Computer-controlled regulation of sodium nitroprusside infusion.

We built and tested a combined proportional/derivative and minimum variance adaptive control algorithm for the regulation of blood pressure using sodium nitroprusside (SNP). In ten dogs the pressure was reduced by 30 mm Hg for 1 hr. The blood pressure came to within 5 mm Hg of the desired pressure in 1.7 +/- 4 min and after 3.4 +/- 0.3 min it remained within +/- 5 mm Hg of the desired value. During the nitroprusside infusion, bolus doses of epinephrine and SNP as well as phlebotomy were used to challenge the controller. The controller responded rapidly and effectively so that blood pressure remained stable throughout each challenge. Control was achieved in ten dogs with very different sensitivities to SNP. After 1 hr of SNP infusion, the rate of SNP infusion required to maintain a 30 mm Hg reduction in pressure averaged 112 ml/hr with a standard deviation of 108 ml/hr. Adaptive control met the challenge of large differences in sensitivity and maintained the desired blood pressure.