Association Between Arterial Carbon Dioxide Tension and Clinical Outcomes in Venoarterial Extracorporeal Membrane Oxygenation

Abstract

Objectives: The manipulation of arterial carbon dioxide tension is associated with differential mortality and neurologic injury in intensive care and cardiac arrest patients; however, few studies have investigated this relationship in patients on venoarterial extracorporeal membrane oxygenation. We investigated the association between the initial arterial carbon dioxide tension and change over 24 hours on mortality and neurologic injury in patients undergoing venoarterial extracorporeal membrane oxygenation for cardiac arrest and refractory cardiogenic shock.

Design: Retrospective cohort analysis of adult patients recorded in the international Extracorporeal Life Support Organization Registry.

Setting: Data reported to the Extracorporeal Life Support Organization from all international extracorporeal membrane oxygenation centers during 2003-2016.

Patients: Adult patients (≥ 18 yr old) supported with venoarterial extracorporeal membrane oxygenation.

Interventions: None.

Measurements and main results: A total of 7,168 patients had sufficient data for analysis at the initiation of venoarterial extracorporeal membrane oxygenation, 4,918 of these patients had arterial carbon dioxide tension data available at 24 hours on support. The overall in-hospital mortality rate was 59.9%. A U-shaped relationship between arterial carbon dioxide tension tension at extracorporeal membrane oxygenation initiation and in-hospital mortality was observed. Increased mortality was observed with a arterial carbon dioxide tension less than 30 mm Hg (odds ratio, 1.26; 95% CI, 1.08-1.47; p = 0.003) and greater than 60 mm Hg (odds ratio, 1.28; 95% CI, 1.10-1.50; p = 0.002). Large reductions (> 20 mm Hg) in arterial carbon dioxide tension over 24 hours were associated with important neurologic complications: intracranial hemorrhage, ischemic stroke, and/or brain death, as a composite outcome (odds ratio, 1.63; 95% CI, 1.03-2.59; p = 0.04), independent of the initial arterial carbon dioxide tension.

Conclusions: Initial arterial carbon dioxide tension tension was independently associated with mortality in this cohort of venoarterial extracorporeal membrane oxygenation patients. Reductions in arterial carbon dioxide tension (> 20 mm Hg) from the initiation of extracorporeal membrane oxygenation were associated with neurologic complications. Further prospective studies testing these associations are warranted.

Figure 1.

Variations of unadjusted mortality according to the initial PaCO₂ category are shown.

Figure 2.

Hospital mortality in relation to the initial pre-ECMO PaCO₂ category is shown. Data is adjusted for SAVE score and support type⁺ and displayed on a logarithmic scale in reference to patients with normocarbia (odds ratio, 1; red dotted line). Differences in mortality with P values <0.05 are displayed (*). Complete data can be found in Supplemental Table 2. ⁺Support type differentiates VA ECMO for cardiopulmonary resuscitation and refractory cardiogenic shock.

Figure 3.

Displayed is (A) adjusted mortality and (B) intracranial complications (intracranial hemorrhage, ischemic stroke and brain death) in similar sized groups stratified by the absolute change in PaCO₂ from pre-initiation of ECMO to 24 hours on support. Displayed is the odds ratio and 95% CI for mortality and neurologic complications, both adjusted for SAVE score, support type⁺ and initial PaCO₂. P values <0.05 are displayed (*). Complete data in Supplemental Table 3. ⁺Support type differentiates VA ECMO for cardiopulmonary resuscitation and all other VA ECMO.