Neonatal vs Adult Cardiac Physiology. Melissa Aromin Anesthesia Clerkship. Adult Circulation. Fetal Circulation. RA LA RA PA Aorta. First breath decrease pulm vascular resistance increase pulm blood flow functional FO closure
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Neonatal vs Adult Cardiac Physiology Melissa Aromin Anesthesia Clerkship
AdultCirculation Fetal Circulation • RA LA • RA PA Aorta
First breath decrease pulm vascular resistance increase pulm blood flow functional FO closure • Increase arterial oxygen functional DA closure • Anatomic Closure • FO: months • DA: 2-3 weeks • Reversal of closures: • hypoxia, hypercarbia, acidosis • Increase pulm vascular resistance open DA • Increase right heart pressure open FO
Fetal Hemoglobin • Fetal Adult hemoglobin at 2-3 months physiological anemia • Fetal hemoglobin left shift decrease oxygen delivery to tissues • Increase oxygen delivery by: • Higher hemoglobin concentration • Increase CO
Cardiac Output • Neonatal myocardium: immature contractile elements and less compliant • Affect on Cardiac Output • CO = SV x HR • Fluids little change in SV • Must increase HR to increase CO
Neonatal sympathetic NS and baroreceptor reflexes: immature • Hypovolemia with decreased vasoconstriction -> hypovolemia without tachycardia • Reduced concentration of neurotransmitter, but mature adrenergic receptors respond better to direct-acting inotropes • 10% reduction in blood volume will cause a 15-30% decrease in MAP
Physiological differences between neonatal and adult myocardium
References • Swamy et al. Applied aspects of anatomy and physiology of relevance to pediatric anesthesia. Indian J. Anaesth. 2004;48(5):333-339. • BrasoveanuE. Neonatal physiology and anesthesia. www.bu.edu/.../05sprgmedanesthesiology/.../Neonatal%20Physiology/Neonatal%20Physiology%20and%20Anesthesia.doc • Burd et al. Neonatal and childhood perioperative considerations. SurgClin North Am. 2006;86(2):227-247.