The addition of opioids to local anaesthetics in brachial plexus block: the comparative effects of morphine, buprenorphine and sufentanil

We compared the duration of analgesia produced by a mixture of lignocaine and bupivacaine, either alone or combined with morphine (75 micrograms.kg-1), buprenorphine (3 micrograms.kg-1) or sufentanil (0.2 microgram.kg-1) in 80 patients after brachial plexus block for orthopaedic surgery of the upper limb. The characteristics of analgesia were evaluated hourly using a visual analogue scale. The analgesia was considered satisfactory for scores of 30 or less. The median duration (range) of satisfactory analgesia was: 11.5 (8-15) h without an opioid, 21 (9-27) h with morphine, 20 (14-34) h with buprenorphine and 24.5 (11-38) h with sufentanil. We conclude that the addition of an opioid to a local anaesthetic mixture lengthens the duration of analgesia.