• Dirk Bruegger, Andreas Bauer, Markus Rehm, Markus Niklas, Matthias Jacob, Michael Irlbeck, Bernhard F Becker, and Frank Christ.
• Clinic of Anesthesiology, Ludwig-Maximilians-University Munich, Germany.
• Crit. Care Med. 2005 Mar 1;33(3):556-63.

ObjectiveTo evaluate the magnitude and cause of metabolic acidosis after infusion of 7.5% sodium chloride 6% dextran 70.DesignRandomized, prospective clinical study.SettingUniversity hospital.PatientsTwo groups of 14 patients each, undergoing repair of abdominal aortic aneurysm.InterventionsPatients were randomly assigned to receive either 250 mL of hypertonic saline dextran (HSD) or a conventional fluid regimen with 250 mL of hydroxyethyl starch in normal saline solution (H-NS) during the period of aortic clamping. Additionally, normal saline was used in both groups to reach a target pulmonary artery occlusion pressure of 15-18 mmHg. pH, Paco2, and serum concentrations of sodium, potassium, magnesium, calcium, chloride, lactate, albumin, and phosphate were measured. Strong ion difference was calculated as (sodium + potassium + magnesium + calcium) - (chloride + lactate). The amount of weak plasma acid was calculated.Measurements And Main ResultsThe infusion of HSD resulted in an immediate large increase in serum sodium (19 mmol/L) and chloride (22 mmol/L), whereas the infusion of H-NS led only to mild increases in serum sodium (3 mmol/L) and chloride (6 mmol/L). Both HSD and H-NS caused concomitant and equal decreases in the amount of weak plasma acid, strong ion difference, and pH (7.28-7.30). The reduction of bicarbonate was also identical and proportional to the extent of dilution due to infusion of HSD and H-NS. This induced metabolic acidosis was corrected spontaneously in both groups 24 hrs after surgery.ConclusionBoth the intravenous administration of 7.5% sodium chloride and the conventional fluid regimen with saline-based 6% hydroxyethyl starch solution resulted in a metabolic acidosis of equal extent. This suggests dilution of plasma buffers or a decrease in strong ion difference to be the primary cause of metabolic acidosis.

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