Additionally, reperfusion and reoxygenation injury promote endothelial and microvascular damage via the production of superoxide anion, hydroxyl, and hydrogen peroxide free radicals. 5 Cells then use anaerobic metabolism, producing toxic byproducts that cause tissue acidosis, increased cell membrane permeability, edema, and cell death.
Unrelieved direct pressure or force on an area causes microvascular circulatory occlusion, which in turn impairs cellular nutrition and removal of waste products. Long periods of low pressure can be as damaging to a patient's skin integrity as short periods of high pressure. Common causes of immobility are excessive pharmacologic sedation or anesthesia, neurologic sequelae, advanced dementia, use of restraints, or injury. Impaired mobility is the most important risk factor that contributes to pressure injury development. Risk factors include pressure, friction and shear, moisture (such as from incontinence), advanced age, malnutrition, diabetes, dehydration, and vascular disease. The pathogenesis of pressure injuries is multifaceted. Pressure injuries are less common on the nose, chin, forehead, occiput, chest, upper back, and elbows. 3 The remainder of pressure injuries affect the lower extremities, including the malleolus, heel, patella, and pretibial areas. 2Īlthough pressure injuries can develop on any part of the body, about 70% occur on the hips and buttocks, most commonly the ischial tuberosity, trochanter, and sacrum. 2 About 60,000 die from pressure-injury complications each year. 1 At any given time, about one-third of patients in acute, long-term, or home-care settings have pressure injuries. 1 Each year in the United States, an estimated 1 to 3 million people, mostly patients in acute care, develop pressure injuries, according to NPUAP. The National Pressure Ulcer Advisory Panel (NPUAP) identifies a pressure injury as an area of increased, unremitting pressure most commonly over a bony prominence, resulting in tissue ischemia and necrosis. Pressure injuries are common in the acute inpatient setting, in chronic long-term care populations, and in patients at home who have risk factors for skin breakdown, such as immobility, advanced age, and history of a pressure injury.
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