Comparison of bupivacaine and etidocaine in extradural blockade

In a randomized, double-blind study, 40 female patients underwent major gynaecological surgery with extradural anaesthesia provided by 0.75% bupivacaine, 0.75% bupivacaine with adrenaline 5 micrograms ml-1, 1.5% etidocaine or 1.5% etidocaine with adrenaline 5 micrograms ml-1, 20 ml in each case. In all patients the resultant blockade was suitable for intra-abdominal pelvic surgery. Mean maximum spread of analgesia was around T3/4 with all four drugs. Onset of sensory and motor block was more rapid following etidocaine than following bupivacaine. The addition of adrenaline increased the speed of onset of sensory block. Patients receiving etidocaine had a denser motor blockade than those receiving bupivacaine, and the addition of adrenaline led to an increase in the density of the motor blockade. There were no differences in the durations of motor blockade. Objective measurements of the duration of sensory blockade showed that there were no differences between the drugs and that the addition of adrenaline increased the duration of blockade. However, pain returned sooner following etidocaine than bupivacaine, and the additive effect of adrenaline was to increase this period of subjective analgesia.