Contradictory responses of the microcirculation to changes in extracorporeal membrane oxygenation pump flow in patients on venoarterial extracorporeal membrane oxygenation: a prospective observational study

Abstract Background: Venoarterial extracorporeal membrane oxygenation (VA-ECMO) pump flow is crucial for maintaining tissue and organ perfusion in patients with cardiogenic shock. Determining the optimal VA-ECMO pump flow rate to maintain adequate tissue perfusion remains a clinical challenge. Poor microcirculation is associated with higher mortality in patients using VA-ECMO. Change in VA-ECMO pump flow is expected to result in a coherent change in microcirculatory blood flow, but this has not been investigated. This study investigated the effect of altering VA-ECMO pump flow rate on sublingual microcirculation. Methods: Sublingual microcirculation images were recorded using an incident dark-field hand held vital microscope at two time points, within 24 h (T1) and at 24-48 h (T2) after VA-ECMO placement. Microcirculation was measured before and 5 minutes after the changes in VA-ECMO pump flow rate at each time point. Events of changing VA-ECMO pump flow rate at T1 and T2 were divided into four groups according to changes in perfused vessel density (PVD): Group A, increased pump flow rate and increased or sustained PVD; Group B, increased pump flow rate and decreased PVD; Group C, decreased pump flow rate and increased or sustained PVD; and Group D, decreased pump flow rate and decreased PVD. The microcirculatory parameters, clinical parameters, and prognosis of each subgroup were recorded. Clinical parameters on 14-day and 28-day survivors and non-survivors were also compared. Results: A total of 25 patients were enrolled, and 38 events with good-quality images at T1 and T2 were categorized. Opposing response of microcirculation was observed in 43.5% of events when VA-ECMO pump flow rate was increased. Microcirculation was decreased in 33.4% of events when VA-ECMO pump flow rate was reduced. No predictive values in microcirculatory or macrocirculatory parameters before changing VA-ECMO pump flow rate were identified. Conclusions: Changes in VA-ECMO pump flow rate may have opposing effects on sublingual microcirculatory functional capillary density. We suggest that tandem measurements of microcirculation before and after altering the VA-ECMO pump flow may help to ensure optimal tissue perfusion.