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Melissa Aromin
Anesthesia Clerkship
Neonatal vs Adult Cardiac Physiology
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
Neonate Adult
Cardiac Output HR dependent SV and HR dependent
Contractility Decreased Normal
Starling Response Limited Normal
Compliance Decreased Normal
Afterload Compensation
Limited Effective
Physiological differences between neonatal and adult myocardium
ReferencesSwamy et al. Applied aspects of anatomy and physiology of relevance to pediatric anesthesia. Indian J. Anaesth. 2004;48(5):333-339.
Brasoveanu E. Neonatal physiology and anesthesia. www.bu.edu/.../05sprgmedanesthesiology/.../Neonatal%20Physiology/Neonatal%20Physiology%20and%20Anesthesia.doc
Burd et al. Neonatal and childhood perioperative considerations. Surg Clin North Am. 2006;86(2):227-247.