A saline conductivity method for detection of cardiac shunts by indicator-dilution technic.

A new method for cardiovascular shunt detection is described using the indicator-dilution principle applied to blood conductivity changes produced by 5 per cent saline. It possesses these distinct advantages over the Evans blue technic: (1) an unlimited number of deter-minations can be made without an increasing blood dye background or bluish discoloration of the patient, (2) oximetric determination of blood oxygen saturation is not interferred with, and (3) a simple modification of the carrier amplifiers of commonly used recording systems supplies most of the necessary instrumentation. A LTHOUGH indicator dilution technics, using chiefly T-1824 (Evans blue dye), have been of value in the determination of the site and type of cardiovascular shunts, 1 " 5 the methods suffer certain major limitations despite refinements in the recording of the dye curves. "With regard to Evans blue, repeated determinations result in an increasing blood background of this protein-bound dye, which restricts both the number and frequency of accurate measurements; frequently it is advantageous to have repeated curves from both the same and multiple sites. In addition, following its use the photometric determination of blood oxygen saturation is no longer possible. One of the lesser objections is the blu-ish discoloration of the patient that may result after multiple determinations. The use of hypertonic saline as the indicator in the determination of cardiac output by the indicator-dilution technic has been described by several authors. 6 " 10 It occurred to us that this conductivity method was applicable to cardiovascular shunt detection and during the past year a modification of the method has been successfully applied to the detection of such shunts. METHOD Twenty-one patients with congenital heart disease , 12 of whom had intracardiac shunts, have been studied. Representative curves are shown on 4 patients as follows: (1) A 21-year-old white female with isolated valvular pulmonic stenosis, (2) a 21-year-old white male with Eisenmenger's syndrome, (3) a 30-year-old white male with a ventricular septal defect and a predominant left-to-right but small right-to-left shunt, and (4) a 3-year-old Xegro female with tetralogy of Fallot. Injection of 5 per cent saline, 2 to 5 ml. depending upon patient size, was accomplished through a standard cardiac catheter into various sites in the right heart and pulmonary artery. In the case of the Eisenmenger's syndrome, 75 mg. of Bromsulphalein (BSP)" was injected with the 5 per cent saline and simultaneous BSP and conductivity curves were obtained. Recording in …