January-February 2006; Issue 1

Acetaminophen-Induced Acute Liver Failure Increasing
Yoga Beneficial For Low Back Pain?
Offer Nursing Home Residents a Choice of Pain Scales
Consider Spinal Stenosis in Diabetic Neuropathy Symptoms
Chiropractic Therapy For Low Back Pain in Pregnancy?
Excess Weight Influences Back/Pelvic Pain During & After Pregnancy
Reducing Opioid-Induced Sedation: Review
Heat Therapy Reduces Acute Low Back Pain
Amitriptyline, Carbamazepine: Cost-Effective For Neuropathic Pain
Postoperative PCA May Relieve More Pain
Acute Pain Management in Patients On OAT

This edition of News/Research Updates was researched/compiled by Winnie Dawson, RN, and edited by Stewart B. Leavitt, PhD; Medical reviewers were: James D. Toombs, MD, Lee A. Kral, PharmD, BCPS, and Steven J. Tucker, MD; Posting Date: February 22, 2006.

Acetaminophen-Induced Acute Liver Failure Increasing

According to this multicenter, prospective cohort study at 22 tertiary care centers in the United States , 42% of acute liver failure (ALF) cases overall were caused by acetaminophen hepatotoxicity. The annual percentage of acetaminophen-related ALF rose during the study period from 28% in 1998 to 51% in 2003 (see Graph ).

Of the 275 cases reported, 131 (48%) were unintentional acetaminophen overdoses, 122 (44%) were suicide attempts, and 22 (8%) were of unknown intent. In the unintentional overdose group, roughly 80% were taking the analgesic for acute or chronic pain syndromes; about a third took 2 or more acetaminophen preparations simultaneously; and nearly two-thirds used narcotic-containing acetaminophen compounds.

An alarming finding in the study was that unintentional acetaminophen overdose accounted for nearly half of the cases. The median dose ingested was 24 grams (equivalent to about 48 extra-strength tablets) but study data suggests that there is a narrow therapeutic margin for liver injury and that consistent use of as little as 7.50 g/day may be hazardous.

Conclusions: Acetaminophen hepatotoxicity far exceeds other causes of acute liver failure in the US . Susceptible patients can have concomitant depression, chronic pain, alcohol or narcotic use, and/or take several preparations simultaneously. Because current data suggests a dramatic recent increase in acetaminophen toxicity, the authors recommend increased education for physicians, pharmacists, and patients regarding the identification of susceptible groups and the potential hazards of this pain reliever.

Source: Larson AM, Polson J, Fontana RJ et al. Acetaminophen-induced acute liver failure: results of a United States multicenter, prospective study. Hepatology. 2005(Dec);42(6):1364-1372.

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Yoga Beneficial For Low Back Pain?

Chronic low back pain is a common patient complaint and treatments are frequently only modestly effective. Researchers engaged 101 chronic back pain patients in a randomized, controlled trial to determine whether yoga is more effective in reducing pain than conventional exercise or a self-help book.

During 12-week sessions, the yoga group practiced the Viniyoga style and the exercise program included a combination of conventional warm-up, aerobic, and strengthening exercises. Control group participants were merely provided with a self-care back pain book. At 12 and 26 weeks, the yoga group was statistically superior in back-related functional status and, at 26 weeks, in symptom relief. Reliance on medications, which was similar in all groups at baseline, decreased most sharply in the yoga group. At 26 weeks, only 21% of yoga group participants reported using medication during the prior week, compared with 50% and 59% of the exercise and book groups, respectively.

Practice Pointer: In this study, the benefits of yoga persisted 14 weeks after the end of classes and did not appear to be caused by other interventions or medications because use of these was lower in this group. For carefully selected patients with chronic back pain yoga may be beneficial in alleviating symptoms; however, patients should be advised that not all forms of yoga are the same and that some styles may be too challenging.

Source: Sherman KJ, Cherkin DC, Erro J, et al. Comparing yoga, exercise and a self-care book for chronic low back pain. Ann Intern Med. 2005(Dec);143(12):849-856.

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Offer Nursing Home Residents a Choice of Pain Scales

The prevalence of pain in nursing home residents can be as high as 84%. Accurate detection of pain also requires accurate self-reporting, which becomes more difficult in elderly patients who may have memory impairments, depression, or cognitive decline.

