Charles Chabal

Prescription opiate abuse in chronic pain patients: clinical criteria, incidence, and predictors.

OBJECTIVES Opiates are commonly used to treat patients with chronic nonmalignant pain. There is much controversy over the definition, incidence, and risk factors of prescription opiate abuse in chronic pain treatment. The present study, done at the Seattle VA Medical Center, was designed to create opiate abuse criteria, test inter-rater reliability of the criteria, apply the criteria to a group of chronic pain patients, and correlate the risk of opiate abuse with the results of alcohol and drug testing. DESIGN/OUTCOME MEASURES A committee of experienced pain providers designed a five-point prescription opiate abuse checklist based on DSM-III-R parameters. The criteria were then applied to patients enrolled in the pain clinic. The reliability of the criteria were determined using two providers who were familiar with every patient in the clinic. Drug, alcohol, and psychosocial testing were correlated with the risk of opiate abuse. RESULTS A total of 19% (76/403) of all pain clinic patients were using chronic opiates. Thirty-four percent (26/76) met one, and 27.6% (21/76) met three or more of the abuse criteria. The criteria had an inter-rater reliability of > 0.9. There were no differences between chronic opiate users (n = 76) and opiate abusers (n = 21) for a history of drug or alcohol abuse or on psychosocial testing. CONCLUSIONS Prescription opiate abuse criteria for use in patients with chronic nonmalignant pain were designed. The criteria had good reliability and can be applied during normal clinic interactions. The percentage of chronic opiate users who become opiate abusers in pain treatment is within the range reported by others. Past opiate or alcohol abuse or psychosocial testing on clinic admission failed to predict who would become an opiate abuser. The criteria can be used to identify patients who will subsequently require more intensive treatment or intervention or can be used as an outcome to measure to test the effectiveness of treatment strategies.

The effect of intravenous lidocaine, tocainide, and mexiletine on spontaneously active fibers originating in rat sciatic neuromas

&NA; The effects of intravenously administered subanesthetic concentrations of lidocaine, tocainide, and mexiletine on spontaneously active fibers (SAFs) originating in 7‐day‐old rat sciatic neuromas were studied. Control injections of normal saline caused no decrease in SAF or discharge rate. Lidocaine and tocainide given in incremental doses of 5, 10, 15, 20 and up to 25 mg/kg caused nearly all observed SAFs to stop firing. Mexiletine given in doses of 3, 5, 7, 10 and up to 15 mg/kg showed similar results at lower doses. All agents decreased the sensitivity of SAF to mechanical stimulation. No conduction blockade occurred at these doses of intravenously administered local anesthetics. The demonstrated reduction in firing rate of SAF may explain the pain relief observed in clinical trials of these orally available agents.

Pain responses to perineuromal injection of normal saline, gallamine, and lidocaine in humans.

&NA; Rat neuromas have shown an increase of spontaneously active fibers to systemically administered potassium channel blocking agents such as tetraethylammonium chloride (TEA) and gallamine. Neuroma formation and spontaneous activity have been associated with autotomy in rats and pain in humans. To evaluate the chemosensitivity of human neurons to potassium channel blocking agents, 9 subjects with neuroma pain underwent perineuromal injection in a single‐blinded fashion of normal saline, gallamine, and lidocaine. Sodium chloride had no effect on control pain levels, while gallamine significantly increased and lidocaine significantly decreased pain from control levels. Three of 4 patients with accompanying phantom limb pain noted an increase in pain after the injection of gallamine. The data suggest that peripheral input plays a modulating but not solitary role in both neuroma and phantom limb pain. Agents which increase potassium channel permeability or decrease sodium influx would be predicted to decreased perceived pain.

The use of oral mexiletine for the treatment of pain after peripheral nerve injury

Neuropathic pain is often a difficult condition to treat. Clinical and laboratory studies using intravenously administered local anesthetics or antiarrhythmic agents support the use of these drugs for the treatment of neuropathic pain. The availability of the oral antiarrhythmic medication, mexiletine, has made it possible to study the effects of an orally administered medication on chronic neuropathic pain. The study used a double-blind placebo-controlled design to examine 11 subjects in whom treatment with conventional pain medications had been unsuccessful. Subjects had a history of peripheral nerve injury or dysfunction, and all complained of symptoms consistent with neuropathic pain. After baseline pain measurements, mexiletine or placebo was given in gradually increasing doses to a maximum daily dose of 750 mg mexiletine. After 1 month at steady state, the subject received the alternative medication. Mexiletine was found to produce a statistically significant reduction in reported pain when compared to baseline or placebo. Pain scores were rated on a scale from 0 (no pain) to 10 (unbearable pain). Median pain scores prior to mexiletine were 7, after placebo treatment 7, and while receiving mexiletine (750 mg/day) 4. Side effects were mild and well-tolerated. Mexiletine may be effective in reducing neuropathic pain for patients in whom alternative pain medications have been unsatisfactory.

