Stability of bicarbonate in normal saline: a technical report

BACKGROUND: The benefit of intravenous sodium bicarbonate administration in patients with severe metabolic acidosis remains controversial, partly due to lack of double-blind trials. From a practical viewpoint, such blinding requires testing of the stability of sodium bicarbonate in polyolefin bags. METHODS: We examined seven samples of 100 mL 8.4% sodium bicarbonate diluted in 150 mL normal saline within a 250 mL polyolefin bag at time 0, 24 and 48 hours after preparation. We measured pH, Pco2, and bicarbonate concentration. RESULTS: Over a period of 48 hours, both pH and Pco2 decreased significantly (hourly rate of change, -0.001 [P = 0.043) and -0.098 [P < 0.001] respectively). However, the concentration of bicarbonate did not decrease, with an hourly rate of change of only -0.009 (P = 0.42). CONCLUSION: When 100 mL of 8.4% sodium bicarbonate are diluted in 150 mL of normal saline within a 250 mL polyolefin bag, changes in pH and Pco2 over a 48-hour period are small and bicarbonate concentration remains stable.