2) Risk factors. A number of antepartum and intrapartum factors may increase the likelihood of positive-pressure ventilation or endotracheal intubation at the time of delivery, including gestational age, multiple gestation pregnancy, and meconium stained amniotic fluid (3).

    a) Important information to obtain when responding to a resuscitation

  i) Estimated gestational age

  ii) Presence of meconium

  iii) Maternal diseases and/or pregnancy complications

  iv) Any fetal anomalies such as congenital heart disease, congenital diaphragmatic hernia, gastroschisis, or syndromes associated with difficult intubation such as Pierre Robin

1) Treatment

    a) Equipment: Having appropriate supplies and equipment ready and available can save invaluable time.

    b) The anesthesiologist caring for the mother’s primary responsibility is to the mother. If called upon to assist with resuscitation of the infant, the benefit to the child must be compared to the risk to the mother (4).

    c) Restoring oxygenation and ventilation is the utmost priority as the infant transitions from intrauterine to extrauterine life. Equipment used for this purpose is listed in Table 102-1.

4) Assessment

    a) The initial assessment should take <30 seconds and includes checking for meconium, respiratory effort, color, heart rate (HR), and muscle tone.

  i) These are the clinical factors that guide further resuscitation and reassessment.

    b) Apgar scores (Table 102-2)

  i) Assigned at 1, 5, and 10 minutes of life

  ii) APGAR scores are a retrospective measure of an infant’s need for and response to resuscitative measure

  iii) Not particularly useful as an assessment tool to guide resuscitative efforts

5) Resuscitation. The Neonatal Resuscitation Program (NRP) algorithm is widely available with key points as follows (Fig. 102-1):

    a) After initial assessment, provide warmth, drying, and stimulation.

    b) Position and clear the airway if necessary.

    c) Provide supplemental O₂ as needed.

    d) If apnea, poor respiratory effort, or HR < 100 bpm → begin effective ventilation either by bag-mask or placing endotracheal tube.

    e) Higher pressures may be required when initiating ventilation to open alveoli. Watch level of chest rise to assess adequate ventilation.

    f) If HR still <100 bpm after 30 to 60 seconds of effective ventilation, start chest compressions.

    g) Chest compressions should occur at a rate of 100 bpm with a breath given after every third compression.

  i) “One and Two and Three and Breathe….”

    h) If HR remains <100 bpm, administer epinephrine.

6) Resuscitation tips

    a) Place infant in sniffing position (shoulder roll may be helpful) and apply gentle chin lift into mask to obtain a proper seal. Avoid downward force onto the mask.

    b) Watch for chest rise as primary endpoint to adequate ventilation.

  i) Keep in mind that higher peak inspiratory pressures up to 40 mm Hg may be initially required to open closed alveoli. A pressure manometer is helpful along with clinical indicators such as chest rise.

    c) Avoid insufflation of the stomach as it may further impair ventilation. Decompress if needed.

    d) Chest compressions can be done by encircling the infant with both hands and placing both thumbs on lower sternum or by placing two fingers perpendicular to the chest.

    e) Chest compressions should depress the sternum one third the depth of the chest while the fingers remain in place at all times.

    f) Compressions to ventilation ratio should be 3:1 at a rate of 90 compressions and 30 breaths per minute.

    g) It can be helpful to keep cadence out loud with “One-and-Two-and-Three-and-Breathe.”

    h) When the HR is >100 bpm and ventilation is adequate, resuscitation may be stopped.

7) Special considerations

    a) Meconium

  i) Occurs in approximately 7% to 20% of live births with up to 10% of these infants developing meconium aspiration syndrome (MAS) (5)

(1) MAS can lead to hypoxic respiratory failure, persistent pulmonary hypertension, pneumonia, and sepsis all with significant potential for long-term morbidity and mortality.

  ii) Current NRP guidelines call for intubation and suctioning of the trachea only if the infant is not vigorous, defined as depressed respirations, decreased muscle tone, or HR <100 bpm (1).

(1) In this case, the infant should be intubated and the trachea suctioned while ETT is withdrawn.

