Earlier extubation using axillary temperature as the endpoint for rewarming following hypothermic cardiopulmonary bypass

Patients having uncomplicated coronary artery bypass surgery (CABG) are extubated within 2–3 hours of surgery. Despite warming to core temperatures of 37°C post bypass, extubation is often limited by postoperative hypothermia caused by redistribution of thermal energy from core to periphery (afterdrop). We hypothesised that rewarming using axillary temperature as an endpoint may eliminate post bypass afterdrop, thus potentially allowing earlier extubation.

Methods

Following ethics committee approval, 39 patients for CABG or aortic valve replacement were randomised to be rewarmed to either a nasopharyngeal temperature (NPT) of 37°C (Group A) or an axillary temperature of 35.5°C (Group B) following hypothermic cardiopulmonary bypass (CPB). Nasopharyngeal and axillary temperatures were recorded at 1 min intervals in all patients until extubation. Extubation occurred when a patient achieved cardiorespiratory stability, blood loss <1.5 ml/kg/hour and a NPT ≥ 36.5°C. The data was statistically analysed using the Mann–Whitney U-test.

Results

From the end of surgery, time to a NPT of 36.5°C (and thus eligibility to extubation on temperature criteria alone) was 84 (± 50) min in Group A and 32 (± 44) min in Group B (P = 0.003). 55% (11/20) of Group B maintained a NPT ≥ 36.5°C post bypass compared with 15% (3/19) of Group A. Lowest postoperative NPT in Group B was 36.5 (± 0.3)°C compared with 36.1 (± 0.5)°C in Group A. Values are mean (SD) above and mean (range) below.

Conclusions

Warming to an axillary temperature of 35.5°C reduces the time taken to achieve core temperatures adequate for extubation following hypothermic cardiopulmonary bypass.

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