Difficulties in Clinical Study of Shock

ABSTRACT To the Editor:— Drs. Smulyan, Cuddy, and Eich in their study on the "Hemodynamic Effects of Pressor Agents in Septic and Myocardial Infarction Shock" (JAMA190:188 [Oct 19] 1964) reported their observations on critically ill patients, observations made under circumstances that were undoubtedly emotionally trying and technically very difficult. Studies of this type are direly needed, and the authors deserve our gratitude for this undertaking.The reliability, significance, and interpretation of the data, however, must be viewed in relation to the techniques employed and the scope of the study. Arterial blood pressures were measured by the indirect technique with the clinical sphygmomanometer. Unfortunately, the indirect measure is inaccurate in comparison with the intra-arterial pressure of patients in shock. Discrepancies exceeding 50% are not uncommon. In their determination of cardiac output, radioiodinated serum albumin was injected into a peripheral vein. The error due to inadequate mixing, which occurs even in