Acute and chronic pain assessment: A necessary skill for pharmacists

Pain is a symptom felt by every individual, acutely in their lifetime. It persists chronically in upwards of 20% of the population.(1) As pharmacists proceed with expanded scope of practice, they are applying their clinical skills to treat more conditions. Pain assessment is a necessary skill for clinical decision-making, as pain is a common symptom of many ailments. This article highlights the various types of pain and how to assess them.Pain terms and definitions Broadly, pain is classified as either nociceptive or neuropathic. Nociceptive pain occurs with actual or potential tissue damage.(2) Subcategories include somatic pain, which arises from tissues that form the structure of the body (e.g., musculoskeletal), or visceral pain, which arises from the internal organs of the body or internal cavities.(3) Somatic pain has a cramping, gnawing, aching and sharp quality with a shorter duration, as opposed to visceral pain that is diffuse, dull, poorly localized and usually of longer duration.(3,4)Neuropathic pain results from nervous system lesions and resulting dysfunction.(2) Common features include pain from normally non-noxious stimulation (e.g., light touching), or sensations such as burning, “pins and needles” (paresthesia), shooting or electric-like pain.(5) Neuropathic pain can be central (damage originating from the brain or spinal cord), with wide distribution, or peripheral (damage occurring in the peripheral nerves), with distribution localized to a particular limb.(6)Certain types of pain are harder to categorize and diagnose. Mixed pain—pain possessing both neuropathic and nociceptive qualities—is usually more difficult to treat.(6) It is also influenced by the psychological state of the individual; depression, insomnia, anxiety and post-traumatic stress can increase pain symptoms, and in some cases cause pain despite not having a physical origin.(7) Table 1 compares the various pain types.Pain assessment methods and toolsSeveral methods can be used to conduct a pain assessment (Table 2). PQRST is commonly taught in pharmacy schools, and is a good mnemonic to remember for performing a basic pain assessment. The main shortcoming of the PQRST method relates to assessing pain severity, which is ranked on a numeric rating scale (NRS), from 0–10.(8) Although the NRS sufficiently identifies average pain intensity score, which is appropriate for short-lived (acute) pain, separate assessment tools are needed to quantify and qualify various domains of chronic pain (lasting > 3 months).(9)The Brief Pain Inventory (BPI) is a validated simple-to-use tool that can be self-administered in less than five minutes. It assesses the intensity of pain on four domains (worst, least, average and current pain out of 10), as well as the efficacy of medical treatments, and how the pain affects mood, sleep, relationships, ability to work and physical function.(9) It is a good tool to repeatedly administer on multiple patient encounters, and is often used by pain specialists to track the progress of pain treatments. A shortcoming of the BPI is that it does not address the distinction between neuropathic and nociceptive pain.(9)To identify a patient with neuropathic pain, and to monitor the efficacy of neuropathic pain medications, I use the Neuropathic Pain Scale (NPS), which is also easily self-administered and takes only a few minutes to complete.(9)Table 2: Selected Pain Assessment Methods and Tools(8,9)PQRSTP – Provocation:What caused it or relieves it?Q – Quality:What does it feel like?R – Region/Radiation: Where is it located and does it radiate?S – Severity: How severe on a scale of 0–10?T – Timing:Constant or intermittent?Website - https://www.mcgill.ca/anesthesia/files/anesthesia/mch_pain_guidelines.pdfBPI – Brief Pain Inventory15 itemsWorst, least, average, and current pain intensityIncludes 7 items that rate impact of pain on functionBody diagram a tool for patient to mark pain locationsWebsite - http://nationalpaincentre.mcmaster.ca/documents/brief_pain_inventory.pdfNPS – Neuropathic Pain ScaleUsed to assess the efficacy of treatment in any patient with neuropathic painWebsite - https://www.mdcalc.com/neuropathy-pain-scale-nps Pharmacists can assess pain and make an impactAlthough it may seem that primary care physicians and specialists manage pain effectively, pain is often under-managed and inappropriately treated. In my practice, I often see inadequate pain diagnoses (e.g., no distinction made between nociceptive and neuropathic pain), and the wrong pain medications having been tried. As pharmacists, we can be more involved by using pain assessments and validated tools to distinguish the type of pain, and suggest appropriate drug (and nondrug) therapy based on treatment guidelines and patient response.Vikas Parihar, BScBiochem, BScPharm, PharmD, is a clinical pharmacist in the Michael G. DeGroote Adult Pain Clinic at McMaster University Medical Centre, and adjunct assistant clinical professor with the Faculty of Health Sciences, Department of Anesthesia at McMaster University, in Hamilton, Ont.References1. Dahlhamer J, Lucas J, Zelaya C, et al. Prevalence of chronic pain and high-impact chronic pain among adults - United States, 2016. MMWR Morb Mortal Wkly Rep 2018;67(36):1001-6. doi:10.15585/mmwr.mm6736a2.2. Nicholson B. Differential diagnosis: nociceptive and neuropathic pain. Am J Manag Care 2006;12(9 Suppl):S256-62.3. Murphy P. Somatic pain, visceral pain. In: Encyclopedia of Pain. Springer Berlin Heidelberg; 2007.4. Ng L, Cashman J. The management of acute pain. Medicine (United Kingdom) 2018;46:780-5. doi:10.1016/j.mpmed.2018.09.009.5. Bottros MM, Rao L, Schwedt TJ, et al. Chapter 17 - Pain management. In: Cummings Otolaryngology Head and Neck Surgery E-Book. 6th ed. Elsevier; 2019:240-51.e3. doi:10.1016/B978-1-4557-4696-5.00017-8.6. Booker SQ, Herr KA. Assessment and measurement of pain in adults in later life. Clin Geriatr Med 2016;32(4):677-92. doi:10.1016/j.cger.2016.06.012.7. Covington E. Psychogenic pain—What it means, why it does not exist, and how to diagnose it. Pain Med 2008;1:287-294.8. Fink RM, Brant JM. Complex cancer pain assessment. Hematol Oncol Clin North Am 2018;32:353-69. doi:10.1016/j.hoc.2018.01.001.9. Morgan KJ, Anghelescu DL. A review of adult and pediatric neuropathic pain assessment tools. Clin J Pain 2017;33:844-52. doi:10.1097/AJP.0000000000000476.

Acute and chronic pain assessment: A necessary skill for pharmacists

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VIKAS PARIHAR

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