Comparison of the effect of subcutaneous injection of Ketamine and Lidocaine in reducing postoperative pain in patients undergoing elective inguinal hernia surgery under general anesthesia

Appropriate analgesia after surgery helps patients feel more comfortable and increase the mobility of them. The purpose of this study was to compare the effect of subcutaneous injection of Ketamine and Lidocaine in reducing postoperative pain in patients undergoing elective inguinal hernia surgery under general anesthesia.

This double blinded, randomized clinical trial study was done on 60 patients undergoing elective inguinal hernia under general anesthesia. Subjects were randomly assigned into three groups including control, Ketamine and Lidocaine groups. Subjects in Ketamine group were received infiltration of subcutaneous Ketamine 0.5 mg/kg/bw after closure of surgical incision. Subjects in Lidocaine group were received infiltration of subcutaneous Lidocaine 1 mg/kg/bw at the time of wound suturing. Subjects in control group did not receive Ketamine and Lidocaine. The visual analogue scale (VAS) of pain and vital signs were continuously assessed. If VAS≥3, 100 mg diclofenac suppository was administered and if there were no response, 30 mg intravenous pethidine was also administered. The complications, including hallucination, nystagmus, nausea, vomiting and drowsiness in patients were also recorded.

The mean VAS at 1, 2 hours after surgery were significantly lower in the Ketamine and Lidocaine group in compared to control group (P<0.05). No significant adverse effect was observed in the Ketamine group.

For reduction of pain, administration of subcutaneous Ketamine is recommended due to no adverse effect and anti analgesic effect of Ketamine is similar to Lidocaine.