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Cardiac magnetic resonance imaging in the assessment of systemic and organ blood flow and the function of the developing heart

Key points Cardiac magnetic resonance (CMR) Imaging techniques provide noninvasive assessments of the newborn circulation with high accuracy and repeatability. Cine CMR produces three-dimensional assessments of chamber volumes and myocardial mass. Phase contrast CMR can quantify blood flow in any major vessel. CMR techniques have provided normative ranges for neonatal left and right ventricular development and quantification of PDA shunt volume and have guided optimization of…

Assessment of cardiac output in neonates: Techniques using the fick principle, indicator dilution technology, doppler ultrasound, electrical biosensing technology, and arterial pulse contour analysis

Key points Cardiac output monitoring in preterm and term neonates is feasible but remains challenging despite the availability of different technologies. The best systems to monitor cardiac output in the clinical setting in neonatal intensive care at present are transthoracic echocardiography, transpulmonary indicator dilution, electrical biosensing technology, and arterial pulse contour analysis. Noninvasive cardiac output monitoring is inversely related to accuracy; hence there will always be…

Advanced cardiac imaging in the newborn: Tissue doppler imaging and speckle tracking echocardiography

Key points Tissue Doppler imaging (TDI) is a modality that employs the Doppler effect to assess muscle wall characteristics throughout the cardiac cycles including velocity, displacement, deformation, and event timings. Two-dimensional speckle tracking echocardiography (2DSTE) is a non-Doppler technique that applies computer software analysis of images generated by conventional ultrasound techniques to assess parameters of myocardial motion (displacement, velocity) and deformation (strain, strain rate) in all…

Assessment of systemic blood flow and myocardial function in the neonatal period using ultrasound

Key points Echocardiography is useful for the assessment of systemic blood flow and myocardial function. Systemic blood flow is a dynamic and complex variable. Blood flow through persistent fetal shunts influences cardiac output measurements from both ventricles. Superior vena cava flow as a measure of cardiac input is a surrogate measure for global cerebral blood flow and systemic blood flow in the transitional period. Fractional shortening…

Ultrasound-guided hemodynamic management

Key points The use of Clinician Performed Ultrasound (CPU) in the care of sick and preterm neonates is rapidly expanding. The benefits of a portable, bedside technique that provides real-time, longitudinal data regarding the physiology of individual patients and allows more targeted treatment are being progressively recognized as important. CPU has an important role in managing the transitioning term or preterm infant, the septic/asphyxiated infant, the…

The immature autonomic nervous system, hemodynamic regulation, and brain injury in the early developing brain

Key points The autonomic nervous system (ANS) plays a key role in maintaining homeostasis in the critically ill preterm or term infant. Prematurity, an adverse intrauterine environment, and intrinsic fetal factors, such as congenital heart disease (CHD), may impact the development and function of the ANS. Autonomic dysfunction may have long-term health (e.g., adult hypertension) and psycho-affective consequences and can be associated with brain injury. Knowledge…

Transitional hemodynamics and pathophysiology of peri-/intraventricular hemorrhage

Key points A period of systemic and cerebral hypoperfusion in the immediate postnatal period predisposes the extremely preterm infant to peri-/intraventricular hemorrhage (P/IVH). Cardiovascular immaturity and maladaptation after birth contribute to postnatal hypoperfusion. Ventilatory support, especially inappropriately high mean airway pressure, can accentuate the early postnatal hypoperfusion. Following the initial hypoperfusion, a period of improvement in systemic and cerebral perfusion precedes occurrence of P/IVH on the…

Hemodynamic significance and clinical relevance of deferred cord clamping and umbilical cord milking

Key points Cardiorespiratory transition at birth is a complex series of changes in which the lungs replace the placenta as the organ of gas exchange and the main source of preload to the left side of the heart. Lung aeration, driven by spontaneous inhalations or mechanical inflation, is the key stimulus leading to pulmonary vascular relaxation. Umbilical cord clamping, prior to lung aeration, reduces cardiac output…

Neonatal cardiovascular drugs

Key points Highlighting the importance of understanding physiology prior to prescribing medications will enable the provider to choose the preferred regimen for each particular patient. Extrapolating data from older pediatric populations and adults must be done with caution, considering the unique physiology and differences in pharmacokinetics and pharmacodynamics in critically ill neonates and infants. Understanding the mechanism of action and therapeutic effects (both desired and side…

Cardiopulmonary interactions in the mechanically ventilated neonate

Introduction Cardiopulmonary interactions are crucial considerations in the intensive care management of critically ill neonates. The understanding of the impact of mechanical ventilation on the heart and lungs permits the prediction of a neonate’s response to the initiation or modification of positive pressure ventilation, or the effect of cardiovascular therapeutics. These interactions are guided by the laws of hydrodynamics as applied to a distensible or compressible…

Blood pressure and cardiovascular physiology

Key points In the context of neonatal care, invasive or noninvasive measurement of blood pressure can be accomplished with acceptable precision across all gestational age categories. Gestational and postnatal-age-dependent population-based normative blood pressure ranges are available. However, their usefulness in the assessment of adequacy of circulatory status remains limited. Interrogation of the individual components of the patient’s blood pressure may provide a greater understanding of the…

Vascular regulation and assessment of blood flow to organs in the neonatal period

Key points Multiple mechanisms operate to regulate blood flow to organs – these are also important in the newborn. Distribution of cardiac output is actively regulated. Autoregulation may best be described as a degree of capacity rather than an on-off phenomenon. Cerebral autoregulation, that is, the ability to buffer the effects of blood pressure on cerebral blood flow, is developed even at the limits of viability.…

Principles of developmental cardiovascular physiology and pathophysiology

Key points 1. A successful hemodynamic transition from fetal to extrauterine life is a complex process and requires the interdependent sequential physiologic changes to take place in a timely manner 2. Immaturity- or pathophysiology-driven disturbances of the transitional process may have significant short- and long-term consequences 3. Timely diagnosis and pathophysiology-targeted management of neonatal shock pose difficult challenges for the clinician 4. Many questions remain unanswered,…

Selected Procedures in Neonatology

Introduction Procedural skills are an important component of care in the neonatal intensive care unit (NICU). Procedures have inherent risks and can be the source of significant morbidity and mortality if the proper techniques are not applied. Historically, the acquisition of these competencies required that trainees observed a procedure and then attempted to perform it under close supervision. Obviously, although this practice served a laudable purpose,…

Normal Values

Chemistry Values Table C-1 Serum Magnesium, Calcium, Phosphate, and Alkaline Phosphatase in the First Month of Life (Mean ± SD) Modified from Noone D, Kieran E, Molloy EJ. Serum magnesium in the first week of life in extremely low birth weight infants. Neonatology 2012;101:274. Day of life Magnesium mmol/L Calcium mmol/L Phosphate mmol/L Alkaline Phosphatase IU/L 1 0.85 ± 0.14 2.18 ± 0.27 1.99 ± 0.48…

Ethical Issues

The mortality rate of imperiled newborns has decreased since the inception of neonatology as a specialty. Neonatologists are now able to save smaller and sicker infants, yet this decrease in mortality has not seen a concomitant decrease in severe morbidity such as impaired neurodevelopmental outcome. The lack of a decrease in morbidity is most apparent in those infants born extremely preterm or on the edge of…