Patient Care

A Prehospital Digest for Physiological Pediatric Care

Issue 7 and Volume 41.

The smaller and incompletely developed organ systems found in infants and children, necessary to facilitate birth, can create diseases and medical conditions not found in adults, affect the child’s physiologic ability to respond to illness or injury, and influence pediatric therapeutic modalities. This can perplex medical caregivers not specialized in pediatrics and lead to missed diagnoses, inadequate medical treatment or marginalization of care. Rather than develop parallel systems for children and adults, appreciation of these anatomic and physiologic changes can help translate what is familiar-adult medical conditions, diagnostics and therapies-to the treatment of children.

Because young children are unable to verbalize specific complaints, information depends on the ability of the medic to interview parents or guardians and interpret the physical examination. Many of the early signs of illness or injury have the common response of elevated sympathetic tone: increased heart rate, elevated blood pressure and peripheral vasoconstriction, along with fear and anxiety. Within this are covert signs of illness and distress which, when missed, allow rapid deterioration. This leads many healthcare providers to believe the condition of children suddenly deteriorates when actually they missed the covert, compensated state of dysfunction.

Central Nervous System

The behaviors of an infant at birth are largely reflexive, with the infant gaining volitional control of these behaviors in the first year of life. This is first seen when the child smiles in response to others at 2 weeks of age; smiling also demonstrates adequate brain function, which in turn shows adequate tissue oxygen delivery.

The infant’s neurologic control and increased muscle strength will develop from the head toward the legs. Head-neck control occurs by 3 months, control of the shoulder girdle that allows the infant to roll from back to front occurs at 4 months of age, and control of the pelvic girdle that allows the infant to sit occurs at 6 months of age. The latter is an important milestone for evaluating submersion events in a bathtub. A child greater than 6 months of age should be able to sit up, indicating the submersion event might be intentional.

In infancy and early childhood, myelin will continue to form and connections between parts of the brain develop. Slower nerve conduction and incomplete connections within the brain alter seizure activity that occurs in the first year of life. Rather than tonic-clonic seizures, seizure activity is slower and rhythmic, including bicycling motions of the legs, swimming motions of the arms, and sucking or tongue thrusting behavior. The lack of developed myelin will slow nerve conduction and thought processes. This is seen in the delay of response by the child to a stimulus, such as loss of balance when reaching for a ball.

Adolescence also has important central nervous system (CNS) developmental milestones as the brain matures for the judgment necessary to achieve independence.1 In early adolescence (12 to 13 years), peer group influence increases over family influence as a youth separates from family. There’s also focus on “self” while the body begins physical and sexual maturation over a two-year period. In mid-adolescence (14 to 16 years), the peer group influence is strongest but concrete thinking and limited abstract thought can create dangers. In late adolescence (greater than 17 years), abstract thought and the future become more important. A middle adolescent asks, “What do you do as a paramedic?” A late adolescent asks, “How do you become a paramedic?” Safety is an issue as the adolescent becomes more independent without sufficient judgment, learns cause-and-effect, and experiments with control over events.

What EMS may encounter:

  • The varying levels of neurologic development in children may confound the EMS caregiver when assessing level of consciousness;
  • The presentation of seizures in children may differ based on age; and
  • Adolescents may engage in adult activities, but still need support and the feeling of security from EMS.

Airway & Respiratory

Significant differences between pediatric and adult respiratory systems occur in the central nervous system receptor and effector mechanisms for the respiratory drive; chest wall stability and respiratory muscle strength; and conducting airways in the alveolar-capillary complex.

Neonates and infants may respond to hypoxemia (the relative concentration of oxygen in the blood) with a brief phase of rapid deep breathing (hyperpnea) followed by shallow breathing and hypoventilation. This occurs even though the child has apparently normal central and peripheral chemoreceptors for oxygen and CO2. The infant and child’s response to hypoxemia is bradycardia of rapid onset, compared to the adult response of increase heart rate. In fact, any precipitous drop in heart rate must be considered loss of airway until proven otherwise.

