General Considerations in Pediatric Otolaryngology

History of Pediatric Otolaryngology

The evolution of pediatric otolaryngology, like that of most subspecialties, began when a group of like-minded colleagues decided to share their experiences with the challenging scenarios each had faced. The Society of Ear, Nose and Throat Advances in Children (SENTAC) was founded in 1973 as an interdisciplinary professional organization. Similar groups were established in Poland (1947), Hungary (1948), Japan (1979), South America (1979), and Australia/New Zealand (1985). These groups helped to define subspecialty training to include an in-depth knowledge of developmental physiology, growth mechanisms, and pediatric pharmacotherapy. The pediatric otolaryngologist must also have a demeanor conducive to caring for young patients and their parents. It is generally accepted that pediatric otolaryngology is based on shared decision making with an emphasis on the best outcomes for the children and their guardians.

Hirschberg and colleagues recorded the rise of the specialty in Hungary from the 1890s onward; it arose because of the need for tracheotomy in children. Infections were the major killers of children in the late 1800s, and diphtheria was responsible for significant mortality from death by suffocation. Literature on acute purulent otitis media was published as early as the late 1890s and early 1900s, and the first successful retrieval of an aerodigestive foreign body occurred in 1908. Lye ingestion in the 1930s was common, and individuals such as Chevalier Jackson, in the United States, were instrumental in campaigning for the labeling of all poisonous or corrosive substances to prevent accidental ingestion. The high mortality from crouplike illnesses and foreign body aspirations led to the development of the “airway foreign body service” in the late 1950s in Hungary. Similarly, courses on pediatric airway management such as the Polish “Days of Pediatric Laryngology” began and continue to this day (see endodays2017.org ). The management of acute airway emergencies continues to be the sine qua non of pediatric otolaryngology.

Severe neonatal and infantile rhinitis is frequently discussed at pediatric otolaryngology meetings, but better understanding came with the introduction, by Hounsfield and Cormack, of computed tomography (CT) in 1972. The developmental anatomy of the nose influences decisions made for treating conditions such as septal deformity, choanal atresia, cystic fibrosis, and genetic syndromes such as Treacher Collins and Crouzon. The ongoing evolution of imaging has enhanced the current use of telescopic miniaturization and camera enhancement in treating skull base lesions through the nostrils of tiny children, which was not possible 20 years earlier.

The Human Genome Project was completed in April 2003 (see www.genome.gov ); it has led to the identification of the molecular etiology of conditions such as hereditary hearing loss (see www.hereditaryhearingloss.org ), a better understanding of the chromosomal anomalies seen in Down syndrome and 22q11.2 deletion syndrome, and various craniofacial syndromes. Nearly 100 years after Gustave Crouzon first described a case in 1912, we now know that Crouzon syndrome results from mutations in the fibroblast growth factor receptor 2 ( FGFR2 ) gene. Helpful Internet and established literature resources include www.genetics.org , www.orpha.net , Online Mendelian Inheritance in Man (see www.omim.org ), and Smith’s Recognisable Patterns of Human Malformation .

The role of the pediatric otolaryngologist in advocating for children’s health is critically important in preventing illness. Pediatric otolaryngologists have participated in campaigns targeting excessive noise exposure and button battery ingestion, advocating for human papillomavirus (HPV) vaccination, and promoting screening for congenital human cytomegalovirus (HCMV) infection, childhood hearing loss, and speech and language delay. In a similar way, the Australian pediatric otolaryngology group promoted the benefits of installing swimming pools in remote Aboriginal communities to significantly reduce otitis media with tympanic membrane perforations and pyoderma in these communities.

The Important Differences Between a Child and an Adult

Pediatric otolaryngologists may be called to evaluate children in the fetal stage after their initial ultrasound imaging, at the time of birth, as neonates or infants, or at any age thereafter up to transitional care in the middle teens. Children differ from adults in all four areas of development: craniofacial, physiologic, psychosocial, and intellectual. In addition, their underlying condition may be associated with developmental delay, presenting management challenges even into adulthood. The anxieties and concerns of the parents, along with their ability to cope and provide care, will also affect decision making. For children not fortunate enough to have parents to care for them, guardianship issues pertaining to cultural organizations, religious bodies, and governmental institutions add to the complexity.

