Lowest Measured Temperature and Adverse Outcomes After Cardiac Surgery

OBJECTIVE: To determine the relationship between the intraoperative lowest measured temperature (LMT) during cardiac surgery using cardiopulmonary bypass (CPB) and the risk for postoperative stroke. Secondarily, to determine the association between LMT and the risk for 30-day mortality and other adverse outcomes. BACKGROUND: The effectiveness of deliberate hypothermia during CPB for the prevention of cardiac surgery-associated stroke and adverse outcomes remains uncertain. METHODS: This cohort study from the Society of Thoracic Surgeons Adult Cardiac Surgery Database included 1,847,808 patients who underwent coronary artery bypass graft surgery, valve surgery, and combined coronary artery bypass graft-valve procedures between July 1, 2011 and March 1, 2022. Using propensity score-weighted regression analysis, we analyzed the effect of LMT on the incidence of postoperative stroke and other adverse outcomes. Since the relationship between LMT and the examined outcomes was nonlinear, LMT was treated as a continuous variable. RESULTS: In risk-adjusted analyses, no association was observed between the LMT and the primary outcome of postoperative stroke ( P =0.316). For the secondary outcomes, encephalopathy or coma ( P =0.649) or 30-day mortality ( P =0.691) were also not associated with lower LMT. Acute kidney injury ( P <0.001) was less common with lower and more common with higher LMTs. Pneumonia ( P =0.002) was less common, yet reoperation for bleeding ( P <0.001) was more common with higher LMTs. CONCLUSIONS: Hypothermia during CPB did not alter the risk of postoperative stroke. Secondary outcomes varied in their directionality of association with temperature, indicating that certain cardiac surgery patients may benefit, but others could be harmed by routine therapeutic hypothermia during CPB.