Recirculation in double lumen catheter veno-venous extracorporeal membraneoxygenation measured by an ultrasound dilution technique

Recirculation is a limiting factor for oxygen delivery in double lumen cath eter veno-venous extracorporeal membrane oxygenation (DLVV-ECMO). This stud y compares three different methods for the determination of the recirculati on fraction during double lumen catheter veno-venous ECMO at ECMO flow rate s of 150, 125, 100, 75, and 50 ml/kg.min in nine lambs: (1) an ultrasound d ilution method, in which the change in ultrasound velocity in blood after i njection of a saline bolus as a marker is used for determination of recircu lation; (2) an SvO(2) method using real mixed venous blood oxygen saturatio n, the gold standard, for determination of recirculation fraction; and (3) the CVL method, in which oxygen saturation of a blood sample of the inferio r vena cava is considered to represent mixed venous oxygen saturation. In a ll methods, the recirculation fraction increased with increasing ECMO flow rate. The correlation coefficient between the ultrasound dilution method an d the SvO(2), method was 0.68 (p < 0.01); mean difference was -2.4% (p = 0. 6). Correlation coefficient between the ultrasound dilution method and the CVL method was 0.48 (p < 0.01); mean difference was -18.1% (p <less than> 0 .01). The correlation coefficient between the SvO(2) method and the CVL met hod was 0.51 (p < 0.01); mean difference was -15.7% (p < 0.01). The ultraso und dilution method is a useful method for measurement of the recirculation fraction in DLVV-ECMO and is easier to use than the other methods.