Physiology

Physiologically, children have a greater ratio of body surface area to volume than adults, and as a result they are at greater risk of excessive loss of heat and fluids. Children are more easily affected by medication, toxins, and microorganisms. Children also have rapidly dividing cells, which assist in the rate of growth, making them quicker in healing but more sensitive to effects such as radiation or chemotherapy. With higher heart rates and respiratory rates, they have proportionately higher minute volumes; hence they are more susceptible to agents absorbed through the airway, responding more quickly to a variety of agents. With an immature blood-brain barrier, children have enhanced central nervous system receptivity; thus they have a higher prevalence for neurologic symptoms from illness and medication. Because of the immaturity of their neurologic system, children have exaggerated responses to insults such as laryngospasm and central apnea. The higher metabolic rate in children means a greater risk for increased fluid loss as a result of stress or illness. The dosage of most medications for children, unlike those for adults, is based on the child’s weight and body size. Children generally are at greater risk for infection and have less herd immunity from certain infections because of their immature immune systems.

Ventilation/Perfusion Relationships

Ventilation and perfusion are imperfectly matched in the neonatal lungs because of persistent anatomic shunts in the newborn circulatory system and a relatively high closing volume in the lungs. A newborn breathing room air has a normal arterial oxygen tension of 50 mm Hg. During the first 24 hours of life, the arterial oxygen tension increases dramatically with changes in the fetal circulation and the maturation of lung parenchyma; then, during the ensuing months and years, it continues to change slowly ( Table 1.1 ).

Newborn Heart and Cardiac Output

The heart of a healthy neonate is quite different from that of an adult. The thickness of the right ventricle exceeds that of the left, as seen by the normal right-axis deviation on the neonatal electrocardiogram. Shortly after birth, with closure of the fetal circulation, the left ventricle enlarges disproportionately. By the age of 6 months, the adult right/left ventricular size ratio is established. The newborn myocardium is also significantly different from that of the adult. Cardiac output is rate dependent in the neonatal heart, which has reduced compliance and contractility. The low compliance of the relaxed ventricle limits the size of the stroke volume; therefore increases in preload are not as important in neonatal physiology as the heart rate. Bradycardia invariably equates with reduced cardiac output because the infant heart cannot achieve the increased contractility needed to maintain cardiac output. It is extremely important to recognize this distinction during surgical and anesthetic procedures that may induce bradycardia. Autonomic innervation is also incomplete in the neonatal heart, with its relative lack of sympathetic elements; this relative underdevelopment may further compromise the ability of the less contractile neonatal myocardium to respond to stress.

Heart rate is crucially important in the very young. The normal range for the newborn is 100 to 170 beats/min and the rhythm is regular. As the child grows, the heart rate decreases ( Table 1.2 ). Sinus arrhythmia is common in children, but all other irregular rhythms should be considered abnormal. The average newborn systolic blood pressure is 60 mm Hg; the diastolic pressure is 35 mm Hg.

Blood Volume

Because the total blood volume of an infant is small, relatively minor surgical blood loss may be hemodynamically significant. It has been observed during exchange transfusions that withdrawal of blood parallels a decline in systolic blood pressure and cardiac output. Replacement of the same blood volume that was removed can reverse this decline to restore normal parameters. When the heart rate is normal, changes in arterial blood pressure are thus proportional to the degree of hypovolemia. A newborn’s ability to adapt the intravascular volume to the available blood volume is limited because of less efficient control of capacitance vessels and immature or ineffective baroreceptors.

Neonatal blood volume is approximately 80 mL/kg at term and is notably 20% higher in preterm infants. The hematocrit is 60%, and the hemoglobin content is 18 g/100 mL, although these values vary by infant and depend on when the umbilical cord is clamped. After remaining stable during the first week of life, the hemoglobin level declines, with the change occurring more rapidly in preterm infants. Approximately 70% to 90% of the hemoglobin in a full-term infant is of the fetal type. Fetal hemoglobin has a higher affinity for oxygen than that of an adult. It combines with oxygen more readily but also releases oxygen less efficiently at the tissue level compared with adult hemoglobin. The increase in hemoglobin content in neonates is required to overcome this higher affinity of fetal hemoglobin for oxygen. A concentration less than 12 g/100 mL constitutes anemia. Correction of anemia by blood transfusion is indicated if the infant requires oxygen or experiences apnea.

