EXPERIMENTS ON THE POTENTIATION OF PROCAINE SPINAL ANESTHESIA IN THE RABBIT

¹ From the Department of Pharmacology, The University of Minnesota Medical School, Minneapolis

1. The spinal anesthetic action of procaine in the rabbit was not prolonged by mixtures of 0.12 molar magnesium chloride and sodium chloride. These salt mixtures produced symptoms of irritation.

2. Spinal anesthesia with procaine was in some instances somewhat prolonged by mixtures of 0.12 molar calcium chloride and sodium chloride. These solutions caused very profound motor effects.

3. All equimolecular mixtures of 0.12 molar magnesium chloride and calcium chloride in sodium chloride solution studied prolonged the spinal anesthetic action of procaine. The greatest prolongation was obtained with a 15-15-70 mixture of the above salts respectively. This mixture increased sensory anesthesia 806 per cent, and motor paralysis 207 per cent over simple addition. These solutions produced no symptoms of irritation.

4. The intraspinal therapeutic ratio of procaine dissolved in the optimum salt mixture, was found to be 12.5 (M.L.D. of 5 per cent per M.A.D. of 0.4 per cent).

5. Solutions containing more magnesium than calcium produced symptoms similar in nature to those caused by magnesium solution without calcium. Solutions containing an excess of calcium produced symptoms similar to those caused by solutions containing calcium without magnesium.

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