major organ failure, up-regulation of acetylcholine receptors, malnutrition, electrolyte and acid-base abnormalities, drug interactions, and muscle atrophy can also have a profound influence in the kinetics and dynamics of relaxants.
In addition, repeated doses of relaxants over relatively long periods without monitoring of neuromuscular transmission may lead to prolonged muscle weakness despite discontinuation of therapy.
Knowledge of neuromuscular pharmacology and its modification by age, concurrent medications, and concurrent disease processes permits a more rational use of neuromuscular blocking agents in patients in intensive care.
[Coran]
How is malignant hyperthermia managed?
MH is a life-threatening condition characterized by hyperthermia, hypermetabolism, and muscle injury that occurs in response to a triggering agent. Potent inhalation agents (not nitrous oxide) and the depolarizing muscle relaxant succinylcholine are two potent triggers in children.
Triggers that stimulate MH cause excessive release of Ca2+ from the sarcoplasmic reticulum of skeletal muscle into the myoplasm, resulting in a chain of metabolic events that culminates in heat production, cell injury, hyperkalemia, and myoglobinemia.
The mortality rate for untreated MH is greater than 60%; rapid treatment with dantrolene reduces mortality to almost zero.
The incidence of fulminant MH is approximately 1 in 50,000 to 1 in 100,000 in adults and 1 in 3,000 to 1 in 15,000 in children.
Most cases of MH occur in patients thought to be healthy.
Predisposition to MH is a familial condition of multigenetic inheritance. First-degree relatives are at high risk; second-degree relatives have a lower but significant risk of MH developing in response to the appropriate triggering agents.
Patients with Duchenne muscular dystrophy are thought to be at high risk for the development of MH. Other diseases associated with the development of MH are central core disease and King-Denborough syndrome.
The classic signs of MH include tachycardia, ventricular dysrhythmias, tachypnea, a rapid increase in temperature to greater than 39.5C, rigidity of the jaw or generalized rigidity, metabolic and respiratory acidosis, and decreased mixed venous oxygen saturation.
Associated laboratory values include hyperkalemia, hypercarbia, respiratory and metabolic acidosis, increased creatine phosphokinase and lactate levels, blood clotting abnormalities, and myoglobinuria.
The clinical diagnosis of MH should be considered before signs of hypermetabolism and elevated temperature reach extremes. The early signs of the disorder include tachypnea, tachycardia, increased end tidal carbon dioxide (ETCO2), and ventricular dysrhythmias.
These signs must be evaluated quickly because they can have many causes, such as iatrogenic hyperthermia, sepsis, pheochromocytoma, hyperthyroidism, ventilator valve malfunction with rebreathing of carbon dioxide, inadequate levels of anesthesia, and faulty temperature and ETCO2 monitors.
Management of an acute episode of MH is outlined in Table 13-6.
The cornerstone of treatment is IV dantrolene, which must be diluted with sterile, preservative-free, distilled water.
The initial IV dose is 2.5 mg/kg, although much higher doses may be required.
The usual dose limit of 10 mg/kg may be exceeded if necessary.
Dosing of dantrolene should be guided by clinical and laboratory signs and carried out every 5 minutes until metabolic acidosis has resolved.
Dantrolene decreases the release of calcium from the sarcoplasmic reticulum by decreasing the mobility of calcium ions or the protein that transports calcium across membranes and is specific for skeletal muscle.
Dantrolene attenuates muscle hypermetabolism, reducing muscle rigidity and restoring normal muscle function.
As skeletal muscle function normalizes, serum potassium levels decrease and abnormal lactic acid production slows.
Patients respond to dantrolene within 20 minutes.
The ETCO2 begins to decrease in 6 minutes, and arterial blood gas analysis demonstrates significant resolution of metabolic and respiratory acidosis within 20 minutes.
By 45 minutes, metabolic and respiratory acidosis and hyperthermia should be resolved.
