Changes of Arterial and Venous Blood Flow During Orthostasis and the Effect of Atropine

Abstract

This study was attempted to clarify the effect of atropine on the tolerance of the cardiovascular system to the upright and head-down tilt, and to investigate the change of blood flow through head and lower leg with Electromagnetic flowmeter in both tilts before and after atropine state. Fourteen anesthetized dogs(10-14kg) were tilted from supine to +77° upright and then to –90° head-down position, and the same course was taken 20 minutes after intravenous administration of 0.5mg atropine. In upright tilt, the blood flow both on the artery and vein through head and lower leg were decreased. And the atropine attenuated the decrement of the blood flow on the carotid artery, but not on the vessels of the lower leg. In upright tilt, arterial Po2 was slightly decreased, but venous Po2 was markedly(p<0.01) decreased and venous Pco2 was increased(p<0.05). Hct was increased in both tilts(p<0.01). The findings of blood Po2, Pco2 and Hct were not interferred by the atropine. In conclusion, the atropine attenuates the severe diminution of the blood flow to the head during orthostasis.