ubp_set_4_extra_topics_copy_20190502182008 Flashcards
If you had been the intensive care physician responsible for this patient with status asthmaticus four days ago, how would you have treated her condition?
(A 12-year-old female presents to the operating suite with acute appendicitis. Her parents inform you that she has severe asthma. They further report that their daughter was hospitalized and treated 4 days ago for status asthmaticus. Her lungs are currently clear to auscultation bilaterally, but she is extremely nauseous. Her current medications include dexamethasone, omalizumab, and salmeterol.)
When treating a patient with this life-threatening condition, I would:
- provide supplemental oxygen to maintain the oxygen saturation above 90%;
- administer B2-agonists (i.e. albuterol), corticosteroids (recognizing that it may take 4-6 hours to realize a therapeutic benefit), aminophylline (to induce bronchodilation, stimulate the central respiratory cycle, reduce diaphragmatic muscle fatigue, and relax vascular smooth muscles), empirical broad-spectrum antibiotics, and intravenous fluids (although the benefits of this treatment are limited);
- order pulmonary function tests and arterial blood gases to monitor the adequacy of oxygenation, ventilation, and the patient’s response to treatment;
- consider the addition of intravenous magnesium sulfate (for bronchodilatory affects), if the patient’s response to other bronchodilators is inadequate; and
- consider mechanical ventilation, if the patient begins to show signs of respiratory fatigue and/or inadequate ventilation and oxygenation (PaCO2 > 50 mmHg).
When would you intubate a patient with status asthmaticus, and what ventilator strategy would you employ?
(A 12-year-old female presents to the operating suite with acute appendicitis. Her parents inform you that she has severe asthma. They further report that their daughter was hospitalized and treated 4 days ago for status asthmaticus. Her lungs are currently clear to auscultation bilaterally, but she is extremely nauseous. Her current medications include dexamethasone, omalizumab, and salmeterol.)
I would consider intubation and the initiation of mechanical ventilation if the patient began to show signs of respiratory fatigue and/or inadequate ventilation and oxygenation.
Therefore, I would monitor the patient’s response to therapy using pulmonary function tests and arterial blood gases.
If pulmonary function testing showed a FEV1 or peak expiratory flow rate = 25% of normal, or if arterial blood gases showed a PaCO2 > 50 mmHg, despite aggressive therapy, I would intubate the patient and initiate mechanical ventilation.
My goals during mechanical ventilation are to decrease the work of breathing, maintain adequate oxygenation, and augment alveolar ventilation without causing intrinsic lung injury.
Therefore, I would employ a pressure control mode of ventilation, recognizing that the decelerating flow pattern associated with this mode of ventilation will more efficiently overcome the high resistance of the asthmatic’s airways, minimize the peak pressures required to deliver a given tidal volume, and improve the distribution of ventilation.
Moreover, I would establish a prolonged expiratory phase to allow for complete exhalation and to avoid auto-PEEP (breath stacking), which can result in barotrauma.
When the patient’s FEV1 or peak expiratory flow rates increased to >/= 50% of normal, I would initiate weaning from mechanical ventilation.
Ok. Back to our current situation, with the patient having been discharged from the hospital several days ago and now presenting to the operating suite with acute appendicitis.
How would you assess this patient’s asthmatic condition, pre-operatively?
(A 12-year-old female presents to the operating suite with acute appendicitis. Her parents inform you that she has severe asthma. They further report that their daughter was hospitalized and treated 4 days ago for status asthmaticus. Her lungs are currently clear to auscultation bilaterally, but she is extremely nauseous. Her current medications include dexamethasone, omalizumab, and salmeterol.)
I would first perform a careful history, focusing on the severity and characteristics of her pulmonary disease, along with the effectiveness of her current therapy.
To this end, I would attempt to elicit information concerning the –
- age of onset,
- triggering events,
- allergies,
- recent respiratory infection,
- changes in symptomatology (cough, sputum, wheezing, etc.),
- current medications,
- anesthetic history, and
- her recent hospital course.
Next, I would perform a physical exam to identify any pulmonary wheezing or crepitations and/or the use of accessory muscle of respiration.
Considering the severity of her disease, I would order:
- pulmonary function tests, before and after bronchodilator therapy, to more accurately assess the severity of obstruction and her response to therapy;
- arterial blood gases, to evaluate the adequacy of ventilaton/oxygenation and to establish baseline levels (helpful in the event of subsequent respiratory dysfunction); and
- chest x-rays, to identify or rule out pulmonary infection.
