Clinical question / background:
- The goals of this study were to determine the incidence and duration of hypotension (SBP <90) and hypoxia (SpO2<92%) in the prehospital setting in patients with potentially survivable brain injuries, and to prospectively examine the association of these secondary insults with mortality and disability.
Definitions:
- Hypotension: SBP< 90mmHg
- Hypoxia: SpO2 < 92%
- Disability rating scale: 0-30 scale with >20 very severe.
- Abbreviated injury scale: score of 0-6 for scale of injury to specific body area. 0 being mild and 6 being maximal injury.
Design:
- Prospective cohort study
- 150 trauma patients at 4 different level 1 trauma centers, identified as having suspected head injury by flight medic/nurse
- Inclusion criteria:
- Diagnosis of acute traumatic brain injury confirmed by CT, operative findings or autopsy
- Head Abbreviated Injury Scale of 3 or greater or GCS 12 or less within first 24 hours of admission. *not influenced by alcohol, sedatives, or muscle relaxants
- Exclusion criteria:
- No abnormal intracranial findings on CT scan
- Non-survivable injury (AIS score of 6 for any body region)
- Death less than 12 hours after injury
Outcome:
- Primary outcome: Mortality.
- Secondary outcomes
- Hospital LOS
- Disability rating scale (Range 0-29) at discharge
Results:
- Mortality:
- Overall: 23.3%
- With prehospital secondary insults: 28%
- Without prehospital secondary insult: 20%
- LOS (days)
- Without insult: 20 days
- With insult: 27 days (p03)
- Disability rating scale at discharge
- Without insult: 10
- With insult: 14 (p02)
Take-home:
- The acute care of patients with traumatic brain injury begins in the prehospital setting. Both hypoxia and hypotension exacerbate traumatic brain injury and lead to worse outcomes. The authors note that as secondary insult, isolated hypoxia is associated with increased mortality while isolated hypotension is not. In both the prehospital setting and while in the emergency department, care should me taken to optimize oxygenation/ventilation and maintain blood pressure.
- The independent variables that were identified as affecting mortality were: hypoxia, older age, lower GCS score, Marshall score, head AIS score, and multiple traumatic injuries significantly affected mortality.
- Multivariate analysis accounting for the above independent variables showed that hypoxia was an independent predictor of mortality (OR 2.66, p 0.05). Age >65 years and GCS score <8 were also significant predictors of mortality in multivariate analysis, but hypotension was not.
Weaknesses / Critiques
- This study excluded those who died within 12hours after injury, perhaps those with the most lethal injuries. Interestingly, most previous data found that hypotension and not hypoxia (the reverse findings of this paper) was linked with increased mortality in TBI. The authors suggest that the exclusion of these high lethality injuries could explain for this discrepancy.
