Direct effect of electrical stimulation on peripheral nerve evoked activity: implications in pain relief.

Experiments were performed with a peripheral neurostimulator, used clinically for pain relief, on isolated cat cutaneous peripheral nerve to determine the effect of electrical stimulation on components of the compound action potential. The results show that neurostimulation alters the conduction velocity and the amplitude of both the A-alpha and beta and the A-delta waves with the more slowly-conducting A-delta component showing the greatest changes. This direct alteration of peripheral nerve activity distal to the first synapse in the spinal cord might contribute to the mechanism of pain relief.

The use of surgical sympathectomy in the treatment of chronic renal pain.

OBJECTIVE: To assess the efficacy of renal sympathetic denervation in the treatment of chronic renal pain. PATIENTS AND METHODS: In a 10-year period, 21 patients suffering from chronic renal pain underwent 27 renal denervation operations, six of which were bilateral. The cause of pain was the loin pain haematuria syndrome in 18 patients. RESULTS: Four operations resulted in complete pain relief to date (median follow-up 53.5 months). pain relief after the other 23 operations in 18 patients lasted a median of 6 months. Assuming that recurrent pain was due to neuronal regeneration, nine of the 18 patients with recurrent pain underwent a total of 10 re-explorations of the renal pedicle, stripping it of all nerve fibres and areolar tissue. Three of these re-explorations produced complete pain relief to date (median follow-up 40 months). The median pain-free interval of the other seven re-explorations in six patients was 19 months. CONCLUSION: Renal denervation cures severe intractable pain in about 25% of patients. Recurrence of pain could be prevented in more patients if there was a way of preventing re-innervation.

Long-term pain relief produced by intrathecal morphine infusion in 53 patients.

The present report details the characteristics of the analgesic effects of morphine administered chronically by infusion pumps implanted in 53 patients suffering from terminal metastatic disease. The median postimplant survival time in these patients was 4 months. Patients (mean age 58 years) were characterized according to the duration of pain before pump implantation (mean 16 months), prior consumption of systemic opioids (mean one to six daily analgesic equivalents of morphine), and their response to a trial intrathecal dose of morphine (1 to 2 mg). The median infusion dose at 2 weeks was 3.8 mg/day. The analgesic index, calculated as (quality of pain relief x duration of pain relief in hours)/morphine dose in mg, that was observed after the trial dose of morphine was determined for each patient. A close correlation was observed between the acute (2-week) infusion dose necessary to produce pain relief and the analgesic index such that the infusion dose = -8.0 x log (analgesic index) + 17.1. By 16 weeks, the mean spinal morphine dose for the group had increased by a factor of about 2.5; however, significant variation in the dose incrementation was documented. The maximum increase was observed in patients with a low analgesic index, and this rapid incrementation was usually correlated with an unsatisfactory overall outcome. Evidence that long-term infusion continues to yield analgesia was evidenced in six cases where there was an unanticipated loss of drug infusion and a corresponding increase in parenteral narcotic consumption. These data indicate the long-term efficacy and safety of spinal opioid infusion in patients with terminal cancer, and emphasize the advantage of assessing the sensitivity of the patient to spinal opioids by a standardized trial injection prior to pump placement as a prognostic indication of outcome.

Ductal drainage or resection for chronic pancreatitis.

We report a 10 year review comparing the results of pain relief after three procedures for chronic pancreatitis: Whipple pancreatoduodenectomy, modified Puestow side-to-side longitudinal pancreaticojejunostomy and distal pancreatic resection. Results of follow-up review at 6 months, 2 years and 5 years were tabulated. Five year follow-up data were available on more than 80 percent of patients. The proportion of good results for pain relief decreased with the passage of time regardless of the procedure performed. Although equally good results are obtained after either pancreatoduodenectomy or pancreaticojejunosotomy, we conclude that in the presence of a dilated duct, the procedure of choice is pancreaticojejunostomy. If the duct is not dilated, we then favor pancreatoduodenectomy, after which the pain relief is significantly better (p = 0.05) than after distal resection. Our data show that, for all factors evaluated, the poorest pain relief was obtained after distal resection. Therefore that procedure has limited value when used specifically for relief of pain in chronic pancreatitis, except in the uncommon circumstance when the disease is confined to the distal part of the gland. Our study also shows that patients who have more radical distal resection have no better pain relief than those who have 50 percent distal resection.