1. 2014;17;E225-E228Opioid Induced Hyperalgesia Altered with Propofol Infusion
   Case Study
   Alan D Kaye, MD, PhD, Keun Sam Chung, MD, Nalini Vadivelu, MD, Catalin Cantemir, MD, Richard D. Urman, MD, and Laxmaiah Manchikanti, MD.

Propofol is a common induction agent that is utilized worldwide in the field of anesthesiology. In recent years, its potential therapeutic role in a variety of patient states has been demonstrated. Controversy exists regarding Propofol mediated analgesic and antihyperalgesic properties. Recent studies have suggested a variety of different mechanisms of action, including modulation of N-Methyl-D- Aspartate receptors and the endocannabinoid system. The N-Methyl-D- Aspartate receptor is part of a larger family of glutamate receptors and is an important mediator of excitatory neurotransmission. In the case presented, the pain experienced by the patient was not well-controlled, in spite of increasing doses of opioids, potentially due to superimposed opioid induced hyperalgesia. In the present case, we demonstrate a cycle of opioid induced hyperalgesia which was successfully affected with a Propofol infusion. Controversial reports exist in animal studies on the analgesic properties of Propofol. Randomized controlled studies in animal models studying the effect of Propofol on pain sensation have shown that Propofol possesses an analgesic effect. This clinical case demonstrates that Propofol could possibly have antihyperalgesic effects on opioid induced hyperalgesia caused by high-doses of chronic opioids and worsened by fentanyl. We postulate that a probable mechanism of complete pain relief after the procedure could be the inhibition of activity of the N-Methyl-D- Aspartate receptor by Propofol because it was the only agent the patient received during the procedure, causing a break of the cycle of opioid induced hyperalgesia. Additional research is required to clarify Propofol mediated or modulated analgesic properties in humans.