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Pain: The underdiscussed vital sign

Pain plays a crucial part in a physical exam

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Example of a wound soaker catheter incorporated into the soft tissue closure of the median sternotomy site in a dog recovering from lung lobectomy for a ruptured bulla. Bupivacaine 5% was infused every six to eight hours for the first 36 to 48 hours of recovery.
Example of a wound soaker catheter incorporated into the soft tissue closure of the median sternotomy site in a dog recovering from lung lobectomy for a ruptured bulla. Bupivacaine 5% was infused every six to eight hours for the first 36 to 48 hours of recovery.

The International Association for the Study of Pain (IASP) provides the following definition: Pain is “an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.”1

Recognition and assessment of the presence of pain is a routine and central part of every physical exam. The pain score has been called the “fourth” vital sign, in addition to temperature, heart rate, and respiratory rate. Hospitalized patients require some degree of continuous care and monitoring, and are perhaps one of the most vulnerable patient populations. Acute and chronic painful conditions must be addressed, and the use of pharmacologic and non-pharmacologic therapies must be considered. Regardless of the reason, once hospitalized, the patient relies completely on the caregiving team for all physiologic, psychologic, and therapeutic needs to be met. A health-care team approach is mandatory to prevent, recognize, assess, and treat pain.

Preventing pain

Prevention of pain means anticipation of painful conditions or procedures. Surgical pain is common in hospitalized patients. A thorough patient history and presurgical workup, including blood work to screen renal and hepatic disease, are considered routine and can be used to guide the premedication plan. Once patients are identified as needing pain management, the Pain Management Guidelines Task Force in dogs and cats advocates a multimodal approach as being ideal.2 The nociception (pain sensation) pathway is made up of five distinct processes: transduction, transmission, modulation, projection, and perception. Multimodal analgesia is aimed at targeting multiple sites in the pain pathway. Benefits of a multimodal approach include using lower doses of each individual drug, thereby sparing unwanted side effects, as well as creating anesthetic-sparing effects.

Pain recognition and assessment

Figure 1
Figure 1

Behavioral signs in animals are the most important indicators of pain. Unlike in human medicine, our patients cannot communicate verbally, and therefore, the care team must rely on nonverbal methods of pain assessment. While helpful, physiologic parameters are not as reliable as careful and continuous evaluation of patient behavior. Catecholamine release and sympathetic nervous system activation can occur in the face of anxiety and fear, making physiologic changes unreliable on their own.

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A pain-scoring system may be utilized to raise awareness regarding the individual patient’s pain severity and can help guide analgesic needs. For example, a numeric rating scale (NRS) can be used to assess pain by evaluating different behaviors and assigning a numeric score to each. Vocalization, movement, and degree of agitation are common behavioral categories used in a simple NRS. While no one tool or system for evaluating pain in cats and dogs has been adopted as gold standard, it is recommended hospitalized patients be assigned a pain score that can be reassessed during each shift, using the same scoring system.3 A combination of physiologic and behavioral signs can be used to construct the pain score (Table 1). Every patient deserves pain-recognition advocacy. Once pain assessment has been made, an effective multimodal treatment plan can be constructed.

Treatment

A team approach is necessary when dealing with acute and chronic conditions.
A team approach is necessary when dealing with acute and chronic conditions.

Managing surgical pain almost always requires the use of opioids in pre-, peri-, and postoperative analgesia protocols. Combined with a sedative or tranquilizer, such as a benzodiazepine (e.g. midazolam or diazepam) and/or acepromazine, and/or an alpha-2 receptor agonist (e.g. dexmedetomidine), neuroleptanalgesia is achieved and offers potent synergistic effect through relieving both pain and anxiety. Neuroleptanalgesia also has been shown to have an anesthetic-sparing effect, which can help minimize the risk of hypotension and other cardiovascular consequences of general anesthesia.

