gms | German Medical Science

Objective: Giant cerebral aneurysm surgery carries a high risk for intra-operative ischemic insults, especially if multiple (and long) periods of temporary clipping are necessary to achieve final aneurysm clipping. Optimal intra-operative cerebral protection remains an open and controversial question. Until today, no clear proof of net neuroprotective effects of barbiturate administration prior to temporary clipping and guided by EEG burst suppression ratio has been reported. The most robust neuroprotection is for sure provided by the application of moderate hypothermia (32°C core temperature). However, in order to obtain stable hypothermia conditions, all methods of surface cooling have shown major limitations, especially in the intra-operative setting. Therefore, we want to report on the intra-operative use of the Coolgard System (Alsius) to induce systemic hypothermia during the clipping of a giant aneurysm.

Methods: A 57-year-old female patient, scheduled for elective surgical clipping of a medial cerebral artery giant aneurysm (3–4 vs. 9cm diameter) will be reported. During surgical approach, a long time period of endovascular proximal occlusion of the carotid artery was anticipated (probably more than 30min). In order to ensure maximal brain protection during this carotid occlusion, intra-operative hypothermia (to 32° core temperature, referring to most recent data on clinical neuroprotection for focal cerebral ischemia) was applied as well as continuous neurophysiological monitoring (SSEP+EEG) to detect any intra-operative ischemic cerebral incident. After induction of anesthesia, the left femoral vein was accessed inserting an ICY catheter (3-lumen Coolgard catheter). Body temperature was measured at different locations (esophageal, rectal and bladder) during the whole procedure.

Results: Coolgard was installed at 32°C “end” temperature with “maximal cooling” speed. Temperature at start of cooling procedure was 34.6°C for esophageal, 35.6°C for rectal, and 35.7°C for bladder location (guide to the Coolgard catheter). 1h 6min after starting up the Coolgard system we obtained the aimed core temperature of 32°C. We did not observe any deleterious systemic effect of this cooling. Mean arterial blood pressure did not deviate from pre-existing values, and remained stable throughout the cooling period with minimal inotropic/vasopressor support. Continuous EEG monitoring revealed a significant increase in burst suppression ratio, observed at body core temperature of below 34.5°C, obtaining burst suppression between 50 and 70% at 32°C. Despite important flattening of the EEG, it was still possible to interpret SSEP displays as to ischemic events. During the surgical procedure we maintained stable body core temperatures (rectal-esophageal and bladder within a narrow range of 31.7 to 32.2°C). This time period lasted for 3h and 4min. Thereafter, rewarming was slowly started; Coolgard was installed at 35°C “end” temperature with maximal rewarming set at 0.65°C per hour. After 3h and 48min, body core temperature reached 35°C, the Coolgard system was stopped, and external surface rewarming (Bair Hugger) was installed. Body core temperature slowly increased to 36°–36.5°C, and the patient was extubated and awake 12h after ICU admission.

During the surgical procedure, 4 periods of temporary occlusion were applied (15min total duration), no ischemic changes were observed in the SSEP monitoring, but unfortunately it was impossible to clip the giant aneurysm due to anatomical characteristics.

Conclusions: This report describes the characteristics of intra-operatively induced systemic hypothermia using an endovascular cooling catheter.