| Objective: Using the limb ischemia model induced by non-invasive preconditioning for different time periods, to investigate the effect of delayed resuscitation on severe burned rat’s heart.Method: One hundred and five SD rats with both sex, at age of 2-3 months, 250-300 g. Experiment animals were placed in water bath at 94℃ for 12 sec after unhairing using 10% sodium sulfide to produce model of severe burn. Those animals were randomly assigned into 4 groups, 25 rats per group.Group F1: immediate resuscitation; Group F2: delayed resuscitation; Group Y1: 3 min limb-ischemia preconditioning; Group Y2: 5 min limb-ischemia preconditioning. Group F1 was treated with fluid resuscitation immediately after burn. ? of fluid resuscitation were treated in the first 8 hours and ? of fluid resuscitation were treated in the second 8 hours after burn. Group F2 were treated with fluid resuscitation 6 hours after burn. ? of fluid resuscitation were provided in 6-8 hours after burn and ? fluid resuscitation were treated in the second 8 hours. Five hours after burn, left limbs of rats in group Y1 were ligated by rubber tourniquet till vessel pulsatility cannot be detected by Doppler blood stream detector for 3 min, and then released for 3 min. This treatment was repeated 3 times. Treatment of fluid resuscitation was started from 6th hour, and the administration pattern was as same as in group F2. The treatment for group Y2 was as same as what in group Y1, except duration of ligation on left limb was 5 min and then released time was 3 min. Blood and heart from each group were collected at 5 time points, namely 1 hour, 3 hours, 7 hours, 10 hours and 14 hours after burn. Five animals from each group were used at each time point. Heart injury was investigated at levels of serum lactate dehydrogenase(LDH),creatine kinase(CK), creatin kinase-mb isoenzyme(CKMB) and histopathologic changes in heart slices.Result: 1. Myocardial enzyme change: myocardial enzyme was increased 1 hour after burn in each group and maximal value was measured at the 7th hour point after burn. The increased value was decreased in 14 hours to the level that observed in 1 hour after burn. Myocardial enzyme is significantly increased(p<0.05)in delayed resuscitation group at each time point compared to other groups, while the difference is most significant at time point of 7 hours. Compare to other groups, immediate resuscitation group shows significant decreased level of myocardial enzyme at each time point(p<0.05). Group Y1 shows a significant increased level of myocardial enzyme at time point of 10 hours(p<0.05)when compared with group Y2, whereas no significant changes observed at other time points. 2. Pathologic result: Swollen cardiomyocytes and disordered fibers are observed at each time point of each group. Group F1 shows a mild damage compared to other groups. Group F2 shows severe damage of cardiomyocyte compare to other groups, especially at time point of 7 hours after burn, cardiomyocyte nucleus dissolution broken myofilament, formation of microthrombus and invasive inflammation cells are observed. Group Y1 shows a less severity of cardic muscle damage than group Y2 at time point of 7 hours, 10 hours an 14 hours. While slighter damage of cardic muscle is observed at time point of 7 hours, 10 hours an 14 hours. Group Y2 shows a slight damage of cardic muscle at time point of 10 hours compare to group Y1, whereas no difference is observed at other time points.Conclusion: 1. Severity of heart damage is severer in delayed resuscitation group than that in immediate resuscitation group. 2. fluild resuscitation shows a protective effect on cardic muscle ischemia-reperfusion in SD rat. 3. Non-invasive limb ischemia preconditioning shows a cardic muscle-protective effect in delayed resuscitation after sever burn. 4. The preconditioning pattern of repeated 5 min ligation- 3 min re-perfusion performs more obvious effect of cardic muscle protection than the pattern of repeated 3 min ligation-3 min re-perfusion. |
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