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8 Approach to the patient with pain: conceptual models of care and related terminology

In treating patients with pain, some conceptual models organize care that is both compassionate and competent. Together, these models provide a robust foundation for approaching the patient in pain.

Balancing treatment and diagnosis: parallel pathway model

The “parallel pathway” model explains the balancing of diagnostic reasoning with compassionate action (Figure 8.1). Because pain is both a symptom and a cause of suffering, we must attend to patients' need for pain‐relief even as diagnosis proceeds. Once we discover pain, we start preliminary pain treatments while simultaneously initiating a diagnostic plan. The parallel pathway model shows how diagnosis and treatment develop in parallel (Murinson et al. 2008). Both are important and time‐sensitive. If definitive treatment precedes clear diagnosis, unnecessary harm can occur if we lose the diagnostic information contained in the patient's report of pain. If diagnosis dominates and treatment is delayed while testing takes place, this unnecessarily prolongs suffering. Thus, in the ideal scenario, safe and effective preliminary pain treatments are given, while diagnostic studies are simultaneously undertaken. In the end, “making a diagnosis” will identify disease modifying approaches that more effectively alleviate pain.

Figure 8.1 Parallel pathway model. Diagnosis and initiation of treatment proceed in parallel so that suffering is relieved as diagnostic efforts are underway.

Understanding pain and choosing rational pharmacotherapy: mechanism based‐classification

The mechanism‐based classification of pain is a simple yet elegant way to think about pain and pain treatments (Chapter 3). In basic terms, pain arises due to three major pathways: the nociceptive pathway, dedicated to sensing injury to the organism; the inflammatory pathway, in which sensory endings are sensitized by the action of inflammatory signaling molecules; and the neuropathic pathway, which involves an error in nervous system processing of sensory information. Thinking about pain in terms of these mechanisms can 1) elucidate the disease process that is causing the problem, 2) attune us distinctive characteristic qualities associated with each mechanism which the patient will include in the pain narrative, and 3) guide the design of a treatment plan (Figure 8.2). Most of the pain treatments available are particularly effective for certain mechanisms of pain and less so for other mechanisms. For example, NSAIDs are very useful for treating inflammatory forms of pain; but not effective against neuropathic pain. The management approaches for pain described in this book reflect the conceptual frame that pain is nociceptive, inflammatory, neuropathic, or a combination.

Patient‐centered care vs. disease‐centered care

The best pain care balances the needs of the individual patient for pain relief and functional restoration with the providers clinical (disease‐specific) knowledge and expectations for healing and recovery (Frankel 2004) (Figure 8.3). This model is related to the parallel pathway model above but highlights that the development of therapeutic approaches needs to incorporate the patient's values and needs, as well as the diagnostic “realities” (Agarwal and Murinson 2012).

Figure 8.2 Mechanism‐based classification of pain overview: rationale for development and how to apply the model.

Figure 8.3 Balancing knowledge of disease with patient‐centered understanding.

Biopsychosocial model

The biopsychosocial model highlights the importance of understanding the patient's psychological and social context which can amplify or diminish pain (Loeser 1982). Like expanding ripples in a pond, dramatic perturbations can arise if frustration builds upon depression upon social isolation to create overwhelming difficulties for the patient who lacks the resources to effectively self‐manage pain and pain‐related affect (Figure 8.4).

Figure 8.4 (a) Normal functioning demonstrating processes of eudynia; (b) Amplification of pain behavior is a multi‐step process (maldynia), this is often associated with the development of chronic pain (Chapter 29).

Source: Adapted from Loeser (1982).

It is in the setting of persistent or chronic pain that the biopsychosocial model of pain moves to the foreground. The classic scenario is the patient who has been to 20 doctors, takes 12 different medications, relies on pills to start their day and lives from injection to injection. This patient's behavior is dominated by “pain” and their life is ruined in the process.

It is helpful to first examine the case of “normal pain‐sensing” or eudynia. Eudynia is pain‐sensing as a normal function of the nervous system, it is more common than aberrant pain signaling, sometimes termed “maldynia.” In eudynia, nociception (primary nociceptive signal transduction) mirrors the degree of injury and is important to ensure survival, Figure 8.2. Each nociception event is mirrored accurately by a perception event. Perception is the conscious awareness of pain mediated by the cerebral cortex and leads a person to recognize the potential for injury. The perception of pain is also associated with suffering. This affective component of pain, subserved primarily by medial brain structures, such as cingulate cortex, has intrinsic survival value, prompting protective action against further injury. These affective brain centers are tightly linked with learning circuits, causing the organism to remember and avoid potentially injurious settings. The next and final link in the model is behavior. In normal pain‐sensing, behavior mirrors suffering which mirrors perception which mirrors nociception. In eudynia, pain behavior serves a useful social purpose of communicating a person's pain to those around him or her and is a highly efficient way to solicit help. For example, a child at play falls down and is unharmed, the person watching the child might be alarmed by the fall but immediately recognizes that the child is not crying and must be fine. A scraped knee or broken bone produce various forms of pain behavior that quickly convey the need for attention and aid.

The system breaks down when chronic pain affects a patient with a perturbed psychological state, disrupted mood, and dysfunctional social support network. Minor nociception is amplified by negative cognitions to a more threatening experience of pain, this in the context of depressed mood leads to amplified suffering, and this, in the absence of adequate social supports leads to aberrant behavior which disturbs the patient and disrupts those around them. It is impossible to unwind this complex type of pain without coordinated support and collaboration of multiple professionals, all proficient in pain, Chapter 16.

References

1 Agarwal, A.K. and Murinson, B.B. (2012). New dimensions in patient‐physician interaction: values, autonomy, and medical information in the patient‐centered clinical encounter. Rambam Maimonides Medical Journal 3 (3): e0017.

2 Frankel, R.M. (2004). Relationship‐centered care and the patient‐physician relationship. Journal of General Internal Medicine 19 (11): 1163–1165.

3 Loeser, J. (1982). Concepts of pain. In: Chronic Low‐Back Pain (eds. M. Stanton‐Hicks and R. Boas), 145–148. New York: Raven Press.

4 Murinson, B.B., Agarwal, A.K., and Haythornthwaite, J.A. (2008). Cognitive expertise, emotional development, and reflective capacity: clinical skills for improved pain care. The Journal of Pain 9 (11): 975–983.