Influence Of Catecholamine On Myocardium In Rabbits With Endotoxin Shock

Objective: Septic shock usually occur in critically ill patients with infection in clinical practice, and the mortality rate is about 40%. The main syndrome of septic shock is cardiovascular disfunction. To avoid oranges impairment, catecholamines are often used to maintain hemodynamic stamlization. However, there is controversy whether catecholamines can worsen myocardial damage in patients with septic shock because of adrenergic receptors activation. This paper aims to determing the effects and mechanism of catecholamines on myocardium in rabbits with endotoxin shock through observing the changes of Serum cTnI, TNF-α, myocardial MDA concentrations and Histologic changes of myocardium.Material and methods: Endotoxin shock was replicated in rabbits by receiving a contious infusion of E-coli lipopolysachaid (LPS. sigma.olllB4) at a dose of 600ug/kg injected within 30 min. Dopamin(DA) Norephephrine(NE) and combination of dobutamine(DB) and NE were used on the lowest dose to maintain the mean aterial pessure(MAP) about 60mmHg. The 35 rabbits were randomly divided into normal control group(group A), endtoxin shock control group(group B), DA-treatment group(group C), NE-treatment group(group D) and NE+DB treatment group. Serum TNF-α concentrations were measured at baseline, 60min, 120min, 180min, 240min after endotoxin shock. Serum troponinI and myocardial malondialdchycle(MDA) concentrations were measured at the time 240min after shock. When the experiments were finishied ,autopsy were performened and myocardial tissue wereexamination under light microscopy.Results: (1) Blood pressure decreased after endotoxin infusion, then increased at low-moderate level and decreased significantly. When the mean aterial pressure was decreased to 60mmHg after two hours of endotoxin infusion, model of endotoxin shock in rabbits was established.(2) A significantly increased cTnI level were found in catecholamine treatment group, compared with group A or guoup B(P<0.05). There were significant positive correlations between the dose of NE/DA administrated and levels of cTnI. (3) Myocardial MDA concentrations in catecholamine treatment group significantly increased higher(p<0.05) than that in group A or group B. (4) Tumor necrosis factor-αconcentrations in NE- treatment group significantly increased higher(p<0.05) than that group B.(5) Histologic examination of myocarcium in rabbits reveals the same degrees of injuries in group B as them in each catecholamine treatment group.Conclusion: Catcholamine can improve hemodynamics, but worsen myocardium damage in rabbits with endotoxin shock. The myocardium damage is more severe in catcholamines treatment group, which may be linked with enhanced release of TNF-α and free radical.