Mortality risk stratification after traumatic brain injury and hazard of death with titrated hypothermia in the Eurotherm3235Trial

Objective: Hypothermia reduces intracranial hypertension in patients with traumatic brain injury (TBI) but was associated with harm in the Eurotherm3235trial. We stratified trial patients by IMPACT extended model sum scores (IEMSS) to determine where the balance of risks lay with the intervention.
Design: The Eurotherm3235Trial was a randomized controlled trial, with standardized and blinded outcome assessment. Patients in the trial were split into risk tertiles by IEMSS. A proportional hazard analysis for death between randomisation and 6 months was performed by intervention and IEMSS tertiles in both the intention-to-treat (ITT) and the per-protocol (PP) populations of the Eurotherm3235 Trial.
Setting: Forty seven Neurological Critical Care units in 18 countries.
Patients: Adult traumatic brain injury patients admitted to intensive care who had suffered a primary, closed traumatic brain injury; had increased intracranial pressure; an initial head injury less than 10days earlier; a core temperature at least 36°C and an abnormal brain CT.
Measurements and Main results: 386 patients were available for analysis in the ITT and 257 in the PP population. The proportional hazard analysis (ITT and PP populations) showed that the treatment effect behaves similarly across all risk stratums. However, there is a trend that indicates that patients in the low-risk group could be at greater risk of suffering harm due to hypothermia.
Conclusion: Hypothermia as a first line measure to reduce ICP to less than 20mmHg is harmful in patients with a lower severity of injury and no clear benefit exists in patients with more severe injuries.