Because oxygen consumption in infants is 2-3 times that of an adult, residual oxygen reserves in the lungs are rapidly depleted if oxygen availability is compromised. Cyanosis, the absolute measure of de-
oxygenated hemoglobin, is a poor indicator of hypoxemia in infants and children because they have less hemoglobin than adults. Cyanosis in children occurs at a lower level of oxygen saturation than in the adult and may not be reached until after cardiac arrest from hypoxemia.

The chest wall in infants and young children is more cartilaginous and therefore more compliant, which allows inward retraction of the chest with increased work of breathing, reducing the ability to increase tidal volume.

The ribs in children under four years of age insert on a more horizontal plane, giving a “box-like” chest that also decreases the ability to increase tidal volume. The compliant chest wall, necessary for birth, is a hindrance to compensating for respiratory disease. However, the compliant mediastinum in infants doesn’t protect against pneumothorax-tension pneumothorax will rapidly develop in infants.

The narrow chest in infants may interfere with the subclavian approach for thoracentesis. This places the needle close to mediastinal structures such as large blood vessels (particularly the pulmonary artery), so providers should consider using the anterior axillary line.

The muscular insertion of the diaphragm on the thorax is also on a more horizontal plane in the infant, similar to the adult with obstructive lung disease with a flattened diaphragm.

To compensate for the inability to increase tidal volume, the child is rate-dependent to maintain minute ventilation. To accommodate this, the diaphragm and intercostal muscles have fast-twitch fibers allowing high respiratory rates, but they’re not fatigue-resistant.2

An increasing respiratory rate in a distressed child may indicate the ability to compensate, while a decreasing rate, even to normal values, may indicate decompensation. These higher rates, when used to compensate for metabolic acidosis, might mislead caregivers to treat for respiratory disease when there’s a non-pulmonary cause of the tachypnea.

Tidal volume remains fairly constant through childhood (6-7 mL/kg body weight), but the fact that this small volume also must be available quickly indicates a need for high intrinsic or externally supplied flow rates. The smaller conducting airways may produce resistance if further narrowed by inflammation, secretions, edema or bronchospasm.

Such high resistance may induce dynamic closure of the airway, trapping air in the distal lung to produce dynamic hyperinflation. Closing capacity in infants is within the functional residual capacity; the effect is to rapidly cause hypoxemia during apnea or during pauses in mask ventilation.

These factors combine to produce less respiratory reserve in the pediatric patient. Therefore, the etiology of cardiopulmonary arrest in pediatric patients is most commonly a primary respiratory disorder. Airway obstruction, aspiration and apnea are also among the major hazards to respiratory function. Infants and small children are more susceptible to airway blockage from secretions, bronchospasm and edema.3 Assuring a patent airway is the important first step in care of the child’s respiratory compromise.

The pharynx changes significantly during growth with descent of the epiglottis in the larynx and movement of the tongue posteriorly, changing the pharynx from a funnel shape to a cylinder.

The epiglottis allows air to pass from nose to trachea by touching the soft palate during swallow. It has an additional function of allowing food to pass on either side of interlocked larynx and nasopharynx into the esophagus without entering the upper tracheal airway.4,5

This function allows the infant to breathe while feeding and to feed while supine. After six months of age the larynx and epiglottis descend to form a system for speech, but now exposes the child, to blockage of the upper airway by food bolus.6

Stress and crying increase flow velocity and airway resistance when the increased flow velocity. Swallowed air from crying, stress or pain may lead to a distended stomach and diaphragm, compromising tidal volume to cause respiratory failure. This can be relieved with a nasogastric tube.

Increased work of breathing can be evaluated by following retractions moving superiorly on the chest and positive response to therapy when the retractions move inferiorly down the chest. Rapid onset of bradycardia indicates loss of airway and requires immediate attention.

When managing the pediatric airway, laxity of the jaw and submental region allows airway obstruction during bag-valve mask (BVM) ventilation when pushing the mask against the face or gripping beneath the chin for a better seal.7 Excessive positive pressure created during BVM ventilation can also quickly cause gastric distention, and the nasogastric tube may be needed.

