Measurement of Regional Sodium Turnover Rates and Their Application to the Estimation of Regional Blood Flow

Abstract

It has been possible to estimate the regional blood flow through quantitative analysis of the sodium wash out curve obtained by a method which involves the injection of sodium 24 into an artery and the subsequent monitoring of the region (limb) supplied by this artery with external counters. The normal resting sodium turnover rate in the human forearm was found to be 10%/min. corresponding to a blood perfusion factor of 0.040 liters of blood per liter of tissue per minute. In addition to these quantitative values this method has given qualitative information on the pattern of the vascular bed. Analysis of the manner in which the removal rate changes with time has indicated that there are regions of widely differing vascularities in the area seen by the counter. Measurements following epinephrine administration have demonstrated not only a quantitative change in flow but a qualitative one as well. The subcutaneous administration of 1 mg epinephrine caused a doubling of the average total sodium turnover rate indicating a twofold increase in blood flow. The observed changes in the shape of the clearance curves could not be explained by a simple increase in linear flow rate and therefore must have involved some change in the character of the vascular bed, i.e. the conversion of some regions of low vascularity to regions of high vascularity.