Superior hypogastric plexus block successfully treats severe penile pain after transurethral resection of the prostate.

BACKGROUND AND OBJECTIVES: Superior hypogastric plexus block has been used to treat cancer pain of the pelvis. METHODS: A patient with severe chronic nonmalignant penile pain after transurethral resection of the prostate underwent a single superior hypogastric plexus block with local anesthetic and steroid. The patient was also started on medications that treat neuropathic pain a few hours after the procedure was finished. RESULTS: The superior hypogastric plexus block resulted in complete pain relief immediately after the procedure. The pain relief continued at 1, 2, 4, and 8 months follow up. CONCLUSIONS: In this case of severe penile pain the superior hypogastric plexus block was useful diagnostically and therapeutically.

Therapeutic drugs for neuropathic pain.

Neuropathic pain is common and may be resistant to usual doses of analgesic medications. However, an improved understanding of the pathophysiology of neuropathic pain and a growing number of adjuvant medications that are useful for the treatment of neuropathic pain provide renewed hope for clinicians and their patients. It is useful to classify adjuvant analgesic drugs into two broad categories. Membrane stabilizing agents, which include the anticonvulsants, antiarrhythmics and probably corticosteroids, may act by blocking sodium channels on damaged neural membranes. Medications that enhance dorsal horn inhibition, which include the antidepressants and some anticonvulsants, may augment biogenic amine or GABAergic mechanisms in the dorsal horn of the spinal cord. Current evidence regarding efficacy generally does not support the use of one agent over another and selection of a particular agent may depend in part on the expected side effects or experience with a given drug. For maximum analgesic effect, more than one agent may be necessary and to improve therapy and minimize side effects, medications generally should be started at lower doses and titrated slowly to effect. Although labor-intensive, this strategy may improve compliance and optimize patient care.

Deafferentation pain exacerbated by subarachnoid lidocaine and relieved by subarachnoid morphine. Case report.

BACKGROUND AND OBJECTIVES: Neuropathic pain syndromes are often resistant to traditional pharmacologic treatment. The authors describe a patient with chronic deafferentation pain of the legs associated with peripheral neuropathy that was refractory to multidisciplinary pain clinic management. METHODS: Numerous medications had been tried, including nortriptyline, mexiletine, and oral and parenteral opioids. Spinal cord stimulation was also ineffective, despite a satisfactory pattern of stimulation-induced paresthesias. For diagnostic purposes, differential spinal anesthesia with lidocaine and morphine was performed, with evoked potential monitoring used to evaluate the intensity of spinal anesthetic block. RESULTS: Paradoxically, lidocaine spinal anesthesia exacerbated pain, whereas subarachnoid morphine provided rapid pain relief. Long-term pain control has been maintained with an implanted spinal infusion pump. CONCLUSIONS: Evoked potential data acquired during lidocaine spinal anesthesia and the rapid pain relief provided by subarachnoid morphine suggest that deafferentation pain may involve segmental, opioid-sensitive dorsal horn pain generators. The long-term pain relief afforded the patient demonstrates that subarachnoid opioids may be efficacious for some forms of neuropathic pain.

Dorsal nerve block for management of intraoperative penile erection.

Intraoperative penile erection during general anesthesia can delay or prevent the completion of cystoscopic or penile surgical procedures. The dorsal penile nerve block is offered as a treatment for intraoperative erection. Advantages of this technique include less potential for cardiovascular complications and improved postoperative analgesia.

Dorsal root entry zone stimulation for deafferentation pain.

Dorsal root entry zone (DREZ) stimulation was performed in 12 patients with chronic pain syndromes after extensive trials of medical therapy, sympathectomy or peripheral nerve stimulation had failed, with 50% of them obtaining excellent long-term benefit. Evoked potential monitoring to facilitate positioning of electrodes under either general or spinal anesthesia, and postoperatively to explore the mechanism of action, revealed findings distinct from those reported with conventional spinal cord stimulation (SCS). DREZ stimulation may function on a different neurophysiologic basis than conventional SCS, involving intersegmental processing and influencing tract of Lissauer functions or the dorsal horn directly.

Sites of action of subarachnoid lidocaine and tetracaine: observations with evoked potential monitoring during spinal cord stimulator implantation.

