Abstract
A total of 22 parturients with uncomplicated pregnancies were given continuous epidural block using a 0.4 per cent, lidocaine drip solution without epinephrine (series I), or with epinephrine (II). The mean total dose of lidocaine administered in series I was 591 mg, and 293 mg in series II. The mean total dose per kg body weight in series I was 8.33 mg, and 4.17 mg in series II. According to the results of a specially designed scoring system adequate pain relief was achieved and maintained in both series trough-out labour and delivery. For the second stage an additional dose of lidocaine was necessary in some mothers in series I, whereas in the second series acceptable analgesia was maintained by a continuation of the initially started low drip rate. The lidocaine concentrations in foetal capillary blood and in maternal venous blood were low in series II. These values were about 40-60 per cent higher in series I, but mean maternal values were never in excess of 1.2 mcg/ml. The highest mean foetal value was 0.7 mcg/ml and the highest individual foetal value 1.0 mcg/ml. In none of the cases were higher lidocaine levels found in foetal blood than in maternal venous blood at corresponding sampling occasions. Differences in lidocaine concentrations found in blood from maternal artery and vein were, under the existing circumstances with the exception of an initial peak, only slight, thus clinically negligible.