When intubating, keep in mind that the vocal cords aren’t as anterior as thought, but likely move from the laryngoscope blade when the elbow is fixed to a surface and the wrist rotates, moving the vocal cords to an anterior position. The epiglottis often obscures the glottic opening because of its angle attachment to the larynx; in infants the glottic opening and the carina are four centimeters apart. The short length of trachea requires special care in placement of the endotracheal tube.

What EMS may encounter for airway:

  • Children may initially have an adequate airway that can deteriorate rapidly;8
  • Infants explore the world and evaluate objects in their mouth, sudden onset of coughing, especially unilateral, may indicate an aspirated foreign body; and
  • The funnel-shaped pharynx may trap incompletely chewed food, becoming a bolus to occlude the airway, the funnel shape interferes with effectiveness of the Heimlich Maneuver to expel a food bolus, but not hard objects such as hard candy.
  • Less than 2 years of age, a cough may indicate pneumonia; and
  • Under 1 year of age grunting may be interpreted as cough but is a response to the lower residual capacity of an infant’s lung below the closing volume, hypoxemia rapidly develops; grunting produces positive airway pressure to increase oxidation.

What EMS may encounter for respiratory:

  • Tachypnea as a medical condition must be evaluated, refraining from premature diagnosis of various respiratory diseases while being vigilant for nonpulmonary cause of tachypnea;
  • Bronchiolitis obstructs small airways leading to tachypnea;
  • When respiratory syncitial virus is the cause, tachypnea may suddenly stop with apnea that responds to stimulation;9,10 and
  • Alternating use of the abdomen and chest indicates diaphragm fatigue.

Cardiovascular

Though the circulating blood volume is higher per kilogram in children than adults, the absolute volume remains low because of the small body size. Therefore, small amounts of blood loss are not tolerated well by children.

Cardiac output in children is largely dependent on the rapid heart rate because the small heart size and fewer contractile elements in the myocardium limit the ability of stroke volume to increase. Although tachycardia is a normal response to any stress, it’s also an early herald of shock. Bradycardia may limit systemic perfusion greatly and is often an ominous sign of significant hypoxemia or acidosis.

Other arrhythmias usually don’t produce significant changes in cardiac output except for sustained supraventricular tachycardia (SVT). Ventricular arrhythmias are uncommon but, when present, may signify congenital heart disease, myocarditis, cardiomyopathy or asphyxia.

In adults, the left ventricle is most affected by ischemic disease, generally failing first in heart failure to cause pulmonary edema. Pulmonary edema is rare in children In children the right ventricle, because of its crescent shape, will fail first to cause liver engorgement-an early sign of heart failure in children. This can be evaluated by palpating the abdomen just below the right costal margin. During fluid resuscitation (initiated with 20 mL/kg isotonic fluid) the liver can act as an endpoint.

Children also have a strong vasomotor tone; in small infants this can give mottling or white skin in shock even though palpable pulses are present. Most significant, however, is a limb temperature margin that occurs from vasoconstriction. Running the back of your hand down child’s leg will reveal a demarcation of temperature from warm to cold within 1 inch or 2 cm.

Shock in children is most easily identified by elevated heart rate and altered consciousness or alertness. It’s not uncommon to see heart rates in excess of 200 bpm, which can be differentiated from SVT by the variability of heart rate. A reset pacemaker keeps the rate at a fairly constant number while shock is a response to adrenaline and the rate has greater variability.

What EMS may encounter:

  • Tachycardia is an early sign of shock, whether from low blood volume, anaphylaxis or sepsis, and is more reliable than blood pressure changes;
  • SVT is generally associated with a consistently elevated heart rate with the recent history of being awake and alert. Any change in level of awareness may indicate decompensation, and a steady, consistent rhythm from a reset pacemaker is more indicative of SVT;
  • A varying rhythm from adrenaline is more indicative of shock or other increased sympathetic tone;
  • Bradycardia is an ominous warning of severe hypoxemia; and
  • Supranormal heart rates, though likely cardiovascular in origin, can still be the consequence of pain, agitation or fear.