How would you prepare her for emergent surgery?
(A 12-year-old female presents to the operating suite with acute appendicitis. Her parents inform you that she has severe asthma. They further report that their daughter was hospitalized and treated 4 days ago for status asthmaticus. Her lungs are currently clear to auscultation bilaterally, but she is extremely nauseous. Her current medications include dexamethasone, omalizumab, and salmeterol.)
My goals in preparing this patient for surgery are to optimize her asthma, control her pain, reduce her anxiety, and minimize the risk of aspiration.
Therefore, I would reassure the patient and family, continue her current medications, and consider chest physiotherapy.
Moreover, I would administer –
- fentanyl, to avoid the pulmonary splinting, decreased ability to cough, and bronchospasm potentially associated with pain (avoid narcotics that release histamine and carefully titrate to avoid respiratory depression);
- diphenhydramine (an H1-receptor blocker), to inhibit histamine-induced bronchoconstriction and reduce the potential for anxiety-induced bronchospasm; a
- stress dose of hydrocortisone (100 mg), given the potential for hypothalamic-pituitary-adrenal suppression with chronic steroid treatment (she is being treated with dexamethasone);
- metoclopramide, to facilitate stomach emptying; and
- ondansetron, to treat her nausea.
Just prior to induction, I would administer –
- a short acting B2-agonist (i.e. albuterol), to minimize the risk of bronchoconstriction during intubation.
Would you give atropine, pre-operatively?
(A 12-year-old female presents to the operating suite with acute appendicitis. Her parents inform you that she has severe asthma. They further report that their daughter was hospitalized and treated 4 days ago for status asthmaticus. Her lungs are currently clear to auscultation bilaterally, but she is extremely nauseous. Her current medications include dexamethasone, omalizumab, and salmeterol.)
Anticholinergic medications may be beneficial for asthmatic patients secondary to reduced mucous gland secretions (possibly improving inflammation) and airway hyperreactivity (secondary to reduced vagal tone and inhibition of muscarinic cholinergic receptors).
However, their preoperative administration is controversial, since they could result in increased inspissation (increased viscosity and thickening of airway secretions), potentially leading to airway plugging and the initiation of an asthmatic attack.
Therefore, considering these potential complications, and recognizing that the intramuscular doses of anticholinergic medications typically used for pre-anesthetic medication are unlikely to significantly decrease her airway resistance (they would be sufficient to reduce airway secretions), I would NOT administer this medication pre-operatively.
If I wanted to administer an anticholinergic, preoperatively, to optimize his asthmatic condition, I would consider providing an inhaled medication, such as ipratropium.
You are planning general anesthesia for the procedure. How will you induce her?
(A 12-year-old female presents to the operating suite with acute appendicitis. Her parents inform you that she has severe asthma. They further report that their daughter was hospitalized and treated 4 days ago for status asthmaticus. Her lungs are currently clear to auscultation bilaterally, but she is extremely nauseous. Her current medications include dexamethasone, omalizumab, and salmeterol.)
My goals when inducing this severely asthmatic patient with a full stomach and nausea, are to achieve an adequate plane of anesthesia to avoid bronchoconstriction in response to mechanical stimulation while, at the same time, minimizing the risk of aspiration.
Therefore, assuming her airway exam were reassuring, I would:
- administer a short acting B2-agonist;
- denitrogenate with 100% oxygen;
- ensure that she had received metoclopramide and ondansetron to facilitate gastric emptying and treat her nausea, respectively;
- administer 2 mcg/kg of fentanyl, 2-3 minutes prior to induction, to avoid light anesthesia during laryngoscopy;
- give 1-2 mg/kg of intravenous lidocaine, 1-2 minutes prior to induction, to prevent reflex-induced bronchoconstriction
- (Topical lidocaine may also be used, but the application may provoke bronchospasm if the depth of anesthesia is insufficient. Since there is significant risk for light anesthesia during a RSI, I would not employ this technique.);
- apply cricoid pressure; and
- perform a RSI using ketamine (induces bronchodilation), propofol (produces bronchdilation and a more reliable depth of anesthesia as compared to thiopental), and succinylcholine.
- While succinylcholine could potentially result in significant histamine release (risk for histamine-induced bronchospasm), I believe that its ability to facilitate the rapid placement of an endotracheal tube is important to reduce the risk of aspiration in this patient presenting for emergent surgery (inadequate fasting), an acute abdominal process (delayed gastric emptying), and active nausea.
