Patricia M. Kenney, Deandra Hoover, Luther C. Williams and Victor Iskersky
Congenital heart disease (CHD) is the most common life-threatening birth defect encountered in the neonatal intensive care unit (NICU). Although the incidence of these conditions has remained constant at approximately 1% of all infants born in the United States, the methods of diagnosis and treatment have undergone tremendous change over the past several decades. 37 It is the responsibility of the practitioner to recognize the presence of CHD and to provide an accurate diagnose and treatment. This chapter reviews the physiology of neonatal circulation, the pathophysiology of congenital heart disease, and the most current evidence-based treatments.
CONGENITAL HEART DISEASE: OVERVIEW
History
In 1892, Dr. William Osler wrote that congenital heart disease was of “limited clinical interest as in a large proportion of cases the anomaly is not compatible with life, and in others, nothing can be done to remedy the defect or even relieve the symptoms.”8 Osler encouraged Dr. Maude Abbott in her CHD finding, and she, along with Dr. Helen Taussig and Dr. Alfred Blalock, suggested surgery to help these “blue babies.”35 This opened up the field of surgical treatment of cyanotic malformations of the heart. In 1938, Dr. Robert Gross was the first to successfully ligate a patent ductus arteriosus (PDA) in a 7-year-old girl at Boston’s Children’s Hospital. The first successful United States heart transplant was done at Stanford University by Dr. Norman Shumway in 1968. 7 What remarkable progress has been made in the area of congenital heart disease. This is the direct result of advances in pediatric and fetal cardiology, cardiac surgery, neonatology, and neonatal intensive care nursing.
Incidence and Survival
Each year, approximately 40,000 babies, or just under 1% of all babies born in the United States, are diagnosed with congenital heart disease. 3 Highly sensitive echocardiography has led to the detection of more trivial forms of congenital heart disease such as tiny ventricular septal defects. This inclusion has led to the higher incidence figures in recent years. The incidence of moderate to severe structural congenital heart defects (in liveborn infants) is 6 to 8 per 1000 live births. 8 Of these infants, approximately 3 per 1000 live births will have CHD that results in death or requires cardiac surgery during the first year of life. 25 Advances in diagnostic imaging, cardiac surgery, and neonatal intensive care have led to significant decreases in mortality rates. The death rate from all congenital heart defects declined nearly 32% between 1994 and 2004. 37
Embryology
The heart is one of the earliest differentiating and functioning organs. In human embryos, the heart begins to beat at about 22 to 23 days of life. Blood begins flowing through the heart in the fourth week of life. The heart develops from the cardiogenic mesoderm that originally lies above the cranial end of the neural tube. The heart forms initially as a simple paired tube inside the pericardial cavity. When the embryonic disk folds, the heart is carried into the correct anatomic position in the chest cavity. A key aspect of heart development is the septation of the heart into separate chambers. This complex process converts this simple tube into a four-chambered heart. Cardiogenesis is such as intricate, complex process that it is of little wonder that congenital heart defects occur.
Physiology
The physiologic changes that occur during the transition from intrauterine to extrauterine life have been well documented. To develop a clear understanding of the various congenital heart defects, knowledge of the basic principles of fetal circulation must be established.
FETAL CIRCULATION
Fetal circulation is intended to use the placenta for gas exchange, whereas postnatal circulation uses the lungs for gas exchange (Figure 24-1). Highly oxygenated blood from the mother enters the fetal circulation through the vein in the umbilical cord. This blood enters the inferior vena cava via the ductus venosus. Nearly one half of the umbilical venous blood goes through the liver and reaches the inferior vena cava via the hepatic veins. Inside the fetal heart, blood enters the right atrium, the chamber on the upper right side of the heart. Most of the blood flows to the left side through the foramen ovale, a special fetal opening between the left and right atria. Blood then passes into the left ventricle and then to the aorta, the large artery coming from the heart. From the aorta, blood is sent to the head and upper extremities. Therefore the brain (via the brachiocephalic vessels) and the heart (via the coronary arteries) are perfused with relatively highly oxygenated blood. After circulation, the blood returns to the right atrium through the superior vena cava. Nearly a third of the blood entering the right atrium stays in the right side of the heart, eventually flowing into the pulmonary artery.