Researchers reported on a total of 477 nursing home patients who participated in quarterly pain assessments. Participants reporting pain or discomfort in the prior 24 hours were asked to choose 1 of 3 pain intensity scales to quantify their current and highest level of pain. The scales were: 1) the 11-Point Verbal Numeric Rating Scale (VNS), 2) the Verbal Descriptor Scale (VDS), and 3) the Bieri Faces Pain Scale (FPS). Additionally, a Checklist of Nonverbal Pain Indicators (CNPI) was completed by research assistants on each participant; however, of those patients reporting pain, only about half had at least one indicator of pain observed by the data collector using the CNPI.

The VDS was the preferred tool for more than half of the residents, compared with about 30% for the VNS and nearly 20% for the FPS. Males preferred the VNS scale over females; minority residents were significantly more likely to prefer the FPS than white residents.

Clinical Implications: The low ratio of CNPI results relative to the resident self-reports of pain implies that when staff members rely on observed pain behaviors alone a significant amount of pain goes undetected and untreated. Nursing home staff members need to use pain self-reports as a primary approach to identifying resident pain. When presented with a choice of intensity scales to report their pain level, almost all residents (94%) were able to select one; therefore, giving older patients a choice of pain intensity scales may improve pain assessment.

Source: Jones KR, Fink R, Hutt E, Vojir C, et al. Measuring pain intensity in Nursing Home Residents. J Pain Symptom Manage. 2005(Dec);30(6):519-527.

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Consider Spinal Stenosis in Diabetic Neuropathy Symptoms

Nocturnal exacerbation of neuropathic symptoms (NENS) is a recognized indicator of diabetic peripheral neuropathy. Symptoms of pain and paresthesias can disrupt sleep and may not be controlled by medication. In a retrospective review of a single practice during one year, 11 diabetic patients were diagnosed with spinal stenosis (SS) following reports of NENS for at least 3 months duration. All patients underwent positional testing, which included modification of sleep positions and full-time use of a wheeled rollator walker for 3 days to one week. The clinician used positional testing and positional modifications as both a diagnostic and therapeutic tool.

Three patients had NENS only in the feet, while the other 8 also had NENS in the legs and/or thighs. Five of the 11 patients reported excellent improvement of NENS, one reported good improvement, and 3 reported moderate improvement. All patients reported maintenance of improvement by long-term use of a walker, as needed, and sleep position modification.

Conclusion: Although this was a small study, it suggests that NENS, especially when affected by body position or when walking limitations are improved by a wheeled support, might lead to a suspicion of spinal stenosis. Positional testing should be considered to help detect possible cases.

Source: Goldman SM. Nocturnal neuropathic pain in diabetic patients may be caused by spinal stenosis. Diabet Med. 2005(Dec);22(12):1763-1765.

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Chiropractic Therapy For Low Back Pain in Pregnancy?

Reports of low back pain during pregnancy have shown prevalence rates of 57% to 69%. While the exact etiology is unknown, increased lumbar lordosis is commonly considered a cause. Pain intensity often increases with duration and can result in significant disability, sleep disturbances, and impaired daily living.

This study examined a retrospective series of cases during 12 consecutive months from one practitioner. Active and passive care was initiated after all patients were screened for signs of serious pathology presenting as low back pain. Care consisted of reassurance, advice on body mechanics, exercise instruction, manual myofascial release, manual joint mobilization, and manual spinal manipulation aimed at the lumbar facet and/or sacroiliac joints.

Sixteen of the 17 pregnant patients (95%) demonstrated clinically important improvement in back pain intensity during the course of treatment with no adverse effects. The average time to initial clinically significant pain relief was 4.5 (0-13) days after initial presentation, and the average number of visits at that point was 2. At termination of care, after about 3 weeks on average, the average Numerical Pain-Rating Scale score was 1.3 (range 1-4 on 10 pt. scale).

Results: The author acknowledges that this was a small retrospective study and, while the approach appeared effective and safe, chiropractic therapy for low back pain in pregnant women needs a more rigorous investigation in a controlled study environment.

Source: Lisi AJ. Chiropractic spinal manipulation for low back pain of pregnancy: a retrospective case series. J Midwifery Womens Health. 2006(Jan);51:e7-e10.

