Anesthetic considerations for surgical procedures in the premature infant, neonates, and pediatrics Flashcards
Preoperative assessment includes
postconceptual age (gestational age + postnatal age)
weight
allergies
co-morbidities, general health, growth & development
physical exam (overall- airway, cardiac, lungs, visible veins)
Describe the special anesthetic considerations for the pediatric patient
infection risk IVH apnea risk temperature control ventilation/oxygenation saturation goals 90-94% glucose, electrolyte, and fluid management
Describe NPO guidelines for elective pediatric surgery
for any age child, this means the minimum acceptable time from ingestion is the following:
2 hours- clear liquids (water, apple juice, pedialyte, or other “see-through” liquids)
4 hours- breast milk
6 hours- formula, non-human milk
General anesthetic considerations for the premature infant
may already be intubated- ICU transport considerations
range of uncuffed and cuffed ETTs options
possibility of difficult intubation and subglottic stenosis
verify ETT position with any changes in position
NG is useful to decompress stomach and facilitate ventilation
ventilation may be difficult- poor compliance, avoidance of barotrauma & excessive oxygen
NSAIDs are contraindicated (immature renal system and may cause premature closure of PDA even in ductal dependent infants)
Consider IV caffeine if at risk for apnea
All anesthetics and sedatives commonly used in pediatrics have shown
widespread loss of nerve cells
The formation of brain structures and rapid brain growth starts
early in pregnancy & continue for up to 3 years
exact age is controversial with milestones being reached with myelination around age 6
Slightly less than ______ of general anesthesia in early infancy does not alter neurodevelopmental outcome at age 5 years compared with awake-regional anesthesia in a predominantly male study population
1 hour
Inhalation agents in prematurity: MAC varies with
age and especially in premature & critically ill infants
slightly less for all agents as neonates, increased as infants, and then drops as small children
A MAC is the
inhaled anesthetic depth at which 50% of patients respond to painful stimulus with movement
Because the neonatal heart is dependent on plasma calcium for contractility, preterm infants may be
more susceptible to the cardio-depressant effects of inhalational anesthetics
Describe the use of fentanyl in the pediatric population:
analgesia, does not reliably produce unconsciousness alone
volume of distribution is higher
reduced elimination half-life (6-32 hours in premature infants vs. 2-3 hours in children & adults)
Describe the use of ketamine in the pediatric population:
analgesia, amnesia, & unconsciousness
Describe the use of propofol in the pediatric population.
does have reported episodes of protracted hypotension and low cardiac output
use of lower doses in preterm and infants
infusions are rarely used long-term (i.e ICU) due to risk of propofol infusion syndrome
Describe the use of midazolam in the pediatric population.
combined with opioid for complete anesthetic
decreased clearance especially in the setting of decreased liver function
The concentration of HbF in utero is ________ than that of the mother
50% greater
Functionally, fetal hemoglobin is able to bind oxygen with
greater affinity than adult hemoglobin (this allows the mother’s oxygen to be delivered across the placenta in the setting of low placental PO2 (30-50 mmHg)
During the first 6 months of life ______ hemoglobin synthesis activity is activated and ____ hemoglobin synthesis is deactivated
adult; fetal
In health term infants, hemoglobin concentration
falls during the 9th to 12th week
- nadir of physiologic anemia in full term infants may be as low as 10-11 g/dL
- this decrease in Hgb is due to a decrease in erythropoiesis and to a shorter RBC lifespan
Premature infants differ in that they have _____ hemoglobin levels at birth
slightly lower
- nadir is lower and is reached earlier (around 4-8 weeks)
average nadir in premature infants is 7-9 g/dL
-transfusions are generally considered with a goal of a Hct >30%
After the 3rd month of life, the Hgb level stabilizes at about ______ until about age 2
11-12 g/dL
Clinically, the younger the baby, the higher the ___________ and the lower the _________.
