• T Naka, M Egi, R Bellomo, L Cole, C French, L Wan, N Fealy, and I Baldwin.
• Department of Intensive Care and Department of Medicine, Austin Hospital and Melbourne University, Melbourne, Australia.
• Int J Artif Organs. 2005 Mar 1;28(3):222-8.

ObjectiveTo evaluate the acid-base effect of low-dose regional citrate anticoagulation (RCA) during continuous veno-venous hemofiltration (CVVH).DesignProspective observational study.SettingICUs of tertiary public and private hospitals.SubjectsThirty critically ill patients with acute renal failure at risk of bleeding or with a major contraindication to heparin-CVVH and/or short filter life.MethodsWe used a commercial citrate-based fluid (11 mmol/L, sodium: 140 mmol/L, chloride: 108 mmol/L and 1 mol/L of potassium) as pre-dilution replacement fluid during CVVH. Further potassium was added according to serum potassium levels. We measured all relevant variables for acid-base analysis according to the Stewart-Figge methodology.ResultsBefore treatment, study patients had a slight metabolic acidosis, which worsened over 6 hours of RCA-CVVH (pH from 7.39 to 7.38, p < 0.005; bicarbonate from 23.2 to 21.6 mmol/L, p < 0.0001 and base excess from -2.0 to -3.0 mEq/L, p < 0.0001) due to a significant increase in SIG (from 5.8 to 6.6 mEq/L, p < 0.05) and a decrease in SIDa (from 37.5 to 36.6 mEq/L, p < 0.05). These acidifying effects were attenuated by hypoalbuminemia and a decrease in lactate (from 1.48 to 1.34 mmol/L, p < 0.005) and did not lead to progressive acidosis. On cessation of treatment, this acidifying effect rapidly self-corrected within six hours.ConclusionsLow dose RCA-CVVH induces a mild acidosis secondary to an increased strong ion gap and decreased SIDa which fully self-corrects at cessation of therapy. Clinicians need to be aware of these effects to correctly interpret changes in acid-base status in such patients.

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