Abstract
The unique fragility of the neonatal circulation in response to disease states and various physiological stimuli is apparent clinically although underlying mechanisms have not been explored. Accordingly, this report examines and compares the influence on cardiac performance of changes in left ventricular (LV) filling pressure in six conscious, unsedated newborn lambs studied serially at one and three weeks of age and five adult sheep. All animals were instrumented chronically to assess LV internal dimensions and pressures and cardiac output. At constant heart rate, infusion of saline to comparably high LV end diastolic pressures was associated in the younger newborns with significantly elevated mean arterial pressures, reduced LV stroke volume, stroke work and mean fiber shortening when compared to older newborns or adults. A separate analysis of the LV pressure-dimension relation ships showed lowest LV compliance in the youngest animals with a progressive increase with age. Thus, these results suggest that the youngest newborns have limited preload reserve related to reduced LV compliance. With volume infusion sarcomeres are stretched fully; the rise in peripheral resistance creates a mismatch between afterload and the level of inotropic state. These findings provide a framework for viewing cardiocirculatory adaptation to left-to-right shunt lesions in the human newborn and support the the contention that age-dependent, disadvantageous myocardial mechanical factors play a critical role in their clinical course.
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Friedman, W., Romero, T. 102 LIMITED CARDIAC RESPONSES TO STRESS IN THE NEWBORN. Pediatr Res 12 (Suppl 4), 380 (1978). https://doi.org/10.1203/00006450-197804001-00107
Issue Date:
DOI: https://doi.org/10.1203/00006450-197804001-00107