Cardiovascular Effects of Tourniquet Application with Cardiac Cycle Efficiency: A Prospective Observational Study.

Objectives: The impact of the tourniquet on cardiac efficiency remains unknown. This study aimed to assess the impact of the tourniquet on cardiac cycle efficiency (CCE) and to interpret how general anesthesia (GA) or combined spinal epidural anesthesia (CSEA) affects this during surgery using cardiac energy parameters. Methods: This prospective observational study included 43 patients undergoing elective unilateral total knee arthroplasty (TKA) with a tourniquet divided into GA (n = 22) and CSEA (n = 21) groups. Cardiac energy parameters were measured before anesthesia (T1), pre-tourniquet inflation (T2), during inflation (T3-T8), and post-deflation (T9). The estimated power of the study was 0.99 based on the differences and standard deviations in CCE at T2-T3 for all patients (effect size: 0.88, alpha error: 0.05). Results: CCE decreased significantly more at T3 in the GA group than in the CSEA group, whereas dP/dtmax and Ea increased more (p < 0.05, p < 0.001, and p < 0.01, respectively). At T9, CCE increased significantly in the GA group, whereas dP/dtmax and Ea decreased (p < 0.05, p < 0.001, and p < 0.001, respectively). Conclusions: The tourniquet reduces cardiac efficiency through compensatory responses, and CSEA may mitigate this effect.