The prognostic significance of an adverse acid–base milieu despite venoarterial extracorporeal membrane oxygenation support in patients with cardiogenic shock remains poorly defined. We examined metabolic and respiratory disturbances in the ELSO (Extracorporeal Life Support Organization) Registry among patients who received venoarterial extracorporeal membrane oxygenation support for refractory cardiogenic shock.

Arterial blood gas acid–base values at 24 hours following venoarterial extracorporeal membrane oxygenation initiation were analyzed, with patients classified by pH, arterial partial pressure of carbon dioxide, and bicarbonate. Multivariable logistic regression and exploratory machine learning analyses were used to assess predictors of in‐hospital mortality.

Among 15 144 adult patients, 74.6% (10 860) had neither respiratory nor metabolic acidosis, 13.1% (1909) had isolated respiratory acidosis, 11.6% (1684) had isolated metabolic acidosis, and 0.7% (100) had combined acidosis. In‐hospital mortality occurred in 7719 (51.0%) patients and increased incrementally across patients with lower pH (adjusted odds ratio [OR], 2.03 with each 0.1‐unit decrease in pH, using 7.4 as a reference point [95% CI, 1.82–2.26]), bicarbonate (adjusted OR, 1.93 per each 5‐mEq/L <24 mEq/L [95% CI, 1.76–2.12]) or base excess (adjusted OR, 1.90 per each 5‐mEq/L <0 mEq/L [95% CI, 1.75–2.07]) (all P<0.01). Mortality varied significantly, being highest for the low‐pH metabolic acidosis cluster (adjusted OR, 1.90 [95% CI, 1.70–2.12], P<0.01).

Survival decreased progressively with worse acidemia or metabolic acidosis despite 24 hours of hemodynamic support with venoarterial extracorporeal membrane oxygenation among patients with cardiogenic shock. Our findings emphasize the prognostic significance of metabolic parameters as potentially modifiable risk factors and underscore the need for early recognition and interventions to mitigate severe metabolic derangements.