Anesth Analg. 2009 Dec;109(6):1963-71. doi: 10.1213/ANE.0b013e3181bdc8a0.
The early and delayed analgesic effects of ketamine after total hip arthroplasty: a prospective, randomized, controlled, double-blind study.
The gist: Ketamine can reduce post-op pain scores and is opioid sparing when given to patients undergoing General Anesthesia hip replacement (note this is NOT generalizable to spinal anesthesia)
Methods: Pts received IV ketamine before incision (0.5 mg/kg), and a 24-h infusion (2 microg x kg(-1) x min(-1)) or a similar blinded saline bolus and infusion. Postoperative analgesia included IV acetaminophen, ketoprofen, plus morphine/droperidol patient-controlled analgesia for 48 h
Results: Ketamine decreased morphine consumption at 24 h from 19 +/- 12 mg to 14 +/- 13 mg (P = 0.004). At Day 30, ketamine decreased the proportion of patients needing 2 crutches or a walking frame from 56% to 31% (P = 0.0035). From Day 30 to Day 180, ketamine decreased the proportion of patients with persistent pain at rest in the operated hip (P = 0.008).
Other evidence [apparently – I’m looking at you DP who never bothers to comment] shows the one time bolus 0.5mg/kg vs. infusion makes little difference in post-op pain scores… so go for the bolus!