Low bicarbonate replacement fluid normalizes metabolic alkalosis during continuous veno-venous hemofiltration with regional citrate anticoagulation

BACKGROUND: Metabolic alkalosis is a frequently occurring problem during continuous veno-venous hemofiltration (CVVH) with regional citrate anticoagulation (RCA). This study aimed to evaluate the effectiveness of switching from high to low bicarbonate (HCO(3)(−)) replacement fluid in alkalotic critically ill patients with acute kidney injury treated by CVVH and RCA. METHODS: A retrospective-comparative study design was applied. Patients who underwent CVVH with RCA in the ICU between 09/2016 and 11/2017 were evaluated. Data were available from the clinical routine. A switch of the replacement fluid Phoxilium(®) (30 mmol/l HCO(3)(−)) to Biphozyl(®) (22 mmol/l HCO(3)(−)) was performed as blood HCO(3)(−) concentration persisted ≥ 26 mmol/l despite adjustments of citrate dose and blood flow. Data were collected from 72 h before the switch of the replacement solutions until 72 h afterwards. RESULTS: Of 153 patients treated with CVVH during that period, 45 patients were switched from Phoxilium(®) to Biphozyl(®). Forty-two patients (42 circuits) were available for statistical analysis. After switching the replacement fluid from Phoxilium(®) to Biphozyl(®) the serum HCO(3)(−) concentration decreased significantly from 27.7 mmol/l (IQR 26.9–28.9) to 25.8 mmol/l (IQR 24.6–27.7) within 24 h (p < 0.001). Base excess (BE) decreased significantly from 4.0 mmol/l (IQR 3.1–5.1) to 1.8 mmol/l (IQR 0.2–3.4) within 24 h (p < 0.001). HCO(3)(−) and BE concentration remained stable from 24 h till the end of observation at 72 h after the replacement fluid change (p = 0.225). pH and PaCO(2) did not change significantly after the switch of the replacement fluid until 72 h. CONCLUSIONS: This retrospective analysis suggests that for patients developing refractory metabolic alkalosis during CVVH with RCA the use of Biphozyl(®) reduces external HCO(3)(−) load and sustainably corrects intracorporeal HCO(3)(−) and BE concentrations. Future studies have to prove whether correcting metabolic alkalosis during CVVH with RCA in critically ill patients is of relevance in terms of clinical outcome. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13613-021-00850-4.