A new technique for measuring cardiac output and shunt fraction during venovenous extracorporeal membrane oxygenation

A new indicator dilution technique is described for measuring cardiac outpu t and shunt fraction in patients undergoing venovenous extracorporeal membr ane oxygenation (ECMO). Shunt fraction is the proportion of the ECMO pump f low which recirculates through the ECMO circuit (passing directly from the inflow cannula to the outflow cannula) instead of flowing through the pulmo nary and systemic circulations. The indicator is an isotonic (150 mmol/l) s olution of lithium chloride which is injected into the ECMO flow returning to the patient. Two lithium sensors are used simultaneously to record the r esulting lithium dilution curves in arterial blood and in the blood in the ECMO circuit. Cardiac output and shunt fraction are derived from these curv es. The technique, which is simple and safe, provides measurements that all ow optimal adjustment of ECMO flow and cardiovascular support.