Cardiovascular response to acute hypoxemia in adult rats hypoxemic neonatally.

Abstract

Objective: To determine the effects of chronic hypoxemia neonatally on the cardiovascular response to acute hypoxemia in adulthood. Methods: Experiments were conducted on adult rats (82±2 days) which had been made chronically hypoxemic (hypobaric hypoxia equivalent to FiO₂=0.14) during the first ten days of life but raised in room air (Neonatally Hypoxemia) as well as on adult rats never previously hypoxemic (Control). The animals were instrumented with catheters in the right common carotid artery and superior vena cava for measurements of mean systemic arterial pressure (MAP), central venous pressure, heart rate (HR), arterial blood gases, and arterial as well as mixed venous O₂ saturation. Oxygen consumption (O₂) was measured allowing calculation of cardiac index (CI), stroke volume index (SVI) and systemic vascular resistance index (SVRI). The rats were made acutely hypoxemic by exposure to FiO₂=0.10 for 20 min. Results: HR increased and MAP decreased to similar extents in both groups during acute hypoxemia. However, SVI and CI increased significantly (PConclusions: Hypoxemia experienced in early life has long-term effects on the cardiovascular response to acute hypoxemia at maturity. This may have important implications for individuals hypoxemic in early life due to congenital cyanotic heart defects or pulmonary disease secondary to prematurity.