EBQ:Prehospital Hypoxia in Brain Trauma

Complete Journal Club Article
Chi JH. "Prehospital hypoxia affects outcome in patients with traumatic brain injury: a prospective multicenter study". J. Trauma. 2006. 61(5):1134-41.
PubMed PDF

Clinical Question

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 at hospital discharge.

Conclusion

Secondary insults after TBI are common, and these insults are associated with disability. Hypoxia in the prehospital setting significantly increases the odds of mortality after brain injury controlled for multiple variables.

Design

Prospective cohort study

Population

150 trauma patients undergoing helicopter transport to 4 Level I trauma centers during a 2 year period identified by flight nurses or paramedics as having a suspected head injury.

Inclusion Criteria

Inclusion criteria were

  1. Diagnosis of acute traumatic brain injury confirmed by CT, operative findings, or autopsy findings
  2. Head Abbreviated Injury Scale (AIS) score of greater than or equal to 3 or Glasgow Coma Scale (GCS) score of less than or equal to 12 within the first 24 hours of admission (not influenced by alcohol intoxication, sedatives, or muscle relaxants).

Exclusion Criteria

  1. no abnormal intracranial findings on the patient’s CT scan
  2. determination of a nonsurvivable injury (based on an AIS score of 6 for any body region)
  3. death in less than 12 hours after injury

Outcomes

Primary Outcomes

Mortality: Overall mortality was 23.3%. Mortality for patients with prehospital secondary insults was 28% compared with 20% for those without.

Secondary Outcomes

Disability Rating Scale (DRS) (range, 0–29) and length of hospital stay (LOS)

Patients with prehospital episodes of hypoxia and/or hypotension have a greater degree of disability at discharge and require longer hospital stays compared with those without secondary insults.

Subgroup Analysis

Univariate analysis with independent variables included were age, sex, mechanism of injury, GCS score, ISS score, AIS score, field resuscitation and intubation, transport time and distance, CT Marshall score, presence of lung injury (defined as lung AIS score >3), presence of multiple trauma (defined as an AIS score >3 for two or more body regions or organs), and surgical procedure (craniotomy vs. noncraniotomy) performed after hospitalization.

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.

Criticisms

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.

CME

1

In this study what percent of patients sustained a secondary injury (hypoxia or hypotension)?

0 to 25%
25 to 50%
50 to 75%
75 to 100%

2

In the authors' previous work looking at secondary injury in TBI patients in the ED, what did they find regarding association with mortality?

Hypotension but not hypoxia are associated with increased mortality.
Hypoxia but not hypotension are associated with increased mortality.
Both hypotension and hypoxia are associated with increased mortality.
Neither hypotension nor hypoxia are associated with increased mortality.

3

After multivariate analysis what did this study find regarding secondary injury and mortality in the prehospital setting and TBI?

Hypotension but not hypoxia are associated with increased mortality.
Hypoxia but not hypotension are associated with increased mortality.
Both hypotension and hypoxia are associated with increased mortality.
Neither hypotension nor hypoxia are associated with increased mortality.

Sources