The retrospective study examined 172 adults who received VA-ECMO across two centres in Thailand. Researchers classified patients according to Kidney Disease: Improving Global Outcomes (KDIGO) creatinine criteria into three groups: those who developed AKI before ECMO initiation, those who developed it after treatment began, and those who had no AKI.
Of the 172 patients included in the study, 81 (47.1%) developed AKI before ECMO, while 82 (47.7%) experienced kidney injury after ECMO initiation. Only nine patients (5.2%) did not develop AKI. The researchers examined whether the timing of kidney injury could provide independent information about the prognosis of patients requiring this form of circulatory support.
The analysis found that patients with AKI before ECMO had more severe renal dysfunction than those who developed the condition after ECMO initiation. They also required renal replacement therapy more frequently. Acute liver injury was more common in the pre-ECMO group, indicating that these patients had a greater burden of organ dysfunction.
The difference was also reflected in unadjusted ICU mortality figures. Mortality reached 82.7% among patients who developed AKI before ECMO, compared with 69.5% among those who developed it after ECMO initiation. The difference was statistically significant, with a p-value of 0.048.
However, the relationship between pre-ECMO AKI and ICU mortality became less pronounced after statistical adjustment. When researchers accounted for age, sex, chronic kidney disease and centre, the adjusted hazard ratio was 1.39, with a 95% confidence interval of 0.98–1.98.
Further adjustment for illness severity reduced the hazard ratio to 1.28, with a 95% confidence interval of 0.86–1.90. Neither adjusted estimate established a statistically significant association between AKI before ECMO and ICU mortality. Similarly, AKI developing after ECMO initiation was not significantly associated with ICU mortality.
The findings indicate that kidney injury occurring before ECMO may reflect more than renal dysfunction alone. It may also be associated with pre-cannulation shock and multiple organ dysfunction. Consequently, the higher mortality observed in this group could partly reflect the severity of patients' underlying conditions rather than the timing of kidney injury itself.
For clinicians assessing patients for VA-ECMO, the study highlights the importance of evaluating renal function alongside overall illness severity and evidence of injury to other organs. Although AKI before ECMO may offer useful prognostic information, the findings do not establish it as an independent predictor of ICU mortality after adjustment for other clinical factors.
The researchers concluded that the timing of AKI should be considered during ECMO candidacy assessment but should not be used as a reason to restrict access to treatment. Further evidence is needed to establish the independent prognostic value of AKI timing among patients receiving VA-ECMO.
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