Background and objective: This prospective, double-blind, randomized, placebo-controlled study compares the effects of ephedrine and ketamine on injection pain, and hypotension from propofol.
Methods: After obtaining the approval of the Ethics Commitee, 75 patients (ASA I–II) scheduled for elective operations with general anaesthesia were divided into three groups. Saline 2 mL (Group S, n = 25), ketamine 0.5 mg kg−1 (Group K, n = 25) or ephedrine 70 μg kg−1 (Group E, n = 25) were administered over 5 s after tourniquet application. After releasing the tourniquet, propofol 2 mg kg−1 was injected in 30 s. Pain was evaluated on a numerical scale (0–10) where 0 represented no pain and 10 the most severe pain possible. Systolic, diastolic blood pressures and heart rates were recorded preoperatively, 1 min after propofol injection, before intubation and 1, 2 and 3 min after intubation in all patients.
Results: The incidences of pain in Groups S, E and K were similar (84%, 80% and 72%, respectively). The mean pain score in Group K (2.1, SD 3.1) was significantly lower than those of Groups S and E (4.9, SD 2.6 and 4.6, SD 3.3, respectively) (P < 0.05). The systolic and diastolic blood pressure values in Group K (120 ± 27 mmHg) and Group E (123 ± 21 mmHg) before intubation were significantly higher than that of Group S (104 ± 25 mmHg) (P < 0.05). There was no significant difference between the mean heart rate values of the groups.
Conclusions: Low dose ketamine or ephedrine pretreatment may prevent hypotension due to propofol induction. Despite the reduction in injection pain intensity after ketamine, the study drugs were found to be ineffective in lowering the injection pain incidence.