Pediatric Anesthetic Techniques: Preoperative Considerations

PEDIATRIC ANESTHETIC TECHNIQUES

Preoperative Considerations

A. Preoperative Interview

Depending on age, past experiences, and maturity, children present with varying degrees of fright (even terror) when faced with the prospect of surgery. In contrast to adults, who are usually most concerned about the possibility of death, children are princi-pally worried about pain and separation from their parents. Presurgical preparation programs—such as brochures, videos, or tours—can be very helpful in preparing many children and parents. Unfortunately, outpatient and morning-of-admission surgery together with a busy operating room schedule often make it nearly impossible for an anesthesiologist to break through the barriers presented by pediatric patients. For this reason, premedication (below) can be helpful. When time permits, one can demystify the process of anesthesia and surgery by explaining in age-appropriate terms what lies ahead. For exam-ple, the anesthesiologist might bring an anesthesia mask for the child to play with during the interview and describe it as like something the astronauts use. Alternatively, in some centers, someone the child trusts (eg, a parent, nurse, another physician) may be allowed to be in attendance during preanesthetic preparations and induction of anesthesia. This can have a particularly calming influence on children undergoing repeated procedures (eg, examination under anesthesia following glaucoma surgery). Some pediatric hospitals have induction rooms adjacent to their operating rooms to permit parental attendance and a quieter, less startling environment for anesthetic inductions.

B. Recent Upper Respiratory Tract Infection

Children frequently present for surgery with evidence—a runny nose with fever, cough, or sore throat—of a coincidental viral upper respiratory tract infection (URI). Attempts should be made todifferentiate between an infectious cause of rhinorrhea and an allergic or vasomotor cause. A viral infection within 2–4 weeks before generalanesthesia and endotracheal intubation appears to place the child at an increased risk for perioperative pulmonary complications, such as wheezing (10-fold), laryngospasm (5-fold), hypoxemia, and atelectasis. This is particularly likely if the child has a severe cough, high fever, or a family history of reactive air-way disease. The decision to anesthetize children with URIs remains controversial and depends on the presence of other coexisting illnesses, the severity of URI symptoms, and the urgency of the surgery. When surgery will be performed in a child with a URI, one should consider giving anticholinergic pre-medication, avoiding intubation (if feasible), and humidifying inspired gases. In this circumstance one should anticipate that a longer-than-usual stay in the recovery room may be required.

C. Laboratory Tests

Few, if any, preoperative laboratory tests are cost effective. Some pediatric centers require no preoper-ative laboratory tests in healthy children undergoing minor procedures. Obviously, this places responsibil-ity on the anesthesiologist, surgeon, and pediatrician to correctly identify those patients who should have preoperative testing for specific surgical procedures

Most asymptomatic patients with cardiac mur-murs do not have significant cardiac pathology. Innocent murmurs may occur in more than 30% of normal children. These are typically soft, short sys-tolic ejection murmurs that are best heard along the left upper or left lower sternal border and that do not radiate. Innocent murmurs at the left upper sternal border typically are due to flow across the pulmonic valve (pulmonic ejection) whereas those at the lower left border typically are due to flow from the left ventricle to the aorta (Still’s vibratory murmur). The pediatrician should carefully evaluate patients with a newly diagnosed murmur, particularly in infancy. Consultation with a pediatric cardiologist, echocar-diography, or both, should be obtained if the patient is symptomatic (eg, poor feeding, failure to thrive, or easy fatigability); the murmur is harsh, loud, holo-systolic, diastolic, or radiates widely; or pulses are either bounding or markedly diminished.

D. Preoperative Fasting

Because children are more prone to dehydration than adults, their preoperative fluid restriction has always been more lenient. Several studies, how-ever, have documented low gastric pH (<2.5) and relatively high residual volumes in pediatric patients scheduled for surgery, suggesting that children may be at a greater risk for aspiration than was previously thought. The incidence of aspiration is reported to be approximately 1:1000. There is no convincing evidence that prolonged fasting decreases this risk. In fact, several studies have demonstrated lower residual volumes and higher gastric pH in pediat-ric patients who received clear fluids a few hours before induction . More specifically, infants are fed breast milk up to 4 h before induc-tion, whereas formula or liquids and a “light” meal may be given up to 6 h before induction. Clear flu-ids are offered until 2–3 h before induction. These recommendations are for healthy neonates, infants, and children without risk factors for decreased gas-tric emptying or aspiration.

E. Premedication

There is great variation in the recommendations for premedication of pediatric patients. Sedative pre-medication is generally omitted for neonates and sick infants. Children who appear likely to exhibit uncontrollable separation anxiety should be given a sedative, such as midazolam (0.3–0.5 mg/kg, 15 mg maximum). The oral route is generally preferred because it is less traumatic than intramuscular injec-tion, but it requires 20–45 min for effect. Smaller doses of midazolam have been used in combination with oral ketamine (4–6 mg/kg) for inpatients. For uncooperative patients, intramuscular midazolam (0.1–0.15 mg/kg, 10 mg maximum) or ketamine (2–3 mg/kg) with atropine (0.02 mg/kg) may be helpful. Rectal midazolam (0.5–1 mg/kg, 20 mg maximum) or rectal methohexital (25–30 mg/kg of 10% solution) may also be administered in such cases while the child is in the parent’s arms. The nasal route can be used with some drugs but is unpleasant, and some concerns exist over potential neurotoxic-ity of nasal midazolam. Nasal dexmedetomidine has also been used by some clinicians. Fentanyl can also be administered as a lollipop (Actiq, 5–15 mcg/kg); fentanyl levels continue to rise intraoperatively and can contribute to postoperative analgesia.

In the past anesthesiologists routinely premedi-cated young children with anticholinergic drugs (eg, atropine, 0.02 mg/kg intramuscularly) in hope of reducing the likelihood of bradycardia during induction. Atropine reduces the incidence of hypo-tension during induction in neonates and in infants younger than 3 months. Atropine can also prevent accumulation of secretions that can block small air-ways and endotracheal tubes. Secretions can be par-ticularly problematic for patients with URIs or those who have been given ketamine. Atropine may be administered orally (0.05 mg/kg), intramuscularly, or occasionally rectally. In current practice, most anesthesiologists prefer to administer atropine intra-venously at or shortly after induction.