How does shock wave lithotripsy disintegrate renal calculi without causing an unacceptable amount of tissue damage?
(A 64-year-old man with an automatic internal cardiac defibrillator (AICD) and pacemaker is scheduled for extracorporeal shock wave lithotripsy (ESWL) of right renal calculi. Your hospital utilizes a first-generation lithotripter.)
During ESWL, the sudden vaporization of water by an energy source generates a pressure wave that is focused (F2 focal zone) on the urinary stone.
When this generated shock wave encounters a sudden change in impedance, such as occurs at the tissue-stone interface, compressive energy is released causing shear forces on the stone.
Since the acoustic impedance of water and body tissues is similar, the shock wave travels through body tissues without a significant dissipation of energy, causing minimal tissue damage.
However, some signs of tissue injury, such as skin bruising, flank ecchymosis, and hematuria (secondary to endothelial injury to the kidney and ureter), do commonly occur (especially with the more powerful first generation lithotripters).
Moreover, when the shock waves are focused on an air-tissue interface, such as found in the lungs or intestine, the difference in acoustic impedance can lead to a dissipation of energy and significant tissue damage.
How would you provide anesthesia for this case?
(A 64-year-old man with an automatic internal cardiac defibrillator (AICD) and pacemaker is scheduled for extracorporeal shock wave lithotripsy (ESWL) of right renal calculi. Your hospital utilizes a first-generation lithotripter.)
While intravenous analgesia and sedation are usually adequate for procedures performed with second and third generation lithotripters, the increased discomfort associated with the more powerful first-generation lithotripters often requires general anesthesia, neuraxial anesthesia, or flank infiltration with/without intercostal blocks.
Therefore, considering the advantages of general anesthesia (when compared to neuraxial anesthesia), such as – rapid onset, reduced diaphragmatic excursion (less stone movement with respiration), and quicker recovery, my preference would be to provide general anesthesia for this procedure.
In choosing this technique, I would recognize that his lack of consciousness increases the risk of – positional injury (due to patient positioning in the bath while unconscious), and complicates patient transport to other locations for adjunctive procedures, such as cystoscopy or stent placement (which are sometimes necessary).
Would your anesthetic plan change if the patient had a Mallampati III airway?
(A 64-year-old man with an automatic internal cardiac defibrillator (AICD) and pacemaker is scheduled for extracorporeal shock wave lithotripsy (ESWL) of right renal calculi. Your hospital utilizes a first-generation lithotripter.)
If I were concerned about difficult airway management, I would consider utilizing an epidural or spinal anesthetic for the procedure.
Either one of these choices eliminates the need for airway manipulation and reduces the risk of peripheral nerve injury associated with positioning and transporting an unconscious patient.
The principal disadvantage of epidural anesthesia is a slow onset and recovery,
while the principal disadvantage of spinal anesthesia is the increased incidence of hypotension.
While these techniques are associated with increased diaphragmatic excursion (due to a spontaneously ventilating patient), the subsequent stone movement, in most cases, does not significantly interfere with the procedure (stone movement is usually limited to the F2 focal zone).
Could you proceed with flank infiltration and intercostal nerve block placement?
(A 64-year-old man with an automatic internal cardiac defibrillator (AICD) and pacemaker is scheduled for extracorporeal shock wave lithotripsy (ESWL) of right renal calculi. Your hospital utilizes a first-generation lithotripter.)
While this technique is a viable option for the procedure,
I believe that neuraxial anesthesia would more reliably provide adequate analgesia (as compared to flank infiltration combined with intercostal nerve blocks),
thus reducing the potential necessity for additional sedation.
Since one of my principal goals in managing this patient with a potentially difficult airway is to maintain spontaneous ventilation and avoid the necessity for airway manipulation,
I would prefer to proceed with the technique that most reliably avoids the need for supplemental intravenous sedation.
What are the risks associated with performing ESWL on a patient with an AICD?
(A 64-year-old man with an automatic internal cardiac defibrillator (AICD) and pacemaker is scheduled for extracorporeal shock wave lithotripsy (ESWL) of right renal calculi. Your hospital utilizes a first-generation lithotripter.)
While the overall risk is low, there is some risk that patients with a cardiac rhythm management device (CRMD),
such as a pacemaker or automatic implantable cardioverter-defibrillator (AICD),
will experience shock wave-induced intraoperative arrhythmias during ESWL (as are those with a history of arrhythmias).
