Abstract
An intravenous injection of adrenalin causes a rapid steep rise of the blood pressure with a gradual fall. An intramuscular injection produces a similar effect. A subcutaneous injection either produces practically no effect or it causes a very slow rise which rarely exceeds fifteen millimeters. In recent years adrenalin was injected into the spinal canal in conjunction with some local anesthetic. The question as to the nature of the effect of these injections upon the blood pressure has to our knowledge never yet been investigated. On the basis of the generally accepted assumption that the absorption from the spinal canal into the circulation is not very prompt we might expect that the intraspinal injection of adrenalin will have no stronger effect upon the blood pressure than that of a subcutaneous injection. We studied this question experimentally and may say at the outset that our results did not bear out this anticipation. Our experiments were made on six monkeys, using each monkey two or three times. The amount injected was either 1 c.c. or 1.5 c.c. of the commercial adrenalin. Most of the injections were made in the lumbar region; but in a few instances the adrenalin was injected in the thoracic region in the fifth intervertebral space. During the experiments the animals were under fairly profound anesthesia and we are unable to state whether the injection had any other effect besides the change in the blood pressure. But it is important to point out that even doses of 1.5 c.c. of adrenalin had no recognizable after-effects upon the animal.
The action upon the blood pressure was in most cases very characteristic. The pressure would begin to rise slowly but steadily, so that in a few minutes it would reach a maximum varying between 150 and 190 millimeters, and would then commence to go very gradually down.
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