Abstract
Hemodynamics of 7 diabetes insipidus (DI) patients secondary to severe head injuries were examined. In DI, without administration of Pitressin® (vasopressin), systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR) were markedly decreased while central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) were rather low. In DI with administration of Pitressin®, mean arterial pressure (MAP), SVR, and PVR were significantly increased. Cardiac index (CI) was decreased, but not significantly. Changes of CVP and PCWP were not significant. It seems that the elevation of MAP is caused by the increase of SVR and that Pitressin® acts mainly on the resistance vessel, and not on the capacitance vessel.
Until recently, it was believed that physiological function of antidiuretic hormone (ADH) is diuresis and that the pressor effect of ADH plays no evident role under physiological conditions. But recent reports from several different laboratories indicate that ADH participates in the normal daily regulation of arterial pressure. The results of this study seems to support this hypothesis.
In DI patients, SVR is markedly decreased and the hemodynamics are rather hypervolemic. In this state, Pitressin® causes decrease of urine volume and increase of body fluid. In the administration of this drug, the possibility of edema of the brain, lung and other organs must be taken into consideration. Pitressin® also causes vasoconstriction of coronary vessels and increase of oxygen demand of myocardial muscle by increase of afterload due to elevated SVR and possibly myocardial ischemia.
