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Program

Palliative Medicine

Training Level

Fellow

Institution

Henry Ford Hospital

Abstract

Background: Sub-anesthetic ketamine is used in the hospice and palliative setting to provide analgesia for opioid refractory cancer pain. While there are case reports supporting its use for this indication, results from the few studies done are mixed. Additionally, there are no widely agreed upon guidelines for dosing. The heterogeneous results may be attributed to small sample sizes and differing doses and routes of administration of ketamine. The objectives of this case presentation is to describe the successful use of sub-anesthetic ketamine in the management of high dose opioid refractory cancer pain and to propose a new area of study in the use of sub-anesthetic ketamine for management of an opioid refractory cancer pain.

Case: A 32 year old male, receiving home hospice, with stage IV gastric adenocarcinoma, complicated by severe cancer-related abdominal pain presented to the ED in a pain crisis, agitated, confused and drowsy. His pain had been managed with a fentanyl PCA at home, with a 650 mcg/hr continuous infusion and a 200mcg demand dose with a 10 minute lockout. His fentanyl use escalated over the preceding days with 31,600 mcg of fentanyl (5266 oral morphine equivalents) in the 24 hours leading up to presentation. In the ED, his fentanyl PCA was continued and he was given hydromorphone 6mg IV and dexamethasone 10mg IV without effect. He was then given a 0.3 mg/kg ketamine bolus with improvement of his pain. He was subsequently admitted to the inpatient hospice unit for further pain management. He was initiated on a low dose ketamine infusion at 0.1mg/kg/hr and was rotated to a hydromorphone PCA at a continuous infusion of 13mg/hr (which is a 25% dose reduction from total fentanyl use) and a 10mg demand dose and 10 minute lockout. His ketamine infusion was titrated upwards to 0.2mg/kg/hr with improvement of his pain. He was maintained at this rate with adequate pain control while his hydromorphone PCA was able to be tapered down to a continuous infusion of 6mg/hr (decreased by 2mg/hr daily) and demand dose of 8mg with a 10 minute lockout. He was subsequently weaned off the ketamine infusion with sustained pain control and a 50% decrease in his opioid requirement. He experienced mild non-disturbing hallucinations and vivid dreams which were adequately controlled with haloperidol and lorazepam. The patient was able to be discharged home with adequate pain control on the hydromorphone PCA with home hospice.

Conclusion: This case presentation adds to the other case reports supporting the utility of sub-anesthetic ketamine in the treatment of opioid refractory cancer pain. It also identifies the use of an initial sub-anesthetic ketamine bolus as a means to identify patients that are more likely to benefit from an infusion. Current studies in the medical literature are of small scale, vary in regards to dosing and routes of administration and provide heterogeneous results. Further studies are needed with larger sample sizes, consistent dosing and consistent routes of administration to draw more definitive conclusions regarding the utility of sub-anesthetic ketamine for opioid refractory cancer pain and to guide clinical practice. It is our suggestion that these studies also investigate the use of a sub-anesthetic ketamine bolus as a means to identify patients more likely to benefit from an infusion.

Presentation Date

5-2020

Low Dose Ketamine for Opioid Refractory Cancer Pain

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