During the first weeks of life, the hematocrit drops as a result of early suppression of erythropoiesis; the fetal type of hemoglobin is replaced with the adult type of hemoglobin with more optimal oxygen-carrying capacity. This physiologic anemia reaches its nadir at 2 to 3 months, with a hemoglobin content of 9 to 11 g/100 mL. Provided that nutrition is adequate, the hemoglobin level will then gradually rise over several weeks to 12 to 13 g/100 mL, which is maintained throughout childhood.

Response to Hypoxia

Because neonates have a relatively high metabolic rate and low reserve for gas exchange, hypoxemia develops rapidly, first manifesting as bradycardia. During surgery, any unexplained episode of bradycardia should initially be treated with oxygen and increased ventilation. Pulmonary vasoconstriction and hypertension occur more dramatically in response to hypoxemia in the neonate than in the adult. With a patent foramen ovale and/or a persistent patent ductus arteriosus (PDA), the increase in pulmonary vascular resistance may favor a shift into fetal circulation with right-to-left shunting, which compounds the problem. Changes in cardiac output and systemic vascular resistance also differ in neonates compared with older children and adults. During hypoxemia in adults, the principal response is systemic vasodilation; this, together with an increase in cardiac output, helps to maintain oxygen transport to the tissues. Fetuses and some neonates respond to hypoxemia with systemic vasoconstriction. In the fetus, hypoxemia shifts blood to the placenta to improve gas exchange and oxygenation. After birth, however, hypoxemia may lead to decreased cardiac output, further limiting oxygen delivery and increasing cardiac work. In infants, early and pronounced bradycardia may result from myocardial hypoxia and acidosis. Neonates exposed to hypoxemia suffer pulmonary and systemic vasoconstriction, decreased cardiac output, and bradycardia. Rapid recognition and intervention are necessary to prevent cardiopulmonary collapse, cardiac arrest, and death.

Fluids and Fluid Management

As in adults, preoperative, intraoperative, and postoperative fluid management is extremely important in children; extreme vigilance, early recognition, and tight control are required. Some of the physiologic differences outlined earlier make fluid administration even more critical. Because of their small intravascular volume (70 to 80 mL/kg), infants who experience small changes in fluid balance can easily become either dehydrated or overloaded with fluid. The compartmentalization of total body water changes with age, but intracellular and extracellular electrolyte composition remains stable ( Table 1.3 ). Maintenance fluid requirements for a child can be calculated by relatively simple formulas that vary according to metabolic and physical activity. The calculation of water loss per calorie is described in Table 1.4 . The correspondence of necessary fluid intake proportional to weight is described in Table 1.5 . Complex fluid and electrolyte deficits are beyond the scope of this discussion. In most cases, consultation with pediatric medical specialists is advised.

Pain Management

The management of pain in infants and children has undergone tremendous advances in recent years. It had been commonly believed that because of their immature nervous systems, infants and newborns did not perceive pain and would not remember any pain that occurred. However, direct physiologic consequences have been observed in infants in response to pain. Changes in heart rate, blood pressure, and respiration rate have been documented in infants experiencing painful stimuli, and such changes can be physiologically and emotionally deleterious to the child.

The perception of pain depends on both sensory and emotional experiences that may be altered by various psychologic factors. These factors may be specific for each individual patient based on his or her expectations and past experiences. Efforts to reduce stress, anxiety, and fear will help to decrease the apprehension and perception of pain during procedures in the office or in the operating room. In patients of appropriate age, relaxation techniques, such as guided imagery, deep breathing, and hypnosis, may diminish the emotional component of pain. An adequate and age-appropriate explanation of expectations will also reduce anxiety, increase cooperation, and decrease perceived pain. The caregiver or parent should also be coached and prepared, because children often look to the psychological state of a parent for cues. An anxious parent often increases the anxiety of the child. Conversely, a calm and collected parent can help calm the child during uncomfortable procedures. The propagation of child life programs and patient-centered/family-centered care principles in pediatric institutions has transformed care in this regard.

Nonnarcotic analgesics are helpful for pain management. Acetaminophen in doses that range from 10 to 15 mg/kg every 4 hours is useful. Nonsteroidal antiinflammatory drugs such as ibuprofen are also excellent for pain management but may inhibit platelet function and should be used only at the discretion of the surgeon.