Trauma

The pediatric patient generally has more compliant structures that can decrease the severity of injury, as in fractures and chest trauma, but can also increase the severity of injury, as in abdominal injuries.11 Because children aren’t specific in their complaints, injuries can be difficult to identify.

Lack of communication skills from the child and blunt solid organ injury requires greater suspicion of hidden injuries upon assessment.

Because contractility is relatively fixed, cardiac output is determined by heartbeat and preload in children. Whereas adults manifest hypotension with 15-20% blood volume loss, children can maintain compensated blood pressure with up to 40% blood loss.12 Smaller airway diameter and lung volume, along with diminished functional residual capacity and higher oxygen consumption, make the pediatric patient more prone to rapid development of hypoxemia.

The limited respiratory reserve requires greater vigilance toward the possibility of early respiratory failure and the need for pre-oxygenation in consideration of early endotracheal intubation. Adult values are reached at about 8 to 10 years of age.

In chest trauma, pliable bones cause the chest to absorb most of the energy. Penetrating chest injury happens less often, mostly from gunshot wounds, and has a higher mortality. Because of the energy required for severe chest injury, children with thoracic injury are more likely to have injuries to other systems. The more compliant chest wall absorbs and distributes forces, producing fewer rib fractures.

The mediastinum is more compliant and freely mobile, easily displaced into the unaffected lung from contralateral pneumo- or hemothorax. This possibility decreases as the child ages and tracheal shifting with tension pneumothorax becomes less likely.

Commotio cordis, a combination of v fib and sudden cardiac arrest from a sudden impact to the anterior chest wall, is almost solely a pediatric injury occurring into adolescence.13

The unique patterns of injury in children with blunt abdominal trauma occur because of decreased protective subcutaneous fat and abdominal musculature and larger relative size of the spleen and liver. The spleen and liver have greater susceptibility to injury from minor blows, such as handlebars from bicycles.14 An enlarged spleen from unrecognized mononucleosis may rupture from blunt abdominal trauma in a healthy athlete. Duodenal wall hematoma, another uniquely pediatric injury, occurs when the duodenum is compressed against the vertebral column.

What EMS may encounter:

  • Blood loss may remain covert and compensated until it reaches 40% of blood volume;
  • Serious injury can occur from apparently benign forces such as a baseball or soccer ball hit to the chest or bicycle handlebars hitting the abdomen; and
  • Pneumothorax can rapidly come under tension because of the compliant and freely mobile mediastinum.

Immune System

In the first two years of life, children in a normal state of health may have a functionally compromised immune system due to the immature and unchallenged (i.e., lack of pathogen exposure) immune system of infants which has similar properties of immunocompromise found in patients with immune defects. Children’s immune system protection won’t reach adult levels until 4-7 years of age.

Children can’t filter bacteria, particularly encapsulated bacteria, from the blood, until 2 years of age when the splenic architecture matures. Bacteria in the blood can then settle in various regions such as meninges of the brain, inner ear or lung. For this reason bacteria that may be less of a threat to adults can cause serious infection in children. By about 3 years of age the child is able to clear from the blood encapsulated bacteria such as Haemophilus influenza, Neisseria meningitidis and Streptococcus pneumoniae.

The lack of a fully developed immune system affects assessment and treatment of fever. A fever > 104 degrees F in children under age 3 may reflect occult bacteremia, particularly in infants < 2 months who may need emergency antibiotics. Fever evaluation includes response to antipyretics if administered by parents prior to arrival and should include a description of the child’s irritability, consolability, and whether the child looks at the examiner or parents. An inability to console a child at normal body temperature suggests serious infection or injury. The temperature measured by EMS providers carries less information than the level of arousal and responsiveness or the heart rate and response to a fluid bolus.

Infants may exhibit signs of hypovolemia because of increased metabolic demands for water with decreased appetite and thirst. Therefore, it’s important to ask parents if the infant takes each feeding and completed the feeding. Medical evaluation and response to fluid bolus are necessary to distinguish between straightforward hypovolemia or infection that could develop into sepsis, or a combination of both these two forms of shock. (See Table 1.) Much of the distinction between the two lies in the body’s effort to retain fluid and core circulation in hypovolemia and the metabolic demands of all tissue for blood causing peripheral vasodilation in sepsis.

