Die Doppelindikatordilution zur Quantifizierung von Herzzeitvolumen und Links-Rechts-Shunt bei Patienten mit kongenitalem Vitium cordis: Ein neuer systemanalytischer Ansatz

THE DOUBLE INDICATOR DILUTION FOR QUANTIFYING CARDIAC VOLUME AND LEFT-TO-RIGHT SHUNTING IN PATIENTS WITH CONGENITAL VITIUM CORDIS.
-A NEW SYSTEM ANALYTICAL APPROACH-
Algorithms are being developed that enables characterization of the primary curve and the recirculation proportion of indicator dilution curves in patients with left-right shunt (LRS). Methodologically, transpulmonary double indicator dilution technique is used, in which ice-cooled indocyanine green dye is injected as a bolus into the right atrium and registered in the aorta using combined fiber-optical and temperature measurement technology. The indicator dilution curves are evaluated using a newly developed mathematical recirculation model based on a system analytical approach.
First, the algorithms are validated on a circulatory model, with different blood flows (CO) and shunt sizes being simulated. The reliability of the thermodilution (TD) and dye dilution technique (DD) for flow and shunt quantification were confirmed by comparison with electromagnetic flow measurements.
In 21 patients without a circulatory shunt, TD and DD-CO show a good correlation to Fick's principle CO, although the DD systematically underestimated CO by 23%. In 30 patients with LRS, a comparable agreement between the cardiac output methods is only observed when the newly developed recirculation model is used. The shunt quantification from the DD curves shows an excellent correlation with the oximetry.
On the basis of patients without a circulatory shunt, normal values for total circulating blood volume (TBV), central blood volume (CBV) and extravascular lung water (EVLW) are initially defined, whereby a linear relationship is found between TBV and body weight (BW) and a non-linear relationship is found between CBV and EVLW to BW. In comparison, patients with circulatory shunts show no deviation from these values, whereas in 5 patients with pulmonary hypertension both TBV and EVLW are increased.
The newly developed evaluation procedure for transpulmonary double indicator dilution curves represents an extension of TD CO measurement and enables fast and reliable circulation and shunt determination. In addition, for the first time it also enables monitoring of cardiac output, TBV and EVLW in patients with LRS.