Cerebrovascular reactivity during hypothermia and rewarming

Area of Science:

• Neuroscience
• Critical Care Medicine
• Neurology

Background:

• Murine models suggest rapid rewarming after hypothermia may harm cerebral microcirculation in traumatic brain injury (TBI).
• The impact of hypothermia and rewarming on cerebral vasoreactivity in human TBI remains unclear.

Purpose of the Study:

• To investigate the effects of hypothermia and subsequent rewarming on cerebral vasoreactivity in human TBI patients.
• To determine if rewarming brain temperature above 37°C influences cerebrovascular pressure reactivity (PRx).

Main Methods:

• Retrospective analysis of prospectively collected neuromonitoring data from 24 TBI patients with refractory intracranial hypertension.
• Continuous monitoring of brain temperature, intracranial pressure (ICP), and cerebrovascular pressure reactivity index (PRx).

Main Results:

• Moderate hypothermia (34.2°C) reduced ICP significantly, without impairing PRx.
• Rewarming up to 37°C did not alter ICP or PRx.
• Rewarming above 37°C in 70.1% of patients led to a significant increase in PRx (0.32), indicating impaired cerebrovascular reactivity.
• Post-rewarming PRx correlated with brain temperature and brain tissue oxygen levels.

Conclusions:

• Rewarming TBI patients above 37°C after moderate hypothermia is linked to significant PRx increase.
• This suggests a temperature-dependent hyperemic derangement of cerebrovascular reactivity.
• Careful control of rewarming temperature is crucial in TBI management.