CHAPTER 48 Pediatric Anesthesia

Brian N. Egan and Danny L. Robinson

Introduction

Anesthesiologists plan and provide safe, effective anesthesia for over 6 million children in the United States annually. Anesthesia has become safer for children as a result of improved monitoring, an improved safety profile of drugs, and guidelines regarding where and from whom children receive anesthesia care, but children remain at increased risk for adverse events compared to adult patients. The anesthesia technician or technologist in a pediatric environment should be familiar with the changes that occur in anatomy, physiology, and pharmacology during growth and development and the equipment and techniques unique to anesthetizing children.

Differences between Pediatric and Adult Patients

Anatomy and Physiology

Growth and development bring changes in anatomy and physiology as well as in size. The pediatric airway is more funnel shaped in comparison to the more cylinder-shaped adult airway, and both the head and tongue are larger. There are eight key differences between the pediatric and adult airway that must be considered in managing a child during anesthesia (Fig. 48.1).

Guimaraes2e-ch048-image001 — FIGURE 48.1. Pediatric airway differences. 1, large occiput; 2, smaller mouth; 3, baby teeth; 4, large tongue; 5, longer, floppy epiglottis; 6, angled vocal cords; 7, vocal cords higher in the neck; 8, narrowest part of airway is at cricoid cartilage.

The combination of a smaller oral cavity and the relatively larger tongue predisposes young children to obstruction during induction of anesthesia; the occiput (back of the head) is large and proper positioning is important. Differences in anatomy across age groups require a wider variety of equipment to be available (Figs. 48.2-48.5), including age-appropriate oral airways, laryngeal mask airways (LMAs), endotracheal tubes, and laryngoscope blades. Formulas and charts can be used as guides (Table 48.1), but individual variation commonly occurs and availability of several sizes is prudent. Difficulty with airway management is a leading factor in anesthetic-related mortality in children.

Guimaraes2e-ch048-image002 — FIGURE 48.2. Variation in laryngoscope blade sizes and designs.

Guimaraes2e-ch048-image003 — FIGURE 48.3. Variations in LMA™ sizes. (LMA™, laryngeal mask airway.)

Guimaraes2e-ch048-image004 — FIGURE 48.4. Variations in nasal and oral airway sizes.

Guimaraes2e-ch048-image005 — FIGURE 48.5. Neonatal intravenous administration kit with a buretrol.

Table 48.1. Age and Size Distribution of Airway Equipment

ETT, endotracheal tube; LMA™, laryngeal mask airway.

The higher-oxygen consumption seen in pediatric patients, nearly twice that of an adult, requires a higher minute ventilation to address this increased demand. Higher respiratory rates are needed to adequately ventilate children, and children’s oxygen saturation falls more rapidly than adults’.

The cardiovascular system of neonates differs dramatically from an adult. Prior to birth, infants’ blood receives oxygen from the mother’s placenta rather than from the lungs. The fetal circulatory system has two “shortcuts” (the foramen ovale and the ductus arteriosus) to shunt blood away from the lungs, which are not yet functioning. At (and shortly after) birth, these close off, sending more blood to the newly functioning lungs. This process can be interrupted, and the fetal connections between the right and left sides of the circulation can remain open, especially for premature babies or those with heart disease. Even when the transition to adult circulation goes well, the neonate’s heart is stiff, with a poorly developed left ventricle and a fixed stroke volume. The only way to increase cardiac output is with an increased heart rate. This makes a neonate’s heart more vulnerable to anesthetic-induced myocardial depression.

At birth, almost all of the neurons that the brain will ever have are present. However, the brain continues to grow for a few years after birth, reaching 80% of adult size at only 2 years old. There is less room in the skull for the pediatric brain to swell in the case of injury, making children more vulnerable in the case of elevated intracranial pressure (ICP).

Fluid and calorie requirements are much higher in infants and babies on a per kilogram basis (Table 48.2).