BACKGROUND: The precise sites of action of local anesthetics on the spinal cord remain speculative. Monitoring spinal cord conduction during spinal anesthesia may provide a more precise localization of anesthetic action. METHODS: Fifteen patients admitted for elective surgical implantation of spinal cord stimulators for treatment of chronic pain participated in the study. Lidocaine (mean dose, 90 mg) was used in 14 patients; one patient received 7.5 mg tetracaine. To assess spinal cord conduction, paresthesias elicited by spinal cord stimulation were monitored during onset and maintenance of spinal anesthesia. In eight patients, evoked potential monitoring was used to further assess cord conduction. RESULTS: Despite complete motor block of the lower extremities and sensory levels to upper thoracic dermatomes (T1-8), all patients felt trial stimulator-induced paresthesias during spinal anesthesia. In addition, cortical evoked potentials from cord stimulation were maintained during spinal anesthesia. However, attenuation of cortical evoked potential amplitudes and paresthesias occurred, which were restored by increasing stimulus intensity. In contrast, even at maximum stimulus intensity, paresthesias and somatosensory evoked potentials from tibial nerve stimulation were abolished during spinal anesthesia. CONCLUSION: Based on these observations, the predominant site of action of subarachnoid lidocaine and tetracaine appeared to be at spinal rootlets, although partial block of afferent cord conduction also occurred.

Interaction of GABA and volatile anesthetics in the nematode Caenorhabditis elegans.

The authors tested whether mutant strains of Caenorhabditis elegans with altered sensitivity to volatile anesthetics have altered responses to GABA or GABA-agonists. They determined the ED50s of the wild-type strain N2 and two mutant strains of C. elegans to a GABA-mimetic ivermectin (IVM) and to GABA. unc-79, a strain with increased sensitivity to halothane, was more sensitive than N2 to IVM and GABA. unc-9, a strain that suppresses the increased sensitivity of unc-79 to halothane, was less sensitive than N2 to IVM and GABA. The authors also tested whether doses of GABA or IVM and volatile anesthetics were additive in their effects on C. elegans. Halothane (2.1%) did not shift the ED50 of IVM, but was antagonistic to GABA. Enflurane (4%) was antagonistic to both IVM and GABA. However, ED50s of halothane and enflurane were unchanged in the presence of IVM (35 nM) or GABA (150 mM). The authors conclude that GABA by itself does not appear to mediate halothane or enflurane sensitivity in C. elegans.

Kidney tubule basement membrane alterations in type II membranoproliferative glomerulonephritis.

Fourteen kidney biopsy specimens from nine patients with type II membranoproliferative glomerulonephritis (MPGN) were examined by electron microscopy for tubular basement membrane (TBM) alterations. In all biopsies, laminal densities, charateristic for type II MPGN, were present in the glomerular basement membranes. The TBM alterations observed included: 1) the presence of laminal, and/or discrete, and/or aggregated densities; 2)focal thickening; 3) multilamination; and, 4) vesicular structures. Laminal densities occurred in 6 of the 9 cases examined. All biopsies had TBM densities representative of at least one of the three forms. The occurrence of electron densities in or near the TBM in type II MPGN may have diagnostic value. In those biopsies where tissue is insufficient for immunofluorescence microscopy and where glomeruli are not found on electron microscopy, an electron microscopic search for densities associated with TBMs would be warranted. Although TBM-associated densities are not pathognomonic for type II MPGN, the observation of such densities, espically laminal densities, would be useful in complementing light miccrscopic and clinical findings.

Myeloid bodies in the renal tubules of humans: relationship to gentamicin therapy.

Ultrastructural changes in renal proximal tubule lysosomes, including the formation of myeloid bodies, occur reliably with gentamicin administration in experimental animals. The present study reviewed the electron microscopic tubular morphology of renal biopsies and nephrectomies performed in our institution over a 2-year period. The frequency of myeloid bodies and their relation to drug therapy and selected clinical features were determined. Myeloid bodies were found in the proximal tubules of 19 of 109 cases that were judged adequate for study. On review of the drug histories of these 19 patients, 15 had received gentamicin within 6 weeks of biopsy or nephrectomy. None of the 90 patients without myeloid bodies had received the drug within 6 weeks of tissue examination. Of 4 patients with myeloid bodies who had not received gentamicin, 1 had received chloroquin and 3 had received drugs with no known or suspected capacity to induce myeloid bodies. The presence of myeloid bodies in proximal tubules did not appear to be related to the total dose of gentamicin, duration of therapy, or serum drug concentration. Clinical evidence of gentamicin nephrotoxicity was present in only 1 case.