higher the fraction of HbF; lower the oxygen carrying capacity and delivery to the tissues; this is offset by a rightward shift in the oxy-hgb dissociation curve with increased 2,3 DPG and production of adult hemoglobin
Premature infants rarely require
surgical intervention unless the condition is life-threatening
Preoperative optimization of the following is important for infants:
cardiac, respiratory, anemia, electrolytes, metabolic acidosis, & coagulopathy
Careful attention to drug delivery includes
tuberculin syringes
saline flush following each medication
administration in stopcock closest to patient to minimize fluid
removal of all air bubbles
avoid fluid overload & free-flowing IV sets
Common procedures requiring anesthesia in the preterm infant include:
PDA ligation
laparotomy for NEC or bowel perforation
inguinal hernia repair
vitrectomy or laser for retinopathy of prematurity
CT/MRI scanning
repair of congenital diaphragmatic hernia
laparotomy or silo for amphalocele and gastroschisis
laparotomy for malrotation or volvulus
tracheoesophageal fistula repair
Describe why patients may need ligation of patent ductus arteriosus.
A PDA (a remnant from fetal circulation) may incur significant left-to-right shunting of blood causing excess pulmonary blood flow, congestive heart failure & respiratory failure
In the fetus, blood from the right ventricle is directed into the ________ but because of high PVR it flows from the ___________. After birth, the PVR ______ and blood flows from
pulmonary artery; descending aorta
decreases; from the aorta to the lungs
In the premature infant with respiratory distress syndrome or persistent pulmonary hypertension
right-to-left shunting may occur producing cyanosis
Describe the medical therapy & surgical therapy for patent ductus arteriosus.
medical: administration of cyclooxygenase inhibitor- indomethacin or ibuprofen
surgical: left thoracotomy, retraction of the left lung
Discuss the preoperative considerations for ligation of patent ductus arteriosus.
assess arterial pressure (typically decreased diastolic), HR, ABG, ventilator settings, and inspired fiO2
- availability of PRBCs- the aorta and pulmonary artery lie in close proximity to the PDA- severe bleeding may occur abruptly
- antibiotics (risk for endocarditis
Describe the intraoperative considerations for the ligation of patent ductus arteriosus.
blood pressure monitoring (right arm reflects cerebral perfusion and pre-ductal blood)
pulse oximeters on right arm and lower extremity- also helps the surgeon confirm which vessel (ductus and not aorta) to ligate
-ETCO2 monitoring
-ETT should have a minimal leak as surgical retraction of the lung may necessitate increasing ventilator inspiratory pressures and inspired oxygen
-opioids, amnesic, and muscle relaxation
-intercostal nerve block by surgeon at completion of surgery
Possible complications of patent ductus arteriosus include
inadvertent ligation or laceration of the aorta or pulmonary artery
- aortic clamp will result in a loss of signal to the lower extremity pulse ox
- pulmonary artery clamp will result in decrease oxygen saturation to both extremities and end-tidal CO2
Successful PDA ligation will result in
increased arterial diastolic and mean pressures as well as the PDA murmur will disappear
Necrotizing enterocolitis is an illness most often found in
low birth weight infants with a mortality up to 50%
85% of cases are found in infants <1500 g birth weight
Morbidity associated with NEC includes
short bowel syndrome, sepsis, and adhesions
The cause of necrotizing enterocolitis is
uncertain and multifactorial. Results in intestinal mucosal injury secondary to ischemia and ulceration of the bowel
Early signs of necrotizing enterocolitis include
abdominal distension, bloody diarrhea, temperature instability and lethargy
While often medically managed in the NICU, __________ is the usual indication for urgent/emergent surgery for resection of dead bowel for necrotizing enterocolitis
bowel perforation and free air within the abdominal cavity
Infants with necrotizing enterocolitis typically present with
