Moderate hypothermia at warmer temperatures is safe in elective proximal and total arch surgery: Results in 665 patients.

OBJECTIVE: To evaluate adverse outcomes after elective aortic arch surgery performed at higher or lower temperatures (24.0°C-28.0°C vs 20.1°C-23.9°C) within the wide range of moderate hypothermia.

METHODS: Over a 9-year period, a total of 665 patients underwent elective proximal (n = 479) or total (n = 186) arch replacement with moderate hypothermia and antegrade cerebral perfusion. Circulatory arrest was initiated at an actual temperature of 20.1°C to 23.9°C in the lower-temperature group (n = 334; 223 proximal, 111 total) and at 24.0°C to 28.0°C in the higher-temperature group (n = 331; 256 proximal, 75 total). Composite adverse outcome was defined as operative mortality or persistent neurologic event or persistent hemodialysis at discharge. Multivariate logistic regression analysis was used to model adverse outcome. In addition to the actual temperature, a new, balanced variable, "predicted temperature," was analyzed to eliminate surgeon bias. We used this variable in a propensity score-matching analysis to validate the multivariate analysis results.

RESULTS: A composite adverse outcome occurred in 7.2% of cases. Operative mortality was 5.1%. The rate of postoperative persistent neurologic deficits was 2.4%. No significant differences were found between the lower- and higher-predicted temperature groups within the moderate hypothermia range in the propensity score-matching analysis. The higher-actual temperature group had a lower rate of ventilator support at >48 hours (P = .036) and less need for tracheostomy (P = .023). Packed red blood cell transfusion and previous coronary artery bypass independently predicted composite adverse outcome (P = .0053 and .0002, respectively), operative mortality (P = .0051 and .0041), and postoperative stroke (P = .045 and .048). Cardiopulmonary bypass time independently predicted composite outcome (P = .0005), operative mortality (P < .0001), ventilatory support for >48 hours (P < .0001), and renal dysfunction (P = .0005).

CONCLUSIONS: In elective proximal or total arch surgery, higher temperatures (≥24.0°C-28.0°C) within the wide range of moderate hypothermia (20.1°C-28°C) are safe and, compared with colder temperatures, not associated with significantly different rates of composite and adverse outcomes.