• M Angdin and G Settergren.
• Department of Cardiothoracic Anaesthetics and Intensive Care, Karolinska Hospital, Stockholm, Sweden.
• J. Cardiothorac. Vasc. Anesth. 1997 Jun 1;11(4):458-62.

ObjectiveDuring cardiopulmonary bypass, there is almost no blood flow through the pulmonary artery. Ischemia and reperfusion are known to attenuate the reaction to acetylcholine. An attenuated reactivity to acetylcholine in the pulmonary circulation after cardiopulmonary bypass was previously shown in children. The current study in adult patients was designed to analyze the change over time of acetylcholine reactivity after cardiac surgery.DesignA prospective study.SettingThe operating room and intensive care unit of a university hospital.ParticipantsEighteen patients with ischemic or valvular heart disease.InterventionsPulmonary vascular resistance was measured with a pulmonary artery catheter before and during an infusion of acetylcholine. This procedure was done after induction of anesthesia before surgery and 1, 4, 8, and 20 to 24 hours after cardiopulmonary bypass.Measurements And Main ResultsPulmonary vascular resistance index decreased during infusion of acetylcholine before surgery by 27% from 286 +/- 27 dyne/sec/cm-5/m2 (mean and standard error of mean) to 209 +/- 28 and at 8 and 20 to 24 hours by 23% and 34%, respectively, 288 +/- 27 to 221 +/- 29 and 229 +/- 22 to 150 +/- 17 (p < 0.001, paired t-test). One and 4 hours after cardiopulmonary bypass, no significant decrease was observed.ConclusionsThese results confirm the finding of altered reactivity to acetylcholine in the pulmonary circulation after cardiopulmonary bypass. In view of the often prolonged tendency toward pulmonary hypertension observed in children, the recovery at 8 hours after surgery was unexpectedly rapid. The attenuated response to acetylcholine is most likely explained by relative ischemia in the pulmonary circulation during cardiopulmonary bypass.

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