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

Background: Retrospective studies have suggested an association between sys temic hypotension and hypoxia and worsened outcome from traumatic brain inj ury. Little is known, however, about the frequency and duration of these po tentially preventable causes of secondary brain injury. Hypothesis: Early episodes of hypoxia and hypotension occurring during init ial resuscitation will have a significant impact on outcome following traum atic brain injury. Design: Prospective cohort study. Setting: Urban level I trauma center. Patients: Patients with a traumatic brain injury who had a Glasgow Coma Sco re of 12 or less within the first 24 hours of admission to the hospital and computed tomographic scan results demonstrating intracranial pathologic fe atures. Patients who died in the emergency department were excluded from th e study. Main Outcome Measures: Automated blood pressure and pulse oximetry readings were collected prospectively from the time of arrival through initial resu scitation. 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 Gla sgow Coma Score, 7). Overall mortality was 43%. Twenty-six patients (24%) h ad hypotension while in the emergency department, with an average of 1.5 ep isodes 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 epi sodes per patient (mean duration, 8.7 minutes). Of these 41 patients with h ypoxia, 18 (44%) died (P=.68). Conclusions: Hypotension, but not hypoxia, occurring in the initial phase o f resuscitation is significantly (P=.009) associated with increased mortali ty following brain injury, even when episodes are relatively short. These p rospective data reinforce the need for early continuous monitoring and impr oved treatment of hypotension in brain-injured patients.