Effects of dexmedetomidine dosage on the short-term cognitive function of elderly patients undergoing cardiac surgery

BACKGROUND: This study aimed to investigate the effects of perioperative dexmedetomidine (DEX) infusion rates on the postoperative short-term cognitive function. METHODS: A total of 88 patients aged ≥ 60 years who underwent cardiac surgery from January 2022 to November 2022 at the First Affiliated Hospital of The University of Science and Technology of China (USTC) were included. Based on a single-center pilot analysis, patients were divided into two groups according to the rate of intraoperative DEX infusion, which started after tracheal intubation and continued until 1 h before extubation in the cardiac surgery intensive care unit. In Group L (n = 44), the infusion rate was 0.1–0.5 µg/kg/h (low-dose group), whereas in Group H (n = 44), the infusion rate was 0.5–0.9 µg/kg/h (high-dose group). Clinical outcomes were then compared between the groups. The Mini–Mental State Evaluation (abbreviated as MMSE(1), MMSE(2), MMSE(3), and MMSE(4)) scale was used for the assessment of cognitive function, which was conducted on postoperative Days 2 (T(1)), 7 (T(2)), 14 (T(3)), and 28 (T(4)), with the score from postoperative Day 2 (MMSE(1)) considered as the primary observation. RESULTS: Patients in Group L had higher MMSE(1) scores compared to those in Group H (26.0 [24.0, 27.0] vs. 24.5 [22.0, 26.0], p = 0.046), and there was no significant difference in the scores between the groups at all subsequent time points. Group H exhibited a higher incidence of hypotension and bradycardia compared to Group L (p = 0.044 and p = 0.047, respectively). CONCLUSIONS: Compared to a high dose (0.5–0.9 µg/kg/h) of DEX infusion, a low-dose (0.1–0.5 µg/kg/h) infusion started after induction of anesthesia and continued until 1 h before extubation improved postoperative cognitive function scores on postoperative Day 2 in patients aged 60 years and older. TRIAL REGISTRATION: URL: www.chictr.org.cn with registration number ChiCTR2100055093, registered on 31/12/2021.