Narcotic analgesics are indicated for moderate to severe pain in all age groups. Optimal use requires consideration of the needs of the individual patient, and neonates require special observation during the administration of narcotics. Ventilation responses to hypoxia and hypercarbia are diminished in this age group. Narcotics may further decrease these responses to potentially life-threatening levels. The metabolism and half-lives of narcotics are different in neonates than those in older children and adults, and the permeability of the blood-brain barrier may also be increased in neonates. However, the use of intravenous, intramuscular, and oral narcotics is safe in the appropriately monitored setting and with proper dose. Unlike adults, who usually self-administer and therefore self-regulate narcotic analgesics, pediatric patients often rely on caregivers to administer pain medication, which can lead to under dosing or over dosing.

Sedation

More often today, professional certification and credentialing for pediatric sedation are required at institutions that care for children. The development of sedation teams, often staffed by pediatric anesthesiologists or critical care specialists, has increased safety and monitoring for these patients. Otolaryngologists can participate in the team effort by assessing the airway of the patient referred for sedation. Occasionally the best way to ensure the safety of a sedated patient is by general anesthesia with a secured airway. To achieve a successful outcome as measured by family satisfaction and patient safety, it is important to adhere to the guidelines of the institution and to work together as a team.

The Faces of Children

The development of the human face results from 500 million years of progressive evolution. In the embryo and fetus, the face takes shape in an impossibly rapid sequence, and any interference with this process can have catastrophic consequences. Thus an understanding of the structural and physiologic processes underlying normal development is required to evaluate and manage craniofacial anomalies. Parents and caregivers are greatly relieved on meeting a clinician who is familiar with the constellation of special clinical features associated with their child’s syndrome.

Rapid differential growth of the head and neck in four dimensions presents challenges for the pediatric otolaryngologist. The frontonasal prominence and the three paired structures—the lateral nasal and maxillary and mandibular prominences—all develop at differing rates according to a preprogrammed sequence, with rate changes affected by tissue interactions and environmental events. The timing of surgical intervention must consider the normal course of development in all affected systems to minimize the long-term functional and cosmetic sequelae, particularly for cleft lip and palate (Chapter 188) and congenital anomalies of the nose and nasopharynx (Chapter 190). For example, the solitary median maxillary central incisor syndrome ( Fig. 1.2A ) is associated with pyriform aperture stenosis (see Fig. 1.2B ), midnasal stenosis, choanal stenosis, holoprosencephaly, absence of the corpus callosum, diabetes insipidus, microcephaly, hypotelorism, cervical hemivertebrae, congenital heart disease, cervical dermoid, hypothyroidism, and intellectual delay.

Development of the face, head, and neck involves cellular differentiation, proliferation, and migration. The branchial arches and their associated vasculature, neural structures, and musculature develop quickly in the fetus but continue to change in the postnatal period until the individual reaches adulthood. Recognizing the two types of bone, endochondral (of cartilaginous origin) and mesenchymal (of membranous origin), provides insight into hereditary disorders. For example, achondroplasia is primarily a disease of endochondral bone; it results from mutations in the FGFR3 gene; and manifestations include disproportionate dwarfism, frontal bossing, flattened nasal bridge, and a small face.

In the postnatal individual, ongoing growth and development of the human head and neck is largely governed by the need to maintain an airway for respiration and an aerodigestive tract for nutrition. The development of other organ systems of eye, ear, nose, and mouth—which determine vision, hearing, balance, smell, and speech—is programmed by developmental control genes, peptide growth factors, and cytoskeletal elements that govern displacement and remodeling. The various growth centers within the quadrilateral cartilage of the nasal septum illustrate the importance of understanding how trauma or surgery can lead to differential growth of the nose, influence the surrounding bony structures, and subsequently functionally affect the rest of the facial skeleton. It is important to appreciate the role of the septodorsal cartilage and how simple fractures or incisions may affect cartilage growth and the normal development of the premaxillary-maxillary sutures. An age-specific anatomy of the nasal skeleton has been defined in children and adolescents, and peak growth velocity differs between boys and girls. Verwoerd and colleagues reflected on the importance of subcategorizing the pediatric age group to define optimal timing for surgical intervention and the appropriate surgical technique that will not affect long-term function detrimentally.