Pulse pressure and end-tidal carbon dioxide for monitoring low native cardiac output during veno-arterial ECLS: a prospective observational study

BACKGROUND: Veno-arterial extracorporeal life support (VA-ECLS) results in cardiopulmonary shunting with reduced native cardiac output (NCO). Low NCO occurrence is common and associated with risk of thromboembolic and pulmonary complications. Practical tools for monitoring NCO during VA-ECLS would therefore be valuable. Pulse pressure (PP) and end-tidal carbon dioxide (EtCO(2)) are known to be related to cardiac output. We have designed a study to test whether PP and EtCO(2) were efficient for the monitoring of NCO during VA-ECLS. METHODS: In this prospective single-center observational study, patients who underwent a VA-ECLS for cardiogenic shock from January 2016 to October 2017 were included, provided low NCO was suspected by a PP < 20 mmHg. NCO was measured with pulmonary artery catheter or echocardiography and compared to PP and EtCO(2). The ability of PP and EtCO(2) to predict NCO < 1 L/min was evaluated with receiver operating characteristics (ROC) curves. RESULTS: Among the 106 patients treated with VA-ECLS for cardiogenic shock during the study period, 26 were studied, allowing the collection of 196 study points. PP and EtCO(2) relationships with NCO were nonlinear and showed strong correlations for NCO < 2 L/min (r = 0.69 and r = 0.78 respectively). A PP < 15 mmHg and EtCO(2) < 14 mmHg had good predictive values for detecting NCO < 1 L/min (area under ROC curve 0.93 [95% CI 0.89–0.96] and 0.97 [95% CI 0.94–0.99] respectively, p = 0.058). CONCLUSIONS: PP and EtCO(2) may offer an accurate real-time monitoring of low NCO events during VA-ECLS support. Further studies are needed to show if their utilization may help to implement therapeutic strategies in order to prevent thromboembolic and respiratory complications associated with VA-ECLS, and to improve patients’ prognosis. TRIAL REGISTRATION: NCT03323268, July 12, 2016