(2) Repeat until lower airways cleared or additional resuscitation should be undertaken (1).

    b) Maternal opioid administration within 4 hours of delivery may contribute to respiratory depression in the neonate.

1) If respiratory depression persists after PPV and normal HR, consider administering nalaxone; however, PPV and supportive care should continue.

2) Keep in mind that the half-life of nalaxone may be shorter than that of the circulating opioid and therefore may need to be redosed.

8) Medications

    a) Epinephrine should be given when the HR remains <100 bpm after 30 seconds of assisted ventilation and an additional 30 seconds of chest compressions.

  i) Can be administered via the endotracheal tube, umbilical vein, or IV

(1) Regardless of route of administration, dose is 10 to 30 μg/kg.

  ii) A quick way to make an epinephrine solution for administration is to dilute one ampule (1 mg) into a 100-mL bag of normal saline for a final concentration of 10 μg/mL. The resuscitation dose is then 1 to 3 mL/kg. However, commercial preparations of epinephrine are available in a 1:10,000 solution (100 μg/mL), and the dose would then be 0.1 to 0.3 mL/kg. It is always best to check what will be available at your institution before an emergency arises.

    b) Nalaxone

  i) Administration can also be via endotracheal or IV routes.

  ii) Recommended dose is 0.1 mg/kg.

PPV, positive pressure ventilation.

References

1. Kattwinkel J, ed. Textbook of Neonatal Resuscitation. 5th ed. Elk Grove Village, IL: American Academy of Pediatrics and American Heart Association; 2006.

2. Rajani AK, Chitkara R, Halamek LP. Delivery room management of the newborn. Pediatr Clin North Am 2009;56;515–535.

3. Aziz K, Chadwick M, Baker M, et al. Ante-and intra-artum factors that predict increased need for neonatal resuscitation. Resuscitation 2008;79:444–452.

4. American Society of Anesthesiologists Guidelines for Regional Anesthesia in Obstetrics at http://www.asahq.org/publicationsAndServices/standards/45.pdf. Accessed 6/23/2010.

5. Dargaville PA, Copnell BC. The epidemiology of meconium aspiration syndrome; incidence, risk factors, therapies, and outcome. Pediatrics 2006;117:1712–1721.

SECTION VIII. Pediatric Anesthesia

Overview of Pediatric Anesthesiology

Christopher L. Ciarallo, MD

1) Ethical and legal considerations

    a) Minors, with the notable exceptions of emancipated and court-determined mature minors, are not competent to provide informed consent for their medical care.

    b) Typically, a surrogate decision maker for the minor (e.g., parent, guardian, or the court) is solicited to provide informed permission on behalf of the minor.

    c) Childhood cognitive and moral development suggest a “rule of sevens” guideline in pediatric decision-making capacity.

  i) In general, decisions made on behalf of children <7 years old should employ their best-interests standard.

  ii) Children 7 to 14 years old can likely differentiate right and wrong and should be involved in informed assent to their medical care.

  iii) Informed assent is vital in the medical care of the adolescent, but it may be superseded in the event of a life-or limb-threatening emergency.

    d) Confidentiality between the anesthesiologist and the pediatric patient

  i) Must be maintained unless nondisclosure may result in serious harm to the patient or others.

  ii) Minor patients and their guardian should be notified that a preoperative pregnancy test is being performed, but a positive result should be reported only to the patient. The patient should be strongly encouraged to discuss this result with her guardian.

    e) Children of Jehovah’s Witnesses

  i) Require early and open preoperative discussion of blood transfusion.

  ii) Children without cardiovascular disease will tolerate a serum hemoglobin of 7 g/dL without significant acidosis or organ dysfunction (1).

  iii) In the situation of potentially critical anemia and guardian refusal of blood products, a court order must be obtained preoperatively to make the “neglected child” a ward of the court for the perioperative period. A hospital ethics service consultation should be considered.

