We have made diligent efforts during the past 10 years to find an anesthetic solution which could be used with safety in clinical anesthesia. We were convinced of the value of epidural anesthesia mainly because, in contrast to spinal anesthesia, it was relatively free of neurological sequelae, e. g., headache. Our difficulty was in finding a solution for epidural use which would afford the same abdominal muscle relaxation as does spinal anesthesia and yet not prove toxic. This was a problem because the great vascularity of the epidural space makes absorption easy and the high concentration of the solution, as well as the vastly increased volume necessary in epidural block, rendered its inherent toxicity manifest on too many occasions. Our credo regarding a drug useful in local or regional anesthesia is summarized in Table 1.
With these principles in mind, we investigated procaine in 2% concentration and found that it