Detection of right-to-left shunts with an arterial potentiometric electrode.

T HE platinized platinum electrode develops a rapidly responding and readily recorded potential in the presence of hydrogen dissolved in blood. A sensitive procedure for detecting and localizing left-to-right shunts in the catheterization laboratory"2 and in the operating room3 has been developed with use of such an electrode on the tip of a cardiac catheter. Hydrogen has been found to be completely cleared from intravenously injected saline solution saturated with hydrogen during its passage through the lungs. Therefore, a test for the detection of right-to-left shunts can be based upon the intravenous injection of saline solution saturated with hydrogen during continuous monitoring for hydrogen in the aorta with a platinum electrode. The lo-calization of such right-to-left shunts, particularly difficult in infants, is determined by a series of injections into the various chambers of the heart. Further, because a platinized platinum electrode develops a potential in the presence of sodium ascorbate,* an injection of this substance serves to verify the responsiveness of the electrode at any time. It is the purpose of this report to describe the procedure and to illustrate its application in the diagnosis of right-to-left shunts with particular reference to infants. Methods Platinum electrodes for use in the artery were prepared by melting a small bead (0.038") on the end of a 45-cm. length of 28-gage (0.0126") platinum wire. The wire is then threaded through polyethylene tubing