The Severity Of Crush Injury Caused By Different Extrusion Forces Based On A New Generation Of Digital Extrusion Platform

Background Long time crush the muscle rich part lead to the tissue ischemia-reperfusion injury and cause the local or systematic injury and lethal complications called crush injury(CI,the local injury)/ crush syndrome(CS,the systematic injury).Earthquake happened at home and broad frequently recent years,kinds of houses and buildings collapsed when disaster happens,CI/CS appear in bulk,become the common disease after earthquake.Since 1941,Bywaters et al discover these disease,numbers of studies for CI/CS spring up,including all aspects such as the mechanism and treatment.However,the patients of CI/CS in hospital are less and the limited earthquake source made the establishment of animal model particularly important.At epicenter area,the environment is complex and the varying materials of the collapsed buildings let the extrusion force apply to the body part not the same.It is not clear whether different extrusion force can influence the development of the disease and then appear the different degree of damage of CI/CS.Objective Establish the rats CI/CS model use the new digital crush platform,explore the correlation between the severity of CI/CS and the extrusion force and observe the effect of simple common fluid treatment for crush injury caused by different extrusion force.Method Part one: Establish the rat CI model with different extrusion forces(Model test)184 male Wistar rats were divided into control group(n=8)and four different extrusion force groups(1 kg,3 kg,5 kg,8 kg,n=44 per group)randomly(random number table in Excel),each extrusion force group divided into four different observation time point again: at once after decompression(n=8),12 h after decompression(n=8),24 h after decompression(n=8),72 h after decompression(n=20).Tested the change of serum biochemical index at every time point in each extrusion force group respectively.Measured the change of the crushed thigh diameter at 24 h time point in each extrusion force group.Observed the change of histopathological at 72 h after decompression.Record 72 h survival rate of each extrusion force group.Part two: Test of simple common fluid treatment(Fluid treatment test)112 health male Wistar rats were divided into four different force group(as above)randomly.n=28 per group.Gave these rats simple common fluid treatment at 1 h before decompression through caudal vein till 6 h after decompression,the fluid speed is 1 ml/kg·h.At 24 h(n=8)and 72 h(n=20)after decompression collected the samples for observation and detection(as above).Result1.Survival rate Model test: No death in control group,the survival rate of four different extrusion force group(1 kg,3 kg,5 kg and 8 kg)was 80%,65%,70% and 70%respectively.Compared with control group,therefore,the damage of crush caused significant death(P < 0.05),but between different extrusion force groups there were no different were found.Fluid treatment test: After treatment with sterilizing normal saline no one died in 1kg group,the death number of 3 kg group was 2,5 kg group was 5 and 8 kg group was 6,the survival rate was 90%,75% and 70% respectively.After treatment the survival rate of the two lighter extrusion force group(1 kg and 3 kg group)improved significantly,P <0.05 compare with untreated.While the other two higher extrusion force(5 kg and 8 kg)group had no obvious improvement.2.Change of relative diameter The diameter of crushed tight raised gradually after decompression,the relative diameter increased,the edema aggravated and peaked at 12 h after decompression,but no different were found between different extrusion force groups at designed time point.3.Wet dry ratio Model test: At 12 h,24 h after decompression,the edema of lower limbers was obvious,the wet dry ratio(W/D ratio)of every extrusion group had significantly increase compare with control group(P < 0.05),however,no significant difference between extrusion groups.At 24 h after decompression,the edema of two higher extrusion force group were more serious than 1 kg group(P < 0.05).At 72 h after decompression,the W/D ratio of lighter extrusion force group almost fall back to control level,however the higher extrusion force were still higher than control group(P < 0.05).Fluid treatment test: After common fluid treatment,the W/D ratio increased,the edema were more serious in every extrusion groups,there were statistical different between treated and untreated in each extrusion force group(P < 0.05).After treatment the aggravate of edema in 1 kg group was more serious,P < 0.05 compare with 8 kg group at24 h and 72 h after decompression.4.Blood biochemical index Model test: All the biochemical index were some degree of increase after decompression in each group,compare with control group P < 0.05.The serum K+,BUN,Cr reach the peak at 12 h after decompression,the peak of serum ALT and AST appeared at24 h after decompression,the serum CK was immediately increased to the peak at once after decompression,and decrease after peak.Two lighter extrusion force group restore faster,and two higher extrusion force group stain at the higher level for a long time after decompression,the recovery was slow.There were statistical different between groups.After treatment the change of blood biochemical index were not significant improved.5.Pathology detection Muscle: Muscle in control group possess the neat rows of the muscle fiber,no broken,the cell completed and homogeneous stain.Obvious bleeding in lighter extrusion groups,large areas of rhabdomyolysis found in higher extrusion force groups and also seen a large number of inflammatory cells infiltration,especially in 5 kg group.After treatment the edema of muscle cell were aggravate,the rhabdomyolysis were improved in higher extrusion force groups and the leakage of inflammatory cells were reduce.Renal: In control group,the glomeruli and renal tubular were complete and clear,not found casts.Small casts could be seen in 1 kg group,in 3 kg and 8 kg group could found large number of renal tubular casts,especially in 5 kg group which also existed the obvious swelling and necrosis of renal tubular epithelial.More casts and swelling degenerate also could be seen in 8 kg group.After treatment the tubular casts reduced,the congestion increased in two higher extrusion force groups.Lung: The alveolar interval were complete in control,no interstitial thickening and blood capillary.Interstitial thickening is obvious in higher extrusion force groups and found focal inflammatory cells infiltration around the tracheobronchial,the pathological grading of lung injury were high.After treatment the thickening of the interstitial were significantly relieved,inflammatory cells infiltration also reduced.Conclusions The severity of CI is related with extrusion force,within a certain range the higher of the extrusion force the more serious of the local or systematic damage.Simple common fluid treatment could improve the lighter injury of lower extrusion force groups but not the higher extrusion force groups,which need combine with other treatment according to the realties to improve prognosis.Fluid treatment could improve pathological damage of every extrusion force group.