Pediatrics 1: Physiologic and Anatomic Considerations Portal
PEDS: Because this entire portal pertains only to pediatric patients, the convention of underlining has been omitted.
Considerations for Infants and Small Children
Pediatric considerations are difficult because of the varying physical sizes of children. Adolescents may be as large as adults. Certain aspects (such as measurements and equipment) may be the same as adults, while other dimensions (such as psychology, continued growth, drug concerns, and cultural/legal issues) are more similar to children. The team must use good judgment.
The ABCs are still the most important aspect of any resuscitation, but special aspects of the physiology and anatomy of children need to be recognized. This is not intended to alarm the emergency care team but rather to assuage the natural tendency to be anxious about the responsibility of resuscitating small children. Do not withhold aggressive resuscitation because of fear of the unknown.
Children are not small adults.
The child’s caregiver adds another complex dimension to resuscitation of children. Patients are often scared and incapable of (much) interaction or cooperation. Assume that anxiety will complicate the evaluation. Deal with anxiety proactively and appropriately. Explanations and honest reassurance help to relieve anxiety and to gain the support of the caregiver.
The decision for family and/or caregivers to be present during resuscitation efforts is a delicate one, considering both the emotional needs of the family and the healthcare providers’ need to focus on the patient. Most families want to be in the room during resuscitation efforts. But their presence may also transform a focused, technical environment into a highly emotional one. Remember, the health care providers’ first responsibility is to the patient. Many elements need to be in place in order that family presence during resuscitation does not jeopardize patient care. These include: Available staff to stay with family to explain and continually assess the family members’ ability to withstand the situational trauma, a controlled environment relatively free of chaos, continued assessment of the appropriateness of family members’ presence, and a willingness to remove family members should the situation require.
Another serious impediment to effective and expedient resuscitation of small children is the need for specific information about drug dosage and equipment sizes. Keep manuals and tables that provide rapid answers to such questions available. The Broselow Pediatric Emergency Tape is a handy reference in the emergency facility. (Vol I—ACUTE CARE PORTALS Pediatric Equipment Sizes)
Pediatric variations include:
An infant is unable to maintain body temperature without support because of a large surface area (relative to body mass) and also because the autonomic nervous system is immature at birth. An infant is unable to shiver. An infant is unable to shunt blood away from the skin when he or she is cold. Keep infant dry and warm.
Infants < 6 months of age are nose breathers. Secretions and foreign bodies easily obstruct their small upper airways. The larynx and trachea are also small and easily occluded. While asleep or unconscious, make sure infant’s airway is open.
The cartilages of an infant’s larynx and trachea are soft and easily compressed by hyperextension and hyperflexion of the neck, resulting in airway obstruction.
An infant’s trachea is surprisingly short. The length of the trachea is not proportional to that of an adult. Remember size so as not to intubate the right main stem bronchus.
The cricoid cartilage forms the narrowest part of the airway in infants and small children. An ET tube that can be inserted past the vocal cords might still be too large to get past the cricoid cartilage. The cricoid cartilage forms an effective seal around the ET tube in children < about 6 to 8 years of age. However, cuffed tubes are now preferred because they prevent air leaks, making ventilation easier.
An infant’s upper airway is very reactive, at times making ET intubation difficult. Stimulation of the hypopharynx may cause a vigorous gagging motion and laryngeal spasm. Because infants are sensitive to vagal stimulation atropine is used in RSI. (See #19.)
The intercostal muscles are poorly developed in infancy, the result being that an infant relies heavily on diaphragmatic movement to breathe. For this reason, gastric and abdominal distension in infants can severely interfere with respirations. Another effect is the inability of infants to sustain increased effort when the work of breathing (WOB) is increased for any reason. When bagging an infant, perform Sellick’s maneuver to prevent air from blowing up the infant’s stomach. Insert a nasogastric tube as soon as possible after intubation.
The sternum and ribs of a small child are soft and compliant. They are not easily broken, but the viscera of the chest are at risk for compression injury, even without rib fractures. The compliant chest wall also retracts easily when there is airway obstruction. In small children with upper and lower airway obstruction, rib and supraclavicular retractions are early signs. This apparent increase in the WOB is useful for indicating distress.
