Pressure Injury

Etiology

The pressure of an individual’s body weight or pressure from a medical device above a certain threshold for a prolonged period is thought to be the cause of pressure injuries. In patients with sensory deficits, an absent pressure feedback response may result in sustained pressure for a prolonged period, leading to tissue injury. Many factors contribute to pressure ulcers and injury formation, such as increased arteriole pressure, shearing forces, friction, moisture, and nutrition status.[1]

Epidemiology

Pressure injuries of the skin and soft tissues affect an estimated 1 to 3 million people in the United States annually. The incidence differs based on the clinical setting. For example, the prevalence of pressure injuries among hospitalized patients is 5% to 15%, with the percentage considerably higher in some long-term care environments and intensive care units.[1] Risk factors for developing pressure injuries, in general, include immobility, reduced perfusion, malnutrition, and sensory loss.[7][8][9] Other patients at increased risk for pressure injury development include those with cerebrovascular or cardiovascular disease, recent fracture of a lower extremity, diabetes, and incontinence.[10][11][2] Older patients are also at increased risk for the formation of pressure injuries due to skin changes associated with aging, which include thinning of the dermis and epidermis and can result in decreased resistance to shearing forces.

Pathophysiology

Pressure injuries of the skin and soft tissue are formed when the pressure above a certain threshold causes prolonged tissue ischemia, eventually leading to necrosis. Injury from reperfusion is also a contributing factor, as the return of blood supply after a period of ischemia can cause the formation of reactive oxygen species, triggering an inflammatory response. In patients positioned at an incline, internal structures such as bone and muscle are displaced downward due to gravity, leading to tissue hypoxia as blood vessels are distorted or flattened.[1]

One type of pressure injury is the Kennedy ulcer, which can occur suddenly in a patient who is terminal. There are gaps regarding the physiopathology of this ulcer as the current knowledge is based on hypotheses. There is a lack of knowledge about care approaches, but the main objective in this situation at the end of life would be to prioritize patient comfort and quality of life.

History and Physical

Areas of skin breakdown should be examined for length, width, and depth. The following characteristics should be evaluated in detail and recorded: the presence of sinus tracts, necrotic tissue, exudate, and granulation. 

While performing the clinical evaluation, the characteristics of the National Pressure Injury Advisory Panel staging should be evaluated:

Stage 1: The skin is intact. However, non-blanchable erythema lasting more than an hour following pressure relief is predicted.[6]

Stage 2: Bullae and or blister formation or dermal breakdown, accompanied by a partial-thickness dermal loss. The presence of infectious evidence is not mandatory at this stage.[5]

Stage 3: Full-thickness tissue loss. Subcutaneous fat might be evident, and tissue damage involving muscular layers is predicted. Further characteristics of this stage are tissue undermining and tunneling.[5][12]

Stage 4: Physical examination reveals a full-thickness tissue loss with bone, tendon, or joint involvement. 

Unstageable: The base of ulcer coverage with either tissue sloughing or eschar formation prevents a discrete classification.

Deep tissue pressure injury: Presence of a localized purple or maroon discoloration due to either a pressure or a shear injury and a blister full of blood.

Obtaining specific patient history information can help determine any potential risk factors for wound development and nonhealing. Providers should ask about a patient’s prior history of wounds, etiology, location, duration, and treatment. Inquiring specifically about medical conditions such as diabetes and associated neuropathy, chronic kidney disease, peripheral artery disease, immunocompromised states, and impaired nutritional status may give providers more information about a patient’s healing potential.[13][14]

Patients may be able to provide qualitative information regarding their current wound history, including:

• Location
• Duration
• Potential causes or inciting factors
• Changes in size
• Pain (type, severity, frequency, aggravating or alleviating factors)
• Previous wound manipulation or treatment
• Presence of erythema, odor, or exudate

Assessing specific locations for any signs of pressure injury during physical exams is important. Pressure injuries commonly develop in these areas:

• Sacrum
• Greater trochanter
• Ischial tuberosity
• Lateral malleolus
• The heel of the foot [1]

Characteristics of pressure injuries that should be assessed include, but are not limited to:

• Location
• Length
• Width
• Depth (both quantitative and qualitative)

 Document the presence of any of the following:

• Undermining
• Tunneling
• Necrosis
• Signs of infection:
  • Erythema
  • Induration
  • Warmth
  • Tenderness or pain with palpation
  • Drainage (also noting amount, type, odor, and color)[15][16]

Evaluation

A staging system should be used to assess all pressure injuries. At this time, there is a lack of a universal classification system for pressure injuries, but the National Pressure Injury Advisory Panel staging system is widely used, as listed below:

• Stage 1: Non-blanchable erythema of intact skin and erythema remains for greater than 1 hour after relief of pressure
• Stage 2: Partial-thickness loss of skin with exposed dermis
• Stage 3: Full-thickness loss of skin tissue; subcutaneous skin and muscle may be visible
• Stage 4: Full-thickness loss of skin tissue; tendons, bone, and joints may be visible
• Unstageable: Full-thickness loss of skin tissue that is obscured by eschar or slough
• Deep tissue: Skin that is persistently non-blanchable, with maroon or purple discoloration [1][2]

The laboratory studies listed below can be obtained to assess for conditions that can lead to the formation of non-healing injuries, such as infection, anemia, poor nutritional status, and diabetes:

• Comprehensive metabolic panel
• Complete blood count with differential
• Albumin and pre-albumin (to assess nutrition status)
• Hemoglobin A1C [17]

Wound cultures from superficial swabs may not be clinically useful as they usually reflect colonization rather than infection. Cultures from bone or deep tissue should not be used as a sole indicator of infection but should be interpreted in the context of the clinical setting and other histopathological data.[18]

Treatment / Management

General Care

General care for pressure injuries includes redistribution of pressure with the use of support surfaces and changes in positioning. Redistribution of pressure and appropriate patient positioning are required to prevent the development and worsening of pressure injuries, as these methods can reduce force from friction and shear. Support surfaces can alleviate pressure in patients with a high risk of developing pressure injuries. This can include higher-speciation foam mattresses, medical-grade sheepskins, continuous low-pressure supports, alternating-pressure devices, and low-air loss therapy. However, the effectiveness of these devices compared to other surfaces in treating existing pressure injuries has not been conclusively established.[19][20] Based on the Americal College of Physicians (ACP) clinical practice guidelines from 2015, providers should select advanced static mattresses or mattress overlays consisting of foam, sheepskin, or gel in patients at increased susceptibility to the formation of pressure injuries. The guidelines also advise against alternating-pressure mattresses or overlays in this patient population. Only moderate-quality evidence supports these 2 recommendations.[21] Although there is inadequate evidence to assess the effectiveness of repositioning patients on the healing rates of pressure injuries, maintaining patient positioning is still good practice, which minimizes wound pressure.[22](A1)

Part of treatment for pressure injuries also includes pain control and nutrition optimization. Pain frequently occurs during dressing-related procedures. Pain control can be achieved with individualized analgesic regimens and skilled wound management.[23] Optimizing total caloric and protein intake in pressure injuries is essential, especially for patients with stages 3 and 4 injuries.[24] ACP guidelines recommend supplementation with protein or amino acids to reduce wound size in patients with pressure injuries. The evidence to support this recommendation is of low quality.[25](A1)

Wound Management

Wound care, including maintaining a clean environment, debridement, application of dressings, monitoring, and various adjunctive therapies, is generally advised to facilitate the healing of pressure injuries. The stage of the pressure injury can guide options for treatment. Stage 1 pressure injuries can be covered with transparent film dressings as needed. Stage 2 pressure injuries benefit from a moist wound environment. Occlusive dressings (foam, hydrogels, and hydrocolloids) and non-occlusive dressings (transparent films) can achieve this. Treatment of stage 3 and 4 injuries is based on the presence of necrotic tissue. Pressure injury treatment also involves preventing wound contamination and maintaining a clean environment.[25] Wounds with necrotic tissue or eschar require debridement, whether by sharp, mechanical, autolytic, or bio-surgical method, to expose granulation tissue, facilitate healing, and reduce the risk of infection before moist placement of absorbent dressing.[17](A1)