Table 48.2. Maintenance Fluid Requirements for Pediatric Patients, by Kilogram

Either intravenous (IV) infusion pumps or infant IV sets with buretrols (Fig. 48.5) should be used to allow accurate amounts of fluid delivery to these patients. Pediatric “microdrip” infusion sets deliver at 60 drops per mL compared to standard sets at 10-20 drops per mL (Fig. 48.6). A standard IV set can rapidly overhydrate an infant.

Guimaraes2e-ch048-image006 — FIGURE 48.6. Standard and microdrip chambers.

The liver and kidneys of an infant are still maturing. Infants, particularly new and very tiny babies, cannot produce and regulate glucose properly yet, and so are at risk of hypoglycemia, which can cause brain damage. Hyperglycemia must be avoided as well, because of its impact on wound healing and increased surgical infections. Liver and kidney functions also serve as the chief mechanisms for drug clearance: both reach adult levels of function around age 1.

Pediatric patients are at increased risk for hypothermia (see Chapter 33, Temperature Management). Children have greater heat loss due to an increased surface area to body weight ratio and less subcutaneous fat; this is particularly true in newborns or premature infants. Evaporative, convective, and conductive heat losses are all increased. Cold operating rooms increase radiative heat loss, so infants are transported in incubators and operating rooms are warmed to 78°C-80°C. Use of convective warming using a forced-air warming blanket is recommended for pediatric patients. Hypothermia can cause increased blood loss and transfusions, adverse cardiac events, prolonged stay in the recovery room and hospital, delayed surgical wound healing, and higher infection rates.

Psychological Issues with Pediatric Patients

Children between the ages of 6 months and 3 years are at the highest risk of emotional trauma when separated from parents or approached with a mask or needle, but children of any age may have distress. General anesthesia is typically induced with a child spontaneously breathing an increasing concentration of sevoflurane; an IV catheter is then placed when the child is unconscious. Strategies for dealing with children and their parents during the perioperative period vary by provider preference and with the individual child: establishing rapport, allowing a parent to be present during induction, administering sedative premedication, creating a supportive environment, and educating children and parents (pamphlets, tours, books, videos).

It is critical to understand that during the initial period after inhalation induction while the anesthesia is “light,” the child is at greatest risk for adverse airway events, including obstruction, apnea, laryngospasm, and bronchospasm, any of which can cause prolonged hypoxia. One of the major roles of the AT in pediatric anesthesia is to assist the anesthesiologist by providing the proper equipment and environment to anticipate, prevent, or treat any of these events during inhalation induction. This is particularly true prior to obtaining IV access, which allows for rapid administration of medications.

Specific Surgeries

Neonatal and Infant Surgery

Anesthesia-related morbidity and mortality are higher in infants, particularly the neonate. Minimizing this risk requires expertise caring for pediatric patients, neonates, and infants on a regular basis. A number of conditions require urgent surgical treatment in the neonatal period.

Congenital diaphragmatic hernia (CDH) is a defect in the diaphragm that allows the abdominal contents to herniate into the chest cavity, usually the left side. CDH is most commonly repaired during early infancy. Patients may already be intubated or have vascular access—umbilical arterial and/or venous lines. Preexisting lines may need to be replaced or supplemented. Some patients’ heart and lungs are so compressed by the herniated abdominal contents that they can require extracorporeal membrane oxygenation (ECMO).

Tracheoesophageal fistula (TEF) is an abnormal opening between the esophagus and trachea. The fistula between the trachea and the esophagus allows esophageal or gastric contents to enter and soil the lungs. Conversely, air from the trachea can enter the stomach causing overdistention and difficulty with ventilation. To avoid these complications, the endotracheal tube must be precisely positioned, or the fistula needs to be occluded with a balloon-tipped catheter. An appropriately sized fiberoptic bronchoscope is essential for the anesthesiologist.

