Controlled hypotension with sodium nitroprusside: anesthesiologist versus computer.

Computer systems developed for the automatic control of blood pressure have been previously shown to induce hypotension with sodium nitroprusside more rapidly and accurately than can be done with manual control. We compared the performance of a computer controller with performances by 10 anesthesiologists during challenges to homeostasis similar (or analogous) to those occurring during a surgical procedure. Hypotension was induced in 10 mongrel dogs and maintained for 2 hours, either by an anesthesiologist or by the computer controller. Challenges to homeostasis were given during the 2-hour period. The computer brought the mean arterial pressure to the desired value in an average of 4.1 minutes compared with 6.3 minutes for the anesthesiologists, but this difference was not statistically significant. There was no statistically significant difference between the computer and the anesthesiologists for 25 performance criteria. The anesthesiologists performed better during two imposed hypertensive perturbations by turning off the sodium nitroprusside sooner when the pressure rapidly decreased. In general, the computer controller performed as well as experienced anesthesiologists who devoted full attention to the control of blood pressure.