Dantrolene treatment at higher doses is necessary if metabolic dysfunction persists.
Parents of an affected child may wish to have a muscle biopsy and contracture testing because negative findings mean that other relatives have no increased risk of MH.
In patients with a personal history or a strong family history of MH, surgery can be safely performed under regional or local anesthesia. General anesthesia with nontriggering agents can also be used. All nondepolarizing muscle relaxants and IV anesthetic agents are safe to use in patients who are susceptible to MH.
Monitoring for the early signs of MH and initiating quick treatment are the most important aspects of caring for these patients.
[Coran]
What is the gold standard for confirming proper endotracheal tube placement and measuring adequacy of ventilation?
The presence of end tidal CO2 (ETCO2) is the gold standard in confirming proper endotracheal tube placement and measuringthe adequacyof ventilation.
Plotting ETCO2 versus time produces the classic time-capnograph curve.
An ideal capnographic tracing cannot always be obtained, but the abnormal curve may be diagnostic or highly suggestive of certain types of problems involving the patient, the anesthesia circuit, or the ventilation technique.
[Coran]
What is the analgesic ladder?
The goal of perioperative pain management is to maximize patient comfort while minimizing side effects such as excessive sedation or respiratory depression.
Multiple techniques are available and are chosen and titrated to effect based on each child’s particular needs. Planning begins with the preoperative anesthesia evaluation and continues throughout the surgical procedure and postoperative period.
Nonpharmacologic techniques, such as distraction and guided imagery, may augment analgesia, enhance patient cooperation, and minimize pharmacologic therapy.
Nonopioid analgesics most commonly include acetaminophen, nonsteroidal antiinflammatory agents, and ketamine.
Oral opioids are often adequate for the treatment of mild to moderate pain, whereas IV opioids are the mainstay of therapy for moderate to severe pain.
Persistent requirement for IV opioids can be managed with continuous infusion or patient-controlled analgesia (PCA) modalities.
Regional anesthesia may also be used as part of a comprehensive analgesia regimen.
A useful paradigm that can be applied to pediatric pain management is the World Health Organization’s analgesic ladder.
[Coran]
What is the role of non-opioid analgesics in pediatric surgical patients?
Often overlooked, nonopioid analgesics are important adjunctive agents in pediatric pain management. They are often adequate for mild to moderate pain and may reduce opioid requirement in cases of moderate to severe pain.
Unlike opioids, nonopioid analgesics generally demonstrate a ceiling effect: exceeding recommended doses does not significantly improve analgesia but does increase the risk of side effects and toxicity.
Common nonopioid analgesics for children include acetaminophen, various NSAIDs, and in appropriate settings ketamine.
[Coran]
What are the indications for oral opioids in perioperative pediatric pain control?
When pain needs allow and gastrointestinal function permits, oral opioids offer freedom from parenteral therapy. Onset of action is relatively slow, rendering oral opioid therapy unsuitable for the acute management of severe pain.
Several lower potency oral opioids are used commonly in children, providing adequate analgesia for mild to moderate pain.
Codeine, available in liquid and tablet preparations, is commonly used in combination with acetaminophen. Codeine has a high rate of gastrointestinal upset.
Hydrocodone, available in liquid and tablet preparations, is also usually used in combination with acetaminophen or an NSAID. Hydrocodone tends to cause less gastrointestinal upset than does codeine.
Oxycodone is available in tablet preparations containing only oxycodone or in combination with acetaminophen or an NSAID; liquid preparations contain only oxycodone. This analgesic causes little gastrointestinal upset and is generally well tolerated. Sustained-release oxycodone is available for chronic therapy.
Although often given IV, higher-potency opioids may also be given orally.
The histamine release induced by morphine may cause urticaria, pruritus, bronchospasm, and even hypotension at higher doses, although these are less common with oral administration.
Sustained-release oral morphine is available for chronic therapy.
Hydromorphone causes less histamine release than does morphine.
