[Non-invasive monitoring of hemodynamic profile during general anesthesia]

This article presents a general vision of a new non-invasive cardiovascular monitoring technique applied to patients during general anaesthesia. This method employs an esophageal eco-Doppler, able to supply a continuous measurement of the aortic diameter (eco-TM) and of the velocity of aortic blood flow (pulsed Doppler) for the calculation of aortic output; a monitor to survey the ECG and a noninvasive device for the measurement of blood pressure. The resulting data, opportunely processed by the computer, supply the values of aortic output, of systemic peripheral resistances and of stroke volume. The last two parameters are indexed with aortic output. Through the computer analysis of ECG and of the aortic velocity curve, it is possible to trace back the systolic time intervals and find out the left ventricular ejection time, the pre-ejection period and the electromechanical systole. All these values are indexed with heart rate. The validation of this method gave good results. The comparison between aortic output, measured by the eco-Doppler, and the value obtained with the thermodilution gave a correlation of r = 0.97, and comparing it with the one obtained with the electromagnetic ring, the correlation was r = 0.96. The aortic diameter was calculated with computerized tomography and the correlation between the two diameters resulted in 0.978. This method is quite useful because it supplies continuous parameters in an automatic and noninvasive way. Therefore it is possible, through a compete hemodynamic profile, to diagnose the variations and control the evolutions of the hemodynamic profile induced by the therapeutical treatments, on the basis of a correct physiopathological interpretation.