The effects of four different crystalloid bypass pump-priming fluids upon the metabolic response to cardiac operation.

The crystalloid solutions used to prime cardiopulmonary bypass pumps frequently contain metabolically active substrates. However, there is a lack of controlled studies to investigate the metabolic response to cardiac operations using different pump primes. We have carried out a prospective, randomized study of 24 patients divided into four groups, each group receiving a different crystalloid prime. The primes contained glucose, lactate, glucose and lactate, or neither glucose nor lactate. Using identical anesthetic, surgical, and perfusion techniques, we estimated the metabolic response to cardiac operation in all patients by frequent blood sampling for measurement of hormone (insulin, glucagon, cortisol, and growth hormone) and metabolite concentrations (glucose, lactate, pyruvate, glycerol, alanine, and 3-hydroxybutyrate) from the day before operation to the seventh postoperative day. The results demonstrated that, after 4 hours postoperatively, the endocrine and metabolic response to cardiac operation was unaffected by the nature of the priming fluid. However, major endocrine and metabolic changes occurred before that time, which were related directly to the glucose and lactate contents of the prime. Very high concentrations of both glucose and lactate were observed at the end of bypass if they were induced in the prime. Given the known dangers of hyperglycemia in cerebral ischemia and the potential gluconeogenic effects of infused lactate, we suggest that glucose-free and lactate-free primes be employed in the extracorporeal circuit.