Successful opioid dose reduction after ganglion impar block in a patient with postoperative micturition pain

Abstract

A 68-year-old man underwent abdominoperineal resection to treat anal fistula carcinoma three years previously, following which he developed perineal pain and dysuria and was prescribed sustained-release and immediate-release oxycodone by his primary physician to treat the cancer pain. The patient subsequently received dose increases and rescue doses of opioids in accordance with the WHO method for cancer pain relief. However, since pain management became difficult, he was referred to our pain clinic. At the time of referral, the tumor had completely disappeared, and the pain was due to chronic postoperative pain and not cancer pain. First, the rescue agent was switched from immediate-release oxycodone and oral fentanyl tablet to acetaminophen 500 mg/dose. Ganglion impar block was performed and the prescribed fixed opioid dose was reduced at this point. In this case, the pain was due to postoperative wound pain, and its treatment by the WHO method for cancer pain relief was not indicated due to the risk of opioid-dependency. Treatment and management conforming to opioid analgesic indications for non-cancer pain were necessary.