Abstract

The intravenous injection of caffein produces the following acute effects:

1. A slow and slight rise of blood pressure and oncometer, referable to the acute influx of fluid. This is followed by

2. A sharp fall of blood pressure and oncometer, indicating acute cardiac depression. The oncometer and respiratory centers are somewhat stimulated by anemia. The heart rate is quickened. There is also some indirect evidence of peripheral vaso depression.

The further course depends upon the total dosage of caffein:

3a. With the earlier injections, corresponding to small and moderate dosage, the blood pressure rises somewhat above the original level. The oncometer shows a greater and more persistent rise. There is consequently cardiac stimulation and simultaneous vasodilation—the latter being the more persistent. Very exceptionally there is a central vaso-constriction.

3b. With the later injections, corresponding to larger dosage, both the blood pressure and especially the oncometer recover only imperfectly. The cardiac depression therefore tends to become persistent, and the additional vasodilation becomes less (the vessels being already permanently dilated).

3c. At the immediate approach of death, the blood pressure and oncometer continue to fall, indicating terminal cardiac paralysis.