Objective: To observe the effect of different time windows and interventions on skin pressure ulcers and ischemia-reperfusion (I/R) injury in rats.
Methods: Sixty?eight SD rats were randomly divided into blank control group (n=4) and model group (n=64). The rats in the model group were randomly divided into group A (n=32) without intervention and group B (n=32) with post?conditioning. The degree of skin compression, neutrophil infiltration and serum levels of free radicals were observed in the rats after compression for 2, 4, 6, and 8 h (8 rats at each time point).
Results: A significant difference was found in the severity of skin damage among the control group, group A, and group B (P=0.001), and the injury was milder in group B than in group A. Severe skin lesions occurred in 2 rats after skin compression for 6 h, as compared with 6 after compression for 8 h (P=0.043), but in none of the rats after compression for 2 or 4. Seventeen rats in group B and 15 in group A showed grade 1 neutrophil infiltration in the skin lesions, and 8 rats in group B and 10 in group A showed grade II neutrophil infiltration (P=0.002). Neutrophil infiltration was the mildest in rats with a 2?h compression, and exacerbated progressively and significantly as the compression time extended (P=0.027). With the prolongation of the intervention time, the rats in both groups A and B showed decreased SOD and increased MDA and NO levels, and overall the I/R injury was milder in 2? and 4?h compression groups than in 6? and 8?h compression groups. The level of serum SOD was significantly higher and MDA and NO levels were significantly higher in group B than in group A (P<0.05).
Conclusion: Ischemic post?conditioning can relieve I/R injury in acute pressure ulcer in rats. The effective time window for intervention is within 6 h of ischemia, and the effect of ischemic post-conditioning is optimal within 2 h. Ischemic post?conditioning can alleviate free radical injury and inflammation caused by I/R injury.
目的: 观察不同受压时间窗及干预方式对压疮大鼠模型的皮肤损伤及缺血再灌注的影响。
方法: 68只SD大鼠随机分为空白组（S组，n=4，不施压）及造模组（n=64）；根据是否采取干预措施，将造模组随机分为不处理（a组，n=32，施压后直接处死）及后处理组（b组，n=32，施压后予缺血后处理后再处死）两小组，分别在受压2、4、6、8 h（每个时间点均为n=8）后观察皮肤受压程度、中性粒细胞浸润程度及血清氧自由基的水平。
结果: S、a及b三组大鼠的皮肤损伤程度构成差异有统计学意义（P=0.001），以b组轻于a组；在时间窗方面，受压6 h组有2只大鼠表现为重度损伤，8 h有6只重度损伤（37.5%）；而受压2 h及4 h均无造成重度损伤，不同时间窗的损伤程度差异有统计学意义（P=0.043）；中性粒细胞浸润程度方面，b组Ⅰ级程度（最轻）只数多于a组（n=17 vs n=15），Ⅱ级少于a组（n=8 vs n=10），不同干预方式下的浸润程度差异有统计学意义（P=0.002）；受压2 h造成的浸润程度最轻，其次为4 h及6 h；8 h最重，不同受压时间所致的中性粒细胞浸润程度有统计学意义（P=0.027）。在缺血再灌注方面，随着干预时间的延长，a及b组均表现血清超氧化物歧化酶含量下降，而丙二醛及一氧化氮上升，总体以2 h及4 h的再灌注损伤程度低于6 h及8 h；组间比较显示b组的超氧化物歧化酶含量显著高于a组，而丙二醛及一氧化氮低于a组（均为P < 0.05）。
结论: 缺血后处理能减轻急性压疮缺血再灌注损伤，其保护作用的有效时间窗为骨骼肌缺血6 h以内，4 h次之，2 h内保护效果更佳。缺血后处理能有效改善大鼠骨骼肌缺血再灌注损伤所致的氧自由基的损伤和炎症反应。