Opioid-sparing effect of preemptive bolus low-dose ketamine for moderate sedation in opioid abusers undergoing extracorporeal shock wave lithotripsy: a randomized clinical trial.

• Volume 116 • Number 1 www.anesthesia-analgesia.org 75 Ketamine as an N-methyl-d-aspartate receptor antagonist has analgesic effects in acute and chronic pain. Ketamine enhances the inhibitory control of pain perception via descending pathways, boosts the peripheral antinociceptive effect of opioids, prevents opioid tolerance, and enhances analgesia via other mechanisms.1–6A growing body of evidence supports ketamine use as an adjuvant therapy in postoperative analgesia.2,3,7,8 However, there are still controversies.9–12 Postoperative analgesia in opioid abusers requires cautious administration of multimodal therapy to minimize adverse events.13 The success of opioid-sparing effects of intraoperative ketamine has been studied in opioid abusers.14,15 Nevertheless, the effectiveness of bolus low-dose ketamine in moderate sedation has not been elaborated in previous studies especially with very low doses such as 0.1 mg/kg. We hypothesized that a single preemptive IV low-dose ketamine bolus would have a remifentanil-sparing effect (primary outcome) in opioid abusers undergoing moderate sedation for extracorporeal shock wave lithotripsy (ESWL). The incidence of bradypnea, apnea, nausea, vomiting, hemodynamic changes, and ready to discharge time were also evaluated as secondary outcomes.