 |
| FIGURE 24-1
(Modified from Patton KT, Thibodeau GA: Anatomy and physiology, ed 7, St Louis, 2010, Mosby.)
|
Fetal lungs are not used for breathing. The work of exchanging oxygen and carbon dioxide is done by the placenta. Because of high pulmonary vascular resistance (PVR), fetal circulation shunts most of the blood away from the lungs. Blood is shunted from the pulmonary artery to the aorta through a connecting blood vessel called the ductus arteriosus.29 Blood then enters the placental circulation and is resaturated.
CHANGES THAT OCCUR IN THE FETAL CIRCULATION WITH BIRTH
In utero, systemic vascular resistance (SVR) is low, primarily because of low resistance in the placenta. Conversely, the PVR is high, with the constricted and hypertrophied pulmonary arterioles being relatively resistant to blood flow. At birth, the placenta is removed from the circulation, thereby greatly increasing the SVR.
Both the labor process and the first few breaths of life begin the termination of fetal circulation and the transition to newborn circulation. Initiation of respirations produces increased oxygen tension, which decreases PVR and increases pulmonary blood flow. The ductus arteriosus is extremely sensitive to the oxygen content of the blood. As the neonatal Pa o2 rises, the connection between the aorta and the pulmonary artery (ductus arteriosus) is no longer needed and begins to close. Functional closure occurs at approximately 72 hours of life, and anatomic closure usually occurs between 1 and 2 weeks after birth. The circulation in the lungs then increases, and more blood flows into the left atrium of the heart. This increased pressure in the left atrium causes the foramen ovale to close. Anatomic closure of the foramen ovale can take several months. Finally, with the clamping of the umbilical cord, umbilical venous flow ceases and the ductus venosus begins to close, with anatomic closure taking approximately 1 to 2 weeks. 29
Once these changes occur, the newborn’s circulation resembles that of an adult (Figure 24-2). Desaturated blood returns to the heart by the inferior and superior venae cavae and enters the right atrium, right ventricle, pulmonary artery, and pulmonary circulation in which oxygen and carbon dioxide are exchanged. The saturated blood then returns to the heart through the pulmonary venous system and enters the left atrium, left ventricle, and ultimately the aorta and systemic arterial system. However, PVR and pressures in the right ventricle and pulmonary system remain elevated in the neonate because of the hypertrophy of the pulmonary vessels. This hypertrophy slowly resolves so that pulmonary vascular resistance and right heart pressures decrease to lower levels between 1 and 2 months of age.
 |
| FIGURE 24-2
(Modified from Hockenberry MJ, Wilson D: Wong’s essentials of pediatric nursing, ed 8, St Louis, 2009, Mosby.)
|
Etiology
The development of the cardiovascular system represents a complicated interaction between form and function. In most cases, the cause(s) of abnormal cardiac development is unknown. Traditionally, the etiology of congenital heart defects has been viewed as multifactorial, involving a complex interaction between genetic and environmental factors. Studies are being done on maternal zinc deficiency and its association with an increased risk for fetal heart malformations. These studies postulate that the mechanism of action is the suppression of HNK-1 expression. 19Table 24-1 lists the most common environmental risk factors and their associated cardiac malformations. Box 24-1 lists less common risk factors associated with CHD. Certain chronic illnesses in the mother contribute to the risk for CHD. For example, women with diabetes are at increased risk for having an infant with a heart defect. However, this risk can be greatly reduced by strict control of maternal blood sugar levels. More recent studies have found that the single greatest risk factor for congenital heart defects is genetic. Table 24-2 shows chromosomal syndromes and their associated congenital heart defects.
