Hypotension in injured children is generally regarded as indicating hypovolemia from significant blood loss despite the effective compensatory mechanisms that make hypotension a late sign of shock in young patients. Partrick and colleagues observed that many children who were treated at a large urban trauma center had documented hypotension without blood loss. They studied all patients aged 18 years or younger treated at a regional pediatric trauma center for blunt injury to determine causes of hypotension, and to establish the role of hemorrhage.

Hypotension was defined by systolic blood pressure (SBP) related to age as in advanced trauma life support guidelines (SBP less than 80 mm Hg up to one year of age, less than 90 mm Hg for ages one to five years, less than 100 mm Hg for ages six to 12 years, and less than 110 mm Hg for ages 12 to 18 years). Hypotension had to be documented by at least two readings for inclusion in the study. Comprehensive data on each of the 194 cases were abstracted from trauma and hospital records. The average age was 7.5 years (age range: eight days to 18 years), the mean injury severity score was 15.4, and the Glasgow Coma Scale (GCS) score was 11.9. Fifty-nine percent of the patients were boys. Falls were the most common cause of injury (25 percent), followed by motor vehicle accidents (22 percent), sports (14 percent), and nonaccidental trauma (10 percent). Ten percent of the children died, and autopsy was performed in all cases. Injuries that could account for significant volume loss were identified in 82 (42 percent) of the hypotensive children. An equal number had isolated closed head injury.

When analyzed by age group, preschool children were more severely injured and had significantly higher mortality than older children. More than 60 percent of preschool children with hypotension following injury had isolated closed head injury with no other identified hemorrhage (see accompanying table). Head injury also was implicated in more than 30 percent of older children with hypotension. Children with head injury had lower GCS scores than other injured children.

The authors conclude that hypotension in injured children is associated with hemorrhage in fewer than one half of cases. Conversely, hypotension may indicate significant head injury, especially in the preschool age group and in children with low GCS scores. Because 25 percent or more of the circulating blood volume has to be lost before signs of shock become evident in children, hypotension and tachycardia are late and ominous signs in hemorrhage. In head trauma, hypotension may be a relatively early sign. The authors recommend that the assessment of hypotensive children following blunt trauma include computed tomography of the head, probably following an initial abdominal ultrasound examination to screen for intra-abdominal blood loss.