The effect of opioids on field block for hernia repair: a study comparing pethidine with a placebo

Abstract

Background: Intramuscular (IM) pethidine injection is used as pre analgesia (pre-medication) in hernia repair under local anaesthesia in some district hospitals. We evaluated the relevance of this practice in a facility based study at one of the district hospitals in Ghana.

Method: One hundred and twenty patients above 10 years of age with a mean age of approximately 49 years diagnosed as having inguinal hernias of different sizes were recruited into the study. Each group of 60 patients was randomly selected. A maximum of 50 ml 1% lignocaine plus 2 ml (100 mg) of pethidine was used in group A and 50 ml 1% lignocaine plus 2 ml of sterile water in group B. A score ranging from 0 to 3 was assigned at the end of each surgery depending on the degree of pain experienced.

Results: 33.3%, 33.3%, 21.7% and 11.7% of patients in group A scored 0, 1, 2, and 3 respectively in pain perception while 26.7%, 33.3%, 25% and 15.0% were the scores in group B. None of the patients in group B experienced an adverse effect to any of the agents used. 2% and 5% in group A experienced nausea and generalized pruritus respectively. Post-operation condition was satisfactory and all patients were discharged the same day.

Discussions and Conclusion: There was no significant difference in pain perception when IM pethidine is combined with local infiltration compared with local infiltration plus sterile water for herniorrhaphy. Good and adequate local infiltration is enough for the repair of simple hernias as the addition of pethidine does not give any significant analgesia but increases the chance of patient developing complications.