Effects of Enflurane on Haemodynamics and Oxygen Uptake with Special Reference to the Influence of Surgical Stress

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Abstract
The influence on central haemodynamics of enflurane, in uniform anaesthetic concentration (1.5 MAC), was studied in 10 normocapnic patients undergoing upper abdominal surgery. The patients were studied awake, during anaesthesia prior to surgery, and during surgery. On institution of anaesthesia, cardiac output (Qt) fell from 5.05±0.51 to 4.12±0.15 l/min and systemic vascular resistance (SVR) decreased from 2.36±0.22 to 1.93±0.18 kPa min 1‐‐3 The arterio‐venous oxygen content difference (AVD) did not change. On commencement of surgery, AVD diminished from 38.5±2.6 to 30.8±1.9 ml/min and QT rose to 5.82±0.46 l/min, while SVR remained unchanged. It is concluded that the fall in Qr seen during enflurane anaesthesia is caused by a diminished tissue oxygen demand. It is also suggested that enflurane acts as an α‐blocking agent.