Pain on Propofol Injection: The Gender Differences in Pain Perception

Abstract

Background: Injection pain, which distresses patients, is a major disadvantage of propofol as an induction agent. Lignocaine pretreatment is the most popular method for reducing this pain but this drug alone cannot eliminate the problem. The aim of this study was to investigate the gender differences in pain perception/responses, and the analgesic effect of lignocaine and metoclopramide combination, compared with lignocaine alone, during propofol injection in an adult Nigerian population at the Lagos University Teaching Hospital (LUTH).
Methods: A total of seventy patients were studied, comprising twenty-seven men (38.57%) and forty-three women (61.43%). Thirty-five patients in each group; who came in for various elective surgical procedures under intravenous general anesthesia were randomly assigned to two different groups, A or B. The effectiveness of a combination of i.v lignocaine 20mg/ i.v metoclopramide 10mg ( group A, n=35) when mixed with i.v propofol 2.0mg/kg in reducing pain on injection at induction of anesthesia was compared with i.v lignocaine 20mg alone mixed with i.v propofol 2.0mg/kg into a dorsal hand vein (group B, n=35). During a ten-second pause, after the first 25% of the calculated propofol dose (mixed with study drugs), the patients were asked standard questions regarding pain on injection before induction of anaesthesia. The incidence and intensity of pain were assessed using a four point Verbal Rating Scale 0 to 3 during propofol injection. Thereafter, the induction of anesthesia was continued and completed with the remainder of the calculated propofol dose and endotracheal intubation facilitated with 0.1mg/kg pancuronium in the two groups. In all other respects, except for the type of surgery, the patients had the same treatment.
Results: With regard to incidence of pain on injection, the difference between the two groups was statistically significant (P<0.05) using the Chi-square test. There was no statistical difference in Verbal Pain Response (intensity) (P>0.05) Female patients had statistically significant greater pain responses/perception than men in both groups (P< 0.05).
Conclusion: A lignocaine/metoclopramide combination was more effective than lignocaine alone for reducing pain on injection of propofol, and in addition, women had significant greater pain perception than men.

Keyword: propofol injection pain, gender differences, pain perception, lignocaine, metoclopramide.