Moreover, lithotripter-induced shock waves can lead to CRMD malfunction, such as – switching to magnet mode, pacing suppression, oversensing of asynchronous shocks, and damage to rate-sensing piezoelectric crystals (affects rate-responsive CRMDs).
However, as long as the CRMD generator is not located in the abdomen (usually located in the pectoral region), ESWL is not contraindicated in patients with these devices.
To minimize the risk of CRMD associated complications, I would:
- ascertain the indication for placement, the patient’s underlying rhythm and rate, and the degree of pacemaker dependency;
- determine the type, manufacturer, programmability, and functionality of the device (i.e battery life, lead integrity, the presence of any alert status, and sensing/pacing thresholds);
- verify the behavior of the device when exposed to a magnet (usually disables tachydysrhythmia detection and therapy);
- ensure the availability of a programming device, trained pacemaker programmer, and alternative pacing modality in the operating room;
- make sure that the patient’s CRMD is not in the shock wave path (the focal point of the lithotripter should be kept at least six inches away from the pacemaker);
- employ continuous telemetry;
- begin lithotripsy with low energy shock waves followed by gradually increasing energy levels, while closely monitoring pacemaker function;
- terminate lithotripsy if the patient developed an arrhythmia; and
- use a magnet only if there were inhibition of the device’s pacemaker function.
I would NOT require preoperative interrogation as long as his device had been checked within the last 6 months
(Recommendation: implantable cardioverter-defibrillators should ideally be checked within last 6 months, and pacemakers within the last 12 months).
Moreover, given the low risk that the acoustic pulse from the lithotripter will interfere with his CRMD, I would NOT require preoperative reprogramming to disable tachyarrhythmia sensing and treatment, or that his device was set to asynchronous mode.
In this case, interrogation would only be necessary if the patient experienced device-related complications.
Postoperatively his hemoglobin has dropped from 14 mg/dL to 10.4 mg/dL.
Are you concerned?
What do you think is the cause?
(A 64-year-old man with an automatic internal cardiac defibrillator (AICD) and pacemaker is scheduled for extracorporeal shock wave lithotripsy (ESWL) of right renal calculi. Your hospital utilizes a first-generation lithotripter.)
A drop of 3.6 mg/dL in the hemoglobin concentration is significant, and would elevate my suspicion of intra-abdominal or retroperitoneal hemorrhage.
In evaluating his progressive anemia, I would –
examine the patient’s abdomen,
stabilize his hemodynamics,
look for other sources of bleeding, and
consider radiographs or CT to identify any hematoma formation.
During this evaluation, I would also –
consider other potential causes of his postoperative anemia, such as hemodilution from excessive fluid administration and/or shock wave-induced damage to the gastrointestinal, pulmonary, or urinary systems.
Does she need further cardiac evaluation prior to surgery?
(A 34-year-old female with a history of mitral valve prolapse (MVP) is scheduled for shoulder arthroscopy in the sitting position. She is otherwise healthy and taking no medications.)
The presence of asymptomatic mitral valve prolapse uncomplicated by other medical conditions is not a sufficient reason for further cardiac testing.
However, if her MVP were associated with significant mitral regurgitation, syncope, chest pain, or symptoms of congestive heart failure, further testing may be warranted.
Therefore, I would begin by performing a focused history and physical exam to illicit signs and symptoms of congestive heart failure or myocardial ischemia such as angina, orthopnea, dyspnea on exertion, exercise tolerance, peripheral edema, pulmonary rales, S3 gallop, systolic ejection click, or murmur.
If she reported significant symptomatology that was insufficiently evaluated by previous cardiac workup, I would consider pre-operative echocardiographic evaluation.
Cardiac echocardiography would be helpful in identifying any mitral regurgitation and the presence or absence of a patent foramen ovale, with the latter being important due to the increased risk of air embolism when undergoing surgery in the sitting position (in the presence of a patent foramen ovale, an air embolism may pass into the coronary or cerebral circulations).
After induction the patient is placed in the sitting position.
Her blood pressure drops to 63/38 and heart rate is 90.
What do you think is the cause?
(A 72-year-old female undergoing CABG is about to go on bypass. The patient was given a standard heparin dose, but the ACT is still low.)
Since normal autonomic responses may be impaired under general anesthesia, her hypotension may simply represent an uncompensated decrease in blood pressure with movement into the head-up position.
However, I would also consider potential contributing factors, such as –
- hypovolemia;
- the systemic vasodilation and myocardial depression associated with excessive anesthesia;
- dysrhythmias (often associated with MVP); and
- the development of acute mitral regurgitation and decreased cardiac output.