Methadone is particularly useful for chronic therapy in opioid-dependent patients.
Treatment of psychopathologic opioid addiction with methadone may be undertaken only in federally licensed facilities.
Oral transmucosal fentanyl citrate (OTFC) is a formulation of fentanyl in a lozenge attached to a stick. Oral transmucosal fentanyl citrate may provide effective preanesthetic sedation in children, as well as analgesia and sedation for painful procedures, although nausea and emesis are common. Appropriate monitoring is required.
[Coran]
How does patient-controlled analgesia work?
With PCA, opioid delivery is controlled by a device that allows administration of small doses of drug in response to patient request, usually by pressing a button; an appropriate lockout interval is programmed to prevent excessive administration.
Analgesia is excellent, and with appropriate doses, serious complications are rare.
With proper instruction, most school-aged children can safely and effectively use PCA for opioid delivery.
Nurse- or parent-controlled analgesia can be used for children unable or unwilling to control their own pumps, although the risk of respiratory depression increases if dosing intervals are not adequately adjusted, particularly in combination with basal infusions.
Overall risk of complications with so-called PCA by proxy in children is not elevated compared with the PCA, although risk of serious complications requiring intervention may be somewhat increased.
Morphine is the most common choice for PCA, but hydromorphone or fentanyl can be used.
Meperidine PCA is not recommended because of the increased risk of toxicity with sustained administration.
Methadone PCA has been described in pediatric cancer patients with significant opioid requirements and tolerance to other agents, but it is neither necessary nor helpful in most children because of the drug’s long half-life.
Routine PCA regimens provide a specified dose every 8 to 10 minutes for patient-controlled administration or every 15 to 60 minutes for nurse- or parent-controlled administration.
Longer dosing intervals may be safer in younger or more medically fragile patients.
Concomitant basal infusion to ensure ongoing analgesia and sustain drug levels during sleep has been advocated but has not been shown to improve analgesia significantly.
PCA basal infusions in adults have been shown to increase the risk of respiratory complications, but this has not been observed in children.
PCA basal infusions in pediatric patients, although safe, appear to offer little analgesic benefit except in the setting of significant opioid tolerance.
Patients receiving PCA should be assessed frequently, and doses and intervals should be adjusted appropriately.
Continuous pulse oximetry is recommended for children receiving any opioid infusion.
Cardiorespiratory monitoring may be appropriate in very young or medically fragile patients.
Instruction of patients, families, and caregivers regarding appropriate PCA use is essential.
[Coran]
What is the role of topical anesthesia in pediatric analgesia?
Numerous formulations of local anesthetics provide cutaneous analgesia without the need for injection, potentially reducing or eliminating the need for systemic analgesia and sedation.
Eutectic mixture of local anesthetics (EMLA) cream is a combination of 2.5% lidocaine and 2.5% prilocaine.
Applied in a thick layer and covered with an occlusive dressing for at least 60 minutes, EMLA provides effective cutaneous analgesia for minor procedures, including circumcision and even chest tube removal.
Analgesia increases with application up to 4 hours.
EMLA cream is easy to apply; patients and families can do so at home. Side effects include erythema, blanching, and rash.
The prilocaine component has caused concern about the risk of methemoglobinemia, particularly with generous application or in infants, but this is rare when the product is used appropriately.
Several other preparations of topical anesthetics are available. ELA-Max is an over-the-counter preparation of 4% or 5% liposomal lidocaine.
Numby Stuff is a unique system of topical anesthesia using mild electrical current to promote rapid iontophoretic intradermal transport of a solution of 2% lidocaine and 1:100,000 epinephrine.
TAC (tetracaine, adrenaline, cocaine) is available in a variety of preparations and provides effective cutaneous analgesia for the repair of superficial lacerations in children.
[Coran]
What is the role of local anesthesia in pediatric analgesia?
