Efficacy of Small Doses of Ketamine With Morphine to Decrease Procedural Pain Responses During Open Wound Care

Objective: The purpose of this study was to evaluate differences in pain intensity, pain quality, physiological measures, and adverse effects when patients received morphine with saline (MS) compared with morphine and a small dose of ketamine (MK) before an open wound care procedure (WCP).

Methods: A randomized, cross-over design was used to determine whether the addition of a small dose of ketamine would potentiate morphine's analgesic effects and decrease WCP pain intensity. Patients were randomized to receive either 0.1 mg/kg of morphine (8 mg maximum) plus saline intravenously (IV) or 0.05 mg/kg of morphine (4 mg maximum) plus ketamine 0.25 mg/kg IV before the WCP. Patients were crossed-over to receive the alternate treatment during the next WCP.

Results: Eleven male patients participated in the study. Mean rank of pain intensity during WCP-MK was significantly less than during WCP-MS (P=0.005). Mean±standard error of mean pain intensity during the WCP-MK was 3.09±0.99, whereas it was 6.82±0.92 during the WCP-MS. However, 91% of the patients had adverse effects (eg, strange sensations, hallucinations, blurred vision) with MK versus 0% with MS. Diastolic blood pressure was significantly higher during the WCP-MK.

Discussion: Ketamine with morphine significantly reduced procedural wound pain intensity during WCP. Adverse effects and higher diastolic BP occurred with MK. Further research is warranted to determine the optimal analgesic dose of ketamine or if the addition of a benzodiazepine would mitigate the psychotomimetic effects of ketamine.