The role of sub-epidermal moisture measurement versus traditional risk assessment and visual skin assessment in the prediction of pressure ulcer risk among adults undergoing surgery.

Aim: To compare the predictive ability of sub-epidermal moisture measurement versus traditional risk assessment and visual skin assessment as a means of detecting early pressure ulcer damage development among adults undergoing surgery.

Method: A non-experimental, comparative, prospective, descriptive design was used. Participants who gave their informed consent had their skin assessed over the areas that were weight bearing during surgery, using visual skin assessment and the sub-epidermal moisture measurement. Visual pressure ulcers were graded according to the EPUAP pressure ulcer grading system. Risk assessment was undertaken using the Braden and Waterlow Scale. Assessments took place pre-operatively, and then daily, on the ward, beginning on day 1 post-operative and continued for 3 days or until discharge.

Background: Surgical population pressure ulcer incidence figures vary between 1.3% - 54.8%, showing that pressure ulcers are a health problem within the surgical population. Pressure ulcers develop when tissues are subject to the action of pressure/shear and VSA only detects damage when it is already present. Surgical patients, in the peri-operative period, are subject to forced immobility and the action of pressure/shear, which causes tissue and cell injury/damage. Because risk assessment scales cannot detect changes that already occurred, new diagnostic methods need to be used for the early detection of pressure ulcer damage. One such method is sub-epidermal moisture measurement.

Findings: From 231 participants, with a mean age of 57.50 years, 55.8% (n=129) were male. Pressure ulcer incidence was 51% (n=116), according to SEM, and 3% (n=7) according to VSA. Most patients were assessed as being not at risk post-operatively, according to the Braden scale conversely, with the Waterlow scale participants were mainly assessed as being at risk. For the population as a whole, the independent variables that had a statistically significant impact on abnormal sub-epidermal moisture measurement deltas were surgery time (p=0.038), orthopaedic surgery (p=0.010) and spinal anaesthesia (p=0.028).

Of the participants who had assessments for 3 days post-operatively, 94% (n=61) had a persistently high SEM delta on day 3 post-operative. The variables that emerged as statistically significantly related to abnormal sub-epidermal moisture measurement deltas among these participants were orthopaedic surgery (p=0.020); supine surgical position (p=0.003); spinal anaesthetic type (p=0.0001); and Waterlow and Braden mobility sub-scale day 1 post-operative (p=0.0001).

For the total population, and also for those who had assessments for 3 days post-operatively, none of the independent variables had a statistically significant impact on the dependent variable, abnormal VSA.

Conclusion: Risk assessment scales measure risk factors that are often impossible to change and many are not related to pressure ulcer development. Surgical patients, because of immobility, are vulnerable to the action of compression and shear forces. These forces cause changes at the cellular level that trigger inflammation, which is a precursor to early tissue damage. Sub-epidermal moisture measurement can detect tissue damage due to an increase in the underlying tissue water content, resulting from inflammation. From the findings of this study, sub-epidermal moisture measurement is very promising in the prediction of pressure ulcer development among the surgical population.