Omphalocele and gastroschisis are defects in the abdominal wall that present with abdominal contents exposed at birth. These require immediate containment of the exposed abdominal contents with a sterile plastic silo. These infants have difficulty regulating temperature, so the operating room is warmed dramatically; they also become dehydrated quickly and require adequate IV access for fluid resuscitation.

Other neonatal gastrointestinal conditions that can require urgent surgical interventions include intestinal blockages and necrotizing enterocolitis (NEC). Each will have specific anesthetic needs and concerns. In particular, infants with intestinal obstructions will require a rapid sequence intubation (RSI). Neonates with NEC are often premature and can be extremely tiny (<1 kg). NEC repairs are often performed in the Neonatal Intensive Care Unit (NICU) therefore, just as with any surgery performed in an intensive care unit, all equipment for vascular access and medications, both routine and emergent, need to be transported to the NICU for immediate availability.

Pediatric Neurosurgery

Common pediatric neurosurgical conditions include trauma, brain tumors, hydrocephalus, and spina bifida (myelomeningocele).

Pediatric head trauma is the most common cause of serious injury and death in children. Brain tumors are the most common solid tumor in children, with a significant number of these patients requiring surgical treatment. Hydrocephalus is an increase in the cerebrospinal fluid (CSF) within the brain that leads to increased ICP. This buildup in pressure can be relieved with the placement of a shunt, either ventriculoperitoneal shunt (VPS), ventriculoatrial shunt (VAS), or external ventricular drain (EVD). As in adults, neurosurgery in children can involve neurophysiologic monitoring (see Chapter 32, Neurologic Monitoring), which provides information to reduce injury to the nervous system during the procedure. This requires minimizing the use of inhaled anesthetic drugs, so that the anesthesiologist may need several syringe pumps or IV pumps for giving alternate anesthetic medications.

Myelomeningocele is a congenital spinal anomaly that causes varying degrees of spinal cord and vertebral bone malformation. The defect, if large enough, can allow the spinal cord and nerves to protrude in a sac. Great care must be taken to prevent sac rupture or damage with movement of the child. Positioning the patient for anesthesia and surgery requires creative building of a special support under the spine (with blankets or towels) to cushion the defect perfectly.

Cardiac

Pediatric patients undergo cardiac surgery for very different reasons than adult patients. Adults most often need cardiac surgery because of coronary artery disease or valve disease. Children rarely suffer from coronary artery disease. They present with “abnormal plumbing.” This means that either the heart itself (atria, ventricles, valves) or the major blood vessels (aorta, pulmonary artery/veins) did not form correctly. Abnormalities include incompletely developed chambers and defects in the walls separating the chambers within the heart.

A detailed discussion of each unique heart defect is beyond the scope of this chapter. The important point to remember is that these children have a delicate hemodynamic balance. The anesthesiologist will be carefully monitoring the depth of anesthesia, fluid therapy, and fraction of inspired oxygen and will need to have medications readily available to manipulate the patient’s blood pressure and heart rate.

The AT must be extremely vigilant for air bubbles when preparing IV lines and pressure tubing in the pediatric cardiac room, as even small air bubbles can cause strokes, with devastating consequences (embolic strokes) in children with certain heart defects. Invasive monitors like arterial lines, central venous lines, and transesophageal echocardiography (TEE) are common. All invasive monitors must be sized appropriately for the patient, and ultrasound guidance is often used. These patients are some of the most delicate in the hospital, and the anesthesiologist requires intensive AT support.

Urology

Pediatric urology procedures are often performed to correct developmental defects or remove tumors. Common procedures include complete or partial kidney removal (nephrectomy), testicular repair (orchiectomy, orchiopexy, etc.), ureteral reimplantation, and penile and vaginal surgery. Most of these procedures are performed under general anesthesia using either an endotracheal tube or a LMA for airway management. For many of these surgeries, anesthesiologists will use regional anesthesia—caudals, epidurals, or truncal blocks—to minimize postoperative pain. Infants and small children are unable to sit still for procedures. Therefore, unlike adult patients, these blocks are typically performed in children after induction of general anesthesia.