Infiltration with local anesthetic provides effective analgesia for minor procedures and can be performed in cooperative or older patients without sedation or anesthesia.
Any appropriate solution may be used. The acid pH of many local anesthetic solutions enhances solubility and prolongs shelf life but is responsible for much of the pain associated with injection.
Buffering pH helps reduce pain in awake patients and may increase efficacy.
Addition of 1.0 mEq sodium bicarbonate to 10 mL local anesthetic significantly reduces pain during injection without precipitation of the solution.
The bicarbonate is added immediately before use.
Infiltration anesthesia provides adequate analgesia after minor, but not major, surgical procedures.
The technique is straightforward, and the risk of local anesthetic toxicity is low if maximum recommended doses are not exceeded.
Wound infiltration during inguinal hernia repair in children provides analgesia similar to that afforded by ilioinguinal-iliohypogastric nerve block or caudal block for 2 to 4 hours after the procedure.
Longer-term analgesia is inferior, however.
[Coran]
What is the role of rectus sheath block in pediatric analgesia?
Recent interest in umbilical surgery in children, particularly the application of laparoscopic techniques, has prompted research on the use of regional anesthesia for such procedures.
Terminal cutaneous branches of the lower thoracic intercostal nerves supply the skin of the anterior abdominal midline.
Although infiltration anesthesia is readily accomplished in this area, specific nerve block offers the advantage of prolonged analgesia.
Rectus sheath block for repair of umbilical and paraumbilical hernias in children has been described and with minor modifications has been described as paraumbilical block.
Injection is made halfway between the umbilicus and the lateral linea alba.
A blunt-bevel needle is introduced through the skin with slight medial angulation until a pronounced give or “pop” is felt as the needle pierces the external rectus sheath.
After negative aspiration for blood and a negative test dose to reduce the likelihood of intravascular injection, 0.25 to 0.5 mL/kg of local anesthetic is deposited; little or no resistance should be felt.
The needle may be withdrawn and a subcutaneous weal made toward the umbilicus for improved coverage of distal cutaneous braches.
Injection is then repeated on the contralateral side.
Rectus sheath block can be used at other dermatomal levels for the repair of midline ventral hernias above or below the umbilicus.
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What is the role of ilioinguinal-iliohypogastric block in pediatric analgesia?
The ilioinguinal and iliohypogastric nerves are terminal cutaneous branches of the lumbar plexus.
The ilioinguinal nerve arises from the first lumbar spinal nerve roots and supplies much of the external genitals and part of the proximal thigh; the iliohypogastric nerve arises from the 12th thoracic and 1st lumbar spinal nerve roots to innervate the skin of the anterior abdominal wall above the inguinal ligament.
The two nerves are usually blocked in conjunction, providing analgesia for procedures on the ipsilateral groin, including inguinal hernia repair and orchiopexy.
Injection is made 1 to 2 cm medial and 1 to 2 cm superior to the anterior superior iliac spine.
A blunt-bevel needle is introduced perpendicular to the skin until a distinct give or “pop” is felt as the needle pierces the Scarpa fascia, adherent to the aponeurosis of the external oblique muscle.
After negative aspiration for blood and a negative test dose to reduce the likelihood of intravascular injection, 0.5 to 1.0 mL/kg of local anesthetic is deposited.
Total volume of local anesthetic required for adequate blockade may be reduced with ultrasonographic guidance.
The needle may be withdrawn and a subcutaneous weal made toward the umbilicus for improved coverage of distal cutaneous branches of the iliohypogastric nerve.
Ilioinguinal-iliohypogastric block provides only cutaneous analgesia; supplemental anesthesia is required for visceral manipulation.
Because of this lack of visceral coverage, ilioinguinal-iliohypogastric block is inferior to caudal block at blunting the neuroendocrine stress response to orchiopexy.
The ilioinguinal-iliohypogastric block may also be paired with a caudal block for superior analgesia.
Bilateral block can be performed, but application may be limited in small children by the dose of local anesthetic required.
