Implications of systemic hypotension for the neurological examination in patients with severe head injury

Thirty-six patients admitted with severe head injury and various degrees of systemic hypotension were studied to determine the effect of hypotension on the validity of the neurological examination in reflecting mechanical brain compression. All patients had clinical signs of transtentorial herniation or upper brainstem compression and underwent immediate bilateral placement of exploratory burr holes for the diagnosis and removal of intracranial hematomas. All patients were initially hypotensive: 10 were in cardiac arrest, 7 had a systolic blood pressure (SBP) less than 60 torr, and 19 had SBP of 60-90 torr. The median score on the Glascow coma scale was 3 (range 3-8). Although 4 of the 10 cardiac arrest patients had anisocoria, only one (10%) had an intracranial hematoma. Among the seven patients with severe hypotension, only two had anisocoria and neither had and intracranial hematoma; one patient in this group (14%) had a hematoma that was diagnosed at autopsy. In contrast, intracranial hematomas were discovered by burr-hole placement and evacuated in 13 (68%) of 19 patients with initially moderate hypotension, including seven (78%) of nine patients with anisocoria. Anisocoria was associated with mechanical brain compression from an intracranial hematoma significantly more often in patients with an initial SBP of 60-90 torr than in those with initial cardiac arrest or SBP less than 60 torr (chi-square p less than 0.05). Intracranial hematomas were significantly more frequent among patients with SBP of 60-90 torr than among those with a lower SBP or initial cardiac arrest (P less than 0.01). Thirty-three of 36 patients died; each of the three survivors had an initial SBP of 60-90 torr, and hematomas were removed in two. In head-injured patients with SBP greater than 60 torr, clinical signs of tentorial herniation or upper brainstem dysfunction remain valid indicators of possible mechanical compression; the high percentage of patients with acute intracranial hematomas in this group warrants immediate diagnostic burr-hole exploration. In patients with severe initial hypotension (SBP less than 60 torr) or cardiac arrest, clinical findings of brainstem dysfunction cannot be relied upon to indicate mechanical compression, and computed tomography scanning should be done immediately after resuscitation to determine the need for surgical exploration.