The Clinical And Basic Research Of Treatment Effects Of Beta Blockers On Sepsis-induced Cardiac Dysfunction

Objective:To investigate the treatment effects of Beta blockers on sepsisinduced cardiac dysfunction and possible mechanism.Methods:Two parts were included in the study.In the first part, ninety patients with severe sepsis,whose heart rate were no less than 95 beats per minute(bpm) after early goal-directed therapy,were included in the analysis. Patients were randomly divided into three groups:control group(C), milrinone group(M) and milrinone combine esmolol group(ME).Patients in C group were treated with early goal-directed therapy(EGDT) according to management guideline of septic shock.Based on the basic treatment in group C, patients in M group were treated with continuous intravenous pumping of milrinone in addition with a loading dosage of 30μg/Kg and maintenance dosage of 0.375~0.5 μg/kg· min. For patients in ME group,we added esmolol on the base treatment of M group and maintain the HR within 75~94 times per minute.Basic indexes of haemodynamics, such as MAP, CVP and HR,were monitored before treatment and 12, 24, 48, 72 and 96 h after treatment.PaO2/FiO2 and blood lactate(Lac) were also monitored with I-STAT portable blood gas analyzer of USA before treatment and 12, 24, 48, 72 and 96 h after treatment,meanwhile Cardiac index(CI) and Stroke volume index(SVI) were monitored with pulse-indicated continuous cardiac output(Picco). Besides,before treatment and 24, 48, 72 and 96 h after treatment, the serum levels of proinflammatory factors(including TNF-α, IL-6 and HMGB-1) and myocardial injury markers(including CK-MB, TnI and BNP) were also tested.In the second part,32 male C57BL/6J mices,aged 8 weeks to 12 weeks, were randomly divided into four groups:Control group(C group);esmolol infusion group(E group);lipopolysaccharide insult group(L group);esmolol infusion plus lipopolysaccharide insult group(EL group).Escherichia coli O55:B5 LPS(6 mg/Kg) was injected intraperitoneally,esmolol was delivered continuously via osmotic pump inserted into the jugular vein fitted with small-tip mouse jugular catheters at a flow rate of 1 μl/h(6.7μg/kg/min).In L group and EL group,all mices were injected LPS intraperitoneally,and then esmolol was delivered continuously via osmotic pump in mices of EL group,while mices of L group were treated with the same dose saline.In E group,all mices were delivered continuously with esmolol after injected saline intraperitoneally.In C group,all mices were both delivered continuously and injected intraperitoneally with saline. Hemodynamic indexes,such as heart rate(HR),systolic blood pressure(SBP),diastolic blood pressure(DBP) and mean arterial pressure(MAP) were recorded using a pressure conductance system coupled with a PowerLab/4SP AD converter at 6h after LPS injection.The cardiac function indexes,such as left ventricular end-systolic pressure(LVESP),left ventricular enddiastolic pressure(LVEDP), and maximal rate of change of left ventricular pressure(+dP/dtmax) were also recorded using a pressure conductance system coupled with a PowerLab/4SP AD converter at 6h after LPS injection and analyzed by PowerLab software.Caspase-3 activity of myocardium was measured using spectrophotometric indicator method.The apoptosis of cardiomyocyte was measured using TUNEL assay.The expression of cleaved caspase-3,Bax,Bcl-2, pan and phosphorylated forms of JNK and p38 in myocardium were measured using western blot analysis.Results:In the first part,there were no difference in all measured indexes before treatment. After combination therapy, no difference in MAP, CVP and PaO2/FiO2 was observed. However,at 12 hours and later after treatment, the HR of patients in ME group were lower than that of patients in C and M groups, while the Lac level of M and ME groups were lower than that of C group at 48 hours and later after treatment.Similarly,the CI and SVI levels in M and ME groups were higher than those in C group at 12 hours and later after treatment.While the serum levels of proinflammatory factors and markers of myocardial injury in ME group were lower compared with C and M groups at 24 hours and later after treatment. Patients in ME group had higher 28-day survival rate and better compliance rate of HR than the other two groups.In the second part, at 6h after LPS injection,the HR of mices were significantly elveted,while the SBP,DBP and MAP were significantly reduced,and above effects were attenuated by esmolol.At 6h after LPS injection,the LVESP and+dP/dtmax of mices were significantly reduced,while the LVEDP was significantly elevated,and above effects were attenuated by esmolol.After LPS injection,thecaspase-3 activity of myocardium and the apoptosis of cardiomyocyte were significantly elevated,while continuously delivering esmolol significantly reduced the caspase-3 activity of myocardium and the apoptosis of cardiomyocyte.After LPS injection,the expression of cleaved caspase-3, Bax, phosphorylated forms of JNK and p38 in myocardium were significantly elevated,while the expression of Bcl-2 in myocardium was significantly reduced. Continuously delivering esmolol significantly reduced the expression of cleaved caspase-3,Bax,phosphorylated forms of JNK and p38 in myocardium,while significantly elevated the expression of Bcl-2 in myocardium.Conclusion:1.Combination therapy with milrinone and esmolol could significantly improve cardiac function in patients with severe sepsis.2.Combination therapy with milrinone and esmolol could significantly alleviate myocardial injury in patients with severe sepsis.3.Combination therapy with milrinone and esmolol could significantly inhibit inflammatory response in patients with severe sepsis.4.Combination therapy with milrinone and esmolol could significantly decrease heart rate in patients with severe sepsis.5.Combination therapy with milrinone and esmolol could significantly reduce motality in patients with severe sepsis.6.Esmolol can significantly improve cardiac function in mice with sepsis.7.Esmolol can significantly attenuate apoptosis of cardiomyocyte in mice with sepsis.8.Esmolol can significantly inhibite the P38 and JNK signal transduction pathway of cardiomyocyte in mice with sepsis.9.Attenuating apoptosis of cardiomyocyte may contribute to the benefit of effects of esmolol treatment on cardiac function in mice with sepsis.