Intravenous low-dose ketamine offers no pre-emptive effect: An

Intravenous low-dose ketamine offers no pre-emptive effect: An updated meta-analysis.

Authors: Lynn Hong, Tony Chow, Colin Goodchild, Elean To & John J McNeil.

Oral Presentation (S121) at the 13^th World Congress of Anaesthesiologists Paris, 20^th April 2004

Purpose: The pre-emptive analgesic effect of iv low-dose ketamine was deemed encouraging in a systematic review by Schmid et al. (1999).¹ However, subsequent randomized trials have not supported this conclusion. This article systematically updates the literature, on the pre-emptive effect of ketamine in the peri-operative setting.

Methods: The computer strategy (double blind$ or random$).af was used to identify randomized trials pertaining to ketamine. This strategy has been shown to have a sensitivity of 97% and specificity of 98%.² Double blinded, randomized trials comparing iv ketamine used before surgical incision versus after incision were identified. Statistical analyses were conducted using Review Manager 4.2.3  Cochrane Collaboration. Using the Random Effects Model the standardized mean difference (SMD) and 95%CI were calculated from the mean 24-hour opioid consumption and initial VAS scores.

Results: Nine studies were identified containing a total of 424 patients. The studies contained iv ketamine regimens ranging from 0.15 to 1.0 mg/kg. The SMD were -0.11 (95%CI -0.49 to 0.26) for opioid consumption and 0.15 (95%CI -0.76 to 1.06) for VAS scores. Both were not statistically significant as the 95%CI included one.

Discussion: Our results suggest that pre-incision ketamine offers no pre-emptive effect in terms of pain relief or subsequent opioid requirements. It is apparent that conclusions drawn as recent as five years ago,¹ may no longer be valid. This article highlights the importance to update medical information as it becomes available. The results of which may significantly impact on our clinical practice.

References:

1 Schmid RL, Sandler L, Kat J. Use and efficacy of low-dose ketamine in the management of acute postoperative pain: a review of current techniques and outcomes. Pain 82;1999:111-125.

2 Chow T, To E, Goodchild C, McNeil J. A simple, fast, easy method to identify the evidence base in pain relief research: Validation of a computer search strategy used alone to identify quality randomized controlled trials. Anesthesia & Analgesia 2004: in press.