Experimental Study Of The Effects Of Ulinastatin On The Survival Of Random Pattern Skin Flaps In Rats

Random pattern skin flaps have long been an important tool in plastic and reconstructive surgery.Because the flap lacks the known artery to supply blood,the distal part of it is prone to ischemia and necrosis.Therefore,finding a way to improving random flap's tolerance to ischemia could potentially facilitate expanding its applications in the field of surgery.Now,the mechanism about the ischemia and necrosis of random skin flaps remains uncompletely elucidated though there have been a lot of researches about it.Many studies have stated that neutrophils would intimately involve in the course of the flaps' ischemic injury. Actually,the gradual reduction of blood supply for distal part of flaps will induce to the accumulation and activation of neutrophils in the setting of ischemia.In addition,activated neutrophils can cause the injury of tissues and endothelial by releasing some materials such as cytotoxic oxygen free radicals and proteases.So pharmacologic manipulation to inhibit neutrophils is one of the important means to treat the ischemic injury of the flaps. Medicaments against neutrophils,such as immunosuppressive agent,anti-neutrophilic antibodies,and anti-EC adhension antibodies,have been shown the ability to alleviate the damage of flaps due to ischemia.However.these agents have obvious toxicities and byeffects,and they will increase potential risks of infection when being used systematically.Therefore,finding an ideal medicament to inhibit neutrophils has become the focus of recent researches.Ulinastatin,a kind of broad-spectrum hydrolase inhibitor,has the ability to inactivate extracellular protease which isSecreted by neutrophils. It can prevent the releasing of inflammatory mediators,and reduce neutrophils infiltration in the ischemic tissue.In addition it has antioxidation effect and membrance stabilization effect;can stabilize lososomal memberance,and suppress the releasing of protease from degranulation of neutrophils.lt can stabilize mitochondrial memberance also,and ameliorate energy metabolism.Finally,it can ameliorate microcirculation. Many studies proved that ulinastatin could ameliorate the state of shock and the tissue injury caused by neutrophils when organs are suffering from ischemia and reperfusion.However,there have not been any studies about the effects of ulinastatin on random pattern skin flaps.The aim of this experiment is to investigate the effects of ulinastatin which is administrated perioperativly on survival of the rats' dorsal random pattern skin flaps and the possible mechanism. Method:Thirty-six femal Sprague-Dawley rats were used in the study.The rats were divided into two groups of eighteen rats each:experimental group (U group) and control groups (C group ) .A caudally based dorsal random pattern skin flap ,measuring 2x8 cm2 was symmetrically raised.In experimental group,at the time of lOminutes before operation and 12 hours after operation, 100,000u/kg of ulinastatin was administrated iv.In the control group,the rats received the same amount of saline in the same way.l At the time of 24 h after operation,8 rats from each group were sacrificed,and three full thickness tissue samples were taken from the flap at 2,4,and6 cm distance from the pedicel respectively.The tissue samples were homogenized for Myeloperoxidase (MPO) and Malondialdehyde (MDA) examinations. MPO is the marker enzyme of neutrophils,and it's activity indicates the degree of neutrophils infiltration. MDA is the product from lipid peroxidation and it's level in the tissue represents the degree of tissue's suffering from free radicals.2 Ten days after operation,the skin paddle survival of remaining 10 rats of each group was measured.The animals were then sacrificed and the tissue samples from proximal,middle,and distal portions were sectioned with haematoxylin-eosin staining for histological analysis.Result:1 Ten days postoperatively,the percentage of the flap's surviving area of experiment group is significantly higher than that of control group(U group:62.40±5.00% vs C group:50.15±5.79%,P<0.001).2 Edema and infiltration of neutrophils observed in tissue sections in experimental group is slighter than that of control group.3 At 24 h postoperatively,MPO activity and MDA content of the flap tissue in the distal portions is significantly higher than that of middle and proximal portions,and in the middle portion is significantly higher than that of the proximal portions (P<0.05) .MPO level is significantly lower in experimental group compared to the control group in the proximal(P<0.05 ),middle(P<0.05) and distal (P<0.05) portions. MDA level is significantly lower in experimental group compared to the control group in middle (P<0.05) and distal (P<0.01) portions. Conclusion:1 Perioperative administration of protease inhibitor-ulinastatin can increase the survival of random pattern skin flaps.2 The mechanism about how ulinastatin improve the survival of flaps may be related to it's effects of alleviating neutrophils' infiltration and accumulation,and of inhibiting the release of cytotoxic oxygen free radicals,of alleviating neutrophils'injury effect to ischemic tissue.