Desflurane pharmacokinetics during cardiopulmonary bypass.

OBJECTIVE

To describe the washin and washout of desflurane when first administered during cardiopulmonary bypass (CPB) for cardiac surgery.

DESIGN

A single-arm prospective study.

SETTING

University-affiliated hospital operating room.

PARTICIPANTS

Ten adult patients presenting for cardiac surgery.

INTERVENTIONS

Consenting patients presenting for cardiac surgery received anesthesia with midazolam and fentanyl. Patients were cooled to 32 degrees C on CPB, then desflurane 6% was administered and blood samples drawn repeatedly from the arterial and venous bypass cannulae as well as from the membrane oxygenator inlet and exhaust from 2 to 32 minutes of desflurane administration. Just before rewarming, final (maximum) washin samples were taken. On rewarming, desflurane was discontinued, and blood and gas samples were taken 2 to 24 minutes thereafter.

MEASUREMENTS AND MAIN RESULTS

CPB time was 116 +/- 10 minutes, and ischemic time was 81 +/- 6 minutes. Mean pump flow was 4.49 +/- 0.03 L/min, and mean arterial pressure was 70.1 +/- 1 mmHg during the study period. Arterial washin of desflurane was initially rapid; arterial concentrations reached 50% of administered concentrations within 4 minutes, but then slowed, reaching 68% of inspired concentrations at 32 minutes (desflurane concentration 4.0% +/- 0.3%). Arterial washout of desflurane was more rapid; arterial concentrations fell to 18% of the maximum concentration reached within 4 minutes, and only 8% of the maximum arterial concentration was present in blood 20 minutes later.

CONCLUSION

Desflurane showed rapid initial washin and washout on CPB when administration was started at 32 degrees C and stopped at time of rewarming.