Written by an expert author team at the renowned Boston Children's Hospital, USA, The Pediatric Cardiac Anesthesia Handbook provides a comprehensive yet concise overview of the anesthetic management of pediatric patients with congenital heart disease.
This book is divided into two parts. The first part provides an introduction to the basic assessment of patients, including cardiovascular physiology, pathophysiology and the underlying concepts in coronary heart disease, preoperative evaluation, intraoperative management, and interpretation of cardiac catheterization data. The second part of the book addresses disorders and diseases in a templated manner covering the anatomical and physiological features, surgical therapies, anesthetic approach and postoperative management. Chapters on the heart and heart and lung transplantation consider the additional complexities of those patients and anesthetic considerations for non-cardiac surgery after heart transplantation.
The anesthesiologist caring for patients with congenital heart disease faces a myriad of challenges in the perioperative management of these complex individuals. This book provides:
* A concise and easily referable guide ideal for use during anesthesiology residency training and fellowships.
* A templated chapter layout ideal for easy referral by wider members of the multidisciplinary team, such as cardiologists, cardiac intensivists, perfusionists, and surgeons.
* Helpful illustrations and a bulleted content for rapid reference.
* Guidelines on specific lesions for the pediatric anesthesiologist caring for cardiac patients presenting for non-cardiac surgery.
This book is a valuable resource for all anesthesiology and cardiac critical care providers who manage patients with congenital heart disease, and an ideal study aid.
Viviane G. Nasr, MD
Dr Nasr graduated from Medical School at the American University of Beirut (AUB), Lebanon in 2003, and pursued a residency in anesthesiology at AUB and Tufts Medical Center, Boston. She completed a pediatric anesthesia fellowship at Children's National Medical Center (CNMC) in Washington DC and a pediatric cardiac anesthesia fellowship at Boston Children's Hospital. She is American Board certified in Anesthesiology and Pediatric Anesthesiology and an active member of the Congenital Cardiac Anesthesia Society.
James A. DiNardo, MD
Dr DiNardo graduated from Dartmouth College and Dartmouth Medical School (with honors). He completed his anesthesia residency and fellowship in Cardiac Anesthesia at Beth Israel Hospital in Boston. He joined faculty at Boston Children's Hospital in 1999 where he currently serves as the Chief of the Division of Cardiac Anesthesia. He spend approximately one third of this clinical time as an Attending in the Cardiac ICU.
Dr DiNardo is certified in perioperative TEE and is former Chairman of the PTEeXAM Committee. He is also a Senior Oral Board Examiner for the ABA, a member of the ABA Pediatric Examination Writing Committee, and Chair of the Pediatric MOCA Examination Committee. He is Past-President of both the Congenital Cardiac Anesthesia Society and the Association of Cardiac Anesthesiologists. He is currently the Anesthesia and Analgesia Executive Editor for Pediatric Anesthesia.
He is the author of a major textbook on cardiac anesthesia and of more than 160 peer-reviewed articles and book chapters.
The incidence of congenital heart disease (CHD) is approximately 7 to 10 per 1000 live births. Most congenital heart defects are the result of an interaction of genetic predisposition and environmental factors. Environmental factors such as drugs, viral infection, maternal diabetes, or maternal alcohol abuse may account for specific lesions. Knowledge of cardiac development is a must to understand congenital heart lesions. This chapter reviews the embryology and cardiovascular physiology at birth.
It is essential to understand the basic embryology and origin of the cardiac structures in order to appreciate the specific lesions described in the next section of the Handbook. It is beyond the scope of this Handbook to discuss the details of cardiac development, including : (i) cardiac sidedness or asymmetry; (ii) cardiac looping; (iii) formation of outflow tracts; and (iv) septation. The embryologic structures and their corresponding adult structures are listed in Table 1.1.
Table 1.1 Cardiovascular embryologic structure and the corresponding structures in adults. Embryologic structure Adult structure
Truncus arteriosus Aorta
Pulmonary trunk Bulbus cordis Smooth part of right ventricle (conus arteriosus)
Smooth part of left ventricle (aortic vestibule) Primitive ventricle Trabeculated part of right ventricle
Trabeculated part of left ventricle Primitive atrium Trabeculated part of right atrium
Trabeculated part of left atrium Sinus venosus Smooth part of right atrium (sinus venarum)
Oblique vein of left atrium Aortic arches
1 * 2 * 3 Common carotid arteries
Internal carotid arteries (proximal part) 4 Right subclavian artery (proximal part)
Part of the aortic arch 5 Regresses in the human 6 Pulmonary arteries (proximal part)
Circulatory changes occur at birth and continue over the first few days and the first months of life, and are considerable. They need to be appreciated in order to understand their profound effects on neonatal cardiovascular physiology. It is not coincidental that 50% of the neonates born with CHD will become ill enough during the first days or weeks of life to require medical or surgical intervention. Optimal perioperative and anesthetic management of the neonate with CHD must be based on a firm understanding of these developmental changes.
Fetal circulatory channels shunt blood away from the lung such that both ventricles, in parallel, contribute to systemic oxygen delivery by pumping blood to the systemic arterial system. This parallel circulation permits normal fetal growth and development even in fetuses with cardiac malformations.
