Microprocessor-controlled hemodynamics: a step towards improved efficiency and safety.

Manual titration of sodium nitroprusside (SNP) is widely used for treatment of hypertension following cardiac surgery. This study compared conventional manual control with control by a research prototype of an automatic infusion module based on a proportional plus integral plus derivative (PID) negative feedback loop. Two groups of coronary artery bypass patients requiring SNP for postoperative hypertension were studied prospectively. In the first group, hypertension was controlled by manual adjustment of the SNP infusion rate, and in the second, the infusion rate was controlled automatically. The actual and desired mean arterial pressures (MAP) over consecutive ten-second epochs were recorded during the period of infusion. The MAP was maintained within 10% of the desired MAP 45.8% of the time in the manual group, compared with 90.0% in the automatic group, and the mean percent error in the automatic group was significantly less than in the manual group (P less than 0.01). It is concluded that adoption of such systems will result in improved patient safety and may facilitate more effective distribution of nursing staff within intensive care units.