In children < 1 year of age, barotrauma is easily produced in the lungs by positive pressure ventilation (PPV). Tidal volume is small, and the respiratory rate is fast, the result being that well-meaning team members may easily hyperinflate the lungs using mechanical devices or mouth-to-mouth breathing, which results in pneumothorax.
Pneumothorax in infants is especially likely to result in tension pneumothorax because the mediastinum may shift easily with resulting decreased filling of the heart and compression of the opposite lung.
The cardiac chambers of infants and small children are small. The myocardium itself is relatively stiff. There is little room for stroke volume reserve. Small children respond to a need for increased cardiac output by beating their hearts faster. With bradycardia or a heart rate > about 200 bpm, cardiac output falls dramatically.
Daily water exchange is great. Dehydration occurs quickly and to a high degree with increased fluid loss or decreased fluid intake.
The blood volume of young children is small in absolute terms, but their cardiac output is high relative to adults. This results in a small circulating blood volume reserve. On the other hand, small children have a highly reactive vascular tree that can mask relatively large volume losses. When small children finally decompensate, they are in mortal danger.
In small children, urine output alone might not be a sensitive indicator of the adequacy of perfusion because renal immaturity may prevent the renal shutdown commonly seen in adults. When renal shutdown does appear, it is a late finding.
CNS and autonomic nervous system immaturity may mask seizure activity in infants and small children. Any repetitive muscle motion, including eye and diaphragmatic motion, may represent seizure activity.
BP, pulse, and respiratory rate vary substantially from that seen in adults. Infants have a systolic BP of 70 to 80 torr, a pulse rate of up to 160 bpm, and a respiratory rate of 25 to 50/min.
Toddlers have a systolic BP or 80 to 90 torr, a pulse rate of up to 140 bpm, and a respiratory rate of 20 to 35.
Older, pre-pubertal children have a systolic BP of 85 to 95 torr, a pulse rate of 60 to 100, and a respiratory rate of 18 to 30.
To estimate normal systolic BP, a good rule of thumb is to multiply the child’s age in years by 2 and add 70.
To estimate body weight: In children > 1 year, multiply the child’s age in years by 2 and add 10 to equal weight in kg. In children < 1 year, multiply the child’s age in months by 0.5 and add 3.5 to equal weight in kg. (This does not work for overweight children.)
The anterior fontanelle closes at about 18 months of age. Until then, it provides a means of assessment for ICP. Palpation of the open fontanelle can detect both dehydration (indicated by depression of the fontanelle) or increased ICP (indicated by bulging), as in meningitis or cerebral edema.
Vasovagal reflexes are prominent in small children. Intubation, pharyngeal stimulation, and medications (such as succinylcholine and ketamine) may cause marked bradycardia. Prior to these measures (and whenever feasible), use atropine at 0.02 mg/kg with a minimum dose of 0.1 mg and a maximum single dose of 0.5 mg.
In almost every emergency situation, consider the possibility of child abuse. Examination of the retina may reveal hemorrhage resulting from the child being shaken. Clues include unusual bruising, unexplained fractures, burns, and an unusual reaction to strangers and caregivers.
Remember, all that wheezes is not asthma. Also consider foreign bodies, bronchiolitis, pneumonia, other causes of thick secretions, and acute respiratory distress syndrome (ARDS).
Rapid sequence intubation (RSI) requires IV access and is therefore dependent on the cooperation of the patient. Repeated IV attempts may upset a child with a compromised upper airway and cause consequential struggling, secretions, and anxiety as well as a decreased probability of securing the airway. An alternative to proceeding directly to IV access is to sedate children by using the following regimen: ketamine 3 to 4 mg/kg IM, atropine 0.02 mg/kg (0.1 mg minimum) IM, with or without midazolam 0.1 mg/kg IM. Then, pursue IV or IO access and further paralysis as needed. Do not sedate the respiratory patient unless you plan to secure the airway. Sedation allows definitive airway control.