Automated infusion of vasoactive and inotropic drugs to control arterial and pulmonary pressures during cardiac surgery

Objective: To evaluate the feasibility of a closed-loop system for simultan eous control of systemic arterial and pulmonary artery blood pressures duri ng cardiac surgery, Design: Feasibility study, Setting: The cardiac surgery operating room. Patients: The performance of the multiple-drug closed-loop system was evalu ated during cardiac surgery in 30 patients who required treatment with more than one vasoactive or inotropic drug. Interventions: A multiple-drug closed-loop system integrated five single-dr ug blood pressure controllers, Arterial hypertension was controlled using s odium nitroprusside or nitroglycerin, arterial hypotension was controlled u sing noradrenaline or dobutamine, and pulmonary hypertension was controlled using nitroglycerin, The anesthesiologist selected target pressures and si ngle-drug blood pressure controllers, The multiple-drug closed-loop system had a set of priority rules that automatically activated from the selected single-drug controllers the optimum single-drug controller for each hemodyn amic state. Drug infusion rates of the nonactive controllers were kept cons tant. The initial knowledge that was used to construct the priority rules w as obtained from standard anesthetic protocols on perioperative management of cardiac surgical patients. A supervisory computer program defined the ac tions to be taken in cases of infusion pump problems, invalid pressure meas urements, and during unexpected increases and decreases in systemic arteria l pressure, Measurements and Main Results: The activation of single-drug controllers by the priority rules was accurate and fast. On average, a different single-d rug controller was activated once every 7.2 mins, As a measure of variabili ty, the average deviation of mean arterial pressure and mean pulmonary arte ry pressure from their target values was evaluated and was 8.6 +/- 4.0 and 4.4 +/- 4.0 mm tig, respectively, before cardiopulmonary bypass and 8.0 +/- 3.6 and 2.4 +/- 0.9 mm Hg, respectively, after cardiopulmonary bypass, Non e of the single-drug controllers showed any signs of unstable response, Conclusion: Closed-loop control of both arterial and pulmonary pressures us ing multiple drugs is feasible during cardiac surgery.