| Potential Teratogen | Frequency of Cardiovascular Disease (%) | Most Common Malformations |
|---|---|---|
| DRUGS | ||
| Alcohol | 25-30 | Ventricular septal defect, patent ductus arteriosus, atrial septal defect |
| Amphetamines | 5-10 | Ventricular septal defect, patent ductus arteriosus, atrial septal defect, transposition of the great vessels |
| Anticonvulsants | 2-3 | Pulmonary stenosis, aortic stenosis, coarctation of aorta, patent ductus arteriosus |
| Trimethadione | 15-30 | Transposition of great arteries, tetralogy of Fallot, hypoplastic left heart syndrome |
| Lithium | 10 | Ebstein’s anomaly, tricuspid atresia, atrial septal defect |
| Sex hormones | 2-4 | Ventricular septal defect, transposition of great arteries, tetralogy of Fallot |
| INFECTIONS | ||
| Rubella | 35 | Peripheral pulmonary artery stenosis, ventricular septal defect, patent ductus arteriosus, atrial septal defect |
| MATERNAL CONDITIONS | ||
| Diabetes | 3-5 | Transposition of great arteries, ventricular septal defect, coarctation of aorta |
| 30-50 | Cardiomegaly, myopathy | |
| Lupus erythematosus | ? | Heart block |
BOX 24-1
Exposure to Environmental Agents During Work and/or Hobby
• Paternal exposure to cold temperature
• Maternal exposure to various solvents, hair dyes, auto body repair work
Drug Exposure
• Diazepam, phenothiazines
• Corticosteroids
• Gastrointestinal drugs
• Paternal exposure to cocaine
Maternal Reproductive History
• Genetic risk factor (family history of congenital heart disease), more than three prior pregnancies and an increased number of miscarriages
• Without genetic risk but with premature births and previous induced abortion
Syndromic Association
• 27.7% of all cases had chromosomal anomalies, heritable syndromes, or an additional major organ system defect (see Table 24-2)
| Population | Incidence of Congenital Heart Disease (%) | Most Common Lesions | ||
|---|---|---|---|---|
| 1 | 2 | 3 | ||
| Trisomy 21 syndrome | 50 | Ventricular septal defect, endocardial cushion defect | Atrial septal defect | Patent ductus arteriosus |
| Trisomy 18 syndrome | 99+ | Ventricular septal defect | Patent ductus arteriosus | Pulmonary stenosis |
| Trisomy 13 syndrome | 90 | Ventricular septal defect | Patent ductus arteriosus | Dextrocardia |
| Turner syndrome | 35 | Coarctation of the aorta | Aortic stenosis | Atrial septal defect |
| DiGeorge syndrome 22q deletion syndrome | 50 | Truncus arteriosus | Tetralogy of Fallot | Interrupted aortic arch |
Since the 1990s, much progress has been made in understanding the genetics of heart disease. Studies in recent years have brought an explosion of information on the identification of potential candidate genes regulating heart development. 5 An example is the relationship between TBX-1 and cardiovascular defects seen in DiGeorge syndrome. 16 Mutations in NOTCH-1 have been found to cause aortic valve disease. 37 Although research defining the signaling cascades that lead to specific forms of congenital heart defects still needs to be done, 27 some information is well established (e.g., 50% of congenital heart defects involve a ventricular septal defect (VSD) alone or in combination with other abnormalities). Studies also demonstrate that preterm infants are two and a half times more likely to have cardiovascular (CV) malformations.32Table 24-3 shows the most common congenital heart defects and their time of presentation.
