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Hypothermia and operative mortality during on-pump coronary artery bypass grafting
Kevin L Greason1, Sunghee Kim2, Rakesh M Suri1
1Division of Cardiovascular Surgery, Mayo Clinic, Rochester, Minn.
Insights
Hypothermia during coronary artery bypass graft surgery significantly reduces operative mortality compared to normothermia. However, moderate hypothermia offers no additional survival benefit over mild hypothermia.
Area of Science:
- Cardiovascular Surgery
- Anesthesiology
- Critical Care Medicine
Background:
- The impact of hypothermia on cardiac surgery outcomes remains debated.
- A large clinical database was utilized to investigate this controversy.
Purpose of the Study:
- To determine the effect of different hypothermia levels on operative mortality in coronary artery bypass graft (CABG) operations.
- To compare outcomes between moderate hypothermia, mild hypothermia, and normothermia during CABG.
Main Methods:
- Retrospective analysis of the Society of Thoracic Surgeons Adult Cardiac Surgery Database (July 2011-December 2012).
- Inclusion of patients undergoing isolated, nonemergency, on-pump CABG.
- Categorization into moderate hypothermia (≤34°C), mild hypothermia (>34°C to ≤36°C), and normothermia (>36°C).
Main Results:
- 142,541 patients were analyzed; 66.5% received moderate hypothermia, 30.3% mild hypothermia, and 3.5% normothermia.
- Operative mortality rates were 1.5% (moderate hypothermia), 1.3% (mild hypothermia), and 2.1% (normothermia).
- Multivariate analysis showed hypothermia (mild and moderate) was protective against operative mortality versus normothermia (P < .0001 and P = .0015, respectively).
Conclusions:
- Hypothermia is protective against operative mortality in on-pump CABG patients compared to normothermia.
- No significant incremental survival benefit was observed between mild and moderate hypothermia grades.
- The findings support the use of hypothermia but suggest mild hypothermia may be sufficient.
Objective:
Controversy surrounds the effect of hypothermia on operative mortality during cardiac surgery. The present study accessed a large clinical database of coronary artery bypass graft operations to address the issue.
Methods:
A retrospective review of the Society of Thoracic Surgeons Adult Cardiac Surgery Database identified patients treated with isolated, nonemergency, on-pump coronary artery bypass grafting from July 2011 to December 2012. The patients were divided into 3 groups according to their lowest core temperature during the procedure: moderate hypothermia (≤ 34 °C), mild hypothermia (>34 °C but ≤ 36 °C), and normothermia (>36 °C). The primary endpoint of the study was operative mortality, defined according to the Database criteria.
Results:
During the study period, 142,541 patients were available for analysis; 94,777 (66.5%) received moderate hypothermia, 42,750 (30.3%) mild hypothermia, and 5014 (3.5%) normothermia. Operative mortality occurred in 1394 patients (1.5%) in the moderate hypothermia, 534 (1.3%) in the mild hypothermia, and 105 (2.1%) in the normothermia group. Multivariate analysis identified hypothermia (both mild [odds ratio, 0.66; 95% confidence interval, 0.54-0.81; P < .0001] and moderate [odds ratio, 0.73; 95% confidence interval, 0.60-0.89; P = .0015]) was protective against operative mortality compared with normothermia. No incremental benefit was noted between the different hypothermia grades (P = .0827).
Conclusions:
Most patients receive hypothermia during on-pump coronary artery bypass grafting. Hypothermia is protective against operative mortality compared with normothermia in such patients. Moderate hypothermia does not provide additional survival benefit.
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