PARALYZING EFFECTS OF SODIUM CITRATE ON THE CARDIAC VAGUS AND ON HEART MUSCLE OF THE CAT

¹ Department of Physiology, Stanford University, California

1. Sodium citrate solution may be injected into the blood of a mammal (the cat) in sufficient amount to temporarily completely paralyze the cardiac vagus with gradual but entire recovery in twenty to thirty minutes. Similar or slightly larger doses tend, also, to lower blood pressure, slow the heart, and impair respiratory movements.

2. Using acetylcholine, evidence is found that the sodium citrate paralyzes the cardiac vagus at the synapses between pre- and postganglionic fibers in case of the cat just as was previously found by direct evidence in case of the turtle.

3. Sodium citrate seems to cause the effects (described in no. 1 above) by lowering the calcium ions in the blood and in the heart to the critical point; and all these ill effects may be prevented (in decerebrate animals) by intravenous injection of calcium chloride solution, in proper amount, either immediately before or during the early part of the sodium citrate transfusion, whether the citrate be given alone or as citrated blood. It is suggested that the immediate "citrate reaction" collapse that sometimes occurs in human subjects during a citrated-blood transfusion might thus be prevented.