Orthopedics

Orthopedic surgeries are common in children, both for trauma (broken bones) and to correct congenital skeletal deformities—scoliosis, hip dysplasia, club feet, etc.

Children presenting for repair of fractures often have “full stomachs.” This means that (unlike patients for elective surgery) they have not been fasting and are at increased risk for aspiration during induction of general anesthesia. They may have a “rapid sequence” IV induction of anesthesia (RSI) instead of inhalation of sevoflurane like most pediatric patients (see Chapter 18, Principles of Airway Management). The AT can assist the anesthesia provider by making sure all equipment for intubation is readily available (e.g., appropriately sized ETT with a stylet) or by performing cricoid pressure as directed to occlude the esophagus.

Regional anesthesia (peripheral nerve blockade) is often a consideration for orthopedic surgery, especially surgery on limbs. Most procedures utilize a combination of general and regional anesthesia. Depending on the age and maturity of the patient, peripheral nerve blocks may be done prior to induction of general anesthesia or afterward. Many of the same tools (i.e., ultrasound, nerve stimulators, catheters, etc.) that are used in adults can be used in children.

Children with spinal deformities often require surgical correction. Scoliosis, or lateral curvature of the spine, can impair a child’s lungs or even heart. These procedures are extensive and, at times, require both posterior and anterior procedures to fully correct and stabilize the spine. As the spinal column is straightened, the spinal cord and nerves can be stretched or damaged. For this reason, neurologic monitoring is routinely used to detect nerve injury and correct it during the procedure (see Chapter 32, Neurologic Monitoring). These cases can require multiple pumps for partial or total IV anesthesia (TIVA) and for vasoactive medications, vascular access equipment, transducers, fluid warmers, forced-air warmers, and possibly intraoperative blood salvage devices like Cell Saver.

Otolaryngology

Pediatric ENT (ear, nose, and throat) surgery is often one of the busiest services in the OR. Procedures range from ear tubes and tonsillectomies to repairs of congenital malformations.

One of the most common and quickest procedures is the placement of ear tubes (myringotomy tubes). Other short procedures include removal of the tonsils and adenoids (tonsillectomy and adenoidectomy). In a room with these cases, a premium is placed on rapid turnover of the room between cases to facilitate a large number of procedures.

Other types of otolaryngology cases involve birth defects or congenital malformation. These are usually defects in the structure of the head, face, palate, lip, and jaw; cleft lips and palates are common. Certain syndromes (i.e., Treacher Collins, Pierre Robin, and Goldenhar syndromes) are associated with facial deformities, and many of these cases involve difficult airways. Unique malformations can make placement of the ETT extremely difficult, and the AT should have all advanced airway equipment ready to go, including fiberoptic bronchoscope, glide scope, intubating stylets and airways, exchange catheters, and other requested equipment.

Otolaryngologists often operate in the oral cavity, pharynx, and larynx. The LMA or endotracheal tube can be in the surgeon’s way. Airway devices and ventilation techniques have been designed to help accommodate surgeons’ preferences. These range from flexible LMAs to oral and nasal RAEs to jet ventilation, which has no airway in place at all. Laser devices are often used (see Chapter 55, Laser Safety). A plan for each patient’s airway will be made between the anesthesiologist and surgeon.

Ophthalmology

Ocular procedures performed in pediatric patients range from basic eye examinations under anesthesia (EUA) to complicated intraocular surgery.

Premature infants who developed the “retinopathy of prematurity” (ROP) may have repeated EUAs and laser treatments under general anesthesia. (The role of supplemental oxygen in causing ROP is uncertain: premature babies are thus not given oxygen unless the SpO₂ is less than 90%-95%.)

Another frequent type of eye surgery for children is strabismus (lazy eye) repair. Pulling on the muscles around the eye can result in a dramatic slowing of the heart rate via the vagus nerve (the “oculocardiac reflex”), which may need to be treated with medications that speed up the heart rate (atropine, glycopyrrolate). An association between strabismus and MH has been described (see Chapter 60, Malignant Hyperthermia).

