(1145) Serum Bicarbonate Levels Among Patients on VV ECMO for ARDS Receiving Kidney Replacement Therapy

Introduction: For patients with ARDS receiving venovenus (V-V) ECMO, the inability to renally compensate for respiratory acidosis in patients with acute kidney injury (AKI) undergoing kidney replacement therapy (KRT) could require increased sweep gas flow to normalize arterial pH. This has the potential to delay weaning from V-V ECMO. We hypothesized that among patients receiving V-V ECMO for ARDS, patients receiving KRT would have lower serum bicarbonate levels, lower arterial pH, and higher sweep gas flow compared to patients not receiving KRT.

Methods: Our retrospective cohort study examined data from adult patients receiving V-V ECMO for ARDS at Vanderbilt Medical Center from 02/2019 to 02/2022. We compared patients who received KRT while undergoing V-V ECMO to patients who did not. Values for serum bicarbonate, arterial pH, PaCO2, and sweep gas flow were collected daily from time of cannulation until the earlier of decannulation, 30 days, or death.

Results: Of the 126 patients included, 53 (42.0%) received KRT and 73 (57.9%) did not. In patients who received KRT, mean serum bicarbonate levels remained between 22 and 28 mmol/L throughout the study period. Patients who did not receive KRT had an increase in mean serum bicarbonate levels over time up to 40 mmol/L throughout the study period [mean difference = -4.4 (95%CI, -6.3 to -2.5); p< 0.0001]. Mean values for PaCO2 [-5.2 (95% CI, -8.8 to -1.7); p=0.004] and pH [-0.03 (95% CI, -0.03 to -0.02); p < 0.0001] were lower in patients who received KRT than in patients who did not despite higher sweep gas flow rates in patients who received KRT than in patients who did not [mean difference = 1.5 (95% CI, 0.8 to 2.3); p< 0.001]. The percentage of patients who survived to discharge was similar (KRT 79.3% vs no KRT 84.9%). ECMO duration was longer for patients who received KRT [19.8 days (8.0 – 28.0)] than for patients who did not (10.1 days (4.7 - 24.9)] (median IQR).

Conclusions: Metabolic compensation that occurs in patients with ARDS and preserved renal function compared to patients with AKI receiving KRT could result in differences in sweep gas flow requirements with potential implications for weaning from V-V ECMO.