Treatment of Painful Cutaneous Wounds
Chronic cutaneous wounds, such as those caused by pressure, venous insufficiency, neuropathy, or arterial disease, may cause considerable pain and can be challenging to treat. Often severe pain interferes with treatment protocols because patients are unwilling or unable to comply with necessary regimens. For example, compression bandaging, which is necessary for the treatment of venous stasis disease,1 may cause extreme discomfort, and noncompliance that significantly delays wound healing. Additionally, pain activates the sympathetic branch of the autonomic nervous system, triggering a physiological response that slows wound healing.2 Treating wound-related pain is essential for optimal wound healing. In the European Wound Management Position Statement, Briggs, Torra and Bou3 demonstrated the complexity of wound pain and its effect on treatment. The authors stressed the importance of using a combination of techniques that focused not only on physiological factors, but also on psychological and emotional factors. This article reviews the neurology and biochemistry involved in wound pain and discusses treatment options, including noninvasive techniques such as electrical stimulation, ultrasound, and pulsed radio frequency energy.
Cutaneous wounds normally heal in predictable stages: hemostasis and inflammation, granulation, epithelialization, maturation and remodeling. However, when the process is disturbed at any stage, a chronic wound may result.4 A variety of factors can contribute to nonhealing, including infection, inadequate pressure relief, uncontrolled swelling, impaired blood supply, malnutrition and poor glycemic control. In general, if an acute wound fails to heal within four to six weeks, it should be considered chronic. Treatment protocols vary according to the wound cause(s) (see Table 1).4
The most common chronic wounds are pressure (decubital) ulcers, venous insufficiency leg ulcers, arterial insufficiency ulcers, and diabetic foot ulcers (which may be a combination of the previous). Pressure ulcers frequently occur in immobile patients or those with some form of paralysis or orthopedic deformity. Pressure from a bed, footrest, shoe or other device restricts cutaneous blood flow causing tissue breakdown and ulceration. Venous leg ulcers are the result of inadequate venous drainage in the legs. Over time, increased tissue congestion and impaired venous blood flow compromises the skin and leads to overt ulceration. Arterial insufficiency ulcers often result from minor skin trauma in the setting of impaired blood flow. Finally, diabetic foot ulcers occur as a result of the repetitive trauma of walking in the setting of impaired sensation and often abnormal mechanics.
Evaluation and treatment of the chronic wound starts with a thorough history and physical examination. Appropriate laboratory and imaging studies should be utilized to help confirm diagnostic suspicions and identify infection. Treatment varies according to the underlying primary etiology but should consider all contributing factors (e.g., diabetic patient with an infected pressure ulcer on the bottom of the foot and concomitant peripheral arterial disease and poor glycemic control; see Table 2). Therapy should be customized for each patient according to his or her own individual needs.
Chronic wounds may take months or, in some cases, years to heal. General principles of wound management include: establishment of a clean, healthy wound base (often through surgical debridement), treatment of infection (both topical and parenteral), coverage of the wound with an appropriate dressing, and maintenance of a moist wound environment.4 Severe wounds—or those in patients with multiple medical problems—may require advanced modalities such as skin grafts or flaps. Despite the goal of healing, amputation is sometimes unavoidable, especially in patients with severe arterial insufficiency or comorbid problems.4
Across all wound types, pain management plays a major role in wound healing. Patients with chronic wounds often report a diminished quality of life because of pain. In addition, with repeated and vigorous medical procedures and restricted lifestyles, patients already may suffer from some degree of depression and anxiety.5-7 Increased anxiety has been shown to be a significant predictor of the intensity of pain experienced during treatment.8 Ongoing inflammation and infection may amplify a patient’s pain experience, and discomfort may increase with each wound treatment instituted.8,9 Evidence suggests that stress significantly slows wound healing and multiple cellular and biochemical mechanisms have been identified that link stress and wound healing.10-13 Understanding the different types of pain and the neurobiology of pain pathways is a critical first step in pain management for a patient with a chronic wound.
Neurobiology of Pain
Wound pain may occur as one of two types (or both): nociceptive and neuropathic. Nociceptors are the free nerve endings that respond to tissue injury. These nerve endings are either small myelinated Ad fibers, which conduct pain quickly and produce sharp localized discomfort, or larger unmyelinated C fibers, which conduct pain slowly and are responsible for dull or throbbing pain. Generally, once damaged tissue has healed, nociceptive pain subsides. If nociceptive pain continues for a prolonged period of time and the nerve fibers are in a constant inflammatory state—such as with repeated wound debridement or dressing changes—sensitization of the nerve fibers may lead to hyperalgesia14 (amplified pain) or allodynia (pain from a benign stimulus, such as light touch). Allodynia, which is more characteristic of neuropathic pain,15 may confound evaluation and treatment.12
Neuropathic pain is caused by insult to the actual nerve fibers or central nervous system. It often occurs after prolonged nociceptive pain from an injury, although it may also be caused by inflammation or compression of a nerve by a lesion or scar tissue. Usually it is chronic and described as burning, tingling, or shooting. Unlike nociceptive pain, neuropathic pain often continues even after the tissue has healed because the damaged nerve fibers continue to misfire.12,15