INTRODUCTION — Children have unique anatomy and physiology compared with adults, which must be taken into consideration when managing pediatric trauma patients. This review will cover specific anatomical and physiologic differences between children and adults that affect medical care. The approach to the injured child is discussed separately. (See "Trauma management: Approach to the unstable child" and "Approach to the initially stable child with blunt or penetrating injury".)
PEDIATRIC ANATOMY
Airway — Several features of the airway in infants and children can make airway management challenging in patients with major trauma:
●Small oral cavities and relatively large tongues and tonsils predispose to airway obstruction, especially in semiconscious or comatose patients. (See "Emergency airway management in children: Unique pediatric considerations", section on 'Anatomic considerations'.)
●The relatively large occiput in the infant or child naturally flexes the neck in the supine position, causing airway obstruction as well as potentially exacerbating any unstable cervical spine injury. (See "Pediatric cervical spinal motion restriction", section on 'Neutral spine position'.)
●The larynx is more cephalad and anterior in the neck, making adequate visualization during endotracheal intubation more difficult. Other factors to consider include the short trachea and the U-shaped, floppy epiglottis in infants and young children. (See "Emergency airway management in children: Unique pediatric considerations", section on 'Anatomic considerations'.)
●A narrow tracheal diameter, a small distance between the tracheal rings, and a cricothyroid membrane that is not easily palpable combine to make needle cricothyroidotomy (to provide percutaneous transtracheal ventilation) a technically challenging option in infants and children. (See "The difficult pediatric airway" and "Needle cricothyroidotomy with percutaneous transtracheal ventilation".)
●With the short trachea (5 cm long in infants, 7 cm long in 18-month-old children), there is a higher risk for initial right mainstem bronchus intubation or subsequent accidental tube dislodgement with any motion of the head. (See "Emergency airway management in children: Unique pediatric considerations", section on 'Anatomic considerations'.)
Taken together, these factors make securing and maintaining the airway of pediatric trauma patients more difficult than in adults, especially in children <3 years of age.
Head — Infants and young children <8 years of age have heads that are disproportionately large relative to the rest of their body. As a result, head trauma is commonly present following blunt injury and is the leading cause of mortality in pediatric trauma. (See "Severe traumatic brain injury (TBI) in children: Initial evaluation and management".)
In addition, burns to the face and scalp in children potentially involve a larger proportion of body surface area (up to 19 percent in young infants) as compared to those in adults (up to 9 percent) (table 1). (See "Moderate and severe thermal burns in children: Emergency management", section on 'Evaluation of burn injury'.)
Brain — Infants have skulls with open sutures, and their brains have a larger subarachnoid space and increased extracellular space. As a result, they tend to tolerate an expanding intracranial hematoma better than older children or adults.
However, the infant brain is less myelinated and the cranium thinner and less protective; therefore, mild forces may still result in skull fractures and/or significant parenchymal injury. In addition, the possibility of abusive head injury in infants and young children must be considered and may present with abrupt altered mental status and severe traumatic head injury (TBI) on head computed tomography (CT) without a plausible mechanism. (See "Minor blunt head trauma in infants and young children (<2 years): Clinical features and evaluation" and "Child abuse: Epidemiology, mechanisms, and types of abusive head trauma in infants and children".)
Spinal cord/spine — Young children are at increased risk for spinal cord injury without radiographic abnormality (SCIWORA; spinal cord injury without plain radiographic or CT abnormality) because of anatomic flexibility that allows the cervical spine to stretch farther without injury than the spinal cord can tolerate. Many of these children will demonstrate abnormalities on magnetic resonance imaging. Despite this anatomic characteristic, SCIWORA occurs rarely in children. (See "Spinal cord injury without radiographic abnormality (SCIWORA) in children", section on 'Terminology' and "Spinal cord injury without radiographic abnormality (SCIWORA) in children", section on 'Epidemiology'.)
Chest — Children have a compliant chest wall, so rib fractures are less common, and pulmonary injury (eg, pulmonary contusion) often presents without bony disruption. In addition, because of their mobile mediastinal structures, children are more likely to develop tension pneumothoraces than adults. (See "Thoracic trauma in children: Initial stabilization and evaluation", section on 'Anatomy'.)
Abdomen — The liver and spleen in infants and toddlers are less protected by the rib cage and are more prone to direct injury. (See "Pediatric blunt abdominal trauma: Initial evaluation and stabilization".)