2) Anatomy and physiology

    a) Airway

  i) Pediatric patients have a proportionately larger occiput and shorter neck than adults. As a result, a shoulder roll rather than a head pillow may improve airway patency during mask ventilation and endotracheal intubation.

  ii) I nfants <6 months old are obligate nasal breathers.

  iii) The pediatric epiglottis is long and floppy, and the pediatric larynx is more anterior and cephalad (at the level of the C3-4 vertebral body rather than C5-6 as in adults).

  iv) Modern bronchoscopic data suggest that the pediatric cricoid cartilage is ellipsoid rather than round and that the pediatric subglottic area is cylindrical with the narrowest portion at the glottis rather than at the cricoid cartilage (2).

  v) Uncuffed endotracheal tubes (ETTs) may not provide effective occlusion for positive-pressure ventilation and may lead to repeated laryngoscopy and intubation for tube exchanges.

(1) Poorly fitted tubes result in unreliable ventilation and capnography, anesthetic gas pollution, and increased fresh gas waste.

  vi) Pediatric cuffed ETTs

(1) Can be safely used for children as young as full-term neonates.

(2) Have smaller internal diameters and increase the work of breathing during spontaneous ventilation.

(3) The cuff should be positioned entirely below the glottis, and the pressure checked frequently when using nitrous oxide.

  vii) Appropriate ETT depth

(1) May be approximated by the various formulae (e.g. 4+[age(in years)/4] for uncuffed; 3.5+[age(in years)/4] for cuffed) or by aligning the ETT double black line markers at the vocal cords.

(2) The most reliable method of determining correct tube depth is to deliberately mainstem the ETT and withdraw it until bilateral breath sounds are heard. The ETT should be secured at a position 1 to 2 cm (depending on age) proximal to this point above the carina (3).

  viii) Single-lung ventilation

(1) Children under the age of 6 years old require a single-lumen mainstem intubation or a 5-Fr bronchial blocker.

(2) The smallest double-lumen ETT (26 Fr) has an outer diameter of 9.3 mm and is likely not appropriate for children under 8 years old.

  ix) Laryngeal mask airways (LMAs)

(1) Sized primarily based on patient weight and can be utilized in infants as small as 3 to 5 kg.

(2) In children 6 months to 6 years old, inserting the LMA backward with a partially inflated cuff and then rotating 180 degrees to an anatomic position provides the highest success rate and the lowest incidence of airway complications (4).

    b) Respiratory

  i) Children have pliable ribs and increased chest wall compliance along with smaller airways, a reduced number of alveoli, and reduced parenchymal lung compliance.

(1) The resulting higher closing volumes and a relative increase in intra-abdominal contents lead to significantly reduced functional residual capacity.

  ii) Children have twice the oxygen consumption of adults (6 to 8 cc/kg/min compared to 3 to 4 cc/kg/min), providing limited reserve during periods of apnea.

(1) Accordingly, true rapid sequence induction is rarely utilized in pediatric anesthesia (e.g., pyloric stenosis, small-bowel obstruction).

  iii) Neonates, particularly premature neonates, have an underdeveloped central respiratory drive and may react to hypercarbia and hypoxemia with apnea.

(1) Opioids should be used judiciously in this population, and questionable neonates should be admitted to the intensive care unit for apnea monitoring.

    c) Cardiovascular

  i) The pediatric autonomic nervous system is parasympathetic dominant, and children frequently respond to noxious stimuli with bradycardia.

  ii) Infants and neonates have a relatively noncompliant left ventricle that cannot increase contractility to increase cardiac output.

  iii) Hypocalcemia should be considered and corrected in hypotensive pediatric patients.

  iv) Hypovolemic pediatric patients may not manifest tachycardia before systemic hypotension.

    d) Vascular access

  i) Intravenous access can be challenging in pediatric patients, and “blind” techniques may be necessary.

  ii) Reliable locations for “blind” access are the saphenous vein just anterosuperior to the medial malleolus, the median cubital vein in the antecubital fossa, and the dorsal hand vein between the fourth and the fifth carpal bones.

  iii) Intraosseous access is more precarious but may be obtained with an intraosseous or Touhy needle in the proximal tibia, distal tibia, or distal femur.

  iv) Central venous access can also be difficult in pediatric patients, but the use of ultrasound has been shown to markedly increase success rates while reducing complications (5).

  v) The Valsalva maneuver is the most effective technique to increase the cross-sectional area of the internal jugular or the femoral veins in children (6), while inguinal compression will also effectively augment the femoral vein (7).

