sábado, 27 de septiembre de 2014

AHRQ WebM&M: Morbidity and Mortality Rounds on the Web ► A Lot of Pain (Medications)

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AHRQ WebM&M: Morbidity and Mortality Rounds on the Web

Spotlight Case: A Lot of Pain (Medications)Hospitalized for a foot amputation, a man with COPD and chronic pain on long-acting morphine experienced post-operative pain and severe muscle spasms. After being given hydromorphone, morphine, and diazepam, the patient became minimally responsive and a code blue was called. The commentary by Shoshana J. Herzig, MD, MPH, of Harvard Medical School, reveals the challenges in managing acute pain in hospitalized patients and best practices for opioid prescribing. (CME/CEU credit available.)

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A Lot of Pain (Medications) Spotlight Case
Commentary by Shoshana J. Herzig, MD, MPH

Case & Commentary—Part 1

A 58-year-old man was admitted to the hospital with a non-healing foot ulcer related to severe peripheral vascular disease. He also had a history of chronic obstructive disease and chronic pain. His pain was long-standing and related to multiple prior neck and back surgeries. For years he had been treated with long-acting morphine (extended-release 40 mg twice daily) as well as additional opioids for breakthrough pain. On admission, he reported 8/10 pain, despite receiving his home opioid regimen. After a surgical amputation to treat the ulcer, his pain worsened to 10/10.

Rates of opioid use, and long-term use for chronic non-cancer pain, have markedly increased over the last 2–3 decades.(1,2) Although data regarding the prevalence of chronic opioid use in hospitalized patients are sparse, one recent study found that more than 25% of patients hospitalized at Veterans Administration Hospitals were receiving chronic opioid therapy, defined as 90 days or more of opioids prescribed in the 6 months prior to hospitalization.(3) Furthermore, patients receiving chronic opioid therapy consume a disproportionate share of health care resources, including significantly more emergency room visits and days in the hospital.(4) The issue faced by providers caring for the patient in the case, therefore, is quite common: How should management of acute pain in hospitalized patients receiving chronic opioid therapy be approached? Embedded in this question are issues relating to efficacy and safety; specifically, finding the right balance between achieving adequate analgesia and avoiding adverse effects or problems with opioid misuse and/or addiction.

Achieving adequate analgesia in patients on chronic opioid therapy is challenging. There are well-described pharmacodynamic issues that make pain control more difficult to achieve in patients on chronic opioids, including tolerance (higher doses of opioids are required to maintain the same level of analgesia) and opioid-induced hyperalgesia (patients experience greater pain with less noxious stimuli). Thus, not only are patients on chronic opioids more likely to be hospitalized, but they may be more likely to experience acute pain while in the hospital. Physicians, on the other hand, may be reluctant to provide additional opioids due to concerns over adverse effects, particularly while prescribing the higher doses often required in this patient population. Physicians and other providers may also have concerns about abuse or contributing to addiction. All of these factors can result in under-treatment of pain in this patient population.(5)

When evaluating a patient on chronic opioids for acute pain, a thorough understanding of the nature or quality of the pain and its relationship to the patient's chronic pain complaint is crucial. We are told that the patient in this case experienced a "worsening" of his pain after his surgery, but it is not clear whether this was worsening of his chronic neck and back pain or worsening of his foot pain. This information would be essential in assessing response to therapy. Opioid escalation for acute foot pain in the setting of a surgical amputation should be identified as such, and opioid requirements should be expected to gradually decrease with passage of time after the operation. Lack of improvement with time could indicate a post-operative complication, tolerance, or possible addiction. Additionally, a better understanding of the nature or quality of the pain could assist in identifying the optimal treatment strategy. For example, inflammatory pain is optimally treated with nonsteroidal anti-inflammatory drugs (NSAIDs), while neuropathic pain may respond well to the addition of gabapentin or pregabalin, or consultation with a pain management specialist for consideration of a nerve block.(6) These non-opioid medications, when combined with opioids, have been demonstrated to improve pain control and lower opioid requirements in the acute care setting.(6) Accordingly, the American Society of Anesthesiologists recommends a multimodal approach to pain management, using at least two different classes of analgesics.(6)

Once a decision has been made to use opioid analgesics to manage acute post-operative pain, identifying the optimal drug, dose, route, and regimen are important in assuring a favorable risk-to-benefit ratio. Guidance on these decisions comes mostly from expert opinion.(6,7) The patient's previous long-acting opioid should be continued, if possible, to deliver the patient's usual baseline analgesia and avoid precipitating withdrawal. When adding additional opioids for acute pain, immediate-release opioids should be used to facilitate dose titration. The oral route of administration is preferred when possible to maximize duration of action and reduce addiction potential. If pain is severe and immediate control is necessary, intravenous opioids may be initially required, and consideration should be given to patient-controlled analgesia in an alert patient. If possible, the immediate-release opioid chosen for management of acute pain should be the same type as that used for chronic pain, to minimize chances of side effects and adverse effects due to incomplete cross-tolerance and facilitate ease of dose calculations. The patient's total daily opioid consumption prior to hospitalization should be ascertained as accurately as possible and converted to a baseline daily oral morphine equivalent—several online or handheld device calculators are available for this conversion. In general, an initial dose of 10%–20% of the baseline total daily dose should be used, with an as-needed frequency based on the estimated duration of action—approximately 4 hours for oral, and 3 hours for intravenous.(8,9)

In the event that adverse effects or other considerations necessitate changing to a different opioid than the chronic medication, guidelines advise starting with a dose 25%–50% lower than the calculated equianalgesic dose, to avoid unintentional overdose in the setting of incomplete cross-tolerance.(10) In selecting an alternate opioid, there are a few key considerations. Due to their metabolism, morphine and hydromorphone have fewer drug–drug interactions than other opioids.(11) However, most opioids, including morphine and hydromorphone, are eliminated primarily in the urine, necessitating dosage adjustment in the presence of renal failure.(11

With respect to the patient in the case, his outpatient dose of 40 mg extended-release morphine twice daily should be confirmed and continued. For his superimposed acute pain, since his primary outpatient opioid is morphine, immediate-release morphine would be an appropriate choice. The recommended dose would be 10%–20% of his baseline of 80 mg daily, which is 8–16 mg orally, every 4 hours as needed, with adjustment based on response. Given the inflammatory nature of his pain, an NSAID should be administered as well, assuming there is no contraindication.

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