Effect of temperature and duration of cardiopulmonary bypass on cerebral saturation.

Background: Maintaining cerebral oxygenation is advocated to decrease these central nervous system morbidity and mortality after cardiopulmonary bypass (CPB). This study aimed to assess the effect of temperature and duration of CPB on cerebral saturation during open-heart surgeries and its correlation with postoperative neurological outcomes.

Methods: Patients aged 18-60 years of either sex undergoing open-heart surgeries on CPB were included in the study. Near-infrared spectroscopy was used to monitor regional cerebral saturation (rSO2). Postoperative cognitive dysfunction (POCD) was assessed by mini-mental state examination (MMSE) and trail-making test (TMT-A). Postoperative neurological deficit was assessed clinically and by the western perioperative neurologic scale (WPNS). All patients were followed up for 6 months.

Results: Sixty patients were included in the study. After the institution of CPB, mean core body temperature (CBT) decreased from baseline (36.29 ± 0.21) till 40 min and mean rSO2 decreased from baseline (72.48 ± 3.81) till 60 min. No significant correlation was found between mean CBT and mean rSO2. For every 5-min increase in total CPB duration, a decrease of minimum rSO2 by 2.48 was observed (P < 0.001). Based on the MMSE score and TMT-A, minimum rSO2 values and POCD were significantly associated at postextubation and 24 h postextubation. Based on the WPNS score, minimum rSO2 and postoperative neurological deficit were significantly associated with 24 h postextubation (P = 0.040).

Conclusion: Early rewarming on CPB is associated with relatively low rSO2. Intraoperative rSO2 desaturation showed a significant association with early cognitive decline, but its role is debatable in assessing late cognitive decline.