Table 1.

Patient characteristics (mean±SD)

	Group 1 (n=13)	Group 2 (n=13)	Group 3 (n=13)	Group 4 (n=13)
Age (year)	60.87±7.9	56.77±9.0	56.81±9.7	57.1±15.7
Weight (kg)	66.12±14.1	73.55±12.2	78.45±11.8	67.4±10.4
Male: female	4:4	5:4	7:4	4:6

p>0.05. Group 1: control group. Group 2: single-bolus dose of 0.5 mg kg⁻¹ ketamine IV at induction. Group 3: bolus dose of 0.5 mg kg⁻¹ ketamine IV at induction and perioperative ketamine infusion at a rate of 0.25 mg kg⁻¹ h⁻¹. Group 4: a bolus of 0.5 mg kg⁻¹ ketamine IV at induction and perioperative and postoperative ketamine infusion at a rate of 0.25 mg kg⁻¹ h⁻¹