Intraoperative mild hypothermia for postoperative neurological deficits in intracranial aneurysm patients

Rupture of an intracranial aneurysm causes aneurysmal subarachnoid haemorrhage, which is one of the most devastating clinical conditions. Clinically, 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 called '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 metabolism rate, thereby protecting organs in cases where metabolism is disturbed and potentially harmful.

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

We searched the Cochrane Stroke Group Trials Register (September 2011), the Cochrane Central Register of Controlled Trials (CENTRAL 2011, Issue 3), MEDLINE (1950 to September 2011), EMBASE (1980 to September 2011), Science Citation Index (1900 to September 2011) and 11 Chinese databases (September 2011). We also searched ongoing trials registers (September 2011) and scanned reference lists of retrieved records.

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

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

We included three studies enrolling 1158 patients. Each study observed an increased rate of good recovery with intraoperative mild hypothermia, but the effect sizes were not sufficient for statistical significance. A total of 76 of 577 patients (13.1%) who received hypothermia and 93 of 581 patients (16.0%) who did not receive hypothermia were dead or dependent. A total of 1086 of the1158 patients (93.8%) had good-grade aneurysmal subarachnoid haemorrhage. A random-effects meta-analysis resulted in a summarised RR of 0.82 (95% CI 0.62 to 1.09, P value 0.17). In patients with poor-grade aneurysmal subarachnoid haemorrhage, one of seven in the hypothermia group and one of six in the control group were dead or dependent (RR 0.86, 95% CI 0.07 to 10.96, P value 0.91). In patients without subarachnoid haemorrhage, three of 30 patients (10%) in the hypothermia group, and four of 29 patients (13.8%) in the control group were dead or dependent (RR 0.72, 95% CI 0.18 to 2.96, P value 0.65).

In patients with good-grade aneurysmal subarachnoid haemorrhage, intraoperative mild hypothermia might prevent death or dependency in activities of daily living for a few of them. However, the confidence intervals include the possibility of both benefit and harm. There is no evidence that intraoperative mild hypothermia is harmful. This treatment should not be routinely applied. In patients with poor-grade aneurysmal subarachnoid haemorrhage or without subarachnoid haemorrhage, there are insufficient data to draw any conclusions. A high-quality randomised clinical trial of intraoperative mild hypothermia for postoperative neurological deficits in patients with poor-grade aneurysmal subarachnoid haemorrhage might be feasible.