Using temperature of pressure-related intact discolored areas of skin to detect deep tissue injury: an observational, retrospective, correlational study.

Pressure-related intact discolored areas of skin (PRIDAS) are generally described as an area of nonblanching erythema (Stage I pressure ulcer) or deep tissue injury (DTI), but the validity of these definitions has not been tested. Preclinical studies and forensic observations have shown that skin temperature may help identify nonviable tissue. To investigate the effect of temperature difference between a PRIDAS and its adjacent intact skin and the subsequent development of skin necrosis, an observational, retrospective, correlational study was conducted. Data from all acute care hospital patients with an observed PRIDAS who received a skin integrity consult, including a skin temperature measurement of a PRIDAS site, were abstracted to ascertain if PRIDAS temperature correlated with the development of skin necrosis after 7 to 14 days and to examine the effect of additional patient variables on the progression or resolution of a PRIDAS. Skin temperatures were measured using a commercial, hand-held, infrared thermography camera, and the presence or absence of capillary refill was documented. Among the 85 patients studied, the difference between PRIDAS temperature and adjacent skin ranged from -3.2 ̊ C. to +3.0 ̊C. Of the 55 PRIDAS with a lower temperature at baseline than adjacent skin ("cool", average -1.2 ̊ C), 29 progressed to necrosis, compared to one of 30 PRIDAS with a higher temperature than adjacent skin ("warm", average + 1.2 ̊ C) (P <0.001). After adjusting for patient age, skin color, and PRIDAS site, the cool PRIDAS were 31.8 times more likely to progress to necrosis than the warm PRIDAS. Combining the presence/absence of capillary refill and PRIDAS temperature, 0% of 26 patients with signs of blanching and a warm PRIDAS versus 65% of 26 patients with a nonblanching and cool PRIDAS developed skin necrosis (P <0.001, Fisher exact test for the difference between the two combined values). Research examining the delayed appearance of DTI and large, multicenter, prospective validation studies are warranted. The current National Pressure Ulcer Advisory Panel definition of a Stage I pressure ulcer needs to be amended to reflect the strong relationship to DTI development.