Differential brain and body temperature during cardiopulmonary bypass--a randomised clinical study

Maintenance of normothermia during cardiopulmonary bypass (CPB) may have advantages over hypothermia but there is a potential increased hazard of neurological injury. A novel aortic cannula (Cobra catheter, Cardeon Corp., Cupertino, CA, USA) which compartmentalises the aorta may allow simultaneous brain cooling during maintained corporeal normothermia. We investigated the thermal efficacy of this technique.

We randomized 60 adult patients to normothermic CPB (n=30, temp=35 degrees C) or to differential temperature management (Cobra cannula). Nasopharyngeal (NPT) and jugular bulb (JB) temperatures were used as surrogates for brain temperature while bladder temperature (BLT) represented the body (corporeal) temperature. Brain (radial) and corporeal (femoral) mean arterial pressure (MAP) together with jugular bulb and mixed venous saturations were monitored to assess perfusion adequacy. Transcranial Doppler was used to assess high intensity transient signals (HITS). All patients had neuropsychometric assessment pre-operatively and at 1 and 8 weeks post-operatively.

Demographic and CPB variables were comparable. A 3.2+/-0.46 degrees C differential between BLT and NPT was reached in all Cobra patients after 5.5+/-3.6 min (P<0.001). A 5 degrees C differential was reached in 29 patients after 12+/-7.5 min. The mean difference was 6.6+/-1 degrees C. MAP was maintained above 50 mmHg and venous saturations above 60% in both groups throughout. Blood requirements, extubation time and ITU stay were no different. Embolic counts and neuropsychometric outcomes were not different between groups.

Differential temperature management using the Cobra aortic catheter is possible. Further studies are necessary to establish whether the hypothesized advantages of combining corporeal normothermia with brain hypothermia can be realised.