A new consensus on temperature for organ protective strategies during circulatory arrest on aortic surgery was established in the 2024 EACTS/STS Guidelines. The aim of this study is to evaluate early postoperative outcomes in patients undergoing hemiarch replacement for acute type A aortic dissection (TAAD) using hypothermic circulatory arrest without adjunctive cerebral perfusion, stratified according to guideline-based core temperature categories. The 358 patients who underwent surgical hemiarch replacement with hypothermic circulatory arrest, no cerebral perfusion, as organ protection for TAAD at Shiga University of Medical Science between August 2012 and August 2022 were included in this study. Patients were classified by nadir core temperature during circulatory arrest into low–moderate hypothermia (20.1–24.0 °C; LMH, n = 30), high–moderate hypothermia (24.1–28.0 °C; HMH, n = 212), and mild hypothermia (≥ 28.1 °C; MH, n = 116). Early clinical outcomes were compared using multivariable adjustment and restricted cubic spline analyses. The overall stroke rate was 11.7% and the 30-day mortality rate was 6.4%. After adjustment, the rate of stroke and reoperation for bleeding was significantly higher in the LMH group (p = 0.002, 0.001; reference to MH group). Restricted cubic spline analysis showed a non-linear association between nadir core temperature and stroke, with higher adjusted risk ratios observed at temperatures below approximately 27 °C. These associations were observed in the context of baseline imbalances, including a higher prevalence of carotid malperfusion in lower temperature groups. In patients undergoing hemiarch replacement without cerebral perfusion, a greater reduction in nadir core temperature was not associated with improved neurological outcomes when core temperature was used as an indicator. The observed association between lower core temperature and adverse outcomes may reflect residual confounding related to preoperative or intraoperative malperfusion rather than a direct causal effect of temperature itself. These findings suggest that core temperature alone may be an insufficient surrogate for brain protection and should be interpreted cautiously in the evaluation of neurological risk.
Wakisaka et al. (Sat,) studied this question.