Abstract

1. The decline of procaine concentration which limits the duration of spinal anesthesia is not due to chemical breakdown of the drug in the spinal fluid, but to absorption into the systemic circulation where it is metabolized to p-aminobenzoic acid and diethylaminoethanol.

2. The concentrations of procaine at various levels of the subarachnoid space decline at the same rate.

3. There is a critical concentration of procaine, about 0.2 mgm. per ml., which is necessary for sensory anesthesia.