Core temperature is routinely used to guide hypothermic circulatory arrest (HCA) for acute type A aortic dissection (ATAAD). However, it remains unclear whether impaired carotid artery flow alters the relationship between cerebral and systemic cooling during HCA. This study aimed to evaluate head–core temperature discordance in patients with carotid artery dissection.

This retrospective study included 358 consecutive patients who underwent emergency hemiarch replacement for ATAAD under HCA without adjunctive cerebral perfusion between 2012 and 2022. Patients were classified according to carotid artery flow status: no carotid dissection, preserved carotid flow, or compromised carotid flow. A temperature discordance index (ΔT) was defined as the difference between bladder (core) and tympanic (head) temperatures at the onset of circulatory arrest.

Tympanic temperature at the onset of circulatory arrest was maintained across all groups (median, 24.5 °C). Postoperative stroke occurred more frequently in patients with carotid artery dissection than in those without carotid involvement (14.8% vs 8.3%; P = .04). Patients with compromised carotid flow exhibited a significantly smaller ΔT compared with patients without carotid dissection (median, 2.3 °C vs 3.2 °C; P < .01). Multivariable logistic regression analysis identified smaller ΔT (odds ratio, 0.77) and compromised carotid flow (odds ratio, 2.40) as predictors of postoperative stroke.

During HCA, compromised carotid artery flow is associated with attenuated ΔT. A narrowed ΔT may reflect impaired cerebral cooling related to compromised carotid perfusion dynamics and was associated with stroke. Monitoring head–core temperature relationships may provide adjunctive intraoperative physiological information beyond core temperature alone.