Ketamine and oxycodone in the management of postoperative pain

Military Medicine, Jun 2000 by Levanen, Jaakko

Awareness was assessed in the recovery room at 0, 90, and 180 minutes on a scale from 0 to 4, with 0 denoting insensibility and 4 denoting full responsiveness. Sedation, anxiety, and awareness were evaluated by a single trained and experienced nurse for all patients.

Pain

Postoperative pain was assessed at 15-minute intervals on a 10-point visual analogue scale (VAS) with 0 denoting no pain and 10 denoting the worst pain imaginable. No attempts were made to differentiate between rest pain and pain induced by swallowing or coughing.

Changes in the averaged relative pulse-wave amplitude (as 10-second averages) trends were compared with the concomitant pain VAS scores (at 15-minute intervals).

Postoperative Analgesia

After having sufficiently recovered from anesthesia, the patients were transferred to the recovery room, where they received for postoperative pain a 0.2-mL bolus injection containing either 10 mg of ketamine or 2 mg of oxycodone in identical syringes coded and labeled with patient numbers to maintain a double-blind experimental design. The doses used were considered equally analgesic. The patients received the analgesic at their own request or according to the VAS score.

After the recovery room period, the patients were transferred to the ward, where they received ketoprofen 100 mg IV every 8 hours as the standard analgesic. At the patient's request, additional pain relief was provided by administering oxycodone 10 mg IM.

Statistics

At the end of the study, the codes were opened and the data were tabulated and subjected to statistical analyses (t test, regression). Analgesic efficacy was determined by comparing the pain intensity and the difference in pain intensity relief (initial pain intensity score minus subsequent VAS pain intensity scores).2 The differences in pain intensity relief were also calculated as percentages of the initial VAS score.

Results

No statistically significant differences were found between the two groups in the demographic data (Table I) or in the duration of anesthesia, recovery room time, or number of required analgesic doses (Table II). Neither were any statistically significant differences found between the groups in the hemodynamic baseline parameters or in preinduction sedation or anxiety.

Postoperative Analgesia

The mean initial recovery room pain VAS score was 6.0 in the ketamine group and 6.2 in the oxycodone group. The difference is not statistically significant.

A statistically significant difference was found in the pain intensity scores between the two groups in favor of ketamine at 165 and 180 minutes (p

Pain VAS Score and Plethysmographic

Pulse-Wave Amplitude

Regression analysis of the coincident mean pain VAS scores and the registered averaged relative pulse-wave amplitude changes showed an inverse correlation between the two parameters. An increase in the VAS score was reflected as a decrease and a decrease in the VAS score was reflected as an increase in the relative pulse-wave amplitude in both groups (ketamine group, r = -0.8637, p