Pulse Oximetry and Arterial Blood Gas Oxygen Saturation Discrepancies and Mortality in Extracorporeal Cardiopulmonary Resuscitation Patients: An Extracorporeal Life Support Organization Registry Analysis.

OBJECTIVES

Previous studies have shown that inaccurate peripheral oxygen saturation (Sp o2 ) readings compared with arterial oxygen saturation (Sa o2 ) may occur in extracorporeal membrane oxygenation (ECMO) patients. We hypothesized that a greater Sp o2 -Sa o2 discrepancy in extracorporeal cardiopulmonary resuscitation (ECPR) patients is associated with higher mortality due to unrecognized hypoxemia.

DESIGN

Retrospective analysis.

SETTING

Data within the Extracorporeal Life Support Organization Registry from 496 ECMO centers (2018-2024).

PATIENTS: Patients 18 years old or older receiving ECPR (first-run only).

INTERVENTIONS: None.

MEASUREMENTS AND MAIN

RESULTS

Laboratory measurements including Sp o2 -Sa o2 were measured at 24 hours of ECMO support. Acute brain injury (ABI) included hypoxic-ischemic brain injury, ischemic stroke, intracranial hemorrhage, and seizures. Based on an inflection point in cubic spline analysis, a Sp o2 -Sa o2 threshold greater than or equal to 4% was used as a binary variable to assess its association with in-hospital mortality. Three thousand nine hundred seventy ECPR patients (median age, 57 yr; 71% male) were included. The median ECMO duration was 4 days (interquartile range, 2-7 d). There were 634 patients (16%) with Sp o2 -Sa o2 greater than or equal to 4% and 3336 (84%) with Sp o2 -Sa o2 less than 4%. Overall mortality was 60% ( n = 2391). Patients with Sp o2 -Sa o2 greater than or equal to 4% had higher mortality compared with patients with Sp o2 -Sa o2 less than 4% (67%, n = 425 vs. 59%, n = 1966; p < 0.001). Patients with Sp o2 -Sa o2 greater than or equal to 4% had higher serum lactate values than those with Sp o2 -Sa o2 less than 4% (3.1 vs. 2.8 mmol/L; p = 0.0017). In multivariable logistic regression adjusted for preselected covariates, Sp o2 -Sa o2 greater than or equal to 4% was associated with increased risk of mortality (adjusted odds ratio [aOR], 1.39; 95% CI, 1.13-1.71). Additional risk factors associated with higher mortality included ABI (aOR, 5.81; 95% CI, 4.70-7.20), hyperoxemia greater than or equal to 300 mm Hg (aOR, 1.93; 95% CI, 1.53-2.43), hyperoxemia 200-299 mm Hg (aOR, 1.76; 95% CI, 1.37-2.25), gastrointestinal hemorrhage (aOR, 1.69; 95% CI, 1.42-2.00), renal replacement therapy (aOR, 1.48; 95% CI, 1.03-2.11), hypoxemia less than 60 mm Hg (aOR, 1.45; 95% CI, 1.00-2.10), older age (aOR, 1.19; 95% CI, 1.13-1.26), and higher lactate (aOR, 1.17; 95% CI, 1.13-1.20). Race/ethnicity was not associated with higher mortality.

CONCLUSIONS

Sp o2 -Sa o2 greater than or equal to 4% in the first 24 hours after ECPR is associated with increased risk of mortality, potentially due to unrecognized hypoxemia, irrespective of race/ethnicity.