Impact of two sedation protocols on cardiac electrophysiology during spinal anesthesia

Background/aim: Perioperative factors such as anesthetic drugs, central blocks, surgical stress, pain, and anxiety can affect cardiac electrophysiology and increase the risk of arrhythmias. Arrhythmia susceptibility can be assessed using ventricular markers such as the QT interval (QT), heart rate-corrected QT interval (QTc), QT dispersion (QTd), time between peak and end of T wave (Tp-e), cardiac electrophysiologic balance index (iCEB), and heart rate-corrected index of cardiac electrophysiologic balance (iCEBc), obtained from noninvasive electrocardiography (ECG) data. This study compared the effects of propofol and dexmedetomidine sedation on these parameters in patients undergoing total knee arthroplasty performed under spinal anesthesia. Materials and methods: This prospective, observational clinical study was conducted at Ankara Bilkent City Hospital between March and August 2023, and included patients scheduled for elective total knee arthroplasty. Patients were divided into two groups based on the clinician's preference: group P received propofol infusion, and group D received dexmedetomidine. All patients underwent spinal anesthesia. The primary outcome was the comparison of iCEB and iCEBc values between the two groups. Secondary outcomes included comparisons of QT, QTc, QTd, and Tp-e values. Results: A total of 74 participants were enrolled, and 70 were included in the final analysis (35 per group). No significant differences were found in demographic data, local anesthetic dose, spinal interventions, sensory block level, or bispectral index values (p > 0.05). QTc increased in both groups after spinal anesthesia; however, group P exhibited significantly higher values at t1 and t15 compared with group D (p = 0.004 and p = 0.046, respectively). iCEBc returned to baseline at t10 in group D and t45 in group P. A significant iCEBc increase from t0 to t1 was observed in group P but not in group D. Conclusion: Compared with propofol, dexmedetomidine sedation under spinal anesthesia was associated with differences in ECG-derived indices related to repolarization duration, homogeneity, repolarization-depolarization balance, and transmural distribution. These findings should be interpreted within the context of the study's observational design and the use of ECG-derived markers rather than clinical arrhythmic endpoints.