Effects of Digoxin on Systolic Time Intervals of Neonates and Infants

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Abstract
Systolic time intervals were measured in 27 normal newborn infants before and after administration of oral digoxin (30 µg/kg). Systolic intervals were also measured in 10 newborns and infants with congestive heart failure before and after this same 30 µg/kg dose of digoxin, but also after administration of a much larger "digitalizing dose" of 80 µg/kg. Preejection period (PEP) shortened significantly in the normal newborns following the smaller dose. Changes in ejection time (ET) were much less striking and appeared to be transient, lasting less than 8 hours. When small doses of digoxin were given to the babies with congestive failure, PEP again shortened significantly. In general, the larger doses of digoxin produced no further changes in PEP or ET, although there were individual exceptions. The demonstration that maximal inotropic effect, as measured by PEP changes, usually occurred with small doses of digoxin may have significant clinical implications in terms of present concepts of loading doses of digitalis in the pediatric age group.