A prospective observational study of the efficacy of ketamine for rescue analgesia in the postanesthesia recovery unit.

BACKGROUND: Early severe postoperative pain is frequently resistant to management with opioid analgesia alone. Perioperative low-dose ketamine as an analgesia adjunct has been studied extensively. Its efficacy as a rescue analgesic in the postanesthesia care unit (PACU) has not been determined. The objective of this study was to evaluate the analgesic efficacy of low-dose bolus ketamine for opioid-resistant pain in the PACU by measuring its effect on numerical rating scale (NRS) pain scores and opioid requirement.

METHODS: This was a prospective observational study of adult noncardiac surgery patients with significant postoperative pain in the PACU. Patients were administered bolus doses of intravenous ketamine in 10-mg increments, repeated two to three times to an approximate maximum dose of 0.25 mg·kg-1 . Primary outcomes were resting pain score reduction and opioid use from time of bolus ketamine administration to 30 min after administration of final ketamine bolus. The secondary outcome was incidence of side effects from ketamine administration.

RESULTS: A convenience sample of 100 patients was chosen. The mean (standard deviation) NRS resting pain score reduction 30 min after iv ketamine administration was 2.7 (1.8) (P < 0.001). Patients with a history of previous opioid use or chronic pain were not more responsive to the effects of low-dose bolus ketamine. There were no ketamine-related adverse effects in any of the study patients.

CONCLUSION: Administration of low-dose bolus ketamine in the PACU for severe opioid-resistant pain was associated with a significant improvement in analgesia in this observational study.