Safety and Acceptability of the Research Lumbar Puncture

Three hundred forty-two subjects underwent 428 research lumbar punctures for studies of cerebrospinal fluid (CSF) biomarkers. Subjects were 67 Alzheimer disease or mild cognitive impairment (AD/MCI) patients and 275 cognitively normal adults aged 21 to 88. Lumbar puncture was performed in the lateral decubitus or sitting position using the Sprotte 24g atraumatic spinal needle. Up to 34 ml of cerebrospinal fluid were collected. Anxiety and pain experienced during lumbar puncture were rated on a visual analog scale. The frequency of any adverse event (11.7%), clinically significant adverse events (3.97%), and typical post-lumbar puncture headache (PLPHA) (0.93%) was low. Risk of post-lumbar puncture headache was unrelated to age, gender, position during lumbar puncture, ml of cerebrospinal fluid collected, or minutes of recumbent rest following lumbar puncture. The frequency of post-lumbar puncture headache was lower in AD/MCI (P = 0.03) than any other subject group. Anxiety and pain ratings were low. Younger subjects reported more anxiety than old (P = 0.001) and AD/MCI subjects (P = 0.008) and more pain than older normal subjects (P = 0.013). Pain ratings for women were higher than those for men (P = 0.006). Using the Sprotte 24g spinal needle, research lumbar puncture can be performed with a very low rate of clinically significant adverse events and with good acceptability in cognitively impaired persons and cognitively normal adults of all ages.

A dose-response study of intrathecal morphine: efficacy, duration, optimal dose, and side effects.

&NA; JACOBSON L, CHABAL C, BRODY MC. A dose‐response study of intrathecal morphine: efficacy, duration, optimal dose, and side effects. Anesth Analg 1988;67:1082‐8. We performed a double‐blind study of the dose‐response relationship of intrathecal morphine (0, 0.3, 1, and 2.5 mg) for postoperative pain relief in 33 subjects who underwent total knee or hip replacement surgery. Assessments commenced 1 hour after the opioid injection, which was given at the end of surgery, and continued for 24 hours. Pain measurements, supplementary analgesia requirements, and adverse effects were recorded. Intrathecal morphine provided effective, long‐lasting pain relief. All doses delayed the initial perception of discomfort (T‐Pain) and also post‐poned the onset of severe pain requiring analgetic supplementation (T‐Morphine) (1.25 hours control with placebo injections; > 20 hours with intrathecal morphine 0.3, 1, and 2.5 mg; P < 0.05). Although 0.3 mg usually provided good analgesia it was unsatisfactory in three of 10 patients (30%), whereas 1 and 2.5 mg were absolutely reliable. Respiratory depression (increased Paco2), common after the administration of 1 or 2.5 mg intrathecal morphine, was slow in onset and prolonged. The respiratory depression after 2.5 mg was more profound than after 1 mg, and produced apnea necessitating large‐dose naloxone therapy. Pruritus was unique to intrathecal morphine administration, but nausea, vomiting, and urinary retention were common in all the groups. We conclude that no ideal dose of intrathecal morphine exists because, even with small quantities, minor adverse effects are evident. Doses between 0.3 and 1 mg, however, should provide good analgesia free from the major complication, respiratory depression.

Long-term transcutaneous electrical nerve stimulation (TENS) use : Impact on medication utilization and physical therapy costs

OBJECTIVE A study was conducted to assess a variety of treatment outcomes in long-term users of transcutaneous electrical nerve stimulation (TENS) who suffer from chronic pain. Key components of the study examined the effects of long-term TENS therapy on pain-related medications and physical/occupational therapy (PT/OT) use. DESIGN From a population of 2,(X)3 chronic pain patients (CPPs) who acquired a TENS device (Epix XL, Empi, Inc., St. Paul, MN, U.S.A.) for pain management, a randomly selected sample of 376 patients who used TENS were interviewed by telephone by an independent research firm. The survey assessed a variety of outcome variables including changes in medication use, number of pain-related medications, and use of PT/OT prior to TENS and after a minimum 6 months of TENS treatment. The data were subjected to a paired t test analysis. A cost simulation model was then applied to the medication and PT/OT data. RESULTS The mean duration of pain, for which TENS was prescribed, was 40 +/- 60 months. As compared with the period prior to TENS use, this long-term TENS user group reported a statistically significant reduction in the following types of pain medications: opiate analgesics, tranquilizers, muscle relaxants, nonsteroidal anti-inflammatory drugs (NSAIDs), and steroids. PT/OT use was also significantly reduced. Cost simulations of pain medications and PT/OT are presented. CONCLUSIONS Long-term use of TENS is associated with a significant reduction in the utilization of pain medication and PT/OT. In this study population, cost simulations of medication and PT/OT indicate that with long-term TENS use, costs can be reduced up to 55% for medications and up to 69% for PT/OT. The potential for TENS associated improvement, combined with reduced medication-related complications and costs, are important points that clinicians should consider when constructing a treatment plan for chronic pain patients. Finally, cost simulation techniques provide a useful tool for assessing outcomes in pain treatment and research.

