Can we detect in vivo hemolysis during extracorporeal membrane oxygenation support using endogenous carbon monoxide production?

ABSTRACT

Introduction: Extracorporeal membrane oxygenation (ECMO) has been widely used in patients with ARDS due to COVID-19. In vivo hemolysis (ivH) is one of its complications, characterised by peaks of plasma free hemoglobin (fHb). However, an increase in carboxyhemoglobin (COHb) has also been observed due to Hb metabolism by heme-oxygenase that releases carbon monoxide. The aim of this study is to evaluate the incidence of ivH events and their relation to COHb in COVID-19 patients undergoing ECMO. Method(s) Single-centre observational retrospective study that included 33 COVID-19 patients with ARDS who received VV-ECMO treatment in the ICU from March 2020 to September 2021. Daily analytical monitoring was carried out including arterial blood gas test with cooximetry and biochemical parameters, incorporating the estimation of fHb using quantitative hemolysis index (HI). Significant ivH was considered with fHb > 50 mg/dL after discarding in vitro hemolysis. Daily maximum values of HI and COHb were recorded and paired in order to evaluate their correlation by generalised linear model. Result(s) The total prevalence of patients having ivH in our cohort was 27.3%. Mortality during ECMO treatment in our study was 57.6%, higher within the group of patients with ivH events (77.8% vs 50%). A total of 777 daily maximum values of fHb from all the patients were obtained. Values of COHb were significantly higher during ivH episodes. Furthermore, positive significant correlation was obtained between daily analytical values of fHb and COHb (B coefficient 42.156;p = 0.042), as shown in Fig. 1. The cut-off value of COHb to be discriminative for hemolysis (fHb > 50 mg/dL) was 3.85% COHb (90.5% sensitivity and 83.3% specificity). Conclusion(s) Point-of-care carboxyhemoglobin is a cheap and widely available parameter that could be useful when detecting in vivo hemolysis during ECMO treatment.