Microcomputer-controlled administration of vasodilators following cardiac surgery: technical considerations.

Hypertension in the early postoperative period after cardiopulmonary bypass is associated with increased morbidity, and is commonly managed by the infusion of short-acting vasodilators. Automatic arterial blood pressure control by closed-loop infusion has been shown to be superior to manual control in several studies. The investigators have developed a closed-loop arterial pressure control system based on the Atari 1040ST microcomputer (Atari, Sunnyvale, CA). The program uses a proportional-integral-derivative control algorithm, developed from that described by Sheppard and his colleagues. The arterial waveform is sampled digitally, and the waveform analysis routine incorporates several artifact detection and rejection functions. Additional safety features are provided in the computer-infusion pump subroutine, which cause alarms to be activated if computer-pump communication fails to occur within a specified time period. A novel feature of this system is the clinical staff's use of a "mouse" to enter data and control the program, which makes keyboard skills unnecessary. This system is in routine service in the cardiac intensive care unit (CICU), both for direct clinical use and for research into various aspects of arterial pressure control, and has proved to be acceptable to the clinical staff.