The latter may occur because patients with MVP often experience worsening prolapsed and/or mitral regurgitation with increased emptying of the left ventricle.
Therefore, factors such as –
- tachycardia (decreased filling time),
- increased myocardial contractility (sympathetic stimulation and inotrope administration),
- decreased systemic vascular resistance (decreased afterload),
- hypovolemia (reduced filling), and
- assumption of the upright posture (decreased filling)
- may result in –
- acute mitral regurgitation,
- decreased cardiac output, and
- hypotension.
- may result in –
Finally, I would consider less likely causes, such as –
- myocardial ischemia,
- tension pneumothorax, and
- pulmonary embolism.
How would you treat this patient?
(A 72-year-old female undergoing CABG is about to go on bypass. The patient was given a standard heparin dose, but the ACT is still low.)
I would –
- inform the surgeon,
- return the patient to the supine position,
- evaluate the EKG,
- auscultate the chest for cardiac murmurs and bilateral ventilation,
- ventilate with 100% oxygen,
- give a fluid bolus,
- administer a pure alpha-1-agonist such as phenylephrine (the tachycardia associated with the administration of an indirect vasoconstrictor, such as ephedrine, may worsen mitral valve prolapse and mitral regurgitation), and
- consider reducing my anesthetic.
During treatment, I would avoid agents that would increase cardiac contractility and accentuate mitral regurgitaiton.
If she remained unstable despite these interventions, I would utilize TEE to further evaluate her cardiac condition.
What is your differential diagnosis?
(A 34-year-old female health care worker is scheduled for an exploratory laparoscopy for a suspected tubal pregnancy. Her medical history is significant for tobacco abuse, with a 20-year history of smoking. Fifteen minutes into the procedure, her systolic blood pressure drops to 44 mmHg and her peak airway pressures increase to 52 cm H2O.)
Given the timing of her symptoms and the fact that she is undergoing laparoscopic surgery,
my differential would include the following:
- upward pressure on the diaphragm and a reflex increase in vagal tone with formation of the pneumoperitoneum;
- mainstem intubation, due to upward movement of the diaphragm during pneumoperitoneum formation;
- tension pneumothorax, secondary to smoking-associated lung disease;
- capnothorax, due to movement of insufflated gas into the pleural cavity (potential communication channels between the peritoneal cavity and the pleural sac may open with increased intraperitoneal pressure);
- CO2 embolism, with “gas lock” in the vena cava and right atrium and/or paradoxical embolism;
- anaphylaxis, with associated bronchospasm and cardiovascular collapse;
- severe bronchospasm (increased risk with tobacco use), with subsequent hypoxia leading to cardiovascular depression; and, if high dose narcotics have been administered,
- stiff chest syndrome, which could lead to reduced venous return and/or hypoxia with subsequent cardiovascular depression.
How does anaphylaxis differ from an anaphylactoid reaction?
(A 34-year-old female health care worker is scheduled for an exploratory laparoscopy for a suspected tubal pregnancy. Her medical history is significant for tobacco abuse, with a 20-year history of smoking. Fifteen minutes into the procedure, her systolic blood pressure drops to 44 mmHg and her peak airway pressures increase to 52 cm H2O.)
Anaphylaxis is a type 1 hypersensitivity reaction that occurs with the second exposure to an antigen that previously evoked the production of antigen-specific IgE antibodies.
Degranulation of mast cells and basophils results in the release of histamine, leukotrienes, prostaglandins, TNF, and various cytokines, with subsequent –
- increased capillary permeability (histamine, leukotrienes),
- peripheral vasodilation (histamine),
- bronchoconstriction (histamine, leukotrienes, prostaglandins),
- negative inotropy (leukotrienes), and
- coronary artery vasoconstriction (leukotrienes).
The initial manifestations of this life-threatening reaction usually occur within 10 minutes of exposure to the inciting antigen.
The clinical presentation of an anaphylactoid reaction is indistinguishable from anaphylaxis, with the primary difference being that –
mast cell and basophil degranulation is triggered by direct interaction with certain allergens, rather than by interaction with antigen-specific IgE antibodies.
Anaphylactoid reactions, therefore, do NOT require prior sensitization and produce anaphylaxis-like symptomatology in a dose-dependent manner.
Classic anaphylaxis, by contrast, does not behave in a dose-dependent manner, since the immune system is primed to recognize even minute amounts of the offending allergen and is able to amplify the reaction via IgE mediation.