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Excess Weight Influences Back/Pelvic Pain During & After Pregnancy

Low back pain and pelvic pain (LBPP) is common during pregnancy and up to 40% of women continue to have symptoms 6 months after delivery. In this study, 464 women who had reported LBPP during pregnancy responded to a questionnaire approximately 6 months after delivery.

Two hundred (43.1%) respondents reported recurrent or continuous LBPP 6 months after delivery. Level and onset of pain during pregnancy were strong predictors of the risk of persistent LBPP after pregnancy. Parity, gestational age, and neonate birth weight did not influence the risk of persistent LBPP after pregnancy. One of the main findings in this study was the importance of body mass index (BMI) as a determinant of persistent LBPP after pregnancy; the women with persistent LBPP had significantly higher weight as well as higher BMI at 6 months after delivery than did women with remission of LBPP.

Clinical Implication: The authors concluded that pre-pregnancy reduction of excess weight would probably reduce the prevalence of LBPP during and after pregnancy.

Source: Mogren IM. BMI, pain and hypermotility are determinants of long-term outcome for women with low back pain and pelvic pain during pregnancy. Eur Spine J. 2006(Jan) [epub].

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Reducing Opioid-Induced Sedation: Review

Opioid-induced sedation is a common dose-limiting side effect of opioid analgesia therapy that can be distressing to patients and difficult for clinicians to manage. Most patients develop tolerance to the sedative effects of opioids within a few days but, when the sedation continues after eliminating other potentially confounding factors, this review describes 4 techniques to minimize or counteract the sedative effects:

• For patients whose pain is in control and can tolerate an opioid dose reduction, it may be possible to decrease the analgesia dose by as much as 50%.
• The addition of another medication to counteract drowsiness or to achieve added pain relief can be beneficial without sacrificing the level of pain control.
• Several small studies have shown good results in sedation reduction by opioid rotation. However, due to cross-tolerance and individual variability, larger placebo-controlled studies are needed to establish the safety and efficacy of this approach.
• Finally, it may be possible to reduce sedation by changing the route of opioid administration. Although subcutaneous, intraspinal, or intravenous delivery have limitations and may be too invasive in some cases, they could offer a safe alternative on a case-specific basis.

Practice Pointers: In evaluating the options for addressing opioid-induced sedation, clinicians must individualize the approach. Occasionally, it may be necessary to try more than one method to find the optimal balance of opioid analgesia and sedation.

Source: Bourdeanu L, Loseth DB, Funk M. Management of Opioid-Induced Sedation in Patients with Cancer. Clin J Oncol Nurs. 2005(Dec);9(6):705-711.

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Heat Therapy Reduces Acute Low Back Pain

In a pilot study of continuous low-level heat therapy, 43 occupational injury clinic patients with acute muscular low back pain (LBP) were randomized to an educational intervention only or education plus low-level heat-wrap therapy (using the ThermaCare Heat Wrap®, Proctor & Gamble Company).

The reference group received written information on the treatment of LBP symptoms and instructions on the use of a pain diary with a pain intensity measurement scale. The treatment group received the same educational intervention plus 3 heat wraps for topical use during 3 consecutive workdays. Assessments were completed on each treatment day and on days 4, 7, and 14 for follow-up.

Overall pain reduction was significantly better in the treatment group for the entire 3-day treatment period and the first follow-up day, but became insignificant at day 7 and beyond. After adjusting for individual differences (gender, age, baseline pain intensity, and pain medications), the pain intensity reduction in the heat wrap group was double that of the reference group. Pain relief and disability scores also were significantly improved by treatment (see Graph).

Clinical Observation: In this company-sponsored study it appeared that heat-wrap therapy offered significant advantages in ameliorating acute, occupation-related, muscular low back pain. The authors do caution that further research in larger sample sizes would be appropriate to evaluate possible interacting factors, such as patient age.

Source: Tao XG, Bernacki EJ. A randomized clinical trial of continuous low-level heat therapy for acute muscular low back pain in the workplace. J Occup Environ Med. 2005(Dec);47(12):1298-1306.

