Left ventricular norepinephrine and epinephrine kinetics at birth in lambs

Area of Science:

• Cardiovascular Physiology
• Neonatal Adaptation
• Autonomic Nervous System

Background:

• Limited understanding of perinatal catecholamine kinetics in the left ventricle (LV).
• Need to correlate LV catecholamine changes with LV function and whole-body kinetics during birth.

Purpose of the Study:

• Investigate changes in LV catecholamine (norepinephrine, epinephrine) kinetics at birth.
• Relate these changes to perinatal alterations in LV function and whole-body catecholamine kinetics.

Main Methods:

• Used radiotracer dilution methodology to measure whole-body and LV catecholamine kinetics.
• Employed radioactive microspheres to assess fetal LV output and myocardial blood flow.
• Measurements were taken in near-term fetuses and 1 and 4 hours after birth.

Main Results:

• LV sympathetic activity (norepinephrine spillover) and epinephrine release increased significantly at 1 hour post-birth.
• LV external work increased by 115% between fetal and 1-hour postnatal periods.
• LV epinephrine spillover decreased to undetectable levels by 4 hours post-birth, while LV norepinephrine spillover returned to near-fetal levels.

Conclusions:

• A transient increase in LV sympathetic activity at birth may enhance immediate postnatal LV performance.
• Organ-specific differences in sympathetic activation patterns are evident during the perinatal transition.
• Birth-related increases in LV sympathetic activity are associated with cardiac epinephrine release.