Blood volume error detector.

THE ESTIMATION OF PLASMA VOLUME has become a very useful and widely applied tool in the diagnosis and treatment of clinical aberrations of water and electrolyte distribution. Methods utilizing the dilution of radioactive iodinated serum albumin (BISA), have been studied and applied extensively, and most of the strictly methodologic difficulties have been overcome. One step, however, that of injection of the RTSA dose, is difficult to accomplish quantitatively in some instances-i.e., small amounts of the dose may be deposited at or about the site of injection (perivascularly or subcutaneously, or even on the clothing or bedclothes), altering the final result to a falsely high plasma volume. In order to be able to recognize this “loss error,” a suitable inexpensive gamma radiation detector was sought. A pocket radiation meter* was purchased which proved to be too insensitive by several orders of