“You matter because you are you, and you matter until the last moment of your life”


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—Dame Cicely Saunders

Pain is “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”1 Pain that is not well-managed contributes to suffering whether patients have restorative functional goals or are transitioning into comfort care. In the early and intermediate stages of their cancer diagnosis, 30% to 40% of patients experience unrelieved pain, while 75% of cancer patients in the terminal phase of their disease are reported to experience unrelieved pain.2 Patients with HIV or AIDS have pain from their disease process or from treatment with antiretroviral agents and this pain can considerably reduce quality of life.3

Pain that is unrelieved creates negative physical effects that impact the cardiovascular, hematologic, pulmonary, gastrointestinal, and immune systems. Uncontrolled pain can produce catecholamines, causing increased workload on the heart. Pain can increase sodium and water retention, which result in edema/fluid overload. Pain, poorly managed, can cause a hypercoagulable state increasing the incidence of thromboembolic events. It will impair pulmonary status by decreasing effective respirations, creating hypoventilation and resultant atelectasis leading to pneumonia. Gastrointestinal motility slows down as a result of unrelieved pain. The immune system is impaired through a reduction of natural killer cells inhibiting healing.3 Lastly, when pain is poorly managed, chronic pain can develop.4

MECHANISM OF ACTION


In caring for patients who are receiving palliative care, nurses need to understand the underlying mechanisms that create pain. There are three subtypes of pain: somatic pain, visceral pain, and neuropathic pain. 


Somatic pain originates from nociceptive activity in the skin, subcutaneous tissue, bones, muscles, and blood vessels. The painful stimulus activates the A-delta fibers and travels through the peripheral and central nervous system rapidly. This pain is localized and is described as sharp, aching, or throbbing. 


Visceral pain is activated in the organs, body cavities, and is transmitted through C fibers. It is more diffuse, and is described as gnawing, cramping, dull, and aching quality. 


Neuropathic pain arises as a direct consequence of a lesion or disease affecting the somatosensory system.5 Neuropathic pain manifests as a regional distribution of pain following along a peripheral innervation, a lesion, or disease affecting the peripheral or central nervous system or when neurologic signs corresponding to the pain distribution and confirmed by laboratory or objective measures are present. Patients may describe this pain as burning, prickling, tingling, or they may have unusual sensations ranging from numbness to lancinating sensations.

Specific details about the chemicals released in the tissue when injury or tumor develops have been identified through advances in neuroscience.6 Chemicals released in the periphery are prostaglandin, bradykinin, serotonin, histamine, and cytokines. Prostaglandins sensitize neurons and excite C fibers. Bradykinin is triggered by the activation of the clotting cascade and evokes a response in both A and C nociceptors, creating inflammatory pain and hyperalgesia. Serotonin is released from platelets, and histamine is released from mast cells. Cytokines are powerful sensitizers of C fibers and are part of the inflammatory process that involves mast cells. These are all inflammatory mediators that result in painful sensations.


These mechanisms are at play in the peripheral nervous system with tissue injury or tumor, and create an action potential. An action potential results from ion exchanges (eg, sodium and potassium) along the neuronal membrane impelling the pain fiber impulse through the neurons terminating in the dorsal horn of the spinal cord. The painful impulse continues to move through the laminae of the dorsal horn of the spinal cord, crossing the dorsal horn and is carried to the brain by way of the spinothalamic tract. Within the brain, pain is perceived in the primary sensory cortex, and the pathway continues back down through the descending pathway into the spinal cord. Pain management is achieved when various combinations of medications work along the pain pathway to create analgesia. 


ASSESSMENT OF PAIN


Pain assessment is the foundation of good pain management, and key elements of pain assessment apply to all patients. Integral to good pain assessment is determining the location, description, intensity, duration, alleviating and relieving factors, and associated factors of the pain.7 The location of the pain can help you determine the etiology of the pain, or if the pain is referred to another location from the point of origin. Descriptors patients use to describe their pain can be burning, prickling, tingling, sharp, stabbing, achey, cramping, or pressure. Neuropathic pain is often noted as having burning, prickling, or tingling features to the pain. Somatic pain is often described as sharp and stabbing, and the patient can be very specific about where it hurts. Visceral pain may be described as aching, cramping, or pressure sensations, and is more diffuse. Moreover, patients relate a dimension of emotional suffering to their pain when they use terms such as agonizing, horrifying, or defeating. 


Pain intensity scores are a self-report in which the patient gives a number indicating the intensity of the pain. For example, the patient is asked to rate his or her pain on a scale of 0 to 10, where 0 indicates no pain and 10 indicates the worst pain possible. Pain intensity assessment provides baseline information so that as pain relieving interventions are performed, the nurse can determine if the pain is better, worse, or staying the same. By asking about the duration of the pain, nurses can determine time-associated features of the pain and the duration of relief achieved by pain-relieving interventions. 


Alleviating or relieving influences of pain can be determined by asking the patient what makes his or her pain better or what makes it worse. Through this line of questioning, often the patient will inform the health care team about particular treatments that work, allowing the health care team to ask further questions to evaluate whether self-medicated interventions such as nonsteroidal anti-inflammatory drugs (NSAIDs) may produce potential harm. Lastly, patients rarely experience pain as a solitary symptom. Associated symptoms that may manifest with pain include nausea, vomiting, itching, sedation, constipation, depression, anxiety, and confusion. These must be addressed concurrently with the pain. 


Various assessment tools provide a means to assess pain from a multidimensional perspective. These tools can measure mood, activity or function, sleep, and medication effectiveness. An example of a multidimensional tool is the Brief Pain Inventory (BPI). This tool was originally developed for patients with cancer, and it has good reliability and validity in other patient populations as well.8 Table 1 lists resources for health care professionals, caregivers, and patients to evaluate the multidimensional aspects of people in pain. A position statement and summary of tools for people unable to report their pain is available through the American Society for Pain Management Nursing.9

 TABLE 1. Multidimensional pain assessment tools

 Brief Pain Inventory
 http://medicine.iupui.edu/RHEU/Physicians/bpisf.pdf
 McGill Pain Questionnaire
 www.fcesoftware.com/images/16_McGill_Pain_Questionnaire.pdf
 Multidimensional Objective Pain Assessment Tool (MOPAT)
 http://pubmedcentralcanada.ca/pmcc/articles/PMC3114254/pdf/jpm.2010.0302.pdf
 Pain Outcomes Questionnaire
 www.midss.ie/sites/www.midss.ie/files/pain_outcomes_questionnaire_sf_rev_2.pdf
 West Haven-Yale Multidimensional Pain Inventory
 www.tac.vic.gov.au/media/upload/west_haven_yale_multidimensional_pain_inventory.pdf