Is ketamine a useful addition for the management of acute pain in patients where opiates alone have failed to provide adequate analgesia?

Opioids have been successfully used as analgesics in the management of acute pain in the emergency department for many years. Unfortunately, in the setting of moderate to severe pain, the large doses required to relieve the pain are associated with adverse side effects. This can range from nausea and vomiting to respiratory depression. We believe that the addition of ketamine (a dissociative agent with analgesic properties) will help to alleviate moderate to severe pain that has not responded to traditional opioid dosing. The added benefit of the use of ketamine is that it has been shown to be a safe analgesic with a limited side effect profile at the doses required to provide adequate analgesia. The primary aim of the project will be to see if patients in the emergency department who have moderate to severe pain (defined as a pain score of >5/10) despite already receiving opiate analgesia can attain significantly better pain relief with the addition of ketamine rather than further doses of opiates.