Characterizing the Racial Discrepancy in Hypoxemia Detection in VV-ECMO: An ELSO Registry Analysis.

Importance : Skin pigmentation influences peripheral oxygen saturation (SpO 2 ) measured by pulse oximetry compared to the arterial saturation of oxygen (SaO 2 ) measured via arterial blood gas analysis. However, data on SpO 2 -SaO 2 discrepancy are limited in venovenous-extracorporeal membrane oxygenation (VV-ECMO) patients. Objective : To determine whether there is racial/ethnical discrepancy between SpO 2 and SaO 2 in patients receiving VV-ECMO. We hypothesized VV-ECMO cannulation, in addition to race/ethnicity, accentuates the SpO 2 -SaO 2 discrepancy due to significant hemolysis. Design : Retrospective cohort study of the Extracorporeal Life Support Organization Registry from 1/2018-5/2023. Setting : International, multicenter registry study including over 500 ECMO centers. Participants : Adults (≥ 18 years) supported with VV-ECMO with concurrently measured SpO 2 and SaO 2 measurements. Exposure : Race/ethnicity and ECMO cannulation. Main outcomes and measures : Occult hypoxemia (SaO 2  ≤ 88% with SpO 2  ≥ 92%) was our primary outcome. Multivariable logistic regressions were performed to examine whether race/ethnicity was associated with occult hypoxemia in pre-ECMO and on-ECMO SpO 2 -SaO 2 calculations. Covariates included age, sex, temporary mechanical circulatory support, pre-vasopressors, and pre-inotropes for pre-ECMO analysis, plus single-lumen versus double-lumen cannulation, hemolysis, hyperbilirubinemia, ECMO pump flow rate, and on-ECMO 24h lactate for on-ECMO analysis. Results : Of 13,171 VV-ECMO patients (median age = 48.6 years, 66% male), there were 7,772 (59%) White, 2,114 (16%) Hispanic, 1,777 (14%) Black, and 1,508 (11%) Asian patients. The frequency of on-ECMO occult hypoxemia was 2.0% ( N =  233). Occult hypoxemia was more common in Black and Hispanic versus White patients (3.1% versus 1.7%, P  < 0.001 and 2.5% versus 1.7%, P =  0.025, respectively). In multivariable logistic regression, Black patients were at higher risk of pre-ECMO occult hypoxemia versus White patients (adjusted odds ratio [aOR] = 1.55, 95% confidence interval [CI] = 1.18-2.02, P =  0.001). For on-ECMO occult hypoxemia, Black patients (aOR = 1.79, 95%CI = 1.16-2.75, P =  0.008) and Hispanic patients (aOR = 1.71, 95%CI = 1.15-2.55, P =  0.008) had higher risk versus White patients. Furthermore, higher pump flow rate (aOR = 1.29, 95%CI = 1.08-1.55, P =  0.005) and higher on-ECMO 24h lactate (aOR = 1.06, 95%CI = 1.03-1.10, P  < 0.001) significantly increased the risk of on-ECMO occult hypoxemia. Conclusions and Relevance : Hispanic and Black VV-ECMO patients experienced occult hypoxemia more than White patients. SaO 2 should be carefully monitored during ECMO support for Black and Hispanic patients especially for those with high pump flow and lactate values at risk for occult hypoxemia.