Methodology of a prospective study of changes in liver enzyme concentrations following repeat anaesthetics

The methodology of a large prospective study on the influence of repeated anaesthetics on liver function is reported and the problems involved are discussed. The most suitable patients were those presenting for endoscopic examination of the bladder and urethra, for urethral dilatation and for cervical implantation of radium. Blood samples were taken immediately before induction of anaesthesia and on days 3-4 and 13-15 after operation, when a clinical assessment of the patient was also carried out. The concentrations of six enzymes (lactate dehydrogenase, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, serum cholinesterase and gamma glutamyl transpeptidase) werechosen specifically as indices of liver function. The eosinophil count was measured to reflect any hypersensitivity reaction. The non-Gaussian distribution of these necessitated using appropriate non-parametric tests together with parametric tests on logarithmic transformed data. In addition a quantal method was used to measure the frequency of patients showing an "abnormal" increase in enzyme concentrations.