Hypotension, hypoxia, and head injury - Frequency, duration, and consequences

Background: Retrospective studies have suggested an association between systemic hypotension and hypoxia and worsened outcome from traumatic brain injury. Little is known, however, about the frequency and duration of these potentially preventable causes of secondary brain injury. Hypothesis: Early episodes of hypoxia and hypotension occurring during initial resuscitation will have a significant impact on outcome following traumatic brain injury. Design: Prospective cohort study. Setting: Urban level I trauma center. Patients: Patients with a traumatic brain injury who had a Glasgow Coma Score of 12 or less within the first 24 hours of admission to the hospital and computed tomographic scan results demonstrating intracranial pathologic features. Patients who died in the emergency department were excluded from the study. Main Outcome Measures: Automated blood pressure and pulse oximetry readings were collected prospectively from the time of arrival through initial resuscitation. The number and duration of hypotensive (systolic blood pressure, less than or equal to 90 mm Hg) and hypoxic (oxygen saturation, less than or equal to 92%) events were analyzed for their association with mortality and neurological outcome. Results: One hundred seven patients met the enrollment criteria (median Glasgow Coma Score, 7). Overall mortality was 43%. Twenty-six patients (24%) had hypotension while in the emergency department, with an average of 1.5 episodes per patient (mean duration, 9.1 minutes). Of these 26 patients with hypotension, 17 (65%) died (P=.01). When the number of hypotensive episodes increased from I to 2 or more, the odds ratio for death increased from 2. 1 to 8. 1. Forty-one patients (38%) had hypoxia, with an average of 2.1 episodes per patient (mean duration, 8.7 minutes). Of these 41 patients with hypoxia, 18 (44%) died (P=.68). Conclusions: Hypotension, but not hypoxia, occurring in the initial phase of resuscitation is significantly (P=.009) associated with increased mortality following brain injury, even when episodes are relatively short. These prospective data reinforce the need for early continuous monitoring and improved treatment of hypotension in brain-injured patients.