| *These numbers are intended as a rough guideline because there is considerable overlap. Infants with congenital heart disease are often active initially and appear well for several hours or days after birth. In contrast, infants with respiratory distress often have characteristic symptoms within the first several hours after birth. |
|||||
| From Flyer DC et al: Report of the New England Regional Infant Cardiac Program, Pediatrics 65:377, 1980. | |||||
| 0-6 Days | (%) | 7-13 Days | (%) | 13-20 Days | (%) |
|---|---|---|---|---|---|
| Transposition of great arteries | (17) | Coarctation of the aorta | (19) | Ventricular septal defect | (20) |
| Hypoplastic left ventricle | (12) | Ventricular septal defect | (15) | Transposition of great arteries | (17) |
| Lung disease | (10) | Hypoplastic left ventricle | (11) | Coarctation of the aorta | (16) |
| Tetralogy of Fallot | (9) | Transposition of great arteries | (9) | Tetralogy of Fallot | (8) |
| Coarctation of the aorta | (7) | Tetralogy of Fallot | (6) | Endocardial cushion defect | (6) |
| Ventricular septal defect | (7) | Heterotaxia | (4) | Heterotaxia | (6) |
| Pulmonary atresia (with intact ventricular septum) | (7) | Truncus arteriosus | (4) | Patent ductus arteriosus | (4) |
| Single ventricle | (4) | Total anomalous pulmonary venous return | (3) | ||
| Heterotaxia | (6) | ||||
| Other | (25) | Other | (28) | Other | (20) |
| Total 896 | (100) | Total 210 | (100) | Total 116 | (100) |
PRENATAL DIAGNOSIS
Because of the widespread use of antenatal ultrasound, it is increasingly common for the fetus to be diagnosed with congenital heart disease. Fetal echocardiography has proven to be a valid, reliable, and accurate tool in the prenatal diagnosis of CHD. 9 The recommended timing of a fetal echocardiogram is between 18 to 20 weeks’ gestation, although reasonable images can be obtained as early as 16 weeks. Physical examination alone picks up 30% of cases of CHD. 20 Pulse oximetry is not an accurate screening tool for CHD because of its relatively high false-positive rate, especially when used shortly after birth when the Sp o2 in neonates is low. 20 Recent studies are investigating serum high-sensitivity C-reactive protein (hs-CRP) and brain natriuretic protein (BNP) levels as markers of CHD. Thus far, hs-CRP and BNP levels are useful only as indicators of hypoxia. 33
Pregnant women are encouraged to undergo fetal echocardiography if (1) genetic evaluation determines that the fetus has a chromosomal or genetic syndrome associated with CHD, (2) the mother or a previous child has CHD, or (3) there is a family history of CHD. Box 24-2 lists CHDs that are diagnosed and CHDs that may be missed on fetal echocardiogram. Magnetic resonance angiography is also an important diagnostic tool, especially for lesions that may be missed by fetal echocardiography. Detailed postnatal examinations are critical in determining the full extent of cardiac malformation.
BOX 24-2
Accurately Diagnosed
• Hypoplastic left heart syndrome
• Tricuspid atresia
• Pulmonary atresia
• Truncus arteriosus
• Tetralogy of Fallot
• Atriovenous septal defects
• Large ventricular septal defect (VSD)
• Transposition of the great arteries
May Be Missed
• Coarctation of the aorta
• Small VSD/atrial septal defect (ASD)
• Total anomalous pulmonary venous return (TAPVR)
• Mild aortic or pulmonary stenosis
Data Collection
HISTORY
A family history of congenital heart disease is significant, since a sibling with CHD increases the recurrence risk threefold. Viral exposure during pregnancy (rubella, Coxsackie B, and enteroviruses) and maternal ingestion of alcohol or drugs should be evaluated. Pregnancy, labor, and delivery complications should be carefully examined as risk factors that could affect the cardiovascular system. For example, intrauterine hypoxia and perinatal hypoxia are risk factors for the development of myocardial dysfunction, as well as persistent pulmonary hypertension of the newborn (PPHN). The timing of the onset of symptoms may indicate the type of anomaly (see Table 24-3).
