The present experiments is to evaluate the possibility of replacing the invasive method by the noninvasive one, namely systolic time interval method for monitoring hemodynamic changes occuring during the induced hypotension employed in clinic for the safety measure.
For this purpose, various hemodynamic parameters were measured by both invasive and noninvasive STI methods simultaneously in mongrel dogs following the induction of hypotensive state by drugs, nitroprusside and nitroglycerin or bleeding procedure. The data obtained by these two different methods were analysed for the above purpose of this study.
The following results were obtained.
1) In the hemodynamic changes checked by the invasive method, there were marked in preload and
systemic vascular resistance (p<0. 05 and p<0.01) in all induced hypotensive groups, but no signi-
ficant changes in heart rate in those groups. Cardiac output was not changed in nitroprusside and bled
groups, but markedly increased in nitroglycerin group(p<0.O1).
2) Comparing the data of invasive method with those of noninvasive STI method, correlation coefficient of tension time index(TTI) to rate-pressure product(RPP) was 0. 85, and that of endocardial viability ratio (EVR) to diastole/systole (dT/sT) was 0.96.
Therefore´RPP and dT/sT are supposed to be the useful indices of cardiac function monitoring in the use of induced hypotensive method.
Abbreviation
NTG : nitroglycerin, SNP : sodium nitroprusside, CO : cardiac output, CPI´ : coronary perfusion pressure CVP : central venous pressure, CVR : cardiac viability ratio, dBP diastolic blood pressure DPTI : diastolic pressure time index, dT : diastolic time, EVR : endocardial viability ratio HR : heart rate, LVET : left ventricular ejection time, LVSW : left ventricular stroke work ´THAP mean arterial pressure, PCWP : pulmonary capillary wedge pressure, PEP : pre-ejection period Q quotient of PEP/LVET, Q-SZ : total electromechanical systole, RPP : rate-pressure product sBP :´systolic blood pressure, sT : systolic time, STI : systolic time intervals, SV´: stroke volume SVR : systemic vascular resistance, TI triple index, TTI : tension time index
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