Background

Optimal anatomical sites for temperature monitoring that most closely correlates with cerebral temperature remain debated in cardiac surgery, particularly during cardiopulmonary bypass (CPB) with deep hypothermic circulatory arrest (DHCA) and subsequent rewarming. This experimental study aimed to identify the monitoring site best correlated with intracerebral temperature during the rewarming phase and to assess whether some sites may underestimate cerebral rewarming, thereby increasing the risk of undetected hyperthermia.

Methods

The study was conducted in six male Landrace pigs (≈58 kg) undergoing CPB with a 45-min DHCA at 18 °C, followed by a gradual rewarming phase. Temperature was monitored throughout the procedure at seven anatomical sites (jugular, bladder, esophageal, rectal, nasopharyngeal, venous, and arterial) and compared with direct intracerebral temperature measured using a Pt1000 probe inserted into the cerebral parenchyma. Correlation analyses were performed between peripheral and intracerebral temperature measurements.

Results

Jugular temperature demonstrated the strongest correlation with intracerebral temperature (r = 0.975), with no statistically significant difference between jugular values and cerebral temperature (p = 0.2189). In contrast, a significant discrepancy was observed between cerebral and esophageal temperatures (p = 0.0247), indicating differences in thermal kinetics during the early rewarming phase. No cases of cerebral hyperthermia were observed.

Conclusions

This study demonstrated that jugular temperature most accurately reflects cerebral temperature during the rewarming phase of CPB following DHCA. Esophageal and nasopharyngeal measurements, although commonly used, may underestimate cerebral temperature during early rewarming, potentially increasing the risk of cerebral hyperthermia. These findings underscore the value of multisite temperature monitoring and highlight the importance of understanding the mechanisms underlying cerebral thermal dynamics.