Dental

Most commonly, dental procedures under general anesthesia are performed in children with neurodevelopmental issues (e.g., autism, cerebral palsy, profound developmental delay), which prevent them from being able to hold still. Some children are so combative as to not be able to take oral sedative medication or cooperate in breathing from an anesthetic mask; intramuscular ketamine can be given to sedate a child enough to safely bring them to the OR. After induction of anesthesia, nasal RAE ETTs are typically inserted for intubation. This allows for a protected airway and better access to the teeth for the dentist. Commonly used equipment for these cases also includes Magill forceps, lubricant, nasal airways (used to test the patency and dilate the nasal passage prior to intubation), red rubber catheters (attached to the tip of the ETT to prevent tissue damage as it is inserted), and oxymetazoline or phenylephrine nasal spray to minimize bleeding.

Recently, it has become recognized that general anesthesia in children carries lower risk than unmonitored sedation in the dentist’s office, and children without profound delays can appropriately present for dental anesthesia.

Pediatric Sedation/Anesthesia Out of the Operating Room

Because young children are unable to tolerate or remain still for many procedures, out-of-operating room locations utilize pediatric anesthesia services extensively both for sedation and for general anesthesia. Routine x-rays, computed tomography (CT), nuclear medicine, radiation therapy, stereotactic radiosurgery, magnetic resonance imaging (MRI), interventional radiology/invasive angiography (IR), endoscopy, and clinical procedure rooms each present their own unique challenge for out-of-OR anesthesia services. Combining adequate preprocedural screening, competent procedural sedation/anesthesia, and postanesthesia recovery care requires an organized off-site anesthesia/sedation team with expertise in pediatrics and in the needs of each procedure area. This need will continue to develop and expand as well as the demand for competent anesthesia coverage will likely increase. Pediatric sedation levels and standards do not differ from those for adults; pediatric sedation, like pediatric anesthesia, carries higher risks.

The minimum equipment required for either sedation or anesthesia includes Suction, Oxygen, appropriate Drugs, and Airway equipment (SODA); an anesthesia machine is not necessarily required. Drugs include sedatives, narcotics, muscle relaxants, cardiac resuscitation medications, and medications for anaphylaxis. Airway equipment includes O₂ tubing, bag-mask ventilation supplies (e.g., Jackson-Rees, Ambu), laryngoscopes, ETTs, tape, stylets, oral and nasal airways, and LMAs. When the sedation or anesthetic planned is for a pediatric patient, the equipment and drugs must be available in the appropriate sizes (see Chapter 15, Sedation, and Chapter 50, Anesthesia Outside the Operating Room).

Risk of Pediatric Anesthesia

The risk of anesthesia over all age groups has decreased dramatically in the last 20-30 years and currently is thought to be around 1 in 100,000 anesthetics in the United States. When compared to adults, the risk of an adverse event during anesthesia has been shown to be consistently higher in children. Analysis of pediatric patients has shown patients of younger age (<1 year) and sicker patients (ASA 3-5), and those having ENT or emergency procedures are at increased risk for complications during anesthesia. The value of identifying risk allows for the best possible anesthesia care to be provided to these children. Pediatric anesthesia delivered in a facility familiar with taking care of pediatric patients and care given by specialty trained care providers has been shown to be safer than that given in smaller community medical centers by practitioners that only occasionally care for children. Pediatric anesthesiologists make a difference!

Though general anesthetics have now been used clinically for over a century, their mechanism of action remains unknown. The clinical significance of anesthetic neurotoxicity is controversial and is currently under investigation. Retrospective data suggest that exposure during critical periods of brain development to many commonly used anesthetic agents results in neuronal injury. Studies suggest that children under 4 years of age receiving multiple exposures to anesthesia and surgery are at greatest risk for this neurotoxic effect of anesthetic agents. A large study (SmartTots) is currently being conducted to further assess this. The current recommendation is not to put off needed surgery or procedures requiring anesthesia, but to weigh the benefits of any elective procedure against potential risk.

