Closed loop control of vasoactive drug infusion. A preliminary report

A closed loop control system for vasoactive drug infusion is described using a dedicated bedside microcomputer and a single volumetric infusion pump. The signal from an indwelling arterial cannula is taken from the bedside monitor through an analogue/digital converter to a microcomputer. After signal validation changes of infusion rate are calculated and communicated to a volumetric infusion pump through an RS 232 interface. The system has been successfully employed in four patients during cardiac surgery prior to cardiopulmonary bypass and in six cardiac surgical patients in the postoperative period. In both groups mean arterial pressure was controlled within 5 mmHg of target value for 75% of infusion time, and within 10 mmHg for 90% of the duration of infusion.