Local analgesia without anesthesia using peripheral perineural morphine injections

Twenty-five patients with chronic pain were treated with nerve blocks. They were divided into two groups, A and B, according to the volume of local anesthetic required for surgical anesthesia by standard nerve block techniques. The 16 patients in group A had pain in the distribution of small nerves, which could be blocked with 5 ml or less. They were blocked in a random, double-blind crossover fashion using 0.5% bupivacaine or 0.02% morphine. The nine patients in group B were injected simultaneously with saline, 30 ml perineurally and 1 ml intramuscularly. Morphine (6 mg) was added, in a random, double-blind fashion, to one of the injections. A second pair of injections was subsequently done, using morphine by the alternative route. Perineural morphine provided statistically longer lasting pain relief than did either intramuscular morphine or perineural bupivacaine.