Relationship between lower oesophageal contractility, clinical signs and halothane concentration during general anaesthesia and surgery in man.

The effects of a range of concentrations of halothane upon lower oesophageal contractility (LOC) and on defined clinical signs has been studied in patients undergoing surgery. Changes in clinical signs were assigned a numerical value by means of a scoring system. One hundred and eighty-one sets of measurements were made in 46 patients exposed to concentrations of halothane between 2.0 and 0.5 minimum alveolar concentration (MAC). The results were examined to identify relationships between (i) the clinical signs and alveolar halothane concentration, (ii) the clinical signs and LOC and (iii) the changes in LOC and alveolar concentration; significant correlations were found between these variables. Decreasing alveolar halothane concentration was associated with an increase in LOC and these increases in LOC were also associated with increases in the clinical score.