1 What are the differences between the adult and pediatric airways?

See Table 57-1.

TABLE 57-1 Differences Between the Adult and Pediatric Airways

ETT, Endotracheal tube.

2 Are there any differences in the adult and pediatric pulmonary systems?

See Table 57-2.

TABLE 57-2 Differences in the Pediatric and Adult Pulmonary Systems

3 How does the cardiovascular system differ in a child?

Newborns are unable to increase cardiac output (CO) by increasing contractility; they can increase CO only by increasing heart rate.

Babies have an immature baroreceptor reflex and limited ability to compensate for hypotension by increasing heart rate. Therefore they are more susceptible to the cardiac depressant effects of volatile anesthetics.

Babies and infants have increased vagal tone and are prone to bradycardia. The three major causes of bradycardia are hypoxia (most common cause), vagal stimulation (laryngoscopy), and volatile anesthetics. Bradycardia decreases CO.

4 What are normal vital signs in children?

See Table 57-3.

5 When should a child be premedicated? Which drugs are commonly used?

Children may have fear and anxiety when they are separated from their parents and during anesthetic induction. Children who are 2 to 6 years old who have had previous surgery or no preoperative tour and education or who fail to interact positively with health care providers in the preoperative area should be premedicated. Children who are anxious during induction may suffer from negative postoperative behavioral changes. Children who receive premedication with midazolam have fewer negative postoperative changes than children who do not.

6 Should parents be allowed to accompany their children to the operating room?

Young children may become anxious and frightened when they are separated from their parents. Allowing parents to accompany children to the operating room (OR) may facilitate anesthetic induction in some cases. Parents and children should be educated and prepared for what to expect, and parents should be prepared to leave when the anesthesiologist believes it to be appropriate. Anxious, reluctant, or hysterical parents are a hindrance. An anesthesiologist who is not comfortable with parental presence probably should not allow them to be present. An uncooperative, frightened child may not benefit from parental presence. Although allowing parents to be present during induction of anesthesia is beneficial to the parents, premedication with midazolam actually is associated with lower levels of anxiety in the child. The benefit of both premedication and parent presence during anesthesia appears to be additive.

7 What medications are available for premedication?

See Table 57-4.

8 Describe the commonly used induction techniques in children

Inhalational induction is the most common induction technique in children younger than 10 years who do not have intravenous (IV) access. The child is asked to breathe 70% nitrous oxide (N₂O) and 30% oxygen for approximately 1 minute; sevoflurane is then turned on. The sevoflurane concentration can be increased slowly or rapidly.

Rapid inhalational induction is used in an uncooperative child. The child is held down, and a mask containing 70% N₂O, 30% oxygen, and 8% sevoflurane is placed on the child’s face. This unpleasant technique should be avoided if possible. Once anesthesia has been induced, the concentration of sevoflurane should be decreased.

Steal induction may be used if the child is already sleeping. Inhalational induction is accomplished by holding the mask near the child’s face while gradually increasing the concentration of sevoflurane. The goal is to induce anesthesia without awakening the child.

IV induction is used in a child who already has an IV line in place and in children >10 years. Typical medications used in children are thiopental, 5 to 7 mg/kg; propofol, 2 to 3 mg/kg; and ketamine, 2 to 5 mg/kg. EMLA cream (eutectic mixture of local anesthesia) applied at least 90 minutes before starting the IV infusion makes this an atraumatic procedure.

9 How does the presence of a left-to-right shunt affect inhalational induction and intravenous induction?

A left-to-right intracardiac shunt leads to volume overload of the right heart and pulmonary circulation, resulting in congestive heart failure and decreased lung compliance. Uptake and distribution of inhaled agents are minimally affected; onset time for IV agents is slightly prolonged.

10 How about a right-to-left shunt?

Right-to-left shunting causes hypoxemia and left ventricular overload. Patients compensate by increasing blood volume and hematocrit. It is important to maintain a high systemic vascular resistance (SVR) to prevent increased shunting from right to left. Such shunts may slightly delay inhalation induction and shorten the onset time of IV induction agents.

11 What other special precautions need to be taken in a child with heart disease?

The anatomy of the lesion(s) and direction of blood flow should be determined. Pulmonary vascular resistance (PVR) needs to be maintained. If the PVR increases, right-to-left shunting may increase and worsen oxygenation, whereas a patient with a left-to-right shunt may develop a reversal in the direction of blood flow (Eisenmenger’s syndrome). If a patient has a left-to-right shunt, decreasing the PVR may increase blood flow to the lungs and lead to pulmonary edema. Decreasing the PVR in patients with a right-to-left shunt may improve hemodynamics. Conditions that can increase shunting are listed in Table 57-5.

