Spread of local anesthetics in the epidural space.

The range of analgesic spread of lumbar epidural analgesia was investigated in 200 surgical patients (ASA class i＆ii)who were divided into three groups. There were 100 patients in group I and 50 patients each in groups ii＆iii. Epidural anesthesia was performed using 15 ml, 20 ml＆15 ml of 2% lidocaine for patients in group I, group ii and group iii respectively. Group iii consisted of 50 pregnant women who were specially selected while the patients in group I and group ii were randomly chosen. The segmental dose requirement(SDR)was plotted separately against age in years, and height in cm. A comparison of the differences among three groups was also made. Ageneral trend towards a smaller dose requirement was found with relation to an increase of age and a decrease in body height and pregnancy. The relationship between age, height and dose requirement revealed statistical significance. However, the segmental dose requirement was greatest in group ii and smallest in group I , both of which suggest that the segmental dose requirement increases with administration of larger doses. Therefore, the range of the epidural spread could not be predicted with merely controlling the dose administration. We found that it was difficult to obtain a reasonably wide analgesic field for young patients even by injecting larger doses of libocaine. In contrast, and unexpected wide range of analgesia could be developed with comparatively smaller doses of lidocaine in the elderly patients.