The Incidence,Risk Factors And Prognosis Of Myocardial Injury In Severely Burned Patients

BackgroundPrevious studies have shown that early myocardial injury widely exists in patients with severe burn.Due to the increased release of cardiac rennin-angiotensin and other vasoconstrictor substances induced by stress,uncontrolled inflammation,blood volume loss,ischemia-reperfusion injury and so on,the cardiac dysfunction and microcirculation disturbance of other body tissues and organs would occur in the early stage of burn,during which hypoxic-ischemic damage and dysfunction would arise.As it is known,the reduction in cardiac function is one of the factors causing shock.Hypoxic-ischemic myocardial injury and cardiac dysfunction lead to reduced heart function,which can not only induce burn shock,but also aggravate burn shock and other organ damage.For burn patients,anti-shock therapy is one of the most crucial and basic steps.Whether patients can smoothly tide over the shock stage directly affects the whole process of treatment and prognosis of burns.In the past,a simple fluid resuscitation was used for anti-shock,but clinical data suggest that for most patients with severe burns,even if replacement fluid treatment is given timely after injury,ischemia and hypoxia is still difficult to be avoided and shock is difficult to be corrected,with Creatine Kinase-MB,troponin and other cardiac injury indicators higher than normal.This suggests that in terms of severe burn patients with shock,the prevention and treatment of myocardial injury is as important as replacement fluid treatment of shock.Although there were a lot of studies about myocardial injury with severe burn,they were not deep enough,and there is a lack of in-depth and multi-central clinical analysis of myocardial injury incidence,risk factors and prognosis of burn.This study is to further investigate the incidence,risk factors and prognosis of severe burn patients with myocardial injury,which can attach more importance to the prevention and treatment of clinical myocardial injury and provide a reference for better prevention and treatment of burn shock and complications and the improvement of cure rate.Objective To explore the incidence,risk factors and prognosis of myocardial injury in severely burn patients for better clinical prevention and treatment of myocardial injury,burn shock and complications.Methods Retrospective analysis of clinical data of 252 severely burned patients cases of 5 Hospitals(Southwest Hospital,Wuhan Third Hospital,Liuyang People's Hospital,The People's Liberation Army 159 Center Hospital,Henan University Affiliated First People's Hospital)was enrolled from January 10,2010 to June 21,2015.The general clinical data,indices of myocardial injury,organ complications,blood volume and tissue oxygenation,as well as mortality were collected and evaluated.According to whether CK-MB level is higher than or equal to three times of the normal upper limit(?75U/m L),patients were divided into non-myocardial injury group(group A,n=118,CK-MB level less than 75 U/mL)and myocardial injury group(group B,n=134,CK-MB level higher than or equal to 75U/mL).To evaluate the incidence rates of myocardial injury in patients with different total burn areas,patients were divided into 3 groups : group C,TBSA larger than or equal to 30% and less than 50%(n=110);group D,TBSA larger than or equal to 50% and less than 80%(n=83);group E,TBSA larger than or equal to 80% to 100% TBSA(n=59).According to optimal threshold of the total burn area that predicts myocardial injury,patients were divided into group F and group G: group F,TBSA less than 51%(n=110)and group G,TBSA larger than or equal to 51%(n=142).Statistical analysis:data were processed with chi-squaresthest,t-test,Wilcoxon test,analysis of variance for repeated measurement,and the values of P were adjusted by Bonferroni.Data of 252 patients were processed with binary logistic regression analysis.Receiver operating characteristic curve of total burn area of 252 patients was drawn to predict myocardial injury.Results1.Analysis of the general clinical data1.1 The results of the general clinical data analysis showed that average levels of CK-MB of group A(n=118)and group B(n=134)were respectively 48 ± 14 U / mL and 134 ± 90 U / mL.The admission time after injury in group A(4.4 ± 4.7h)was earlier than that of group B(6.0 ± 5.1h).The proportion of male and female of group A was 87/31,while that of group B was 113/21.There were statistically significant differences in gender,hospitalization time after injury,and total burn surface area between two groups(?2=5.00,with t values respectively 2.44 and 3.13,P<0.05 or P<0.01).However,no statistically significant differences in age,body mass,full-thickness burn area,and number of patients with inhalation injury between two groups were found(with t values respectively 0.20 and 0.21,?2 values respectively 0.49 and 4.10,P values above 0.05).2.Analysis of myocardial damage2.1 Analysis of risk factor of myocardial injury: binary logistic regression analysis showed that gender,hospitalization time after injury,and the total burn area were independent risk factors related to myocardial injury(with the odds ratio from 1.03 to 3.62,95% confidence interval respectively from 1.315 to 5.175,from 1.916 to 6.839,and from 1.011 to 1.049,P values below 0.01).2.2 Correlation between total burn area and the incidence of myocardial injury: the incidence of myocardial injury of patients in group C,group D,group E were 38.2%(42/110),54.2%(45/83),61.0%(36/59)respectively,with statistically significant differences