The Effect of Spinal Anesthesia on Arterial Tone

In a previous study1it was shown that the cardiac output in dogs under spinal anesthesia remained at a nearly normal level unless a marked diminution in blood pressure took place. The decrease in blood pressure came first and was usually of greater degree than the later decrease in the output of the heart. This sequence of events is just the opposite of that found in experimental traumatic shock and experimental hemorrhage.2It was believed that a further comparison of these states might throw light on the nature of the different types of shock. These subjects have received a great deal of study in the past fifteen years, but, so far as one can judge from the literature, many of our concepts as to their exact nature are vague and incomplete. METHOD Dogs were used. They received barbital (0.3 Gm. per kilogram) intravenously from one to two hours