Formation of precipitate in priming solutions for extracorporeal perfusion

A precipitate observed in Hartman's solution used to prime a cardiopulmonary bypass circuit was identified as calcium carbonate. Analysis of the chemical equilibrium showed that the precipitation was caused by sodium bicarbonate added to prevent acidosis. Although this practice is acceptable for haemic primes, in which buffers and albumins will prevent precipitation, it should not be done with non-haemic primes prior to bypass.