Air bubbles should be meticulously avoided. If there is a communication between the right and left sides of the heart (ventricular septal defect, atrial septal defect), air injected intravenously may travel across the communication and enter the arterial system. This may lead to central nervous system symptoms if the air obstructs the blood supply to the brain or spinal cord (paradoxical air embolus).

Prophylactic antibiotics should be given to prevent infective endocarditis. Recommendations for medications and doses can be found in the American Heart Association guidelines.

Avoid bradycardia.

Recognize and be able to treat a “tet spell.” Children with tetralogy of Fallot have right ventricular outflow tract (RVOT) obstruction (pulmonary artery stenosis or atresia), an overriding aorta, ventricular septal defect, and right ventricular hypertrophy. They may or may not have cyanosis at rest. However, many are prone to hypercyanotic spells (tet spells) as they get older. Such episodes are characterized by worsening RVOT obstruction, possibly as a result of hypovolemia, increased contractility, or tachycardia during times of stimulation or stress. Patients are frequently treated with β-blockers, which should be continued perioperatively. Hypovolemia, acidosis, excessive crying or anxiety, and increased airway pressures should be avoided. The SVR should be maintained. If a hypercyanotic spell occurs in the perioperative period, treatment includes maintaining the airway, volume infusion, increasing the depth of anesthesia, or decreasing the surgical stimulation. Phenylephrine is extremely useful in increasing SVR. Additional doses of β-blockers may also be tried. Metabolic acidosis should be corrected.

TABLE 57-5 Conditions that can Increase Shunting

PVR, Pulmonary vascular resistance; SVR, systemic vascular resistance.

12 How is an endotracheal tube of appropriate size chosen?

An endotracheal tube (ETT) a half size above and a half size below the estimated size in Table 57-6 should be available, the leak around the tube should be <30 cm H₂O, and the ETT should be placed to a depth of approximately three times its internal diameter.

TABLE 57-6 Guidelines for Endotracheal Tube Size

ETT, Endotracheal tube.

13 Can cuffed endotracheal tubes be used in children and laryngeal mask airways?

Most of us have been taught for years that cuffed ETTs should not be used in children <8 years old. The reasons are twofold:

Many patients who are intubated (in either the operating room or intensive care unit) are mechanically ventilated; thus the WOB is not as much of an issue as it used to be. Newer circuits and anesthesia machines have also helped decrease the problem of WOB.

Tracheal mucosal inflammation and injury are related to a number of factors, including duration of intubation and number of intubation attempts. Several recent studies have found that cuffed ETTs decrease the number of intubation attempts and are associated with decreased air leak (resulting in decreased OR pollution and greater ability to use low fresh gas flows) and provide better protection from aspiration.

Cuffed ETTs can be used in children and neonates. Of course, the cuff takes up space, thus limiting the size of the ETT. Use the cuffed tube one size smaller than the appropriate uncuffed tube. The advantages of cuffed ETTs are that they avoid repeat laryngoscopy and may allow use of lower fresh gas flows.

New Microcuff ETTs are formulated with microthin polyurethane cuff material that is reputed to seal the airway with half the pressure of conventional cuffed ETTs. Their cuff is short and cylindric and placed near the tube tip. This positions the cuff lower in the airway.

Laryngeal mask airways (LMAs) are also useful in pediatrics. They can help secure a difficult airway, either as the sole technique or as a conduit to endotracheal intubation, and are being used increasingly for routine airway management in minor procedures.

14 How is an appropriate-size laryngeal mask airway chosen?

See Table 57-7.

TABLE 57-7 Laryngeal Mask Airways for Children

LMA, Laryngeal mask airway.

15 How does the pharmacology of commonly used anesthetic drugs differ in children?

The minimal alveolar concentration (MAC) of the volatile agents is higher in children than adults. The highest MAC is in infants ages 1 to 6 months. Premature babies and neonates have a lower MAC, but it is still higher than in adults.

Children have a higher tolerance to the dysrhythmic effects of epinephrine during general anesthesia with volatile agents.

In general, children have higher drug requirements (mg/kg) because they have a greater volume of distribution (more fat, more body water).