Musculoskeletal system — Children have immature bones, which have growth plates and are more pliable than in adults. These anatomic features predispose children to fractures of the physes (growth plates) (figure 1) and to greenstick (figure 2 and image 1) and buckle fractures (image 2). Blood loss associated with an isolated fracture, including femur fracture, is less than that of adults and by itself should not cause hemodynamic instability [1]. (See "General principles of fracture management: Fracture patterns and description in children".)
Vascular system — Vascular access for fluid resuscitation is often more difficult to achieve in children than in adults. (See "Vascular (venous) access for pediatric resuscitation and other pediatric emergencies".)
PEDIATRIC PHYSIOLOGY
Vital signs — Normal vital signs change with age in children (table 2). In general, heart and respiratory rates are higher than in adults and blood pressure is lower. The 5th percentile systolic blood pressure for age can be approximated by the following formula for children 1 to 10 years of age:
Systolic pressure (5th percentile) = 70 mmHg + 2 X (age in years)
Metabolism — Children are prone to hypothermia and insensible fluid losses because of their large body surface area to weight ratio and higher metabolic rate. Hypothermia can complicate an already critical situation as it may worsen metabolic acidosis and exert a negative inotropic effect on the heart. (See "Hypothermia in children: Clinical manifestations and diagnosis", section on 'Pediatric considerations'.)
Breathing and ventilation — Hypoxia is the most common cause of cardiac arrest in children. Adequate oxygenation is essential, as is adequate ventilation to maintain acid-base balance. Because of limited functional residual capacity and increased oxygen utilization relative to adults, infants and children become hypoxemic much more quickly when ventilation is inadequate. Infants and young children also have smaller tidal volumes (6 to 8 mL/kg), and are at greater risk for iatrogenic barotrauma with overly aggressive artificial ventilation. (See "Emergency airway management in children: Unique pediatric considerations", section on 'Physiologic considerations'.)
Shock — Tachycardia followed by poor skin perfusion are the initial signs of circulatory failure in children (table 3). Their increased physiologic reserve allows children to maintain their blood pressure despite a loss of 30 to 45 percent of total blood volume. Thus, hypotension with uncompensated shock is a late and sudden finding that requires an immediate response. (See "Initial evaluation of shock in children" and "Trauma management: Approach to the unstable child".)
In infants, uncompensated shock with hypotension in the early stages is accompanied by tachycardia, which may change to bradycardia if blood loss continues unchecked. (See "Pediatric advanced life support (PALS)", section on 'Shock'.)
SUMMARY
●Unique pediatric anatomy and physiology – Although the priorities and organization of trauma care for children are the same as for adults, unique pediatric anatomy and physiology create specific challenges in assessment and management. (See 'Pediatric anatomy' above and 'Pediatric physiology' above.)
●Airway – Securing and maintaining the airway of a pediatric trauma patient may be more difficult, especially in children <3 years of age. (See 'Airway' above.)
●Head and brain – Head trauma and brain injury commonly occur after blunt injury; child abuse is an important mechanism. (See 'Head' above and 'Brain' above.)
●Chest – Children are more prone to develop pulmonary contusion in the absence of rib fracture and tension pneumothorax. (See 'Chest' above.)
●Abdomen – The liver and spleen are more prone to direct injury. (See 'Abdomen' above.)
●Vascular system – Vascular access for fluid resuscitation is often more difficult to achieve. (See 'Vascular system' above.)
●Vital signs – Normal vital signs change with age in children (table 2). In general, heart and respiratory rates are higher than in adults and blood pressure is lower. The 5th percentile systolic blood pressure for age can be approximated by the following formula for children 1 to 10 years of age: Systolic pressure (5th percentile) = 70 mmHg + 2 X (age in years). (See 'Vital signs' above.)
●Breathing and ventilation – Infants and children become hypoxemic when ventilation is inadequate much more quickly than adults. Infants and young children also have smaller tidal volumes (6 to 8 mL/kg), and are at greater risk for iatrogenic barotrauma with overly aggressive artificial ventilation. (See 'Breathing and ventilation' above.)
●Metabolism – Children are prone to hypothermia and insensible fluid losses. (See 'Metabolism' above.)
●Signs of shock – Tachycardia and poor skin perfusion are the initial signs of circulatory failure in children, which should be recognized early and managed with fluid resuscitation and close monitoring (table 3). Children can maintain their blood pressure despite a loss of 30 to 45 percent of total blood volume. Thus, hypotension with uncompensated shock is a late and sudden finding that requires an immediate medical response. (See 'Shock' above.)
In infants, uncompensated shock with hypotension in the early stages is also accompanied by tachycardia, which may change to bradycardia if blood loss continues unchecked. (See 'Shock' above.)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Gary R Fleisher, MD, who contributed to earlier versions of this topic review.
