The Relationship Between Right Atrial Pressure and Blood Volume

Introduction Present clinical criteria for detecting alterations in blood volume in postoperative patients are inadequate. Laboratory studies to support suspected findings also leave much to be desired. Blood volume studies using radioactive substances and dilution techniques approximate most accurately the existing state at a particular unit of time but they do not determine the rate of replacement, rate of withdrawal, or effectiveness of such therapy except as judged by repeat blood volume or reevaluation and interpretation of clinical signs. It is the purpose of this study to determine the efficacy of continuous monitoring of right atrial pressure in the detection of blood volume changes as previously reported in the experimental animal.¹,² Methods Twenty-five consecutive thoracotomy patients were studied with regard to their cardiovascular status, including frequent preoperative and postoperative blood volumes, measurement of hourly urine output, blood pressure, respirations, pulse rate, and clinical evaluation of each patient during the