Effect of preoperative β-blocker use on Analgesia-Nociception Index during laparoscopic cholecystectomy.

Background The Analgesia-Nociception Index (ANI), derived from heart rate variability, reflects parasympathetic activity and is used to assess intraoperative nociception. β-blockers modulate autonomic tone and heart rate variability and may influence responses to nociceptive stimuli. This study investigated whether preoperative β-blocker use was associated with altered intraoperative ANI dynamics during laparoscopic cholecystectomy. Method The data of 49 patients with hypertension who underwent elective laparoscopic cholecystectomy under a standardized propofol-remifentanil anesthetic protocol were analyzed in this prospective observational study. Patients were classified according to chronic β-blocker use (β-blocker group, n = 24; non-β-blocker group, n = 25). Four predefined nociceptive stimuli were applied under stable anesthetic conditions. The minimum ANI value within 2 min after each stimulus (ANI_min) and the change from the pre-stimulus value (ΔANI) were analyzed using repeated-measures analysis of variance. Results Repeated-measures ANOVA demonstrated a significant main effect of time, indicating a consistent decrease in ANI in response to standardized nociceptive stimuli. No significant time × group interaction or main effect of group was observed for ANI_min or ΔANI. The temporal patterns and magnitudes of ANI changes were comparable between groups across all predefined time points. Conclusions Preoperative β-blocker therapy did not substantially alter stimulus-related ANI dynamics during laparoscopic cholecystectomy under propofol-remifentanil anesthesia. These findings suggest that ANI may remain interpretable as a dynamic within-patient autonomic response in chronically β-blocked patients under these anesthetic conditions.