The Clinical Usefulness of Hydrogen Gas as an Indicator of Left-to-right Shunts.

SEVERAL indicators have been recommended for the detection of intracardiae left-to-right shunts. The complexity of in-strumentation, the difficulties in handling radioactive materials, and the time involved in the sampling required have precluded the general acceptance of any one method as a routine screening procedure. Furthermore, oxygen saturations, as well as methods utilizing radiopaque contrast material, dyes, and even radioactive indicators, may give equivocal results in the presence of very small left-to-right shunts. Therefore, an inexpensive indicator that permits easy administration and rapid detection of small quantities while still in the bloodstream, by a system requiring a minimum of instrumentation, would be of significant value. Hydrogen gas is such an indicator, easily detected by an intravascularly located platinum tipped electrode catheter, which because of its affinitv for hydrogen molecules will serve as a hydrogen electrode. Hydrogen, after leaving the alveolar space, is carried in gas form. Upon contact with platinum a partial change from the molecular to the ionic state occurs witb the simultaneous release of electrons (H2-> 2H+ + 2e-). The electrical potential obtained from such an electrode is a function of the partial pressure of hydrogen in its immediate vicinity and the surface area of the platinum electrode. Details of the underlying principles have been well described by Clark and associates'-6 and its clinical application has been discussed byers9 have pointed out its usefulness in eight patients with small left-to-right interventric-ular shunts, the danger of explosion inherent in the handling of hydrogen and the hazard of an intracardiae electrode'0 may have precluded its general acceptance thus far. Since no detailed evaluation of the use of this system in other conditions has appeared in the literature, 210 observations carried out in 60 patients with congenital heart disease are presented. This study emphasizes its present place in a diagnostic cardiae catheterization laboratory and gives examples of typical diagnostic tracings as well as of commonly encountered artifacts. Material and Methods During routine cardiac catherization 210 observations were made in 60 patients with varying types of congenital heart disease. All procedures were carried out at the Cardiopulmonary Laboratory of the Children's Hospital Medical Center, Boston (table 1). Although hydrogen inhalation for the detection of left-to-right shunts was more frequently applied in cases in which oxygen saturation data were considered equivocal in this regard, in general, the patients were unselected and were representative of a cross-section of our patients with congenital heart disease. They …