AKI Timing Influences Prognostic Assessment in VA-ECMO Patients

Patients who develop acute kidney injury (AKI) before undergoing veno-arterial extracorporeal membrane oxygenation (VA-ECMO) show an unadjusted intensive care unit (ICU) mortality rate of 82.7%, according to a study published in Scientific Reports.

The research, led by T. Jungteerapanich, examined 172 adults across two medical centers in Thailand to determine if the specific timing of renal failure serves as a reliable predictor for survival in patients requiring this high-level circulatory support. While the raw numbers suggest a significant gap in outcomes, the statistical relationship shifts when clinicians account for the broader health profile of the patient.

The statistical shift in mortality risk

The study categorized patients based on Kidney Disease: Improving Global Outcomes (KDIGO) creatinine criteria into three groups: those with AKI before ECMO, those with AKI after initiation, and a small group of only nine patients who developed no kidney injury at all. The data revealed that nearly half of the participants fell into each of the two AKI categories, with 47.1% experiencing injury prior to the procedure and 47.7% experiencing it afterward.

When researchers applied statistical adjustments to the data—accounting for variables such as age, sex, existing chronic kidney disease, and the specific medical center—the perceived impact of AKI timing diminished. The adjusted hazard ratio for pre-ECMO kidney injury sat at 1.39, but this did not reach statistical significance. When the researchers further adjusted for the overall severity of the patient’s illness, the hazard ratio dropped to 1.28, moving even further away from a statistically significant association.

The following table illustrates the raw mortality data observed in the study cohort:

Patient Group	Unadjusted ICU Mortality Rate
AKI before ECMO initiation	82.7%
AKI after ECMO initiation	69.5%
No AKI recorded	Not specified

Distinguishing kidney injury from systemic shock

The findings suggest that the high mortality rate seen in the pre-ECMO group might not be caused by the kidney injury itself, but rather by what that injury represents. Patients who arrived at the point of needing ECMO with existing kidney dysfunction often presented with more severe renal impairment, a higher need for renal replacement therapy, and more frequent acute liver injury.

This distinction is critical for medical teams evaluating whether a patient is a candidate for VA-ECMO. The researchers argue that AKI occurring before the procedure may simply be a marker of pre-cannulation shock and multi-organ dysfunction. In these cases, the kidneys are reacting to a body-wide crisis rather than acting as the primary driver of the patient’s prognosis.

Because of this, the study concludes that while the timing of kidney injury provides important clinical context, it should not be used as a definitive reason to deny a patient access to ECMO treatment. Instead, clinicians should weigh renal function as one component of a much larger assessment of overall illness severity and evidence of other organ damage.

While the study provides a clearer picture of how kidney timing correlates with ICU outcomes, the researchers noted that further evidence is required to establish whether AKI timing holds any independent prognostic value once all clinical complexities are fully controlled.