Preinduction cardiac output (CO) is a small but significant predictor of induction dose of propofol. We hypothesized that glycopyrrolate, by inducing tachycardia (although to a small extent) would increase CO, and hence the induction dose of propofol. Aim of the study was to find out the dose of propofol required to induce anesthesia in patients receiving glycopyrrolate as compared to those not receiving it.

Eighty female patients (25-60 years, ASA-1, 2) undergoing elective procedures under general anesthesia were randomized into group G (glycopyrrolate) and group C (control). Patients received 1 ml (0.2 mg) glycopyrrolate (group G) or 1 ml normal saline (group C) intravenously 5 minutes before induction. Anesthesia was induced with propofol at a rate of 0.8 mg/kg/min titrated to achieve a target BIS = 40. Dose of propofol required for induction of anesthesia (loss of consciousness) and to reach the target BIS, heart rate (HR) and mean arterial pressure (MAP) at various intervals were compared. Correlation between the dose of propofol required to reach target BIS = 40 and heart rate after giving the test drug was performed by regression analysis.

The dose of propofol required for achieving target BIS was significantly higher (p < 0.001) in group G (2.08 ± 0.42 mg/kg) (mean ± SD) as compared to group C (1.66 ± 0.23 mg/ kg). There was a significant positive correlation between the preinduction HR (3 minutes after giving the test drug) and the propofol dose required to reach target BIS = 40 (r = 0.356, p < 0.01).

Administration of 0.2 mg of glycopyrrolate intravenously before induction of general anesthesia significantly increased the dose of propofol required for induction of anesthesia.

Arora S, Hegde HV, wig J, Puri GD. The Effect of Glycopyrrolate on Induction Dose of Propofol during General Anesthesia. J Postgrad Med Edu Res 2015;49(2): 62-65.