Comparison of the preventive effect of ketamine, paracetamol and metoclopramide on postoperative pain intensity in general anesthesia: a double-blind clinical trial

Postoperative pain is one of the most common complications after eye surgeries, especially cataract. Use of analgesic drugs before surgery can be effective in decreasing the pain. The purpose of this study was to investigate preemptive effect of ketamine, paracetamol, and metoclopramide on the postoperative pain in the patients following cataract surgery with general anesthesia. In this double-blind clinical trial, 80 adult patients who were candidate for cataract surgery were randomly divided into four groups. Every one of the groups received one of the following prescriptions: 0.1 mg/kg metoclopramide, 0.2 mg/kg ketamine, 1 g paracetamol and placebo before induction of anesthesia. Postoperative pain severity (based on visual analogue scale) and complications were evaluated in the groups. There was a significant difference between the groups in regard to postoperative pain in the recovery room and 2 hours after the operation (P<0.05), but no significant difference was found at 8 and 24 hours after operation. Also, there was no significant difference between the groups in relation to the need for analgesic drugs for pain relief and anti emetic medications to control nausea and vomiting after surgery (P> 0.05). Use of metoclopramide, ketamine, and acetaminophen can lead to prevention of postoperative pain and decreased need for analgesics in the patients following cataract surgery with general anesthesia.