Elucidation of Ischemic Mechanisms of Early Pressure Injury during Post-Decompression and Detecting Methods

Abstract

Background: Pressure injuries (PIs) generally result from prolonged ischemia through localized skin compression, and ischemia persists and exacerbates damage even post-decompression. The mechanisms of ischemia post-decompression are still unclear, and appropriate methods for detection are lacking. Methods: We used blanchable erythema (BE) and early PI rat models. We assessed the perfusion using Evans Blue (EB) and thrombus formation under a light microscope. Furthermore, we performed a capillary refill time test (CRTT) to detect ischemia after depression coupled with the transparent disk method using a spectrophotometer. Results: Compared with the BE group, the early PI group showed significantly slow and insufficient perfusion, as determined by EB staining (p < 0.001). Histological observations revealed that ischemia during post-decompression of early PI was caused by a greater amount of thrombi. The CRTT results showed that although both groups exhibited varying degrees of insufficient refilling volume, the early PI group had significantly slower refilling than the BE group (p < 0.001), which persisted during the deterioration or disappearance of erythema. Conclusions: Our results showed that persistent ischemia caused by thrombi is an important cause of early PI deterioration post-decompression. Therefore, the performance of CRTT coupled with the transparent disc method may become a promising method for detecting ischemia post-decompression.

A comprehensive analysis of multi-circulatory disorders in early pressure injury and their diagnostic significance in rat models

“…Our study showed that progression to ulceration also takes more than 36 h. During this process, multiple circulatory disorders are involved and interact with each other. As is shown in Figure 9, recent studies have revealed that, in addition to the above-mentioned hemorrhage and hyperemia, congestion and ischemia are also found within lesions [8,9] . Furthermore, hemorrhage is a pathology that comes afterwards, so testing methods prior to hemorrhage, including the transparent disc method, are rarely mentioned.…”

“…The wound area of the rats was placed on a round platform (2 cm in diameter) and then compressed. As described previously [9], the pressure applied in the current study was set at 150 mmHg. The pressure instrument used an electric stand (MX500N; Imada Co., Toyohashi, Japan) to regulate the pressure.…”

“…Two rat models representing either BE or early PI were made and analyzed according to the methods of a previous study [9]. In brief, hairless rats were anesthetized with iso urane inhalation (import: 4%-5%; maintenance: 2%-3%) (Meiji Seika Pharma Co., Ltd. Tokyo, Japan).…”

“…The other four rats were used for pathological observation, and the models were made as above. Then we intravenously injected black ink solution which was considered to distinguish vascular hyperemia or clots from thrombi as previously reported [9]. The skin specimens were collected at 24 h after decompression and xed in a 10% neutral formalin solution.…”

“…We con rmed the presence of ischemia using biomarkers and a spectrophotometer to record the presence of ischemia based on the CRTT in early PI. 9 However, which of these circulatory disorders is more relevant for the diagnosis during the deterioration of early PI remains unclear.…”