AN ANALYSIS OF THE THIOCYANATE METHOD FOR DETERMINING THE DISTRIBUTION OF THE BODY FLUIDS

Abstract

Optimum dosage of thiocyanate to determine available fluid vol. is 25 mg./kg. of body wt., yielding a thiocyanate conc. of around 8 mg./l00 cc. of plasma. The diffusion time varies but ranges around 1 hr. The time should be ascertained in each detn. by serial sampling. The disappearance rate averages 2.3% per hr. but should also be detd. in each instance and correction made accordingly. Reinj. detns. of available fluid check within 6% of the original detn. The disappearance method with a single inj. is advocated as the preferable method for determining changes in extracellular water vol. subsequent to the original detn. This method should be checked by reinj. of thiocyanate and Na detns. In determining exptl. extracellular water changes, reasonably concordant results are obtained with the thiocyanate method and the Na method. The thiocyanate method is considered to be a.satisfactory method for roughly measuring changes in extracellular water. Changes in the extracellular water vol. in excess of 6% probably have a definite significance by the method.