  vi) Guidewire-assisted radial artery cannulation may be more efficient and successful than a direct cannulation technique in pediatric patients (8).

    e) Hepatorenal

  i) Neonates have relatively increased total body water and reduced plasma protein concentration.

  ii) Total protein and albumin binding do not reach adult values until 10-12 months old.

  iii) Hepatic P-450 enzymes mature over months to years, and glucuronidation does not mature until 6 months of life.

  iv) Importantly, amide local anesthetics, morphine, barbiturates, and diazepam are cleared more slowly in infants than older children (9).

  v) Morphine should be used with caution in unmonitored infants <6 months old.

  vi) Glomerular filtration and renal concentrating ability do not mature until 5 to 6 months of life, and excessive intravascular sodium cannot be effectively excreted. Intraoperative fluid resuscitation should be made with an isotonic balanced salt solution.

  vii) As hepatic glycogen stores are minimal during the first few months of life, prolonged fasting in neonates mandates blood glucose testing and/or supplemental IV dextrose at a rate of 6 to 8 mg/kg/min.

  viii) In general, all children <3 months old and those with significant liver disease, sepsis, or prolonged parenteral nutrition should have intraoperative glucose supplementation.

    f) Hematologic

  i) Physiologic anemia occurs between the second and the third months of life, with a hemoglobin nadir around 11 to 11.5 g/dL.

  ii) Estimated blood volumes are around 100 mL/kg for premature neonates, 90 mL/kg for term neonates, 80 mL/kg for infants, and 70 to 75 mL/kg for small children.

  iii) Red blood cell transfusions in neonates and immunocompromised children should be crossmatched, leukoreduced, and irradiated. Other children require only cross-matched and leukoreduced red blood cells.

  iv) Stored blood may have elevated plasma potassium levels, but small-volume transfusions very rarely cause hyperkalemia.

(1) In the event of anticipated massive transfusion, fresh (<7 days from collection) or washed red blood cells may be requested from the blood bank.

    g) Gastrointestinal

  i) Compared with adults, pediatric fasting gastric contents are of larger volume (on a mL/kg basis) and of lower pH (10).

  ii) The overall incidence of pediatric perioperative pulmonary aspiration is approximately 1:2,000 to 1:3,000 anesthetics, with 80% occurring during induction of anesthesia (11). Surprisingly, morbidity associated with pediatric pulmonary aspiration is very low, and patients not requiring supplemental O₂ within 2 hours of an aspiration event may be safely discharged home without sequelae (11) (Table 103-1).

    h) Dermatologic

  i) Pediatric patients dissipate heat readily during anesthesia as a result of their relative large body surface area, thin skin, and insufficient fat stores.

  ii) Forced air warmers, heating lamps, and warmed IV fluids are important in pediatric temperature maintenance. Operating room temperatures may be raised to 75°F to 80°F.

1) Preoperative evaluation

    a) Separation anxiety

  i) During normal development, children become distressed when removed from their caregivers at around 8 to 9 months of life.

  ii) Oral midazolam at a dose of 0.3 to 0.5 mg/kg (maximum 20 mg) is an effective sedative and anxiolytic when given 10 to 30 minutes before induction.

  iii) Parental presence at induction

(1) Surprisingly, as compared with midazolam, parental presence during induction of anesthesia does not appear to alleviate the objective or the subjective anxiety in either the parent or the child (13).

(2) Appears to increase parental satisfaction with the anesthetic, provided they are forewarned of the peculiar ocular and body movements observed during Stage II anesthesia. (Table 103-2)

    b) Preoperative labs (9)

  i) Routine preoperative laboratory testing of pediatric patients is not indicated. However, certain disease states warrant further evaluation.

  ii) Former premature infants <56 weeks postconceptual age (PCA) should have a preoperative hematocrit, as a value <30 may be associated with apnea after anesthesia.

  iii) Pediatric patients with sickle cell disease should have a preoperative hemoglobin electrophoresis and hematocrit, as percentage of hemoglobin S HbS > 40% or Hct < 30 are risk factors for sickle crisis.