EMS prehospital pediatric care

What EMS may encounter:

  • Children, particularly infants, that are later in the course of their infection than adults who rapidly develop into a medical emergency with systemic inflammatory response syndrome (SIRS);
  • Children under 2 years of age in early stages of serious bacterial illness, pneumonia or meningitis;
  • Fever in an infant or child immunocompromised by chemotherapy, splenectomy, or sickle cell disease (i.e., functional splenectomy when repeated sickle crises damage the spleen);
  • An infant with tachycardia and temperature instability, including hypothermia, suggesting covert serious bacterial disease;
  • Infants and children with an acute loss of spontaneous activity and responsiveness or irritability without consolability suggesting infection or physical trauma; and
  • Infants with fever who exhibit signs of moderate to severe hypovolemia because of poor oral intake (not taking or not completing feedings).

Thermoregulation & Metabolism

Our bodies make heat by our body mass and we lose or gain heat through our skin. Adults create more heat than can readily dissipate through skin. Infants, on the other hand, have a difficult time creating sufficient heat to make up for the loss through skin. The environmental temperature where energy isn’t used to increase or decrease body temperature (i.e., the thermoneutral zone) differs significantly between fadults and infants. It’s about 90 degrees F in naked newborns and 80 degrees F in naked adults. An infant can readily lose heat in an air conditioned room.

The stored heat (i.e., heat capacity) is the same for infants and adults: 830 cal/kg degrees C. This means it takes 830 calories to change one kilogram of body weight one centigrade degree. Evaporation is the only method to lower temperature below ambient temperature. Using heat content and heat of vaporization (580 calories of heat per mL H2O at body temperature), we calculate that 5 mL of water evaporated from a newborn infant can lower the body temperature 1 degree C without continuing heat production. This is significant for newborn babies because evaporative water loss as the amniotic fluid dries, or if the neonate is exposed to drafts or light wind, produces life-threatening hypothermia.

This heat capacity is responsible for the difficulty in rewarming a cold infant. Infants must be dried (evaporative heat loss), protected from drafts or winds (convective heat loss), kept on soft surfaces (conductive heat loss), and covered (radiant heat loss). Placing warmed IV bags against the skin will burn because tissue doesn’t conduct heat well, a result of this heat capacity. You see this with cooked meat over a fire-the outside can be blackened while remaining cool, if not cold, internally.

Panting is an effective cooling method used by many animals.15 During respiratory or cardiorespiratory arrest, evaporative heat loss from hand ventilation in infants may contribute to the development of hypothermia by the same mechanism as panting. Rewarming is efficient through warmed ventilator gas, which can’t be accomplished with hand ventilation.

Because infants don’t shiver, we lose an early sign of hypothermia. Instead, infants use non-shivering thermogenesis, the metabolism of brown adipose tissue (BAT), for heat production. BAT produces fewer energy molecules (ATP) than white fat, and it’s this inefficiency that allows the infant to convert fat to heat.

Shivering, as a strategy to create heat, is not available for infants possibly because the immature neuromuscular system doesn’t allow the rapid transmission of nerve signals. It begins to appear about 2 years of age, becoming developed by about 6 years of age.16 Other strategies not available to infants for warming or avoiding cold are mobility and verbalization, making hypothermia a covert cause of cardiac arrest and death. However, make sure to differentiate causes of bradycardia between hypothermia, hypoxemia, vagal stimulation, hypothermia due to sepsis, and chronic encephalopathy. (See Table 2, below.)

EMS prehospital pediatric care

Insensible water loss is higher in children than adults because of the larger surface area to body mass ratio. This higher evaporative loss, combined with a higher metabolic rate, emphasizes that dehydration may occur quickly. Therefore, children require a greater amount of fluid per kilogram than adults do, but this is still a low absolute amount because of the child’s small size.