Relief of persistent postamputation stump and phantom limb pain with intrathecal fentanyl

Two patients with postamputation stump and phantom limb pain respectively responded favorably to intrathecal fentanyl which temporarily abolished the pain, normalized sensations and produced euphoria without supraspinal effects. One of the patients subsequently received intrathecal, extradural and intravenous fentanyl as well as intrathecal lidocaine. The neuraxial (intrathecal and epidural) fentanyl temporarily abolished the pain. Intravenous fentanyl and intrathecal lidocine were unable to reproduce this effect. Neuraxial fentanyl apparently produced its effects by a segmental spinal action. Spinal modulation of postamputation pain was important in these patients.

Educating Generalist Physicians about Chronic Pain: Live Experts and Online Education Can Provide Durable Benefits

OBJECTIVE Determine whether lectures by national experts and a publicly available online program with similar educational objectives can improve knowledge, attitudes, and beliefs (KAB) important to chronic pain management. DESIGN A pretest-posttest randomized design with two active educational interventions in two different physician groups and a third physician group that received live education on a different topic to control for outside influences, including retesting effects, on our evaluation. PARTICIPANTS A total of 136 community-based primary care physicians met eligibility criteria. All physicians attended the educational program to which they were assigned. Ninety-five physicians (70%) provided complete data for evaluation. MEASUREMENTS Physician responses to a standardized 50-item pain management KAB survey before, immediately after, and 3 months following the interventions. RESULTS The study groups and the 41 physicians not providing outcomes information were similar with respect to age, sex, race, percent engaged in primary care, and number of patients seen per week. Physician survey scores improved immediately following both pain education programs (live: 138.0-->150.6, P < 0.001; online: 143.6-->150.4, P = 0.007), but did not change appreciably in the control group (139.2-->142.5, P > 0.05). Findings persisted at 3 months. Satisfaction measures were high (4.00-4.72 on 1-5 scale) and not significantly different (P = 0.072-0.893) between groups. CONCLUSIONS When used under similar conditions, national speakers and a publicly available online CME program were associated with improved pain management KAB in physicians. The benefits lasted for 3 months. These findings support the continued use of these pain education strategies.

Intrathecal methadone: a dose-response study and comparison with intrathecal morphine 0.5 mg

&NA; The analgesic and adverse effects of intrathecal methadone 5 mg, 10 mg and 20 mg were assessed and compared with intrathecal morphine 0.5 mg. The study was conducted on 38 patients who underwent total knee or hip replacement surgery. The intrathecal opioid was administered at the end of surgery and assessments began 1 h thereafter and continued for 24 h. Pain measurements, supplementary analgesia requirements, and adverse effects were recorded. Intrathecal morphine 0.5 mg provided effective and prolonged analgesia. Intrathecal methadone 5 mg, 10 mg, and 20 mg produced good analgesia of 4 h duration. Thereafter the median pain scores with intrathecal methadone were consistently higher (worse) than those with intrathecal morphine (P < 0.05). The time to the onset of discomfort severe enough to require supplemental morphine was longer after intrathecal morphine than following methadone (15 h with morphine 0.5 mg; 6.25 h, 6.5 h and 6 h with methadone 5 mg, 10 mg, and 20 mg respectively: P < 0.05). Central nervous system depression manifesting as respiratory depression, hypotension, and excessive drowsiness occurred in 3 of 8 patients injected with methadone 20 mg intrathecally. Generalized pruritus, nausea, vomiting, and urinary retention were common and equally distributed among the treatment groups. We conclude that both intrathecal morphine 0.5 mg and methadone 5, 10, and 20 mg provide excellent analgesia but that morphine has a more prolonged effect. Methadone 20 mg produced unacceptable side effects. Clinical evidence for rostral spread of methadone within the CSF, as indicated by facial itching and excessive drowsiness, was less apparent with 5 mg than with 10 and 20 mg. Various explanations for the observed differences between the drugs are discussed.