Differential Effects of Glycopyrrolate on Heart Rate and Heart Rate Variability in Patients with Varying Baseline Heart Rates

Objective To evaluate the effects of glycopyrrolate on heart rate (HR) and heart rate variability (HRV) in patients with different baseline HR levels during general anesthesia. Methods A total of 46 patients aged 18–65 years undergoing elective non-laparoscopic surgery under general anesthesia were divided into Group L with basal HR 40–60 bpm and Group H with basal HR 60–100 bpm. All patients received an intravenous dose of glycopyrrolate (0.006mg/kg). HR, mean arterial pressure (MAP), and HRV parameters were recorded before anesthesia induction (T0), at baseline (T1), and 30 minutes after glycopyrrolate administration (T2). The absolute (∆HR) and relative (∆HR%) increases in HR from T1 to T2 were also calculated. Results Group L showed significantly lower HR values at T1 and T2 compared to Group H ( p  < 0.01), while both ∆HR and ∆HR% were significantly higher ( p  < 0.01). In both groups, HR increased significantly at T2 compared to T1 ( p  < 0.01). LF and HF values were significantly reduced at T1 and T2 compared to T0 ( p  < 0.01), with further reductions at T2 relative to T1. The LF/HF ratio increased significantly at T2 ( p  < 0.01), suggesting altered autonomic tone. Conclusion Glycopyrrolate produces a greater HR increase in patients with lower baseline HR and alters HRV by decreasing parasympathetic activity and increasing the LF/HF ratio. These findings suggest that glycopyrrolate may help stabilize autonomic function during general anesthesia, particularly in patients with bradycardia. Trial registration ClinicalTrials.gov NCT06237478, registered on 2 February 2024. Retrospectively registered.