[Coran]
What is the role of penile block in pediatric analgesia?
Penile block provides analgesia for circumcision and other distal penile procedures, including simple hypospadias repair; caudal block is preferred for more proximal procedures, such as repair of complex hypospadias.
In general, penile block has fewer complications than does caudal block, in particular a lower incidence of motor block, but caudal block has a higher success rate and provides more prolonged analgesia.
Penile block is not free of risk; puncture of dorsal penile vessels may lead to hematoma, and gangrene of the glans penis has been reported.
Local anesthetic solutions for penile block should not contain epinephrine or other vasoconstrictors.
Injection is made at the base of the penis lateral to the midline at approximately the 10 and 2 o’clock positions.
Alternatively, a single injection can be made in the midline.
A blunt-bevel needle is introduced perpendicular to the skin until a distinct give or “pop” is felt as the needle pierces the Buck fascia.
After negative aspiration for blood and a negative test dose to reduce the likelihood of intravascular injection, 0.5 to 1.0 mL/kg of local anesthetic, up to 10 mL, is deposited; little or no resistance should be felt.
The process is then repeated on the contralateral side.
Ring block at the base of the penis superficial to the Buck fascia provides equivalent analgesia and may reduce the risk of hematoma.
[Coran]
What is the role of caudal block in pediatric analgesia?
The most common neuraxial block in children is caudal block, in which the epidural space is accessed via the sacral hiatus created by the failure of fusion of the spinous process of the fifth sacral vertebra.
The technique is relatively straightforward, the success rate is high, and the complication rate is low.
Injection is made between and slightly inferior to the sacral cornua.
A blunt-bevel needle is introduced with approximately 45 degrees of cephalad angulation until a distinct give or “pop” is felt as the needle pierces the sacrococcygeal ligament, the most inferior aspect of the ligamentum
flavum.
If bone is encountered, usually representing the posterior aspect of anterior sacral elements, the needle is withdrawn slightly and redirected more parallel to the skin.
Correct positioning of the needle tip within the epidural space is confirmed by loss of resistance to injection.
After negative aspiration for blood and a negative test dose to reduce the likelihood of intravascular injection, the full dose of anesthetic is injected.
Serious complications associated with caudal block include intravascular or intraosseous injection, inadvertent dural puncture with resultant spinal anesthesia, injury to pelvic contents, and hematoma; these complications are rare.
Caudal block is most commonly performed as a single injection of anesthetic providing reliable analgesia below the umbilicus in patients weighing less than approximately 30 kg.
Perhaps because of their lower overall sympathetic tone, infants and children do not generally demonstrate hemodynamic instability after neuraxial block.
Caudal block in pediatric patients induces significant changes in regional blood flow but does not significantly alter heart rate or blood pressure.
The agents administered determine the duration of analgesia after caudal block.
Local anesthetic may provide analgesia for several hours and does not cause urinary retention at usual doses.
Bupivacaine 0.0625% to 0.25% is used most commonly.
The addition of an opioid prolongs analgesia but increases the risk of side effects, particularly respiratory depression.
Duration of analgesia and risk of side effects are greater with increasing opioid hydrophilicity, which promotes uptake into the cerebrospinal fluid and enhances distal spread.
Caudal fentanyl, a highly lipophilic opioid, can be used for outpatient and ambulatory surgery in children.
Caudal morphine, a highly hydrophilic opioid, provides analgesia for more than 12 hours but entails a significant risk of side effects, including pruritus and respiratory depression, for up to 24 hours.
Neuraxial morphine should not be used for outpatient analgesia.
Caudal hydromorphone provides more prolonged analgesia than does caudal fentanyl, with less risk of respiratory depression than does caudal morphine.
Caudal administration of clonidine and ketamine has been described and may be particularly advantageous in patients with potentially increased sensitivity to opioids, including neonates and children with chronic respiratory disease.
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