The Effect of Bicarbonate Administration via Continuous Venovenous Hemofiltration on Acid-Base Parameters in Ventilated Patients

BACKGROUND Acute kidney injury (AKI) and metabolic acidosis are common in the intensive care unit. The effect of bicarbonate administration on acid-base parameters is unclear in those receiving continuous venovenous hemofiltration (CVVH) and mechanical ventilatory support. METHODS Metabolic and ventilatory parameters were prospectively examined in 19 ventilated subjects for up to 96 hours following CVVH initiation for AKI at an academic tertiary care center. Mixed linear regression modeling was performed to measure changes in pH, partial pressure of carbon dioxide (pCO2), serum bicarbonate, and base excess over time. RESULTS During the 96-hour study period, pCO2 levels remained stable overall (initial pCO2 42.0±14.6 versus end-study pCO2 43.8±16.1 mmHg; P=0.13 for interaction with time), for those with initial pCO2≤40 mmHg (31.3±5.7 versus 35.0±4.8; P=0.06) and for those with initial pCO2>40 mmHg (52.7±12.8 versus 53.4±19.2; P=0.57). pCO2 decreased during the immediate hours following CVVH initiation (42.0±14.6 versus 37.3±12.6 mmHg), though this change was nonsignificant (P=0.052). CONCLUSIONS We did not detect a significant increase in pCO2 in response to the administration of bicarbonate via CVVH in a ventilated population. Additional studies of larger populations are needed to confirm this finding.