metabolic & hematologic abnormalities
-hyperkalemia, hyponatremia, metabolic acidosis, hyper or hypo glycemia, coagulopathy/DIC, anemia
Patients with NEC presentation are often already
intubated due to abdominal distension with NG/OG suctioning and hemodynamic instability
NEC is a ______
surgical emergency
In NEC, the intestine can no longer hold waste so
bacteria may pass into the bloodstream and lead to life-threatening sepsis
NEC involves either initial primary
peritoneal drainage or a laparotomy with resection of necrotic bowel
primary peritoneal drainage requires a smaller incision and fewer anesthetic requirements- often performed at the bedside
With NEC, anesthetic management includes
aspiration risk may necessitate RSI
avoid nitrous oxide
vascular access- at least 2 IVs and an a-line
inhalation agents are poorly tolerated–> narcotic technique with muscle relaxation for hemodynamic instability- septic and volume depleted, titrate carefully
vasopressor infusions (dopamine & epinephrine) for maintenance of renal perfusion and CO
-large fluid loss and blood loss so resuscitate with PRBCs, FFP, PLTs
-correct electrolytes and glucose
Transfusions in neonates is per
kilogram
- can order portions and prefilled syringes
- hypovolemia comprises tissue oxygenation- EBV in preterm neonates: 90-100 mL/kg
- PRBCs 10-15 mL/kg
- FFP 10-15 mL/kg
Describe the formula to calculate allowable blood loss.
ABL= EBV x (starting Hct-allowable Hct)/starting Hct
newborns EBV is 100 mL/kg
A relatively small amount of blood loss can result in
severe hypovolemia in babies
Inguinal hernias are
common in preterm infants (approx 1/3 of premature infants)
Complications of inguinal hernia include
incarcerated bowel, intestinal obstruction, gonadal infarction, infection, hematoma, and recurrent hernias
Describe the surgical considerations for inguinal hernia repair.
general and/or regional anesthesia are appropriate
- if the defect is small a LMA may be sufficient
- inadequate depth of anesthesia may result in laryngospasm when the surgeon pulls on the hernia sac*****
- ETT is required for large defects and needed muscle relaxation
- ilioinguinal, iliohypogastric, or caudal/epidural blocks
ROP may be treated with
cryotherapy, laser photocoagulation, or scleral buckling surgery and/or virectomy
Describe considerations for the use of diode laser photocoagulation to treat ROP
for moderate ROP may be performed at bedise
10-30 minute treatments in a series every few weeks
topical anesthesia alone, IV sedation, or GA
Describe considerations for the use of cryotherapy for ROP.
cryotherapy applies a freezing probe to the avascular retina in the OR
- requires GA
- often between 32 and 42 weeks PCA
Describe considerations for scleral buckling and vitrectomy.
less frequently used with better screening and earlier treatment, performed for severe ROP with retinal detachment in the OR
- requires GA
- child is often older 6 months to 1 year
Describe anesthesia for radiologic imaging.
may require immobility
anesthesia can range from oral medications, sedation to general
off-site anesthesia considerations along with MRI compatible monitoring equipment
monitoring for postoperative apnea considerations
At some centers, all preterm infants less than
30 weeks gestational age at birth undergo brain MRI
MRI is gradually replacing ultrasound and CT for assessment of
IVH due to lack of radiation exposure and is able to identify congenital lesions, vascular malformations, and ischemic injury
The diaphragm completes formation during 7th-10th week. _____ permit intrusion of abdominal contents into thoracic cavity
anatomic defects
Describe early vs. late congenital diaphragmatic hernia.
early- the abdominal mass inhibits normal cardiopulmonary growth; the severity of lung hypoplasia-associated with morbidity and mortality-negatively correlates with gestational age at the time the hernia occurred
Late- occurs near or even after deliver; are associated with mature, well developed lungs and minimal problems with ventilation
Infants with the _________ are more likely to have concurrent birth defects including CHD and chromosomal abnormalities.
