Serial cerebrospinal fluid tryptophan and 5-hydroxy indoleacetic acid concentrations in healthy human subjects.

The role of the serotonergic system in the pathogenesis of behavioral disorders such as depression, alcoholism, obsessive-compulsive disorder, and violence is not completely understood. Measurement of the concentration of neurotransmitters and their metabolites in cerebrospinal fluid (CSF) is considered among the most valid, albeit indirect, methods of assessing central nervous system function in man. However, most studies in humans have measured lumbar CSF concentrations only at single time points, thus not taking into account rhythmic or episodic variations in levels of neurotransmitters, precursors, or metabolites. We have continuously sampled lumbar CSF via subarachnoid catheter in 12 healthy volunteers, aged 20-65 years. One ml (every 10 min) CSF samples were collected at a rate of 0.1ml/min for 24-hour (h), and the levels of tryptophan (TRP) and 5-hydroxy indoleacetic acid (5-HIAA) were measured. Variability across all 12 subjects was significantly greater (P < 0.0001) than the variability seen in repeated analysis of a reference CSF sample for both 5-HIAA (32.0% vs 7.9%) and TRP (25.4% vs 7.0%), confirming the presence of significant biological variability during the 24-hr period examined. This variability could not be explained solely by meal related effects. Cosinor analysis of the 24-hr TRP concentrations from all subjects revealed a significant diurnal pattern in CSF TRP levels, whereas the 5-HIAA data were less consistent. These studies indicate that long-term serial CSF sampling reveals diurnal and biological variability not evident in studies based on single CSF samples.

Major controversies in chronic pain

Pain medicine is a relatively new speciality in clinical medicine. While it is widely accepted and recognized, there are some areas of controversy which makes this speciality interesting and open to diverse kinds of research opportunities and clinical innovations. In this presentation, several controversial areas have been selected for discussion because of their scientific merit, clinical applicability, and evolving status in the physician's armamentarium. EPIDURAL STEROIDS FOR LOW PAIN: Epidural steroid injections remain one of many modalities for managing chronic low back pain. The frequency, dose, kind of steroids used and management of complications are still open to discussion. Meta-analysis of the applicability of epidural steroids for low back pain leaves a lot to be desired. More importantly, the criteria for epidural steroid injection have not yet been clearly delineated. REFLEX SYMPATHETIC DYSTROPHY (RSD) AND NEUROPATHIC PAIN: Most clinicians propose that RSD has become a "legal phenomenon" rather than a medical one. This observation indicates the adversarial focus that the injured patient possesses as far as his recovery and rehabilitation are concerned. The different diagnosis techniques and the corresponding diverse therapeutic modalities available for treating RSD are still controversial. CANCER PAIN MANAGEMENT: Cancer pain management is very important in the overall management of the cancer patient, especially when dying and death appear inevitable. A proposed fourth step of the World Health Organization three-step ladder for pain management and its implication will be discussed. MORPHINE AS ANTI-ANALGESIC AGENT: Review of the pharmacological activity of morphine metabolities will be undertaken. A re-evaluation of morphine-3-glucuronide and its analgesic activity may help to explain some interesting physiological phenomena observed during morphine administration. PAIN EDUCATION AND PAIN CERTIFICATION: In the United States of America the education of medical and nursing students regarding pain therapy has been largely ignored. The situation is unfortunate since most young health care professionals have to deal with chronic pain problems as soon as they commence their practices. As pain medicine develops, it is important to have adequate credentialing.(AU)

Pulsating magnetic therapy (PMT) attentuates hyperalgesia in rat model on neuropathic pain - abstract

The aim of this study was to investigate if Pulsating Magnetic Therapy (PMT) could modify the pain response in the peripheral neuropathy produced by sciatic nerve ligation in the rat. Male Sprague-Dawley rats were anaesthetized and the right sciatic nerve loosely ligated in the mid-thigh. A second group were sham operated. Starting on the fifth post-operative day, half of each group of animals were subjected to one hour of PMT for five consecutive days. The pain response was measured on both sides, using radiant heat method on post-operative days five, seven and nine. The animals with the ligated sciatic nerve developed the typical neuropathic syndrome on the operated limb. Following PMT, the pain-induced withdrawal response was significantly decreased in the nerve-ligated limbs compared with the sham operated group on days five and seven after surgery. On day 9, no differences in pain-induced withdrawal response were noted. No statistically significant differences in withdrawal response of the unaffected hind paw was noted in any of the animals. It was concluded that PMT reduces hyperalgesia induced by sciatic nerve ligation in rats and that PMT does not produce direct analgesic effect in acute pain (AU)

The influence of physical and psychosocial factors on accuracy of memory for pain in chronic pain patients.

Pain patients' retrospective reports of pain are important to physicians and other health professionals in helping to decide on future treatment plans. Unfortunately patients' memory of pain can be inaccurate and subject to overestimation. This study examined variables which influenced accuracy of remembering pain in 93 chronic pain patients. The patients were initially evaluated by a physician and completed a comprehensive pain questionnaire and an SCL-90. All patients were asked to monitor their pain intensity every hour for 1 week. At the end of this period each patient was asked to estimate their average pain intensity ratings for 4 times during the day for the previous week. These estimations were compared with the actual mean pain ratings. Results showed that most patients tended to overestimate their pain intensity levels. Cervical and low back pain patients were found to be more accurate than headache and abdominal pain patients in remembering their pain. Patients who reported more emotional distress, who had conflicts at home, who were less active and who relied on medication tended to be the most inaccurate in remembering their pain.

New frontiers in chronic pain management - abstract

Chronic pain, unlike acute pain, represents a failure of modern medical science. In 1956, John Bonica proposed the concept of the multidisciplinary pain clinic and since then the issues of chronic pain have become popular and have assumed increasing importance in medical care. Those issues have included social, economic, medical and political aspects of chronic pain. This abstract deals with the recent advances relating to the medical issues of chronic pain. The following issues would be considered: 1. Classification of chronic pain; 2. Clinical features of chronic pain; 3. Psychological features of chronic pain; 4. Sympathetic blocks and pain implications; 5. Thermography and its diagnostic applications for pain management; 6. Cancer pain management; 7. Tachykinins and substance; 8. Somatostatin; 9. Opiate receptors:endorphins and enkephalins; 10. Epidural blood patch and chronic headaches; 11. Magnetotherapy; 12. Laser therapy and chronic pain. The above-mentioned recent advances in chronic pain have served or may serve to improve the quality of chronic pain management. These advances serve as the catalyst to explore new frontiers in chronic pain management (AU)

Chronic pain assessment using heat beam dolorimetry.

The heat beam dolorimeter (HBD) was developed to evaluate cutaneous pain thresholds in humans. In the present study, the hypothesis that a patient's underlying pain status affects his pain tolerance to an incident HBD stimulus was tested. Twenty-seven chronic pain patients with a variety of clinical problems unresponsive to conventional algological therapy were scheduled for neurosurgical procedures. These patients were evaluated pre- and postoperatively by the HBD procedure. On initial testing, drug-free pain patients showed significantly higher pain tolerance thresholds than normal volunteers (P less than 0.02, Mann-Whitney U test). Postoperatively, incident pain tolerance thresholds in the HBD test were reduced from pre-surgical levels in these patients and were indistinguishable from the second evaluation latencies of volunteers (P greater than 0.05). Twenty-four of the 27 patients reported significant pain relief following surgery. Our results show that, in chronic pain patients, endogenous pain significantly affected incident pain perception in the HBD test when compared with the responses of normal pain-free volunteers. Consequently, HBD may be useful in objectively assessing chronic pain and its relief by neurosurgical procedures.