Oxygen uptake and central circulation during ketamine anaesthesia.

Cardiac output, oxygen uptake and plasma catecholamines were studied in patients when awake and during ketamine anaesthesia prior to and during upper abdominal surgery. Oxygen uptake was determined by using a masspectrometer and cardiac output was measured according to the Fick principle. Plasma catecholamines were analysed by high performance liquid chromatography. Stroke volume had fallen by 27% while heart rate had increased after 15 min of anaesthesia, maintaining cardiac output at the awake level. Concomitantly, the oxygen uptake had fallen by 18%. During the succeeding hour of anaesthesia and surgery, cardiac output displayed a transient decrease and oxygen uptake returned to the awake value. The plasma adrenaline concentration fell during the initial phase of anaesthesia and then returned to the awake level. The noradrenaline concentration was increased during the whole anesthetic period. The data suggest a relationship between oxygen uptake and cardiac output during ketamine anaesthesia, similar to that seen during neurolept-nitrous oxide and halothane anaesthesia, except for the initial hyperkinetic period following the induction. No relationship could be shown between catecholamine concentrations in plasma and the central haemodynamics.