  iv) Hemophiliac patients should have preoperative factor VIII or IX level drawn to assist in factor replacement therapy.

  v) Patients with diabetes mellitus should have preoperative glucose checked.

  vi) Patients with diabetes insipidus should have preoperative electrolytes documented.

    c) Congenital heart disease

  i) Preoperative consultation with a pediatric cardiologist or a pediatric cardiac anesthesiologist is strongly recommended to address the cardiac anatomy, function, and altered physiology in congenital heart disease.

  ii) Recent (i.e., within the last 3 to 6 months) cardiac catheterization and echocardiography reports should be obtained.

    d) Asthma

  i) The patient’s home medication schedule, known triggers, and overall control should be assessed.

  ii) Prior emergency room visits, endotracheal intubation or intensive care admissions, and corticosteroid use are markers of more severe disease.

  iii) Parents should be questioned about familiarity with nebulizer masks or metered-dose inhalers.

  iv) Home medications should be taken preoperatively, even in asymptomatic patients.

  v) Airway management may consist of an LMA or ETT.

(1) Laryngeal masks may be less likely to induce bronchospasm, but will be ineffective in delivering high positive airway pressures, if required.

(2) Adequate anesthesia is critical during intubation, and consideration should be given to deep extubation.

  vi) In children with reactive airways, sevoflurane is a more effective bronchodilator than desflurane at 1 minimal alveolar concentration (MAC) (14).

  vii) Inhaled β-agonists and IV corticosteroids should be readily available.

    e) Upper respiratory infection (URI)

  i) Recent (within 4 weeks) or concurrent URI in children increases the perianesthetic risk of oxygen desaturation, breath holding, laryngospasm, bronchospasm, and coughing.

  ii) Independent risk factors for respiratory complications include endotracheal intubation in a child <5 years old, history of prematurity, history of reactive airway disease, paternal smoking, airway surgery, presence of copious secretions, and presence of nasal congestion (15) (Fig. 103-1).

    f) Ex-premature infant

  i) The care of an ex-premature infant must include documentation of the patient’s gestational and post conceptual age (PCA [current chronologic age corrected for prematurity]) PCA and consideration of associated comorbid diseases (e.g., patent ductus arteriosus, intraventricular hemorrhage, necrotizing enterocolitis, chronic lung disease).

  ii) A history of prolonged intensive care, endotracheal intubation, or O₂ therapy should alert the anesthesiologist to an increased risk of potential airway (e.g., stenosis/malacia) or respiratory complications.

  iii) As mentioned above, a preoperative hematocrit should be evaluated.

  iv) During the neonatal period, the patient’s oxygen saturation should be maintained between 88% and 93% to minimize the O₂-mediated risk of retinopathy (18).

  v) Conservative studies recommend continuous pneumocardiography (apnea monitoring) for all ex-premature infants <60 weeks PCA, for a duration of 36 hours if <45 weeks PCA or 24 hours if >45 weeks PCA (19).

(1) Most postanesthetic apnea occurs within 12 hours of discontinuation of anesthesia, and ex-preterm infants <44 weeks PCA display the highest risk (20).

(2) At our institution, ex-preterm infants <56 weeks PCA are admitted for 24 hours for continuous apnea monitoring.

4) Induction, maintenance, and emergence

    a) Inhalational induction

  i) For most pediatric patients at low risk for pulmonary aspiration, an inhalational mask induction may be better tolerated than an awake IV placement and induction.

  ii) Nitrous oxide may marginally reduce the inhaled induction time with sevoflurane, but it minimizes the preoxygenation reserve of the patient in the event the airway becomes compromised.

  iii) Pediatric patients may better tolerate the mask adjacent to their face during induction, with the mask closely approximated only after they are asleep.

(1) Agitated patients are best managed with the clinician’s hand securely fitting the mask to the face, while the other hand is stabilized against the patient’s occiput.

