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

Abstract

Early pressure injury (PI) progression is associated with multi-circulatory disorders and they interplay with each other, resulting in a lack of a satisfactory diagnostic method. We generated early PI and blanchable erythema hairless rat models. Transparent disc method and capillary refilling time test (CRTT) results were recorded with ultraviolet camera to capture the dynamics changes, and the blanching index and refilling index were set for comprehensive analysis. The deteriorated areas of early PI showed non-blanchable erythema (NBE) and an increase in erythema at 0.5 and 6 h with the transparent disc method. CRTT showed a marked refilling delay at 12 h. The comprehensive analysis of blanching index and refilling index showed a significant change in erythema from NBE at 0.5 h and ischemia progressing to hemorrhage at 18 h. There was also a marked difference in the deteriorating and improving areas within the same erythema. Pathological analysis showed inflammatory cell infiltration, with marked edema accompanied by increased hemorrhage and tissue necrosis. Furthermore, small arteries and veins with thrombosis and microthrombi were observed. Consistent ischemia after decompression and subsequent hemorrhage are important indicators, and comprehensive analysis can help increase the positive diagnosis rate over that for other circulatory disorders alone.

Figure 1

(A) Schematic illustration of the construction of models. The models were established by pressing the dorsal skin for different times between two circular neodymium magnets (10 mm in diameter). The procedure for detecting ischemia at different times after decompression using CRTT coupled with UV photography methods. *Transparent disc method + CRTT. (B) CRTT was performed coupled with the transparent disc method by applying temporary pressure at 150 mmHg in the BE and early PI groups (upper). A represent the gray values at pre-pressure, B indicates the gray value at pressure load, and C indicates the gray value post-depression (bottom). BE, blanchable erythema.

Figure 2

Ultraviolet photographs of the pressure injury (PI) wound and gray values of each area in the early PI group. The left shows the PI wound at 12 h after decompression, and the right shows the same area at 48 h when the ulcer had developed. WA, whole area; UA, ulcer area; IA, improvement area.

Figure 3

The representative images of macroscopic observation of the two models. In the BE group (upper), the erythema became reddish first but gradually faded until it almost disappeared at 60 min after decompression. In contrast, in the early PI group (bottom), the erythema showed a little bit pinkish and appeared the features of ulcer at 96 h after decompression. BE, blanchable erythema.

Figure 4

Photos taken by the dermal camera (visual and UV images) at different times after decompression in the two groups. The UV shadow showed even but decreased over time in BE group. In contrast, the UV shadow shows even at 0.5 h and pan-white area appeared at 6 h in the early PI group. BE, blanchable erythema.

Figure 5

The visual observation of CRTT by white and UV LED. Photos taken by the dermal camera coupled with CRTT. The two groups were collected at the pre-pressure period, pressure load and post-depression. The UV shadow was significantly reduced after compression but rapidly recovered after CRTT. In the early PI group, pan-white area showed different trend with CRTT. BE, blanchable erythema.

Figure 6

Quantitation of UV gray values by the transparent disc method and CRTT. Gray values at different times after decompression with transparent disc method and CRTT in the two groups. The UV gray value represents three points: pre-pressure, pressure load (150 mmHg) and after depression. In BE group, the results showed the gray values at the start, 5 min and 10 min after decompression using CRTT. In the early PI group, the results showed the gray values of WA, UA and IA at different times after decompression. WA, whole area; UA, ulcer area; IA, improvement area. n = 10 for each group. *< 0.05 **< 0.001. BE, blanchable erythema.

Figure 7

(A) The analysis of blanching index (upper) and refilling index (bottom). Gray values ratios at different times after decompression in the two groups. Blanching index (pre-pressure/pressure load) above 1 was considered as NBE while below 1 was considered as BE. Refilling index (pressure load/post-depression) above 1 was considered as mild ischemia while below 1 was considered as severe ischemia. Erythema in the early PI group increased from a delayed refilling at 0.5 h to a subsequent increase in refilling, especially at 18H in WA, UA and IA. n = 10 for each group (*p < 0.001 vs. 0.5 h). (B) Comprehensive analysis of blanching index and refilling index. Based on the distribution of values, Y = X (red dotted line) was set as a proportional to distinguish between the WA of BE group below the boundary and the WA, UA and IA of the early PI group above the boundary. WA, whole area; UA, ulcer area; IA, improvement area. Each point represents time after decompression. n = 10 for each group. BE, blanchable erythema.

Figure 8

Representative pathological features of early PI. Serial sections were collected and stained with HE (left) and Masson’s trichrome staining (right). Infiltration of polymorphonuclear leukocytes (black arrow) and focal necrosis of the subcutaneous fat (*) and edema (#) were seen in HE staining. In addition, panniculus carnosus muscle (PC) necrosis were also observed. Hemorrhage changes (red arrow) and microthrombi (white arrow) were focally observed in Masson’s trichrome staining.

Figure 9

Representative micrographs of pathological observation and quantification of thrombi. BE, blanchable erythema. Thrombus in veins and artery were observed in (A) and (B) (left). Thrombus was calculated and expressed as % of the total small arteries. n = 8 for each group. **p < 0.001.

Figure 10

Causes and associations of multi-circulatory disorders in early PI. *1 from Reference.