Disturbed cerebral circulation during opening of the venoarterial bypass bridge in extracorporeal membrane oxygenation

PURPOSE: To describe the effects on cerebral blood flow velocity (CBFV) of intermittent opening of the venoarterial bridge (VA bridge) during venoarterial extracorporeal membrane oxygenation (VA-ECMO). STUDY DESIGN: Prospective study in 22 newborns during VA ECMO. CBFV was measured in the pericallosal artery by Doppler ultrasound. Changes in peak systolic flow velocity (PSV), end diastolic flow velocity (EDV) and time-averaged mean flow velocity (TAM) on day 1, 2, 3, and 5 and at low ECMO flow (50- 150 ml/min) were analyzed (mean percentage+/-standard deviation (t-tests, p<0.05)). Changes >25% were considered relevant. The relationship between changes in CBFV and ECMO flow rate (Pearson correlation, p<0.01) was studied. RESULTS: Opening of the VA bridge resulted in statistically significant and relevant decreases in PSV (35 +/- 18%), EDV (93 +/- 15%) and TAM (68 +/- 13%), persisting during the consecutive days of treatment. Smaller changes in CBFV at low ECMO flow were statistically significant and mostly relevant: PSV (15 +/- 7%), EDV (76 +/- 21%) and TAM (40 +/- 12%). Changes in CBFV were positively correlated to the ECMO flow. CONCLUSION: Use of the VA bridge results in significant and relevant ECMO flow-dependent changes in CBFV, persisting during the treatment. The VA bridge should be used in such a way as to allow regular unclamping to be omitted.