Impact of continuous veno-venous hemodiafiltration with regional citrate anticoagulation on the acid-base balance of critically ill patients

Background

Continuous veno-venous hemodiafiltration (CVVHDF) with regional citrate anticoagulation (RCA) has been applied to the treatment of critically ill acute renal failure (ARF) patients for years. It has a substantial effect on acid-base homeostasis. Accordingly, we investigated a cohort of patients requiring CVVHDF and assessed their acid-base changes by quantitative biophysical principles (Stewart-Figge approach).

Methods

We studied 32 consecutive critical care ARF patients on CVVHDF with RCA. All relevant variables for acid-base analysis were measured according to the Stewart-Figge methodology.

Results

Before CVVHDF treatment, the patients had metabolic acidosis with mild increase of the anion gap. The excess of unmeasured anions was the most important component of acidosis. Median lactate, phosphate and chloride levels were in the normal range. The median albumin was 2.3 mg/dl and had an alkalinizing effect.

On the third CVVHDF day, the median pH, bicarbonate, anion gap, BE and SIG had significantly decreased. The median value of the total calcium-ionic calcium ratio, a surrogate marker of citrate accumulation, did not change significantly over treatment, and was maintained below 2.5 mg/dl.

Conclusion

In critically ill ARF patients, CVVHDF with RCA is a safe RRT modality and it corrected metabolic acidosis through its effects on unmeasured anions.

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