Sub-epidermal moisture versus traditional and visual skin assessments to assess pressure ulcer risk in surgery patients

Publication Name

Journal of wound care


OBJECTIVE: To compare the predictive ability of subepidermal moisture (SEM) measurement versus traditional risk assessment and visual skin assessment (VSA) as means of detecting early pressure ulcer (PU) damage development among adults undergoing surgery. METHOD: A non-experimental, comparative, descriptive cohort study design was used. Following ethical approval, participants who had given their informed written consent had their skin assessed over the areas that were weight-bearing during surgery, using VSA and the SEM measurement. Visual PUs were graded according to the European Pressure Ulcer Advisory Panel and National Pressure Ulcer Advisory Panel ulcer grading system. Assessments took place preoperatively, then daily on the ward, beginning on day one postoperatively and continuing for three days or until discharge. RESULTS: Of the 231 participants, who had a mean age of 57.50 years, 55.8% (n=129) were male. The most common comorbidity was cardiology/vascular (n=42; 18.2%). Just over half (52.4%; n=121) underwent orthopaedic surgery and 47.6% (n=110) underwent non-orthopaedic surgery; 70% (n=163) received a general anaesthetic and 43% (n=100) were in the supine decubitus position during surgery. PU incidence was 51% (n=116), according to SEM measurement, and 3% (n=7) according to VSA. Among the seven participants who developed a visual PU, 10 PUs at stage 1 developed (31%); some patients developed more than one PU. Of the participants who had assessments for three days postoperatively, 94% (n=61) had a persistently high SEM delta on day three. The variables that emerged as statistically significantly related to abnormal SEM measurement deltas among these participants were: surgery duration (p=0.038); having orthopaedic surgery (p=0.020); supine surgical position (p=0.003); spinal anaesthetic type (p=0.0001); and Waterlow and Braden mobility subscale day one postoperatively (p=0.0001). None of the variables had a statistically significant influence on abnormal VSA. CONCLUSION: Surgical patients, because of immobility, are vulnerable to the action of compression and shear forces. These forces cause changes at a cellular level that trigger inflammation, which is a precursor to early tissue damage. SEM measurement can detect this tissue damage from the increase in the underlying tissue water content that results from inflammation. From the findings of this study, SEM measurement is very promising in the detection of early tissue damage in those at risk of PU development among the surgical population.

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