STUDIES OF CYCLOPROPANE VIII. THE EFFECT OF PREMEDICATION WITH MORPHINE OR AMYTAL UPON THE HEART RATE, RHYTHM, AND BLOOD PRESSURE IN DOGS UNDER CYCLOPROPANE ANESTHESIA

¹ From the Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee

1. The effect of cyclopropane anesthesia upon the heart rate, rhythm, and blood pressure has been investigated upon 14 non-premedicated dogs, 14 morphine-premedicated dogs, and upon 4 receiving amytal as preanesthetic medication. In addition, 39 other dogs have been used for similar work except that blood pressure records were not obtained.

2. In non-premedicated dogs cyclopropane produces an increase in heart rate and blood pressure; cardiac irregularities were rarely observed before the respiration was greatly depressed.

3. In dogs receiving morphine premedication, cyclopropane decreased the heart rate and blood pressure; cardiac irregularities were routinely observed in moderate and deep surgical anesthesia; these irregularities could be abolished by an intravenous dose of amytal (1 to 2.5 mgm. per kilogram).

4. In dogs receiving amytal-sodium premedication the heart rate and blood pressure were maintained during anesthesia with cyclopropane at the preanesthetic level. Cardiac irregularities were observed in only one of 14 dogs before respiratory arrest.

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