Dressings and topical agents are commonly used to treat pressure injuries, but it is unclear whether one dressing or topical agent is superior to another. Appropriate selection of dressings may be based on wound characteristics, cost, or patient preference and includes hydrocolloids, hydrogels, transparent films, foams, and alginates.[26][17] ACP clinical practice guidelines from 2015 recommend using foam or hydrocolloid dressings to reduce the size of pressure injuries.[25] Additional therapies such as negative-pressure wound therapy, electromagnetic therapy, phototherapy, therapeutic ultrasound, and reconstructive surgery treat pressure injuries. Still, there is limited data regarding their efficacy in wound healing.[27][28][29][30][31] Based on moderate-quality evidence, ACP guidelines recommend using electrical stimulation as a supplemental therapy to accelerate wound healing in patients with pressure injuries.[25] In addition to the above treatments, monitoring to assess the healing of pressure injuries should be implemented, which can be done using healing scales. The most common instruments include the Pressure Ulcer Scale for Healing and the Pressure Sore Status Tool.[2](A1)

Various adjunctive therapies, including electrical stimulation, therapeutic ultrasound, hyperbaric oxygen, and topical oxygen, with equivocal effectiveness and impact, have been introduced to manage pressure injuries. Accordingly, no specific studies have explored the details of pressure-injury management with hyperbaric oxygen therapy. However, the systematic reviews of studies evaluating the role of HBOT in wound treatment demonstrated that while hyperbaric oxygen therapy (HBOT) is beneficial in treating some types of wounds, including non-healing osteomyelitis, there is still a lack of robust evidence of sustained benefit.[40][41] Moreover, some serious treatment-related adverse events with HBOT, including seizures and pneumothorax, should not be underestimated.[32][43] (A1)

Ultrasound has also been utilized as a wound therapy measure. With a limited sample size, the current trials could not clarify the benefit or harm of ultrasound therapy.[33] However, applying high-frequency ultrasound (1 MHz), with penetration to greater tissue depths, resulted in significant reductions in wound surface area.[45][46][47] A limited number of studies have verified enhanced healing of wounds with adequate granulation tissue with peri-wound electrical stimulation.[34][48][52][50](A1)

Differential Diagnosis

The differential diagnosis for pressure injuries is important to consider to treat this condition appropriately. This differential can include but is not limited to:

• Venous insufficiency ulcers
• Diabetic neuropathic ulcers
• Arterial/ischemic ulcers
• Ulcers associated with malignancy
• Hypertensive ulcers [35]

Staging

The following are the various levels of staging for pressure injuries:

Stage 1: The skin is intact. However, non-blanchable erythema lasting more than an hour following pressure relief is predicted.[6]

Stage 2: Bullae and or blister formation or dermal breakdown, accompanied by a partial-thickness dermal loss. The presence of infectious evidence is not mandatory at this stage.[5]

Stage 3: Full-thickness tissue loss. Subcutaneous fat might be evident, and tissue damage involving muscular layers is predicted. Further characteristics of this stage are tissue undermining and tunneling.[5][12]

Stage 4: Physical examination reveals a full-thickness tissue loss with bone, tendon, or joint involvement. 

Unstageable: The base of ulcer coverage with either tissue sloughing or eschar formation prevents a discrete classification.

Deep tissue pressure injury: There is presence of a localized purple or maroon discoloration due to either a pressure or a shear injury and a blister full of blood.

Prognosis

The presence of a pressure injury can be indicative of a poor overall prognosis for a patient.[36] An increased risk of death in both elderly and intensive care patients has been associated with the presence of pressure injuries, which may be a sign of the underlying severity of the disease instead of an independent predictor of mortality.[37] Additional clinical conditions that remain unmeasured may be contributing to the increased morbidity and mortality associated with pressure injuries.[38]

Complications

Infection is a significant complication of pressure injuries, and the manifestations can be widely variable. This can include local wound infection as well as soft tissue infection, osteomyelitis, and bacteremia. Osteomyelitis can manifest as a wound with delayed healing and does not always include systemic signs such as sepsis or leukocytosis. Bacteremia is usually more apparent as signs of a systemic inflammatory response typically accompany it. Evaluation of pressure injuries for infection can require a combination of clinical assessment and judgment, microbiological and histopathological evaluation, and imaging studies. The infection control goals include preventing the spread of pathogens to other patients, staff, and the surrounding environment and avoiding the selection of resistant microorganisms.[18]