(2) Gentle bag-mask assistance of the patient in sync with their respiratory pattern will help the progress through Stage II anesthesia.

  iv) For anticipated awake IV access, EMLA (eutectic mixture of local anesthetic) cream (APP Pharmaceuticals, Schaumburg, IL, USA) may be beneficial. It should be preemptively applied at multiple sites, covered with an occlusive dressing, and allowed 60 minutes to work (Table 103-3).

    b) Skeletal muscle relaxation

  i) Unless otherwise contraindicated, succinylcholine may be used for rapid sequence intubations and for the treatment of refractory laryngospasm.

  ii) The pediatric intubating dose of succinylcholine is 2 mg/kg IV or 4 mg/kg IM.

  iii) The laryngospasm dose for succinylcholine is 0.1 mg/kg IV (22).

  iv) As children are particularly prone to bradycardia, succinylcholine should be coadministered with atropine 0.01 to 0.02 mg/kg IV or IM.

  v) Pediatric patients are routinely intubated without skeletal muscle relaxation.

(1) Deepening an inhaled anesthetic with intravenous propofol (1 to 3 mg/kg) OR remifentanil (3 to 5 μg/kg for neonates/infants, 1 to 2 μg/kg for older children) AND atropine (0.01 to 0.02 mg/kg) or glycopyrrolate (0.004 to 0.01 mg/kg) are appropriate choices to assist with laryngoscopy.

  vi) Topical lidocaine (2 to 4 mg/kg) to the vocal cords and subglottis may blunt the coughing and laryngospasm reflexes during intubation.

  vii) As in adults, nondepolarizing muscle relaxants are dosed according to weight, and should be monitored and reversed according to train-of-four monitoring.

  viii) Neuromuscular reversal of all nondepolarizing relaxants is strongly encouraged, as children are at an increased risk of postoperative complications.

(1) Of note, vecuronium is a long-acting muscle relaxant in neonates and infants, with only 10% recovery of neuromuscular function at 60 minutes (9).

    c) Deep extubation

  i) Unless contraindicated by aspiration risk, altered mental status, or difficult intubation, deep tracheal extubation may be appropriate for pediatric patients.

  ii) The clinician should be comfortable with managing a pediatric airway, and appropriate personnel and equipment should be immediately available to monitor and assist with complications during emergence.

  iii) No difference in supplemental O₂ requirements or airway-related complications was apparent between awake and deep tracheal extubation in elective cases (23).

  iv) Laryngospasm has an incidence of 0.1% to 1.7%. Failure to effectively recognize and treat laryngospasm may result in hypoxemia, bradycardia, or negative pressure pulmonary edema.

    d) Stridor

  i) Postextubation stridor may be a result of edema (i.e., sustained coughing or an inappropriately sized ETT), inflammation (i.e., URI), or glottic secretions/foreign body.

  ii) Initial management should include supplemental O₂ (consider positive pressure) and dexamethasone (0.5 mg/kg IV).

  iii) Nebulized racemic epinephrine (0.5 mL of 2.25% solution in 2.5 mL normal saline) may help reduce tissue edema but mandates a 4-hour post-treatment observation period because of the risk of rebound edema and stridor.

  iv) Refractory stridor may necessitate tracheal reintubation with a smaller ETT and possible otolaryngology evaluation.

    e) Emergence agitation

  i) Across multiple studies, emergence agitation in pediatric patients receiving volatile anesthesia is approximately 30%.

  ii) Desflurane, sevoflurane, and isoflurane appear to be of higher risk than halothane or propofol (25,26).

  iii) Propofol (1 mg/kg IV) at the end of surgery may reduce the incidence of emergence agitation (27).

  iv) Hypoxemia, hypercarbia, and urinary retention should be excluded as contributing factors to emergence agitation.

  v) Addressing this issue preoperatively with the family may help preempt escalation of parental anxiety in this situation.

    f) Postoperative nausea and vomiting

  i) Postoperative vomiting is rare in neonates and infants.

  ii) School-aged children have a higher incidence of nausea and vomiting than adults (34% to 50%), and prophylaxis should be considered (9).

  iii) The combination of dexamethasone (0.15 to 0.5 mg/kg IV) and 5-hydroxytryptamine receptor antagonist (e.g., ondansetron 0.1 mg/kg IV) provides a 50% to 60% relative risk reduction (28). Metoclopramide (0.1 to 0.15 mg/kg IV) may be an effective rescue antiemetic.

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