Designing a Comprehensive Acute Pain Treatment Plan

Marian Sherman

Stephanie G. Vanterpool

Introduction

A comprehensive pain treatment plan for optimal pain management must address all causes of pain and functional limitation in a patient. In order to do so, the clinician should have a clear process for both identifying and addressing the underlying pain causes. As each patient is unique, the same treatment plan, dosing or approach, will likely not work similarly for all patients. While most clinicians today acknowledge that poorly controlled pain is a common and unresolved health outcome,¹,² many physicians report inadequate knowledge of clinical pain management. Specifically, clinicians report that medical schools lack dedicated course structure to understanding and treating pain and that curricula underemphasize assessment of pain knowledge and related clinical competence.³ It is imperative that future medical training expand and elevate the quality of pain management education to address the negative public health impact of poorly controlled pain. At this moment, to bridge this gap, we present a process by which clinicians can both identify the applicable causes of pain and functional limitation in their patients and develop a collaborative and comprehensive plan to address those causes.

First, we must delve into why accurately identifying all underlying causes of pain is critical to optimal pain treatment. A patient presenting with acute pain may have multiple causes at play. There may be physiologic causes, such as the sterile inflammation seen in a gout flare, or anatomic causes, such as the fractured bone in the case of musculoskeletal injury. Functional causes related to poor posture, body mechanics, or prolonged immobility may also contribute. Finally, we must also be cognizant of any psychosocial causes of pain that may contribute to pain perception, catastrophizing, and response to treatment.

If a patient with multiple pain etiologies presents for acute pain treatment, and all causes are not appropriately identified and addressed, that patient risks developing both prolonged suffering and mid to longer term disability. The development of a comprehensive treatment plan must therefore start with an understanding and accurate diagnosis of the underlying causes of pain. It is therefore our responsibility as clinicians to ensure that all causes of pain are accurately diagnosed and treated in a targeted fashion.

Pain States and Mechanisms

In their landmark article “Toward a Mechanism-Based Approach to Pain Diagnosis,” Vardeh and colleagues highlight that understanding the underlying pathological processes associated with pain is key to improving patient management.⁴ The more specific the identification of applicable pain states and mechanisms in a given patient, the more targeted the treatment plan that can be developed. A treatment plan that addresses only one pain state when more than one is present, or only targets one pain mechanism, or worse yet, is completely un-targeted in its approach, will likely result in suboptimal relief, and potentially produce additional,
unintended consequences. Indeed, we have seen the result of this in the present opioid epidemic, as un-targeted opioid medications have been used to attempt to treat pain indiscriminately, irrespective of the underlying pain states and mechanisms, and often with unintended side effects and suboptimal overall relief.

Following is a brief discussion of pain states and mechanisms, which will be used to inform the treatment recommendations presented later in this chapter.

Pain States

The International Association for the Study of Pain recently updated the definition of pain as follows: “An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.”⁵ Different pain states are defined as result of the duration, etiology, or perception of the painful experience.⁶ In this chapter, we will focus the discussion of pain states on the underlying etiology, understanding that these etiologies can be present in both acute and chronic pain presentations.

There are four broadly accepted general pain states: nociceptive pain, inflammatory pain, (sterile or infections), neuropathic pain, and central/dysfunctional pain.⁴ The underlying clinical evidence, signs, and symptoms that allow identification of these pain states are highlighted in Table 6.1. While these criteria are not highly specific, as there is no gold standard for diagnosing these pain states, the signs and symptoms highlighted will often help the clinician discern the key characteristics on which to base further diagnostic efforts.

More often than not, more than one pain state can be present at the same time. For example, a patient with poorly controlled diabetes who presents with an acute lumbar disk herniation may be experiencing both nociceptive pain from the herniation and also chronic neuropathic pain from peripheral diabetic neuropathy. It is therefore important that one seeks to clarify all applicable pain states in a given patient.

Pain Mechanisms

Once the pain state is identified, the next step in determining appropriate targeted treatment is to identify the mechanism by which the pain is being transmitted and perceived. Understanding the pain mechanism is critical in guiding the selection of pharmacologic treatment options. By tailoring the selected pharmacologic treatment to the mechanism by which the pain is transmitted, clinicians can provide patients with more targeted and effective relief, while concurrently avoiding or minimizing nonspecific treatment options such as opioids.

The five pain mechanisms are as follows: nociceptive transduction, peripheral sensitization, ectopic activity, central sensitization, and central disinhibition.⁴ Table 6.2 highlights the clinical
diagnostic criteria and specific examples for each pain mechanism. As with pain states, the diagnostic criteria for pain mechanisms are not highly specific but are more of a guide to help the clinician discern what mechanisms are present. It is important to note that just like there can be multiple pain states present simultaneously, the same can be said for pain mechanisms.

TABLE 6.1 PAIN STATES

Pain State	Pathology	Symptoms
Nociceptive	Evidence of noxious (mechanical, thermal, chemical) insult	Pain localized to area of stimulus/joint damage
Inflammatory	Evidence of inflammation (sterile or infectious)	Redness, warmth, swelling of affected area
Neuropathic	Evidence of sensory nerve damage	Burning, tingling or shocklike, spontaneous pain; paresthesias, dysesthesias
Dysfunctional/centralized	Pain in the absence of detectable pathology	No identifiable noxious stimulus, inflammation or neural damage; evidence of increased amplification or reduced inhibition
Modified from Table 1 in Vardeh D, Mannion R, Woolf C. Toward a mechanism-based approach to pain diagnosis. J Pain. 2016;17(9):T50-T69. doi:10.1016/j.jpain.2016.03.001. Review (used with written permission).

TABLE 6.2 GENERAL PAIN MECHANISMS AND SPECIFIC TREATMENT EXAMPLES

Pain Mechanism	Clinical Diagnostic Criteria	Clinical Example	Specific Treatment Example
Nociceptive transduction	Proportionate pain in response to identifiable noxious stimulus	Mechanical nerve root compression	Remove mechanical stimulus
Peripheral sensitization	Primary hyperalgesia due to decreased transduction threshold of nociceptor terminal	Rheumatoid arthritis, cellulitis	Anti-inflammatory (eg, NSAID, COXIBs); immunosuppressant
Ectopic activity	Spontaneous pain in the absence of obvious trigger, relieved by local nerve block	Trigeminal neuralgia	Na channel blockers, Ca channel blockers
Central sensitization	Secondary hyperalgesia; temporal summation, allodynia	Complex regional pain syndrome (CRPS)	NMDA antagonists (eg, ketamine)
Central disinhibition	Secondary hyperalgesia, allodynia	Fibromyalgia	GABA-A subunit agonists Dual amine uptake inhibitors (eg, SNRI)
Adapted from Table 2 in Vardeh D, Mannion R, Woolf C. Toward a mechanism-based approach to pain diagnosis. J Pain. 2016;17(9):T50-T69. doi:10.1016/j.jpain.2016.03.001. Review (used with written permission).