Mild hypothermia as a protective therapy during intracranial aneurysm surgery: A randomized prospective pilot trial

OBJECTIVE: To conduct a pilot trial of mild intraoperative hypothermia during cerebral aneurysm surgery. METHODS: One hundred fourteen patients undergoing cerebral aneurysm clipping with (n = 52) (World Federation of Neurological Surgeons score less than or equal to III) and without (n = 62) acute aneurysmal subarachnoid hemorrhage (SAH) were randomized to normothermic (target esophageal temperature at clip application of 36.5 degrees C) and hypothermic (target temperature of 33.5 degrees C) groups. Neurological status was prospectively evaluated before surgery, 24 and 72 hours postoperatively (National Institutes of Health Stroke Scale), and 3 to 6 months after surgery (Glasgow Outcome Scale). Secondary outcomes included postoperative critical care requirements, respiratory and cardiovascular complications, duration of hospitalization, and discharge disposition. RESULTS: Seven hypothermic patients (12%) could not be cooled to within 1 degrees C of target temperature; three of the seven were obese. Patients randomized to the hypothermic group more frequently required intubation and rewarming for the first 2 hours after surgery. Although not achieving statistical significance, patients with SAH randomized to the hypothermic group, when compared with patients in the normothermic group, had the following: 1) a lower frequency of neurological deterioration at 24 and 72 hours after surgery (21 versus 37-41 %), 2) a greater frequency of discharge to home (75 versus 57%), and 3) a greater incidence of good long-term outcomes (71 versus 57%). For patients without acute SAH, there were no outcome differences between the temperature groups, There was no suggestion that hypothermia was associated with excess morbidity or mortality. CONCLUSION: Mild hypothermia during cerebral aneurysm surgery is feasible in nonobese patients and is well tolerated. Our results indicate that a multicenter trial enrolling 300 to 900 patients with acute aneurysmal SAH will be required to demonstrate a statistically significant benefit with mild intraoperative hypothermia.