The peripheral vascular effects of isoflurane and halothane were compared in five critically ill patients in whom a Jarvik-7 artificial heart had been implanted. The lungs of all patients were mechanically ventilated in the postoperative period and the patients were monitored with an arterial catheter and with catheters that had been surgically inserted into the right and left atria and into the pulmonary artery. Norepinephrine and epinephrine plasma concentrations were measured using a radioenzymatic assay. The Jarvik-7 settings were modified to render the artificial heart "preload independent" and to maintain cardiac output constant. Each patient was anesthetized twice using halothane and isoflurane at two different MAC levels, 1 and 1.5 (Datex vapour analyzer), with the interval between each anesthetic ranging from 12 to 26 h. Both anesthetics significantly decreased mean arterial pressure (from 100 +/- 11 mmHg to 66 +/- 13 mmHg for halothane and from 102 +/- 17 mmHg to 48 +/- 11 mmHg for isoflurane; mean +/- SD) and systemic vascular resistance index (from 27 +/- 11 Wood units/m2 to 18 +/- 6 Wood units/m2 for halothane and from 30 +/- 6 Wood units/m2 to 13 +/- 3 Wood units/m2 for isoflurane; mean +/- SD), but with isoflurane to a significantly greater extent than with halothane (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)