9.3 Integumentary - Wounds & Pressure Injuries

Skin Integrity in Critical Illness

The skin is the body's largest organ and its first barrier; in the ICU it is under constant threat from immobility, vasopressors, poor perfusion, moisture, edema, malnutrition, and devices. Pressure injuries (renamed from pressure ulcers by the NPIAP in 2016) are localized damage to skin and underlying soft tissue over a bony prominence or under a medical device, caused by sustained pressure, often combined with shear and friction. Capillary closing pressure is roughly 32 mmHg, so tissue over the sacrum, heels, ischium, trochanters, and occiput can become ischemic within hours of unrelieved loading - faster when perfusion is already low from shock or high-dose vasopressors.

Pressure Injury Staging (NPIAP)

Staging describes the deepest tissue visible and does NOT reverse - a healing Stage 4 is documented as a healing Stage 4, never down-staged to a Stage 2.

Common traps: a serum-filled blister is Stage 2, but a blood-filled blister is a deep tissue injury; mucosal membrane pressure injuries (from tubes) are not staged with this system; and moisture-associated skin damage (incontinence dermatitis) is not a pressure injury even when the two coexist.

Risk Assessment - the Braden Scale

The Braden Scale is the most widely used validated tool. It scores six subscales - sensory perception, moisture, activity, mobility, nutrition, and friction/shear. Five subscales score 1-4 and friction/shear scores 1-3, so the total ranges from 6 (highest risk) to 23 (lowest). General interpretation: 9 or below very high risk, 10-12 high, 13-14 moderate, 15-18 mild; ICU patients frequently fall into the high-risk band. Reassess on admission, at set intervals, and with any change in condition. A low score should trigger a full prevention bundle, not a single intervention.

Prevention Bundle

Prevention is a tested nursing priority because most pressure injuries are considered avoidable (CMS treats hospital-acquired Stage 3/4 injuries as non-reimbursed never events):

• Reposition at-risk patients on an individualized schedule (commonly every 2 hours, sooner if perfusion is poor) and use the 30-degree lateral tilt to offload the trochanter.
• Offload heels - float them on a pillow so the calf bears weight, not the heel.
• Redistribution surfaces - low-air-loss or alternating-pressure mattresses for high-risk patients.
• Manage moisture - barrier creams, prompt cleansing, absorbent wicking pads; keep skin dry.
• Prophylactic multilayer foam dressings over the sacrum and heels for high-risk patients.
• Device rounds - rotate and pad ETT ties, SpO2 probes, cervical collars, and NG tubes; reposition lines.
• Optimize nutrition and perfusion - adequate protein and calories, correct hypoperfusion, and keep the head of bed at or below 30 degrees when tolerated to limit sacral shear.

Wound Care Principles

Management follows moist wound healing: keep the wound bed moist and the surrounding skin dry, and match the dressing to the wound. Debride devitalized tissue (except stable heel eschar) to allow granulation.

Assess and document size, depth, undermining, tunneling, exudate, odor, and periwound condition each shift. Signs of local infection - increasing pain, erythema, warmth, purulence, odor, and delayed healing - warrant a tissue culture (not a surface swab) and systemic therapy if cellulitis or sepsis develops. In critical illness a wound will not heal without addressing the whole patient: perfusion, oxygenation, glycemic control, nutrition, and offloading matter as much as the dressing itself.

Pressure versus shear, friction, and moisture

The exam expects you to separate the mechanisms because they call for different interventions. Pressure is perpendicular loading over a bony prominence; shear is the deeper, parallel force that occurs when the skeleton slides (as when the head of bed is raised and the patient slides down) while the skin stays fixed - shear tears deeper tissue and is a major cause of sacral injury, which is why keeping the head of bed at or below 30 degrees matters. Friction is surface rubbing that abrades the epidermis, reduced by lift sheets and avoiding dragging. Moisture-associated skin damage from incontinence or wound drainage macerates skin and is managed with barrier products, not staging. Distinguishing these guides whether you reposition, tilt, protect from friction, or manage moisture.

Nutrition and advanced therapies

Healing is protein-driven: at-risk critically ill patients generally need adequate calories and higher protein (roughly 1.25-1.5 g/kg/day), with attention to hydration and, where deficient, vitamin C and zinc; albumin and prealbumin trend nutritional status but are also depressed by inflammation. For large, clean, exudative Stage 3-4 wounds, negative-pressure wound therapy (NPWT, a wound VAC) promotes granulation, removes exudate, and reduces edema; it is not used over exposed vessels or untreated infection. Consistent turning schedules, a dedicated wound-care consult, and daily reassessment close the loop on prevention and treatment.