CARDIOVASCULAR EFFECTS OF SEVOFLURANE COMPARED WITH THOSE OF ISOFLURANE IN VOLUNTEERS

Background: Sevoflurane is a new inhalational anesthetic with desirabl e clinical properties. In some clinical situations, an understanding o f the detailed cardiovascular properties of an anesthetic is important , so the authors evaluated the hemodynamic effects of sevoflurane in h ealthy volunteers not undergoing surgery. Methods: Twenty-one subjects were randomized to receive sevoflurane, isoflurane, or sevoflurane: 6 0% N2O. Anesthesia was induced and maintained by inhalation of the des ignated anesthetic. Hemodynamic measurements were performed before ane sthesia, during controlled ventilation, during spontaneous ventilation , and again during controlled ventilation after 5.5 h of anesthesia. R esults: A few subjects became excessively hypotensive at high anesthet ic concentrations (2.0 minimum alveolar concentration [ILIAC] sevoflur ane, 1.5 and 2.0 MAC isoflurane), preventing data collection. Sevoflur ane did not alter heart rate, but decreased mean arterial pressure and mean pulmonary artery pressure. Cardiac index decreased at 1.0 and 1. 5 MAC, but in subjects with mean arterial pressure greater than or equ al to 50 mmHg returned to baseline values at 2.0 MAC when systemic vas cular resistance decreased. Sevoflurane did not alter echocardiographi c indices of ventricular function, but did decrease an index of afterl oad. Sevoflurane caused a greater decrease in mean pulmonary artery pr essure than did isoflurane, but the cardiovascular effects were otherw ise similar. Administration of sevoflurane with 60% N2O, prolonged adm inistration or spontaneous ventilation resulted in diminished cardiova scular depression. Conclusions: At 1.0 and 1.5 MAC, sevoflurane was we ll tolerated by healthy volunteers. At 2.0 MAC, in subjects with mean arterial pressure greater than or equal to 50 mmHg, no adverse cardiov ascular properties were noted. Similar to other contemporary anestheti cs, sevoflurane caused evidence of myocardial depression. Hemodynamic instability was noted in some subjects at high anesthetic concentratio ns in the absence of surgical stimulation. The incidence was similar t o that with isoflurane. The cardiovascular effects of sevoflurane were similar to those of isoflurane, an anesthetic commonly used in clinic al practice since 1981.