Opioid-refractory rectal tenesmus treated with burst ketamine

Rectal tenesmus is the painful sensation of incomplete evacuation of the bowels, which is distressing and difficult to manage. Tenesmus is often caused by rectal carcinoma. It is thought there is a significant neuropathic component to tenesmus pain. Ketamine is an antagonist to the N-methyl D-aspartate receptor and has been used for neuropathic pain. We describe the case of a man with difficult-to-manage rectal tenesmus who experienced adverse effects to several medications, limiting titration. A trial of 'burst' ketamine over seven days via a continuous subcutaneous infusion, combined with midazolam and dexamethasone, resulted in a decrease in his pain, as shown by his improved self-reported pain scores and reduced PRN and background opioid requirements. To the authors' knowledge, this is the first report of using ketamine for rectal tenesmus.