RECENT STUDIES have revealed that enflurane (Ethrane| or 1,12-trifluoro-2-ehlorethyl difluoromethyl ether is a potent anaesthetic in both animals and man. 1,~,3 Dobkin and his associates have reported that circulatory dynamics and cardiac rhythm remain relatively stable during enflurane anaesthesia in man, 1 but their findings are complicated by preanaesthetic medication, induction agents, muscle relaxants, surgical trauma, controlled respiration, and respiratory alkalosis. Accordingly, the present study was designed to obtain information on the haemodynamic effects of enflurane in man at constant carbon dioxide tension. METHODSTen male volunteers ranging in age from 21 to 35 years were interviewed and informed consent obtained. The procedures were approved by the Committee on Human Experimentation, Clinical Study Unit, Tufts University School of Medicine and New England Medical Center Hospitals. Each volunteer was admitted to the Clinical Study Unit three days prior to the study for complete history, physical examination, and laboratory tests, including electrocardiogram, chest X-ray, haematocrit, haemoglobin, creatinine, blood urea nitrogen, bilirubin, SGOT, SGPT and LDH, prothrombin time, alkaline phosphatase, sedimentation rate, and urine analysis. To prevent control of ventilation by positive pressure being a factor during the study, the volunteers were trained to use the ventilator. On the day following admission, they were instructed in the use of the Bennett anaesthesia ventilator. Tidal volume and frequency of respiration were set according to the Radford nomogram and the frequency was adjusted to achieve normal ad:erial pH and PaCO_,. The values obtained were noted.On the morning of the experiment, after fasting for at least nine hours, the trained volunteer was brought to the study room. The radial artery was cannulated. A venous catheter (#18 Sorensen) was inserted into the right ventricle through the right basilic vein for measurement of right ventricular end-diastolic pressure. Four surface EKC electrodes were applied. Needle electrodes were placed to obtain bipolar EEG tracings.