Effects of Spinal Anesthesia and Adrenalectomy on Blood Pressure Responses to Histamine

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Abstract
Experiments were made in dogs to determine the effects of graded doses of histamine on the blood pressure of the adrenalectomized and nonadrenalectomized animal before and after total spinal anesthesia. Before spinal anesthesia adrenalectomy had no significant effect other than the changes due to the lowering of the control blood pressure. After total spinal anesthesia adrenalectomy had no significant effect on the blood pressure responses to histamine. The effects seen as the result of the total spinal anesthesia were a decrease in the amount of fall in blood pressure, a prolongation of the duration of the fall in blood pressure and a lowering of the minimum to which the blood pressure will fall as the result of the histamine action. In dogs under total spinal anesthesia there is no indication of a rise in blood pressure due to a direct release of pressor amines from the adrenal medulla due to the histamine action.