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Amitriptyline, Carbamazepine: Cost-Effective For Neuropathic Pain

Neuropathic pain –– caused by a nervous system malfunction associated with nerve damage due to traumatic injury or medical conditions, such as diabetic neuropathy –– can be effectively controlled with oral medications. This study evaluated the effectiveness and economics of amitriptyline, carbamazepine, gabapentin, and tramadol for pain therapy in patients with diabetic neuropathy and postherpetic neuralgia.

The investigators performed a systematic review of the literature to gather efficacy and safety data. For drug cost comparisons, a model for incremental ratios was created from the total cost for a one-month supply of medication against estimates of the amount of each drug necessary for effectiveness.

The authors concluded from their comparisons that, while amitriptyline and carbamazepine were equally effective, a 1-month supply of amitriptyline was only about 60% of the cost of carbamazepine. At the same time, the costs of using tramadol and gabapentin were 3 and 9 times greater that that of amitriptyline, respectively. Due to documented side effects and an amitriptyline-associated increased risk of myocardial infarction, patients using amitriptyline or carbamazepine should not have existing cardiovascular, renal, or hepatic disease.

Clinical Implications: The cost-effectiveness of a medication – defined as the cost to achieve effective pain relief – is important to the patient and, therefore, also should be important to the clinician.

Source: Cepeda MS, Farrar JT. Economic evaluation of oral treatments for neuropathic pain. J Pain. 2006(Feb);7(2):119-128.

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Postoperative PCA May Relieve More Pain

Pain management in the immediate postoperative period is important to patient satisfaction, but existing studies conflict about whether the amount of analgesia used is greater with the use of patient-controlled analgesia (PCA) or intramuscular injection (IMI). This retrospective study reviewed the pain management records of 115 patients for the 3 days following abdominal surgery to compare the total opioid use with PCA versus IMI administration.

Total mean opioid consumption for 3 days of pain management in the PCA group was approximately 137 mg compared with 51 mg for the IMI group. On day 1 alone, opioid use for the PCA group was almost 50% more than that of the IMI group. Furthermore, results showed that the amount of PCA over IMI analgesic-use diverged even more on days 2 and 3: the mean opioid use in the IMI group was about 30% of the PCA group on day 2 and only 20% on day 3. Differences on all 3 days were statistically significant (p < 0.01; see Graph).

Clinical Implications: Pain assessment is crucial to good pain management in the early postoperative period. The results of this study suggest that the use of PCA –– allowing the patient to choose the timing of analgesic therapy without the need to communicate their needs to caregivers –– may have been providing more adequate pain relief. The disproportionate reduction in IMI administration suggests that interpersonal or intrapersonal barriers might influence patients' verbal requests for adequate help in pain management. The authors recommend an increased use of pain assessment tools as well as increased education for the nursing staff and patients in the methods of effective pain management.

Source: Everett B, Salamonson Y. Differences in postoperative opioid consumption in patients prescribed patient-controlled analgesia versus intramuscular injection. Pain Manag Nurs. 2005(Dec);6(4):137-144.

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Acute Pain Management in Patients ON OAT

Effective pain management for patients receiving opioid agonist therapy (OAT) for addiction can be challenging. Maintenance treatment with methadone or buprenorphine can put patients at risk for undertreatment of moderate to severe acute pain.

Four common misconceptions often interfere with effective pain management in these patients:

• The methadone or buprenorphine maintenance dose already provides adequate analgesia;
• Using opioids as pain therapy will increase the potential for addiction relapse;
• Combined effects of OAT and opioid analgesics will hazardously depress CNS or respiratory systems; and
• An OAT-maintained patient's request for pain treatment has an underlying motive of drug abuse.

The authors of this review examine the additional physiological complexities of hyperalgesia or analgesic tolerance, as well as the emotional concerns of the patient and the clinician. Theoretical and experiential evidence is presented for patient care and specific recommendations are made for pain management in OAT-maintained patients.

Clinical Implications: Adequate pain relief can be accomplished with the use of good assessment skills and an understanding of the potential physiological issues specific to OAT-maintained patients. It is important to reassure the patient that pain management will not interfere with their OAT maintenance and that their pain can and will be managed appropriately and aggressively.

Source: Alford DP, Compton P, Samet JH. Acute pain management for patients receiving maintenance methadone or buprenorphine therapy. Ann Intern Med. 2006(Jan17);144(2):127-135.

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