title: Hypotension, hypoxia, and head injury: frequency, duration, and consequences.
abstract: 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.
  
  
  OBJECTIVE
  Early episodes of hypoxia and hypotension occurring during initial resuscitation will have a significant impact on outcome following traumatic brain injury.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Urban level I trauma center.
  
  
  METHODS
  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.
  
  
  METHODS
  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, < or =90 mm Hg) and hypoxic (oxygen saturation, < or =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 1 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.
authors.affiliation: Department of Surgery, San Francisco General Hospital, Ward 3A, 1001 Potrero Ave, San Francisco, CA 94110, USA.
authors.forename: G
authors.initials: G
authors.lastname: Manley
authors.forename: M M
authors.initials: MM
authors.lastname: Knudson
authors.forename: D
authors.initials: D
authors.lastname: Morabito
authors.forename: S
authors.initials: S
authors.lastname: Damron
authors.forename: V
authors.initials: V
authors.lastname: Erickson
authors.forename: L
authors.initials: L
authors.lastname: Pitts
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D006259:Craniocerebral Trauma / Q000150:complications* / Q000401:mortality / Q000628:therapy; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D007022:Hypotension / Q000209:etiology*; D000860:Hypoxia / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012151:Resuscitation; D012307:Risk Factors; D015996:Survival Rate; D016896:Treatment Outcome