Oxygenated blood from the placenta returns to the fetus via the umbilical vein, which enters the portal venous system. The ductus venosus connects the left portal vein to the left hepatic vein at its junction with the inferior vena cava (IVC). This allows approximately 50% of umbilical venous blood to bypass the hepatic sinuses. The remainder of the umbilical venous flow passes through the liver and enters the IVC via the hepatic veins. Fetal IVC blood is a combination of blood from the lower fetal body, umbilical vein, and hepatic veins. The stream of blood from the ductus venosus has a higher velocity in the IVC than the stream from the lower body and hepatic veins. This higher velocity facilitates delivery of this higher-oxygen content blood across the foramen ovale (FO) into the left atrium (LA) (Figure 1.1).
Figure 1.1 Course of the fetal circulation in late gestation. Note the selective blood flow patterns across the foramen ovale and the ductus arteriosus.
Reproduced from Greeley, W.J., Berkowitz, D.H., Nathan, A.T. (2010) Anesthesia for pediatric cardiac surgery, in Anesthesia, 7th edition (ed. R.D. Miller), Churchill Livingstone, Philadelphia.
The IVC blood enters the right atrium (RA) and, due to the position of the Eustachian valve, Chiari network and FO, enters the LA during 80% of the cardiac cycle. During the other 20% (atrial systole), IVC blood crosses the tricuspid valve and enters the right ventricle (RV). The overwhelming majority of superior vena cava (SVC) blood crosses the tricuspid valve and also enters the RV. Blood from the RV is ejected into the pulmonary artery (PA). Approximately 10-15% of blood from the PA passes through the lungs to reach the LA, and the rest is shunted to the distal aorta via the ductus arteriosus (DA). As a result, two-thirds of the total fetal cardiac output is provided by the RV, with the remaining one-third provided via the LV.
The dynamics of shunting at the level of the ductus venosus, FO, and DA result in a preferential delivery of the most highly oxygenated blood to the coronary and cerebral circulations. Obviously, this preferential delivery of oxygenated blood may be compromised in utero by cardiac lesions that prevent or reduce left ventricular output. At birth, a series circulation is established in which each ventricle pumps into a specific vascular bed (RV to pulmonary artery; LV to aorta). The removal of the placenta and the initiation of alveolar ventilation at birth have the immediate effect of establishing this series circulation. To maintain the adult series circulation, the fetal channels must be closed (Table 1.2). Complex neurochemical and hormonal influences affect the closing of these fetal shunts. Acidosis, sepsis, hypothermia, hypoxia and hypercarbia may cause a re-opening of the shunts and persistence of the fetal circulation (PFC). Most neonates that are critically ill from CHD have one or more of these inciting factors at the time of presentation. In some instances, the persistence of fetal circulatory channels may be beneficial or even mandatory for survival.
Table 1.2 Fetal structures and their corresponding structure in adults. Fetal structure Adult structure
Foramen ovale Fossa ovalis Umbilical vein Ligamentum teres Ductus venosus Ligamentum venosum Umbilical arteries Medial umbilical ligaments, superior vesicular artery Ductus arteriosus Ligamentum arteriosum
Closure of the Ductus Arteriosus
In the fetus, patency of the ductus arteriosus is maintained by high levels of prostaglandins (PGI2 and PGE1). There are two stages of ductal closure in the newborn: functional closure, and permanent anatomic closure. Functional closure occurs by contraction of the smooth muscle of the ductal wall and usually occurs within the first day of life. An increase in PO2 and a decrease in prostaglandin levels contribute to functional closure. Oxygen is a dose-dependent ductal constrictor that acts by increasing the rate of oxidative phosphorylation within smooth muscle cells. In addition, the response to oxygen may be age-related; full-term neonates have a more dramatic response to oxygen than an immature newborn. Norepinephrine and epinephrine, by changing pulmonary and systemic vascular resistances, may secondarily contribute to ductal closure. Acetylcholine has a direct constrictor effect on ductal tissue. Permanent anatomic closure of the duct usually is accomplished by two to three weeks of life in the normal full-term neonate. The lumen is sealed by fibrous connective tissue, leaving the vestigial structure, known as the ligamentum arteriosum.
The survival of some neonates with congenital cardiac lesions is dependent on ductal patency. Because functional closure is a reversible event, the use of PGE1 infusions (0.01-0.05?µg?kg-1 min-1) has been one of the major medical advances in the stabilization of neonates with ductal-dependent heart lesions. Preterm neonates are at risk of delayed ductal closure. This may be due to a decreased degradation of PGE1, an increased production of PGE1, or a diminished sensitivity to the ductal-constricting effects of oxygen. In instances in which delayed ductal closure is disadvantageous, prostaglandin inhibitors such as indomethacin (0.1-0.3?mg?kg-1 PO or IV) have been used successfully to promote ductal closure and establish normal patterns of pulmonary blood flow.
Closure of the Foramen Ovale
In utero, the right atrial pressure is higher than the left atrial pressure. IVC blood flows in such a manner as to keep the FO open. The cessation of umbilical vein flow causes a significant decrease in venous return to the right heart, leading to a decrease in right atrial pressure. In addition, ventilation causes a marked increase in pulmonary arterial and venous blood flows, resulting in an increase in...