Low Dose Intermittent Epidural Anaesthesia with Lidocaine for Vaginal Delivery

Abstract

Abstract. In 190 women with uncomplicated pregnancies, intermittent epidural analgesia was given by means of injections of about 50 mg lidocaine without (Series I), or with epinephrine 1:200,000 (series II) at one hour intervals during the first stage of labour. During the second stage the analgesia was maintained by 100 mg of lidocaine at an average interval of one hour. The mean total dose of lidocaine administered in series I was 409 mg, and 258 mg in series II. The degree of pain relief in series II was most satisfactory according to results obtained by a specially designed scoring system. In series I the method was less efficacious, since the preliminary scheme for administration of the drug, e.g. 50 mg per hour, was not practicable. In series I an increase in the blood lidocaine concentrations was observed after each injection in a majority of the parturients. The highest lidocaine concentration in maternal venous blood was in this series 2.6 mcg/ml. In series II the lidocaine concentrations in maternal venous blood and foetal scalp blood were generally low and showed a minimal tendency to accumulate. In this series the highest lidocaine concentration in maternal venous blood was 1.3 mcg/ml, and 0.6 mcg/ml in foetal scalp blood. The umbilical venous concentration of the drug was on an average about 56 per cent, and the umbilical arterial concentration 43 per cent of the maternal venous levels. With the exception of an initial peak, the lidocaine concentrations in maternal arterial and venous blood were found to be very similar when the presented low dose regimen was practised. The rate of vacuum extraction was in series I 40 per cent and in series II 31 per cent.