Wound infusion of bupivacaine following radical retropubic prostatectomy: a randomised placebo-controlled clinical study.

CONTEXT: The effectiveness of postoperative analgesia through a wound catheter is subject to considerable debate. OBJECTIVE: To test the hypothesis that local wound infusion with bupivacaine followed by continuous infusion could reduce postoperative need for opioids in patients undergoing retropubic prostatectomy. DESIGN: Single-centre prospective, double-blinded, placebo-controlled trial. SETTING: A major university hospital in Denmark. PATIENTS: Following written informed consent, 60 patients scheduled for prostatectomy were recruited to the study and 50 completed the protocol to reach data analysis. INTERVENTIONS: Thirty millilitre bolus of bupivacaine (2.5 mg ml) or isotonic saline was injected through a subfascially placed wound catheter followed by continuous infusion at 5 ml h during the following 48 h. All patients were prescribed paracetamol, non-steroidal anti-inflammatory drugs, morphine and oxycodone if needed. OUTCOME MEASURES: Primary outcome was the opioid requirement. Secondary outcomes included pain scores at rest and with activity, and nausea and vomiting scores. RESULTS: The total amount of morphine required during the postoperative period was not significantly higher (P=0.49) in the placebo group (12 mg, 25 to 75% percentile 5 to 18) than the bupivacaine group (10 mg, 25 to 75% percentile 0 to 16). Similarly, the total amount of oxycodone required was not significantly different (P=0.99) and was equal among the groups (5 mg, 25 to 75% percentile 5 to 10). At 2 h postoperatively, a significantly (P=0.0488) higher number of patients required additional morphine in the placebo group. No differences between the groups were detected at any time point regarding pain scores or the presence of nausea and vomiting. CONCLUSION: Additional use of a wound catheter in patients undergoing prostatectomy in the present perioperative setting appears superfluous.

The effect of Ketamine on stimulation of primary and secondary hyperalgesic areas induced by capsaicin--a double-blind, placebo-controlled, human experimental study.

The non-competitive NMDA-antagonist, Ketamine, was infused (i.v.) in healthy volunteers to study the effect on central excitability with the presence of cutaneous hyperalgesia. Hyperalgesia was established experimentally on the dorsum of the foot by topical application of capsaicin (1%). Different thermal and mechanical conditioning stimuli were applied to the primary and secondary hyperalgesic areas to modulate the central nociceptive excitability monitored by the nociceptive reflex. When the elicited reflex was combined with an activation of the secondary hyperalgesic area by continuous, non-painful, electrical stimulation, a facilitation of the reflex was observed. This indicates that summation of activity in non-nociceptive and nociceptive afferents can occur under mild pathological conditions. Conditioning thermal stimuli of the primary hyperalgesic area were employed to intensify the allodynia prior to testing this interaction between tactile and nociceptive activity. The same reflex facilitation was inhibited by Ketamine. Furthermore, Ketamine decreased the pain intensity associated with the stimuli eliciting the reflex. Psychophysical measures to single and repeated electrical and thermal (laser) stimuli applied within the hyperalgesic areas were also obtained. The intensity of pain sensations produced by single, painful, electrical stimuli applied to the primary hyperalgesic region was reduced after Ketamine infusion. Finally, five repeated, electrical stimuli applied to the secondary hyperalgesic area were used to assess the temporal summation threshold. Ketamine caused an increase in the summation threshold compared to the placebo treatment. In conclusion, these results demonstrate that (1) summation of activity in non-nociceptive and nociceptive afferents occurs under hyperalgesic conditions and, (2) this summation can be inhibited by NMDA-antagonists. Therefore, the study shows an apparent involvement of NMDA-receptors in some of the central mechanisms underlying secondary hyperalgesia.

Low-dose intra-articular morphine analgesia in day case knee arthroscopy: a randomized double-blinded prospective study.

The aim of this study was to demonstrate the effect of intra-articular morphine following knee arthroscopy performed in infiltration analgesia. Fifty-two healthy patients were randomized to receive either 1 mg of morphine or placebo. The pain was assessed 2, 4, 8 and 24 h after the procedure by (1) a VAS scale and (2) the amount of acetaminophen consumed. Demographic data in the 2 groups were similar. The pain scores at 8 and 24 h and the acetaminophen consumption after 8 h were lower in the morphine group (P < 0.05). Our results support the hypothesis of peripherally distributed opioid receptors. Stratifying data in therapeutic versus diagnostic arthroscopy indicated additional effect of morphine in patients undergoing therapy (P < 0.1), an aspect supporting the hypothesis of peripherally administered morphine as a potential suppressor of the substance P-mediated cytokine cascade and the peripheral leukocyte activity. Intra-articular morphine (1 mg) after knee arthroscopy offers efficient analgesia lasting more than 24 h. The method is devoid of side effects and deserves wider recognition.