[Choice of a local anesthetic in obstetrical analgesia]

A local anaesthetic may be selected from amongst the two major groups of drugs of this type: amino-alcoyl-esters and amino-acylamides. In practice, three substances are available or will shortly be available in France: lignocaine, etidocaine and bupivacaine, thus limiting the choice. This choice is guided by the toxicity of the substance, its clinical effects and 1st side effects. 1-Toxicity depends upon the nature of the substance, the dose necessary to obtain analgesia and to prolong it for a sufficient time. 2-Amongst the clinical effects which should be noted in the choice of a local anaesthetic are the latent period before analgesia is obtained, the degree of sensory block, the degree of motor block and the duration of action. The three substances available are compared in relations to these parameters and in the light of the specific requirements of obstetric analgesia. The value of the addiction of adrenalin is discussed. 3-The side effects are those of the local anesthetic itself and of its possible association with adrenalin. On the basis of the various criteria mentioned, it would seem that the analgesic of choice for obstetric analgesia is bupivacaine used with or without adrenalin.