Low glycogen stores and increased metabolic rate make hypoglycemia more common in infants during stress. It’s important for EMS providers to check blood sugar early and evaluate for dehydration separately from other medical conditions.

What EMS may encounter:

  • Evaporative water loss and hypothermia due to amniotic fluid on a newborn infant, submersion accidents, rain or snow;
  • Decreased ambient temperatures below the thermoneutral zone for infants, due to factors such as air conditioned rooms, exposure of an infant for evaluation and resuscitation, drafts, light and strong winds, and helicopter rotor wash; and
  • Resuscitation-induced hypothermia, which can mimic cardiac arrest. (See Table 3, below.)
EMS prehospital pediatric care

References

1. van Stralen D, Perkin RM. Adolescence 101: An EMS primer on teenage development and behavior. JEMS. 1999;24(3):58-64.

2. Keens TG, Ianuzzo CD. Development of fatigue-resistant muscle fibers in human ventilatory muscles. Am Rev Respir Dis. 1979;119(2 Pt 2):139-141.

3. Koninckx M, Buysse C, de Hoog M. Management of status asthmaticus in children. Paediatr Respir Rev. 2013;14(2):78-85.

4. Laitman JT, Crelin ES, Conlogue GJ. The function of the epiglottis in monkey and man. Yale J Biol Med. 1977;50(1):43-48.

5. Sasaki CT, Levine PA, Laitman MP, et al. Postnatal descent of the epiglottis in man: A preliminary report. Arch Otolaryngol. 1977;103(3):169-171.

6. Nishimura T, Mikami A, Suzuki J, et al. Descent of the larynx in chimpanzee infants. Proc Natl Acad Sci U S A. 2003;100(12):6930-6933.

7. Perkin RM, van Stralen D. Pediatric passages: 10 pitfalls to avoid in pediatric airway management. JEMS. 2000;25(3):50-64.

8. Pfleger A, Eber E. Management of acute severe upper airway obstruction in children. Paediatr Respir Rev. 2013;14(2):70-77.

9. Church NR, Anas NG, Hall CB, et al. Respiratory syncytial virus-related apnea in infants. Am J Dis Child. 1984;138(3):247-250.

10. van Stralen D, Perkin RM. RSV not the common cold. Signs and symptoms of respiratory syncytial virus. JEMS. 2000;25(2):72-79.

11. Kenefaje ME, Swarm M, Walthall J. Nuances in pediatric trauma. Emerg Med Clin North Am. 2013;31(3):627-652.

12. Bliss D, Silen M. Pediatric thoracic trauma. Crit Care Med. 2002;30(11 Suppl):S409-415.

13. Maron BJ, Estes NA 3rd. Commotio cordis. N Engl J Med. 2010;362(10):917-927.

14. Klimek PM, Lutz T, Stranzinger E, et al. Handlebar injuries in children. Pediatr Surg Int. 2013;29(3):269-273.

15. Hales JR, Webster ME. Respiratory function during thermal tachypnea in sheep. J Physiol. 1967;190(2):241-260.

16. Lyons A, Taylor A, Power C, et al. Postanaesthetic shivering in children. Anaesthesia. 1996;51(5):442-445.


Key Points: Pediatric vs. adult patient considerations

  • Irritability is an early sign of mental status changes in the young child;
  • Early signs of respiratory distress include tachypnea, grunting and nasal flaring;
  • The perfusion status in children is best assessed initially by the heart rate, capillary refill and extremity temperature (limb-temperature margin)-hypotension is a late finding;
  • Assuring a patent airway is the most important first step in the child with respiratory compromise;
  • There are important anatomic differences between the airway of a child and an adult that must be considered when intubating;
  • Hypoglycemia is common in infants during stress and must be corrected promptly;
  • Infants don’t maintain body heat well and care must be taken to avoid hypothermia;
  • Young infants are at increased risk of infection because of an immature immune system.
  • High fever in infants may be a medical emergency;
  • Children don’t tolerate small amounts of blood loss because of low absolute blood volume; and
  • The chest absorbs most of the energy in trauma due the pliability of the bones.