Bochdalek-type hernia****
Hallmark signs of congenital diaphragmatic hernia include
hypoxia, scaphoid abdomen, and evidence of bowel in the thorax- may be diagnosed in utero
CDH is a potentially lethal anomaly due to
pHTN, pulmonary hypoplasia, and associated cardiac or congenital defects **** with a 40-50% mortality
In regards to CDH, although the mere presence of abdominal viscera in the thoracic cavity is not in itself life-threatening, the _______
compression effects on developing pulmonary structures obstructs smooth transition from fetal to neonatal circulatory pattern
- hypoplastic lungs
- intrapulmonary shunting and inadequate gas exchange
- decreased total cross-sectional area results in pulmonary arteriole hypertension
CDH often requires (anesthetic management)
secured airway, mechanical ventilation, and gastric decompression soon after delivery
may require ECMO, HFOV, and inhaled nitric oxide
Describe the CDH surgical approach.
subcostal incision or thoracic laparoscopic (left sided lesions are 7x more frequent than right)
- recurrent defects may be approached through the abdomen and minimally invasive
- primary closure vs. synthetic patch for large defects
- may be delayed until cardiorespiratory and medically stabilized
- may occur before, during or after ECMO
In CDH, surgery transiently worsens
pHTN and may cause persistent fetal circulation (fetal circulation reopens the PDA and shunts blood which results in bypassing of the lungs)
CDH outcomes are a function of the
underlying pulmonary hypoplasia and pulmonary hypertension
Describe anesthetic management in regards to CDH repair.
initial management includes definitive airway control and optimization of oxygenation and ventilation
avoid mask ventilation to limit gastric insufflation- placement of NG and gastric decompression
Describe positioning and monitoring for the patient presenting for CDH repair.
Supine or lateral (variable presentations)
-pre and post ductal monitoring (provide early warning of R–> L shunt/pulmonary HTN)
PIV x 2, +/- CVC, aline- serial ABGs
Reactive pulmonary vasculature may occur during
CDH repair- avoid conditions that increase pulmonary vascular resistance (hypoxemia, acidosis, hypotension, significant hypercarbia)
Describe EBL and anesthetic choices for patients with CDH repair.
EBL 5-10 mL/kg
paralytics, narcotics, and limited inhalation agent
limit inspired O2, avoid nitrous oxide
Supportive care during transport may be challening
Neonates have had improved survival rates with surgery in recent years due to:
strategy of delaying surgery to ensure stabilization of the transitional circulation
- adopting a lung-protective, or “gentle ventilatory” strategy using small tidal volumes and as low as possible PEEP
- accepting higher PcO2 (permissive hypercapnea)
Inhaled nitric oxide is a specific
- pulmonary vasodilator (with avoiding systemic hypotension)
- used for refractory pulmonary hypertension to decrease right-to-left shunting and improve oxygenation
- short acting, must be delivered through a specially metered apparatus
ECMO is a
temporizing measure permitting lungs to rest and mature while providing appropriate gas exchange through membrane oxygenators
-multiple inclusion and exclusion criteria (IVH is a contraindication because of systemic heparinization)
-venovenous (VV) or venoarterial (VA)- location of inflow and outflow catheters
-VV is a double-lumen resides in the internal jugular
vein
- VA is two catheters one in the internal jugular and other in carotid artery
CDH may have _____ presentation
variable; and degrees of severity
In CDH, sedation is important to limit
catecholamine response which increase PVR
In CDH, severe CV compromise should be
treated with volume support and inotropic support (dopamine)
In CDH, when oxygenation remains compromised,
global tissue hypoxemia will result in significant metabolic acidosis which may be treated with bicarb infusions, if adequate ventilation is ensured
In general for CDH, there has been a trend to stabilizing the
cardiorespiratory status during the transition from intrauterine to extrauterine environment before introducing surgical repair of CDH (from within 48 hours to 4 to 6 days of life)
