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 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): Brasoveanu E. Neonatal physiology and anesthesia. anesthesiology /.../ Neonatal %20 Physi ology / Neonatal %20 Physiology %20and%20 Anesthesia.doc anesthesiology /.../ Neonatal %20 Physi ology / Neonatal %20 Physiology %20and%20 Anesthesia.doc Burd et al. Neonatal and childhood perioperative considerations. Surg Clin North Am. 2006;86(2):