Opioids should be used carefully in children less than 1 year old who are more sensitive to the respiratory depressant effects.

16 How is perioperative fluid managed in children?

Maintenance is calculated as follows:

Infant <10 kg: 4 ml/kg/hr

10 to 20 kg: 40 ml/hr plus 2 ml/kg/hr for every kg over 10

Child >20 kg: 60 ml/hr plus 1 ml/kg/hr for every kg over 20

Estimated fluid deficit (EFD) should be calculated and replaced as follows:

EFD = maintenance × hours since last oral intake

½ EFD + maintenance given over the first hour

¼ EFD + maintenance given over the second hour

¼ EFD + maintenance given over the third hour

All EFDs should be replaced for major cases. For minor cases 10 to 20 ml/kg of a balanced salt solution (BSS) with or without glucose is usually adequate.

Estimated blood volume (EBV) and acceptable blood loss (ABL) should be calculated for every case.

17 What is the most common replacement fluid used in children? Why?

A BSS such as lactated Ringer’s (LR) with glucose (D₅LR) or without glucose (LR) is recommended. Hypoglycemia may occur in healthy children undergoing minimally invasive procedures if glucose-containing fluids are not used, but administration of 5% glucose-containing solutions results in hyperglycemia in the majority of children. Perhaps fluid containing 1% or 2.5% glucose is best. Others still use 5% glucose solutions for maintenance but recommend nonglucose-containing BSS for third space or blood loss. In major operations it is prudent to check serial glucose levels and avoid hyperglycemia or hypoglycemia.

18 What is the estimated blood volume in children?

See Table 57-8.

TABLE 57-8 Guidelines for Estimated Blood Volume in Children

EBV, Estimated blood volume.

19 How is acceptable blood loss calculated?

where ABL = acceptable blood loss, EBV = estimated blood volume, pt = patient, and hct = hematocrit. The lowest acceptable hematocrit varies with circumstances. Blood transfusion is usually considered when the hematocrit is <21% to 25%. If problems with vital signs develop, blood transfusion may need to be started earlier. For example, a 4-month-old infant is scheduled for craniofacial reconstruction. He is otherwise healthy, and his last oral intake was 6 hours before arriving in the operating room; weight = 6 kg, preoperative hct = 33%, lowest acceptable hct = 25%.

Maintenance = weight × 4 ml/hr = 24 ml/hr

EFD = maintenance × 6 hr = 144 ml

EBV = weight × 80 ml/kg = 480 ml

ABL = [EBV × (pt hct − lowest acceptable hct)]/average hct = [480 × (33 − 25)]/29 = 132 ml

20 How do the manifestations of hypovolemia differ in children?

Healthy children compensate for acute volume loss of 30% to 40% before blood pressure changes. The most reliable early indicators of compensated hypovolemic shock in a child are persistent tachycardia, cutaneous vasoconstriction, and diminution of pulse pressure.

21 What are the systemic responses to blood loss?

See Table 57-9.

22 What is the most common type of regional anesthesia performed in children? Which local anesthetic is used and what dose is appropriate?

Caudal epidural block is the most common regional technique. It is usually performed in an anesthetized child and provides intraoperative and postoperative analgesia. It is used most commonly for surgery of the lower extremities, perineum, and lower abdomen. Lumbar and thoracic epidural blocks are also used for postoperative pain relief.

Bupivacaine (0.125% to 0.25%) is most commonly used. Bupivacaine 0.25% produces intraoperative analgesia and decreases the required volatile anesthetic. However, it may produce postoperative motor blockade that interferes with discharge of outpatients. Bupivacaine 0.125% causes minimal postoperative motor block but may not provide intraoperative analgesia or decrease the anesthetic requirements. Bupivacaine 0.175% produces good intraoperative analgesia and minimal motor block and decreases the required MAC of volatile anesthetics. The toxic dose of bupivacaine in the child is 2.5 mg/kg; in the neonate, 1.5 mg/kg. Commonly used doses are listed in Table 57-10.

TABLE 57-10 Commonly used Doses of Local Anesthetic for Caudal Block

UOP, Urine output.

Data from Gunter JB, et al: Optimum concentration of bupivacaine for combined caudal-general anesthesia in pediatric patients, Anesth Analg 66:995–998, 1982.

