A single infusion of intravenous ketamine improves pain relief in patients with critical limb ischaemia: results of a double blind randomised controlled trial.

Abstract

We report the first double blind randomised controlled trial of regular opioids and an infusion of low dose (0.6 mg/kg) intravenous ketamine compared with opioids and placebo in patients with allodynia, hyperalgesia and hyperpathia secondary to critical limb ischaemia. Thirty-five patients completed the study, 18 received regular opioids plus ketamine, while 17 received regular opioids plus placebo. Using the Brief Pain Inventory, the % pain relief that the patients in the ketamine group attributed to their medication improved significantly from 50% immediately pre-infusion to 65% 24 h post-infusion and 69% 5 days post infusion. Over the same period, the pain relief achieved by the placebo group rose from 58% pre-infusion to 56% 24 h post infusion and then 50% relief 5 days later. This was statistically significant (P<0.05) using both the t-test and the Wilcoxon Rank Sum test. The ketamine group also showed a statistically significant difference 24 h post infusion of the effect of pain on their general activity (P=0.03) and on their enjoyment of life (P=0.004). This study shows that combining a single infusion of low dose ketamine with regular opioid analgesia can result in a significant improvement in pain relief for this patient group.