Loss of nitroglycerin to cardiopulmonary bypass apparatus.

An in vitro model of a cardiopulmonary bypass (CPB) circuit using a bubble oxygenator was developed to assess the potential of this system to extract nitroglycerin (NTG). A NTG solution (100 ng/ml) was circulated through a CPB circuit at 5 L/min for 60 min. Samples obtained for NTG analysis revealed a significant loss of drug to the circuit. By 60 min, only 18% of the initial NTG concentration was present. In a separate experiment, the bubble oxygenator was shown to be the major source of drug extraction because less than 15% of the drug concentration infused directly into the oxygenator appeared in the arterial outlet. These results indicate that patients may not receive the expected dose of NTG during CPB even if caution is taken to administer the drug through nonadsorbing iv tubing.