among them(?2=9.46,P<0.05).2.3 The predictive effect of TBSA on myocardial injury : the total area under receiver operating characteristic curve of total burn area for predicting myocardial injury of 252 patients was 0.71,TBSA 51.5% was chosen as the optimal threshold value,with sensitivity of 62.6% and specificity of 65.3%.2.4 To further analyze the predictive effect of TBSA on myocardial injury,patients were divided into group F and group G.The results showed that the levels of CK-MB in group F(68±39U/L?86±46U/L?61±42U/L?44±26U/L)were lower than that in group G(95±53U/L?102±69U/L?84±73U/L?56±36U/L)at admission and 24,48 and 72 post burn hours(PBH,with t values respectively-4.696 and-2.221,with Z values respectively-2.209 and-2.761,P<0.01 or P<0.05).There were no statistically significant differences in levels of CK between two groups at admission and 24,48 and 72 PBH(P>0.05).The levels of LDH of group F(459±213U/L)were lower than that of group G(664±440U/L)on admission(Z=-4.272,P<0.01).There were no statistically significant differences in levels of LDH between two groups at 24,48 and 72 PBH(P>0.05).The levels of AST of group F(58±62U/L?43±36U/L?35±30U/L?58±88U/L)were also lower than that of group G(73±37U/L?53±34U/L?55±44U/L?58±88U/L)at admission and 24,48 and 72 PBH(with t values from-6.026 to-2.600,P<0.01).3 Analysis of the indices of circulatory blood volume,perfusion and tissue oxygenationThe results showed that the levels of Hb of group B(169±28g/L?161±28g/L)were higher than that of group A(157±23g/L?151±25g/L)at admission and 24 PBH(with t values respectively-2.75 and-2.31,P<0.05).There were no statistically significant differences in levels of Hb between two groups at 48 PBH(P>0.05).The levels of hematocrit of group B(50±8%?47±9%)were higher than that of group A(46±7%?45 ± 5%)at admission and 24 PBH(with t values respectively-2.80 and-2.06,P<0.05).There were no statistically significant differences in levels of hematocrit between two groups at 48 PBH(P>0.05).The levels of blood lactate of group B(5.3±2.3mmol/L?5.5±2.0mmol/L?4.6±1.6mmol/L)were higher than that of group A(4.5±1.9mmol/L?4.9±1.8mmol/L?4.1±1.8mmol/L)at admission,24 and 48 PBH(with t values from-2.41 to-2.06,P<0.05).Volumes of urine output of group B(1.03±0.50 m L·h-1·kg-1,1.29±0.53 m L·h-1·kg-1)were less than that of group A(1.20±0.54mL·h-1·kg-1?1.62±0.57 m L·h-1·kg-1)at 24 and 48 PBH(with t values respectively 2.05 and 3.68,P<0.05 or P<0.01),while no significant differences were found betwwen the volumes of fluid input of patients in myocardial damage group at 24 and 48 PBH(with t values respectively 1.01 and 1.08,P>0.05).4 Analysis of the indices of organ damageThe results showed that the levels of creatinine of group B(91±59?mol/L?96±50?mol/L?89±69?mol/L)were higher than that of group A(72±20?mol/L?81±43?mol/L?71±34?mol/L)at admission,24 and 48 PBH(with Z values from-2.91 to-1.99,P<0.05 or P<0.01).There were no statistically significant differences in levels of urea nitrogen between two groups on admission(P>0.05).The levels of urea nitrogen of group B(8.2±6.9?mol/L?8.0±5.0?mol/L)were higher than that of group A(6.1±2.8?mol/L?6.0±3.5?mol/L)at 24 and 48 PBH(t=-4.75 and Z=-4.95,P<0.01).There were no statistically significant differences in levels of total bile acid between two groups at admission,24 and 48 PBH(P>0.05).The levels of diamine oxidase of group B(107±27U/ml?133±80U/ml)were higher than that of group A(73±35U/ml?99±43U/ml)at admission,24 PBH(with t values respectively-3.97 and-2.02,P<0.05 or P<0.01).There were no statistically significant differences in levels of diamine oxidase between two groups at 48 PBH(P>0.05).5 Comparition of the mortality5.1 The mortality: The mortality rate of group A is 5.1%(n=6).However,it is 14.1% in group B(n=19),which is about three times higher than that in group A.Mortality of patient in non-myocardial injury group(group A)was significantly declined compared with that in myocardial injury group(group B)(?2=5.81,P<0.05).5.2 Analysis of risk factors of myocardial injury of the mortality: binary logistic regression analysis showed that myocardial injury and the total burn area were independent risk factors related to mortality in the patients(with the odds ratio respectively 1.401 and 1.090,95% confidence interval respectively from 1.203 to 1.631,from 1.056 to 1.125,P values below 0.01).Conclusions1?Severe burn patients had high incidence of myocardial injury,closely related to the total burn area.The total burn area was an important risk factor of myocardial injury in patients with severe burn.The incidence of myocardial injury was significantly higher when the total burn area of patients were equal to or greater than 50%.Incidence of myocardial injury maybe predicted by total burn area: The total area under receiver operating characteristic curve of total burn area for predicting myocardial injury was 0.71,TBSA 51.5% was chosen as the optimal threshold value,with sensitivity of 62.6% and specificity of 65.3%.2 ? Analysis of the indices of circulatory blood volume,perfusion and tissue oxygenation showed that severe burn patients with myocardial injury were more likely to suffer decline of effective circulating volume,tissue oxygenation disorders and organ damage in shock stage.3?The mortality rate of severe burn patients with myocardial injury reach up to 14.1%,which was about three times higher than patients without myocardial injury,indicating that early attention and prevention of myocardial injury is not only beneficial to shock resuscitation,but also for reducing complications and improving the cure rate.