23 Describe the common postoperative complications

Postoperative nausea and vomiting (PONV) is the most common cause of delayed discharge or unplanned admission. Factors associated with PONV include age >6 years, length of surgery >20 minutes, previous history of PONV, eye surgery, inner ear procedures, history of motion sickness, tonsillectomy/adenoidectomy, preoperative nausea or anxiety, hypoglycemia, female gender, gynecologic procedures, and use of opioids and N₂O. The best treatment for PONV is prevention. Prophylactic administration of an antiemetic should be considered for patients at high risk for PONV. Avoiding opioids decreases the incidence of PONV as long as pain relief is adequate (e.g., patient has a caudal block). Management includes administering IV fluid, limiting oral intake, and administering dexamethasone, metoclopramide, or ondansetron.

Laryngospasm and stridor are more common in children than in adults. Management for laryngospasm includes oxygen, positive pressure ventilation, jaw thrust, succinylcholine, propofol, and reintubation if necessary. Stridor is usually treated with humidified oxygen, steroids, and racemic epinephrine.

Emergence agitation has increased in incidence with the use of short-acting volatile agents (sevoflurane and desflurane). Pain can worsen, and analgesics improve agitation. Agitation can occur even in patients undergoing nonpainful procedures, although fentanyl, 1 mg/kg, reduces agitation.

24 What is the significance of masseter muscle rigidity?

Rigidity of the masseter muscles occurs in 1% of children receiving halothane and succinylcholine. Masseter muscle rigidity (MMR) may be the first symptom of malignant hyperthermia (MH), but it may also occur in patients who are not susceptible to MH. When MMR develops, the major issue is whether to substitute a nontriggering technique or stop the procedure. We usually switch to a nontriggering technique and continue with the operation unless other signs of MH develop or such severe masseter muscle spasm occurs that intubation is impossible.

After surgery patients should be admitted and followed for signs of MH (tachycardia, blood pressure lability, hyperthermia [which is usually a late symptom], urine myoglobin). If creatine phosphokinase (CPK) is >20,000, the patient should be considered to have MH. If the CPK is <20,000 but still significantly elevated, an MH work-up should be considered, including a muscle biopsy. If CPK is normal or minimally elevated, the patient is probably not at increased risk for MH.

25 Should children with upper respiratory infection receive general anesthesia?

The risk of adverse respiratory events is 9 to 11 times greater up to 6 weeks after an upper respiratory infection (URI). Underlying pulmonary derangements include decreased diffusion capacity for oxygen, decreased compliance, increased airway resistance, decreased closing volumes, increased shunting (ventilation-perfusion mismatch), hypoxemia, and increased airway reactivity (desaturation, bronchospasm, laryngospasm). Associated factors predicting an increased likelihood of perioperative complications include airway instrumentation, fever, productive cough, lower respiratory tract involvement, a history of snoring, passive smoking, induction anesthetic agent, copious secretions, nasal congestion, and anticholinesterase use.

General recommendations for a child with a mild URI include the following:

Discuss increased risk with parents.

Try to avoid intubation (LMA or mask use has a lower risk).

Use anticholinergics to help decrease secretions and airway reactivity.

Humidification and hydration are thought to decrease airway dryness and maintain ciliary clearance.

The child who has a fever, rhonchi that do not clear with coughing, an abnormal chest x-ray film, elevated white count, or decreased activity levels should be rescheduled. The child presenting with symptoms of an uncomplicated URI and who are afebrile with clear secretions and appearing otherwise healthy or those with noninfectious conditions should be able to undergo surgery.

26 What are the implications of sleep-disordered breathing in children?

Sleep-disordered breathing (SDB) is a continuum that ranges from normal breathing and oxygenation to chronic intermittent desaturation (CIND) and obstructive sleep apnea (OSA).

Obstructive sleep apnea is known to be associated with decreased CO₂ response curve and a higher incidence of perioperative respiratory problems such as desaturation, obstruction, apnea, and increased opioid sensitivity. It is important to assess the severity and comorbidities present in each particular patient.

In children SDB can be caused by narrowing of the upper airway usually secondary to adenotonsillar hypertrophy, obesity, neuromuscular problems and/or craniofacial abnormalities. Children with SDB can have significant behavioral and performance problems. Tonsillectomy and adenoidectomy have been shown to completely eliminate airway obstruction in 85% to 95% of otherwise healthy patients with OSA and result in significant improvement in clinical symptoms. Recent studies have challenged the myth of adverse effects from preoperative sedation in these children.