Local anesthetics are another class of drugs that should be considered for use in every surgical case. Local anesthetics (e.g. lidocaine, bupivacaine) are the only drugs that result in complete local or regional analgesia, and are considered safe in small animals. The use of a local anesthetic block, such as a linea block upon celiotomy closure, or of a wound soaker catheter
(Figure 1), has demonstrated an analgesia and anesthesia-sparing effect, and reduced morbidity in hospitalized patients.

A common class of drugs with a wide range of uses in dogs and cats, NSAIDs also are known for their lengthy list of adverse effects, with uncomplicated gastrointestinal (GI) signs being the most common. They also can include more severe GI ulceration or perforation, as well as renal injury. Idiosyncratic hepatotoxicity has been described in dogs, but this is considered rare. The administration of an NSAID is always dependent on individual patient selection centered on risk factors and preexisting conditions. There also is evidence to support the use of lower doses than those published in commonly used veterinary formularies for many NSAIDs.4

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Non-pharmacologic therapies, such as acupuncture, nutraceuticals, and rehabilitation have not been well-described in the acute setting. However, there is evidence to support consideration of some of these therapies.5 Recently, the U.S. Food and Drug Administration (FDA) approved a non-pharmaceutical anti-inflammatory device (NPAID) magnetic-loop therapeutic for use in animals, and there is evidence to support its utility in managing acute and chronic painful conditions.6 Incorporating this type of integrative practice into hospitalized patient management may reduce the need for traditional NSAIDs, thus avoiding unwanted adverse effects (Figure 2).

Take home points

Multimodal pain management is an integral part of every hospitalized patient’s care plan. Each patient deserves a pain-prevention advocate, and collaboration amongst doctors, nursing staff, and clients is crucial. While every patient must be assessed based on individual needs (underlying disease processes, stability and American Society of Anesthesiologists [ASA] score, procedure being performed, etc.), core values of pain management should be applied to all cases. These include prevention, recognition, assessment, and reassessment, as well as treatment that is titrated to the individual’s needs. A multimodal approach can optimize analgesia by targeting multiple nociceptive pathways, while minimizing morbidity through anesthetic-sparing effects and reduced dosing needs of any one drug. Integrative approaches to pain management also deserve consideration as more FDA-approved products become available.

Pain should no longer go underdiscussed in our hospitals—we can be on the forefront of this movement through diligent patient-centric practices and a team approach to care. Reduced pain means decreased morbidity, shorter hospital stays, and improved quality of life, plus client satisfaction as animals are reunited with their owners sooner for ongoing recovery.

Figure 2
Figure 2

References

1Perkowski S. Pain and sedation assessment. Ch. 141. In: Small animal critical care medicine 2nd ed. St. Louis: Elsevier; 2015. p. 749-753

2Epstein ME, Rodan I, Griffenhagen G, et al. 2015 AAHA/AAFP pain management guidelines for dogs and cats. J Fel Med Surg (2015); 17:251-272.

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3Mellema MS, McIntyre RL. Patient suffering in the intensive care. In: Small animal critical care medicine 2nd ed. St. Louis: Elsevier; 2015. p. 64-66.

4Papich, MG. An Update on Non-steroidal anti-inflammatory drugs (NSAIDs) in small animals. Vet Clin Small Anim 38 (2008) 1243–1266.

5Robinson NG. Complementary and alternative medicine. In: Small animal critical care medicine. St. Louis: Elsevier; 2015. p. 777-781.

6https://bit.ly/2zhawee

7Plumb, DC. Plumb’s veterinary drug handbook 9th ed. Ames, IA: Wiley-Blackwell; 2018.

Melissa Bucknoff, DVM, DACVECC, is an assistant professor of biomedical sciences and clinical pharmacology at Ross University School of Veterinary Medicine (RUSVM). Dr. Bucknoff completed her DVM at RUSVM, clinical year rotations at North Carolina State University, and internship and residency at Tufts University. Her clinical and research interests include coagulation disorders, hemostatic therapeutics, and pain management.

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