Continuous Renal Replacement Therapy: Does Technique Influence Electrolyte and Bicarbonate Control?

Abstract

Background and objectives Different techniques of continuous renal replacement therapy (CRRT) might have different effects on electrolyte and acid-base control. The aim of this study was to determine whether continuous veno-venous hemodiafiltration (CVVHDF) or continuous veno-venous hemofiltration (CVVH) achieve better control of serum sodium, potassium and bicarbonate concentrations. Design Retrospective controlled study. Setting Two tertiary intensive care units. Patients Critically ill patients with acute renal failure (ARF) treated with CVVHDF (n=49) or CVVH (n=50). Interventions Retrieval of daily morning sodium and potassium values and arterial bicarbonate levels from computerized biochemical records before and after the initiation of CRRT for up to 2 weeks of treatment. Statistical comparison of findings. Measurements and results Before treatment, abnormal (high or low) values were frequently observed for sodium (65.1% for CVVHDF vs. 80.0% for CVVH; NS), potassium (45.9% vs. 34.0%; NS), and bicarbonate (73.3% vs. 68.0%; NS). After treatment, however, CVVHDF was more likely to achieve serum sodium concentrations within the normal range (74.1% vs. 62.9%; p=0.0026). Both treatments decreased the mean serum potassium concentration over the first 48 h (p=0.0059 and p <0.0001, respectively), but there was no difference in terms of the normalization of serum potassium concentration during the entire treatment period (88.3% vs. 90.5%; NS). Both treatments increased the mean arterial bicarbonate concentration over the first 48 hours (p=0.011 and p <0.0001, respectively). However, CVVH was associated with a lower incidence of metabolic acidosis (13.8% for CVVH vs. 34.5% for CVVHDF; p <0.0001) and a higher incidence of metabolic alkalosis (38.9% vs. 1.1%; p <0.0001) during the entire treatment period. Conclusions CRRT strategies based on different techniques have a significantly different impact on sodium and bicarbonate control.