Effects Of Nonspecific Nitric Oxide Synthase Inhib Ition On Resuscitation Success And Postresusci Tation Myocardial Dysfunction After Cardiac Arrest In Habbit Models

Objective : To investigate the effects of nonspecific nitric oxide synthase inhibition N^G-nitro-L-arginine methyl ester (L-NAME) on resuscitation success and early postresuscitation myocardial dysfunction after cardiac arrest in habbit models.Methods:Thirty habbits were randomly divided into normal nontrol group( group C),CPR group(group E) and L-NAME group (group E+L).Ventricular fibrillation(VF) was induced by the external electricity for 5 mins except in groupC, after 1 mins of CPR, group E receive epinephrine (EN)(20ug/kg; n =10); group E+L receive EN(20ug/kg) and L-NAME(25mg/kg, n =10) ;groupC receive saline placebo 2ml (n =10) at the same time. Cardiopulmonary resuscitation (CPR) were performing for 5 min except in groupC.The coronary perfusion pressure(CPP),the peak positive first derivative of left ventricular pressure (dp/dt_max ),the peak negative first derivative of left ventricular pressure (-dp/dt_max),the concentration of nitric oxide (NO) were measured before VF, during VF and the early stage of postresuscitation (15-240min) in three groups .After 240 min, the animals were killed.Results : There was no significant difference on weight,CPP,dp/dt_max,-dp/dt_max and NO concentration before VF in three groups, After 5 min of CPR 7/10 habbits in group E+L versus 8/10 in group E achieved ROSC ,there is no significant difference between this two groups. The CPP in group E+L is higher than those in group E at2,3,4,5 min during CPR (p<0.05) . During the early stage of postresuscitation period the myocardial function significantly reduced and progressively declined in group E+L and groupE , dp/dt_max,-dp/dt_max in group E+L is higher than those in group E(p<0.05 ),and dp/dt_max,dp/dt_min in group C is also higher than group E and group E+L (p<0.05) ; NO concentration significantly increased during VF and 15min after postresuscitation versus baseline (p<0.05 )and than progressively declined in all habbits. There was no significant difference between group E+L and group E during VF,but after 15min of postresuscitation, NO concentration in group E+L was significantly lower than those in group E (p<0.05) .Conclusion : 1. Nonspecific blockade of nitric oxide synthase L-NAME during CPR was associated with an increase in CPP but did not result in better initial resuscitation when compared with EN. 2.There was myocardial dysfunction on postresuscitation habbits after cardiac arrest with NO and oxygen free radical generation. 3.L-NAME combined with EN can reduce the concentration of NO and oxygen free radical, enhance the CPP ,thus improve postresuscitation myocardial dysfunction when compared with EN.