Musculoskeletal & Integumentary · Topic 8 of 11

Pressure Injuries

Skin & wounds · pressure injury

Pressure Injuries

Pressure over bone kills tissue from the inside out. Stage by the deepest tissue you see, and turn the patient at least every 2 hours.

Key numbers

Reposition bed-bound patients every 2 hoursturn ≥ q2h

Braden score 18 or lower means riskBraden ≤ 18

01 · Defined byStage 3 fat; stage 4 bone

Stage 3 = full-thickness skin loss into subcutaneous fat, down to but not through fascia. Stage 4 = full-thickness loss exposing muscle, tendon or bone. Stage by the deepest tissue visible.

02 · Defined byDeep tissue injury: purple or maroon skin

Deep tissue pressure injury = persistent nonblanchable deep red, maroon or purple skin or a blood-filled blister, from pressure and shear at the muscle–bone interface; it may evolve rapidly to full-thickness loss.

03 · DoReposition bed-bound patients every 2 hours

Offloading is the most important treatment: turn bed-bound patients at least every 2 hours, use a 30° side-lying tilt, keep the head of bed as low as possible, and reposition patients in chairs every hour.

Causes & risk factors

Why it happens

Immobility, incontinence, undernutrition, lost sensationRisk factors are age > 65, immobility (sedation, coma, spinal cord injury), incontinence, undernutrition, impaired perfusion (PAD, diabetes) and impaired sensation; the sacrum is the most common site, then the heels.

Diagnosis & monitoring

Work-up

Stage 1 intact; stage 2 partial thickness must knowStage 1 = intact skin with nonblanchable erythema over a bony prominence (harder to see in dark skin). Stage 2 = partial-thickness loss with exposed dermis or a serum-filled blister; no fat, slough or eschar.

Unstageable: slough or eschar hides the base must knowUnstageable = full-thickness loss with slough or eschar hiding the base; once cleared it is stage 3 or 4. Leave stable, dry eschar on a heel or ischemic limb in place; never debride just to stage.

Device injuries take the device's shapeMedical device–related pressure injuries (masks, tubing, casts, splints) conform to the device's shape and are staged with the same system; mucosal membrane pressure injuries (from endotracheal tubes, dentures) cannot be staged.

Braden score 18 or lower means riskThe Braden scale sums 6 subscales (sensory perception, moisture, activity, mobility, nutrition, friction/shear) for 6–23 points; lower is worse: 15–18 mild, 13–14 moderate, 10–12 high risk.

Management

Orders

Do not swab-culture every pressure injuryAll pressure injuries are colonized, so skip routine surface cultures. Culture tissue, not a swab, when signs suggest infection; give systemic antibiotics only for cellulitis, bacteremia or osteomyelitis.

Protein 1.25–1.5 g/kg/day for healingAssess nutrition clinically in every stage 3–4 injury — albumin and prealbumin alone are unreliable — and give protein 1.25–1.5 g/kg/day, by supplement or tube feeding if needed.

Order a dynamic surface for stage 3–4Static foam or air overlays suit prevention and stage 1; order a dynamic surface (alternating-air or low-air-loss) for stage 3–4 injuries, and air-fluidized beds for nonhealing stage 3–4 or multiple truncal injuries.

Clean with saline; match dressing to exudateClean with normal saline, not cytotoxic antiseptics (povidone-iodine, hydrogen peroxide). Use film, hydrocolloid or hydrogel for dry, shallow wounds; foam, alginate or gelling fiber for heavy exudate; fill deep cavities.

Debride necrotic tissue, sharply if infectedNecrotic tissue must be removed: sharp debridement for thick eschar or infection (operating room if deep or bone is exposed); autolytic dressings only for small, uninfected wounds; enzymatic (collagenase) or biologic (maggot) options exist.

Red flags & don'ts

Avoid harm

Nonhealing stage 4: look for osteomyelitis complicationSuspect underlying osteomyelitis (up to 32% of patients) in a nonhealing deep injury: check CBC, blood cultures, ESR/CRP; MRI is sensitive but not specific, and bone biopsy with culture is diagnostic.

The rules

Know these

Never reverse-stage a healing injuryStaging is for initial assessment and worsening only: a healing stage 4 is never re-staged as stage 3. Track healing with serial measurements, photographs or a healing scale such as PUSH.

Stage 1 or deep tissue pressure injury?

Commonly confused

Color	Nonblanchable erythema
Skin surface	Intact
Where the damage is	Skin, before ulceration
Course	Ulcerates only with continued pressure, shear or moisture

Commonly confused

Tell apart

Moisture damage and skin tears aren't stage 2Skin tears, tape burns, maceration and incontinence-associated dermatitis are excluded from stage 2; arterial, venous and neuropathic ulcers can mimic pressure injuries on the legs.

More detail

Reference

Show 4 reference facts

Large stage 3–4 defects over the sacrum, ischia or trochanters are closed with myocutaneous, fasciocutaneous or perforator flaps after nutrition and comorbidities are optimized; skin grafts suit only large, shallow defects.

Pressure above capillary pressure (about 12–32 mmHg) causes ischemia within 3–4 hours; muscle is more ischemia-sensitive than skin, so a small surface wound may hide extensive deep necrosis.

Treat pain with acetaminophen or an NSAID and premedicate before dressing changes or debridement; avoid routine opioids where possible because sedation worsens immobility.

A chronic nonhealing ulcer can harbor squamous cell carcinoma (Marjolin ulcer); sinus tracts can connect a sacral ulcer to bowel. Negative-pressure wound therapy is an adjunct for clean wounds with limited evidence.

Pearl

Staging describes the deepest tissue seen and never runs backward — a healing stage 4 is still a stage 4.

Sources · Merck Manual Professional — Pressure Injuries (full review Sept 2025, updated Feb 2026) · Edsberg LE et al. Revised National Pressure Ulcer Advisory Panel Pressure Injury Staging System. J Wound Ostomy Continence Nurs 2016;43(6):585–597 (the staging used by the 2019 EPUAP/NPIAP/PPPIA international guideline) · Open RN Nursing Fundamentals — 10.5 Braden Scale (LibreTexts) · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).