Intraoperative Ketorolac Dose of 15 mg Versus the Standard 30 mg on Early Postoperative Pain After Spine Surgery: A Randomised, Blinded, Non-Inferiority Trial

Opioids have traditionally been the cornerstone of acute postoperative pain management. Problematic side effects such as nausea, vomiting, ileus, urinary retention, excess sedation, and respiratory depression are significant disadvantages with the use of opioids. Alternative treatments have been sought. The concept of adding a nonsedating non opioid analgesic agent is appealing and has been validated by previous studies. Nonsteroidal anti-inflammatory drugs (NSAID) are nonsedating and combine analgesic and anti-inflammatory properties ideal for pain after surgery.

Ketorolac is a potent intravenous nonsteroidal anti-inflammatory drug (NSAID), and a non selective cyclooxygenase inhibitor which mediates pain, inflammation and fever. It has been evaluated and used for treatment of moderate to severe pain including postoperative pain. Although intravenous route is not approved by Health Canada, its use is supported in medical literature and clinical practice.

Previous studies have demonstrated the effectiveness of standard 30 mg intravenous ketorolac as an adjunct to opioids for postoperative pain relief. Standard parenteral dose recommended by manufacturer for healthy non elderly population is 30 mg based on a number clinical trials.

Alberta Health Services (AHS) Pharmacy formulary has approved the intravenous use of ketorolac in the dosage range of 10-30 mg depending the patient's weight and medical comorbidities.

NSAIDs, including ketorolac, have an analgesic ceiling effect in which higher doses do not provide any additional pain relief but may increase the likelihood of side effects. Single dose IM ketorolac have been studied in the past showing no difference in analgesia with the 30 and 90 mg dose. Because of risk of drug toxicity and unwanted side effects, patients should be given the lowest effective ketorolac dose. Low dose ketorolac was studied in the adolescents undergoing spine surgery and showed that dose of 0.2mg/kg (11mg) provides supplemental analgesia postoperatively. However, there were no previous studies found on review of the literature using medline search that look at parallel comparison between intraoperative doses of ketorolac in terms of efficacy and safety profile.