Cell Saver Autologous Transfusion: Metabolic Consequences of Washing Blood with Normal Saline

OBJECTIVE To evaluate acid-base and electrolyte changes in high volume cell saver autologous blood transfusion when normal saline (0.9% NaCl) is used as the wash solution. DESIGN Open-label study. MATERIALS AND METHODS Nine anesthetized and anticoagulated mongrel dogs underwent 15 cycles of cell saver autologous blood transfusion. Eight percent of the circulating blood volume (125 mL) was withdrawn, washed with normal saline, and retransfused for each cycle. MEASUREMENTS AND MAIN RESULTS Analyses of acid-base, electrolyte, and hematologic parameters were performed on both systemic and the washed blood. The washed blood had increased levels of sodium and chloride. There were decreased levels in pH, Pco2, total CO2 (bicarbonate), lactic acid, potassium, total and ionized calcium, magnesium, inorganic phosphorus, total protein, and albumin. Systemically, in the animals, by the end of the study, there were significant increases in the levels of chloride, inorganic phosphorus, hemoglobin, and hematocrit and significant decreases in the levels of pH, total CO2, total and ionized calcium, magnesium, total protein, and albumin. CONCLUSIONS Acid-base, electrolyte, and hematologic changes occur when normal saline is used as the wash solution in high volume cell saver autologous blood transfusion. The washed blood with its elevation of sodium and chloride appears to reflect the constituents of the wash solution, normal saline. The depletion in the washed blood of Pco2, total CO2, potassium, total calcium, ionized calcium, magnesium, phosphorus, total protein, and albumin we feel is because of the absence of these electrolytes in the wash solution and their physical removal during salvaged blood separation and washing. The systemic acid-base and electrolyte changes primarily reflect the electrolyte pattern of the reinfused washed blood except for inorganic phosphorus. Inorganic phosphorus was maintained systemically, despite its wash out in the cell salvage process. This paradoxical finding may be caused by intracellular to extracellular inorganic phosphorus flux caused by the progressive systemic metabolic acidosis.