Summary

Children are at an increased risk for adverse events during anesthesia. A thorough understanding of pediatric anatomy and physiology and how that impacts their anesthetic care needs to be known and used regularly to provide appropriate and safe anesthesia to pediatric patients. More than anything, it is the experience and skill of the personnel taking care of the child that determines the safety of a child’s anesthetic.

Review Questions

1. Concerning younger pediatric patients and IV’s, which of the following statements are true?

A) Air bubbles must be removed from IV tubing and stopcocks.

B) Microdrip tubing is preferred to macrodrip tubing.

C) Buretrols are used for only older children.

D) All of the above.

E) A and B only.

Answer: E

Younger children, especially those younger than 2 years, may have a patent foramen ovale (PFO). This anatomic abnormality can allow air bubbles in the blood stream to pass directly from the right atrium into the left atrium and into the systemic circulation. This can lead to systemic ischemic complications, such as a stroke. The fluid requirements of children differ significantly from adults, and anesthesia providers must closely monitor the amount of IV fluids that are administered to pediatric patients. Microdrip IV tubing and buretrols allow more precise volumes of IV fluids to be administered than does a standard adult set (macrodrip tubing).

2. When are regional anesthesia procedures (epidural, caudal, and peripheral nerve blocks) performed in the course of a pediatric anesthetic?

A) In the preoperative area with the child sedated.

B) In the OR with the child sedated.

C) In the OR after induction of general anesthesia.

D) In the postanesthesia care unit (PACU) after surgery is completed.

E) Regional anesthesia is not indicated for pediatric patients.

Answer: C

Unlike adults, most children will not be able to understand or cooperate with regional anesthetic procedures being done awake or lightly sedated. Therefore, most will be performed safely under general anesthesia in the OR.

3. Compared to adults, which statement regarding children’s body temperature under general anesthesia is true?

A) Surface area to weight ratio is less than adults.

B) Temperature decreases more quickly than adults.

C) Pediatric ORs should be warmed and intraoperative warming devices routinely used.

D) A and C only.

E) B and C only.

Answer: E

Compared to adults, infants have a much greater surface area to weight ratio (i.e., the area of their skin is large, but their weight is small) and are at increased risk to develop intraoperative hypothermia. Special attention needs to be given to keep operating rooms warm and use of active warming devices for pediatric patients.

4. Which of the following is true regarding the anesthetic care of pediatric patients?

A) All anesthetic care of pediatric patients involves general anesthesia.

B) All anesthetic care of children must use approved monitoring practices throughout the hospital.

C) All pediatric anesthesia providers are required to have completed a pediatric anesthesiology fellowship.

D) The continuum of mild, moderate, and deep sedation does not exist for children.

E) All of the above.

Answer: B

All anesthesia services provided to pediatric and adult patients, including sedation, regional, and general anesthesia, must follow federal guidelines regarding their provider credentialing and monitoring practice.

5. Which of the following often requires intravenous anesthesia and neuromonitoring?

A) Surgery for children under 4 years old

B) Ventriculoperitoneal (VP) shunt for hydrocephalus

C) Pediatric cardiac surgery

D) Scoliosis surgery

E) Surgery for congenital diaphragmatic hernia

Answer: D

Scoliosis surgery, because of the risk of traction or other damage to the nerves of the spinal cord or nerve roots, often involves neurologic monitoring, which inhaled anesthetics can interfere with, so intravenous anesthetics are also used. Hydrocephalus surgery, although it is intracranial, does not involve a serious risk of brain damage. Pediatric cardiac surgery and CDH surgery are serious cardiovascular challenges but do not usually involve neurologic monitoring. There is a question about neurotoxicity in children under four undergoing repeated anesthetics, but neither TIVA nor neuromonitoring is particularly involved with this controversy.