In VivoSuction Pressures of Venous Cannulas During Veno-venous Extracorporeal Membrane Oxygenation

Extracorporeal lung support includes the risk of hemolysis due to suction pressures. Manufacturers measure the negative suction pressure across drainage cannulas for their products in vitrousing water. Clinical experience suggests that hemolysis occurs in vivoalready at much lower flow rates. The aim of this study was to analyze the in vivosuction pressure for veno-venous extracorporeal membrane oxygenation (VV-ECMO) cannulas. Prospective, observational study at a tertiary-care intensive care unit: 15 patients on VV-ECMO for severe ARDS were prospectively included. In vitro, the 25 Fr drainage cannula pressure drops below a critical level of around –100 mm Hg at a flow rate of 7.9 L/min, the 23 Fr drainage cannula at 6.6 L/min. In the clinical setting, critical suction pressures were reached at much lower flow rates (5.5 and 4.7 L/min; p< 0.0001, nonlinear regression). The in vitrodata largely overestimate the safely achievable flow rates in daily clinical practice by 2.4 L/min (or 44%, 25 Fr) and 1.9 L/min (or 41%, 23 Fr). In vivomeasurement of suction pressure of venous drainage cannulas differed significantly from in vitroderived measurements as the latter largely underestimate the resulting suction pressure.