THE RELATIONSHIP BETWEEN ANESTHETIC UPTAKE AND CARDIAC-OUTPUT

The hypothesis that anaesthetic uptake during maintenance of anaesthes ia is related to cardiac output was tested on 21 patients undergoing c ardiac surgery. Using a computer-controlled closed breathing system, e nflurane was administered to maintain an end-expired concentration of 1%. Cardiac output was measured by thermodilution using a pulmonary ar tery catheter. A clear qualitative but not quantitative relationship w as demonstrated. Changes in anaesthetic requirements at a constant end -expired concentration are a better guide to changes in cardiac output than changes in end-expired carbon dioxide with constant ventilation in patients undergoing cardiac surgery.