Can a pharmacological pain analysis be used in the assessment of chronic low back pain?

Abstract

A battery of pharmacological tests was used to differentiate the pain in patients with chronic low back pain (CLBP) referred for pain diagnosis and assessment of whether surgery was indicated or not. Forty patients (mean age 39 years, range 22-51 years) suffering from CLBP (mean pain duration 5.9 years, range 1-12 years) participated. Three pharmacological approaches were used: (1) intravenous infusion of morphine, (2) intravenous infusion of lidocaine and (3) a diagnostic epidural opioid blockade. The patients were tested in a single-blind, placebo-controlled fashion. The pain was considered nociceptive if it decreased by 50% or more in response to both intravenous morphine and epidural fentanyl, but increased in response to intravenous naloxone. The pain was considered neuropathic if it decreased by 50% or more in response to both intravenous lidocaine and the epidural local anaesthetic. Patients who registered a pain decrease of 50% or more in response to saline were classified as placebo responders. Those who registered less than 50% pain decrease in all the tests were considered nonresponders. According to the results of the tests, 16 of the patients were classified as having nociceptive pain, 8 neuropathic pain, 2 were placebo responders, 10 non-responders and 4 were unclassified. The results support the idea that this battery of pharmacological tests can be used in the classification of CLBP patients into different pain categories. This approach may prove useful as a guide for further patient evaluation and as a basis for choice of a suitable treatment strategy.

Cost-effectiveness and pain medicine

“…Modifications of the venerable differential spinal block, such as the "pharmacological pain analysis" proposed by Sorensen et al [60], can be a helpful adjunct to the history and physical examination as long as the limitations of the tests are realized. Recent literature has documented the presence of "transient" neurologic symptoms occurring with the use of lidocaine as the intrathecal local anesthetic.…”

“…The potential cost savings of choosing the most appropriate diagnostic or therapeutic intervention involve the elimination of unnecessary modalities. Sorensen et al used a series of pharmacologic interventions designed to determine "nociceptive" versus "neuropathic" pain [15]. The results of these interventions were used to identify four groups of patients: nociceptive, neuropathic, placebo responders, and nonresponders.…”

The Responses to Pharmacological Challenges and Experimental Pain in Patients With Chronic Whiplash-Associated Pain

“…Among patients with chronic low back pain, 25% were classified as nonresponders. 27 We believe that the relatively large nonresponder group should be taken under consideration in the clinical setting, especially when therapeutic interventions are considered. In this context, it is important to state that we only have investigated the effects of 3 active drugs and that other drugs might have effects in the present subgroup of nonresponders.…”

“…26,27 Systemic lidocaine can be effective in the treatment of several neuropathic pain disorders at plasma concentrations below those required for block of axonal conduction. 39 Sodium channel blockade is the most often described major pharmacological property of lidocaine, and experimental data suggest prolonged central effects.…”

“…Using the efficacy of ketamine (a NMDA receptor antagonist), lidocaine, and morphine (different pain blocking in the central nervous system on pain intensity and pressure sensitivity), we subdivided patients with fibromyalgia into different subgroups. [26][27][28] According to these 3 studies, which included 58 patients, we found that 57% were classified as ketamine responders. 26,28,29 These results support the association of central sensitization/central hyperexcitability with activation of NMDA receptors as part of the pathophysiology of the pain and allodynia in a prominent subgroup of patients with fibromyalgia.…”