Administration of drugs during cardiopulmonary bypass. An analysis of the fate of a bolus injected through different routes using radio-active technetium.

This study was conducted to determine the efficiency of delivery of drugs injected as boluses by the common routes available during cardiopulmonary bypass. Radioactive technetium (99mTc) was injected in a 50 microCi bolus into the central venous line or into the arterial or venous lines of the oxygenator and its passage monitored downstream by suitable radiation detectors. When injected into the central venous line, delivery was unpredictable and at times 50% or more of the dose may not appear for 5 min. When injected into the venous line of the oxygenator an average 5% of the total dose had not reached the detector during first passage, and had completely cleared at 2 min. No significant difference was found between the different oxygenators and it is concluded that the venous line of the oxygenator is the most efficient site for the achievement of rapid action of drugs.