Intraoperative mild hypothermia for postoperative neurological deficits in people with intracranial aneurysm

Rupture of an intracranial aneurysm causes aneurysmal subarachnoid haemorrhage, which is one of the most devastating clinical conditions. It can be classified into five Grades using the Hunt-Hess or World Federation of Neurological Surgeons (WFNS) scale. Grades 4 and 5 predict poor prognosis and are known as 'poor grade', while grade 1, 2, and 3 are known as 'good grade'. Disturbances of intracranial homeostasis and brain metabolism are known to play certain roles in the sequelae. Hypothermia has a long history of being used to reduce metabolic rate, thereby protecting organs where metabolism is disturbed, and may potentially cause harm.

To assess the effect of intraoperative mild hypothermia on postoperative death and neurological deficits in people with ruptured or unruptured intracranial aneurysms.

We updated the search in the Cochrane Stroke Group Trials Register (August 2015), the Cochrane Central Register of Controlled Trials (CENTRAL 2015, Issue 8), WHO International Clinical Trials Registry Platform (ICTRP; December 2015), MEDLINE (1950 to September 2015), EMBASE (1980 to September 2015), Science Citation Index (1900 to September 2015), and 11 Chinese databases (September 2015). We also searched ongoing trials registers (September 2015) and scanned reference lists of retrieved records.

We included only randomised controlled trials that compared intraoperative mild hypothermia (32°C to 35°C) with control (no hypothermia) in people with ruptured or unruptured intracranial aneurysms.

Two review authors independently selected trials and assessed the risk of bias for each included study. We presented data as risk ratio (RR) and risk difference (RD) with 95% confidence intervals (CI).

We included three studies, enrolling 1158 participants. Each study reported an increased rate of recovery with intraoperative mild hypothermia, but the effect sizes were not sufficient for certainty. A total of 1086 of the 1158 participants (93.8%) had good grade aneurysmal subarachnoid haemorrhage. Seventy-six of 577 participants (13.1%) who received hypothermia and 93 of 581 participants (16.0%) who did not receive hypothermia were dead or dependent (RR 0.82; 95% CI 0.62 to 1.09; RD -0.03; 95% CI -0.07 to 0.01, moderate-quality evidence) after three months.Reported unfavourable outcomes did not differ between participants with or without hypothermia. The quality of evidence for these outcomes remains unclear because the outcomes were reported in a variety of ways. No decompressive craniectomy or corticectomy was reported. Thirty-six of 577 (6.2%) participants with hypothermia and 40 of 581 (6.9%) participants without hypothermia had infarction. Thirty-four of 577 (6%) participants with hypothermia and 32 of the 581 (5.5%) participants without hypothermia had clinical vasospasm (temporary deficits).Duration of hospital stay was not reported. Only one study with 112 participants reported discharge destinations: 43 of 55 (78.2%) participants with hypothermia and 39 of 57 (68.4%) participants in the control group were discharged home. The remaining participants were discharged to other facilities.Thirty-nine of 577 (6.8%) participants with hypothermia and 39 of 581 (6.7%) participants without hypothermia had infections. Six of 577 (1%) participants with hypothermia and 6 of 581 (1%) participants without hypothermia had cardiac arrhythmia.

It remains possible that intraoperative mild hypothermia could prevent death or dependency in activities of daily living in people with good grade aneurysmal subarachnoid haemorrhage. However, the confidence intervals around this estimate include the possibility of both benefit and harm. There was insufficient information to draw any conclusions about the effects of intraoperative mild hypothermia in people with poor grade aneurysmal subarachnoid haemorrhage or without subarachnoid haemorrhage. We did not identify any reliable evidence to support the routine use of intraoperative mild hypothermia. A high-quality randomised clinical trial of intraoperative mild hypothermia for postoperative neurological deficits in people with poor grade aneurysmal subarachnoid haemorrhage might be feasible.