Role of Low Dose Ketamine (0.05 and 0.1 Mg/Kg) in Alleviating Propofol Injection Pain

Introduction: Pain from propofol injection can be severe and distressing in some patients. Various methods and agents has been used to alleviate this pain. One of the agents is ketamine which has been used in different sub-anaesthetic doses to reduce propofol injection pain in comparison with different agents. None of the studies till date have used ketamine in dose less than 0.1 mg/kg. The aim of the present study was to compare ketamine in doses of 0.05 and 0.1 mg /kg to attenuate propofol injection pain. Material and Method: 48 ASA I and II adult patients undergoing different elective surgical procedures under general anaesthesia were randomised into 3 groups of 16 patients each. Group A patients received ketamine 0.05 mg/kg in 2 ml while group B patients received ketamine 0.1mg/kg in 2ml. Group C patients served as placebo control and were administered 2ml 0.9% normal saline intravenously. The venous drainage was occluded manually by rubber tourniquet at mid-arm. Subsequently the study drug or the placebo was administered as per group allocation. One minute later, 25 % of calculated propofol induction dose was injected over 5 seconds. VAS score for pain of propofol injection was assessed at 0, 1 and 2 minutes after the propofol injection. Thereafter, general anaesthesia technique was continued as per standard technique giving the remaining 75% of propofol. Patient’s heart rate and blood pressure were recorded at 0, 1 and 2 minutes after the administration of 25% of the calculated dose of propofol. Any evidence of hallucination was observed in the recovery room. Results: Demographic profile and the ASA grade of the patients in the 3 groups was uniformly distributed. The mean VAS score for pain perception in group B patients at 1 and 2 minutes was 0.56 and 1.06 respectively. In contrast, the mean VAS for pain was 3.88 and 5.06 at 1 and 2 minutes respectively in group C. The VAS score of patients belonging to group A was closer to that seen in group B patients. This difference in VAS score was statistically highly significant between the groups at 1 and 2 minutes. A significant fall in systolic blood pressure was noted at 2 minutes after administering 25% of the propofol induction dose in all the 3 groups. In contrast, no significant changes were noted at one minute when compared to baseline. There was insignificant fall in the heart rate at 1 and 2 minutes following the administration of 25 % propofol in group A and B. In contrast, an insignificant rise in heart rate was noted at 1 and 2 minutes in group C. Conclusion: The results of this study demonstrate that 0.01 mg/kg of ketamine administered one minute prior to propofol injection is effective and superior to 0.05 mg / kg of ketamine in relieving propofol injection pain without any side effects.