CLINICAL PRESENTATION OF INFANTS WITH SEVERE CARDIAC DISEASE
In many neonates, congenital heart disease is not suspected until after birth when the newborn presents with one or more signs or symptoms (see the Critical Findings box on p. 684). 36 Timing of presentation of signs or symptoms depends on severity of the defect, in utero effects of the defect, and alterations in cardiovascular physiology during transitional circulation (i.e., closure of the ductus arteriosus and the fall in PVR). Despite the presence of many heterogeneous forms of heart disease, a surprisingly limited number of signs and symptoms present in the neonate.
Murmurs
Heart murmurs are a common finding in neonates. Estimates of prevalence of heart murmurs in neonates range from 1% to 70% depending on the study. 8Although cardiac murmurs in the neonatal period do not necessarily indicate heart disease, they must be carefully evaluated. The absence of a murmur does not exclude severe life-threatening cardiac anomalies. Pathologic murmurs tend to appear at characteristic ages (e.g., murmurs associated with semilunar valve stenosis and atrioventricular valve insufficiency tend to be noted very shortly after birth). In contrast, murmurs caused by left-to-right shunt lesions (PDA, VSD) may not be heard until the second to fourth week of life. Therefore the age of the neonate when the murmur is first noted and the character of the murmur give important clues about the nature of the cardiac defect.
Cyanosis
Cyanosis (a bluish discoloration of the skin, nail beds, and mucous membranes) is one of the most common presenting signs of congenital heart disease in the neonate. Depending on the underlying skin complexion, clinically apparent cyanosis is usually not visible until there is more than 3 gm/dL of desaturated hemoglobin in the arterial system. 20 Cyanosis depends on both the severity of hypoxemia (which determines the percent of oxygen saturation) and the hemoglobin concentration. True central cyanosis should be differentiated from acrocyanosis, blueness of the hands and feet only, which is a normal finding in the neonate.
Cyanosis in the newborn must be differentiated between cardiac and respiratory causes. Pulmonary disorders cause cyanosis in the neonate because of intrapulmonary right-to-left shunting. Varying degrees of hypoxemia manifest as cyanosis and can be to the result of primary lung disease (see Chapter 23) and central nervous system abnormalities. Clinical cyanosis can occur without hypoxemia in a neonate with methemoglobinemia and polycythemia.
Respiratory Distress
Most infants with cyanosis from CHD do not have respiratory distress (e.g., tachypnea, intercostal retractions, grunting, nasal flaring, dyspnea, rales, cyanosis). Often the degree of cyanosis is not proportional to the degree of respiratory distress evaluated from the physical and chest x-ray examinations. If cyanosis is present and is caused by a fixed right-to-left shunt (cardiac lesion), increasing inspired oxygen will have little effect on the arterial blood gases. However, if the cyanosis is caused by a diffusion defect in the lungs (pulmonary disorder), the degree of cyanosis often decreases with increasing inspired oxygen.
The hyperoxia test is beneficial in differentiating respiratory disease from cyanotic heart disease. This single test is perhaps the most sensitive and specific tool in the initial evaluation of the neonate with suspected congenital heart disease and is used to investigate the possibility of a fixed (intracardiac) right-to-left shunt. The hyperoxia test is performed by obtaining arterial blood gas measurements (preferably from the right radial artery) when the infant is in room air and then after the infant has been in 100% oxygen for 5 to 10 minutes. If the Pa o2 is greater than 150 mm Hg, the presence of a right-to-left shunt and cyanotic congenital heart disease as the cause of cyanosis is unlikely. Pulse oximetry cannot be used for documentation.
Congestive Heart Failure
Congestive heart failure (CHF) occurs when the heart cannot meet the metabolic demands of the tissues. Signs and symptoms of congestive heart failure reflect decreased cardiac output and decreased tissue perfusion. In the early stages, the neonate may be tachypneic and tachycardic with an increased respiratory effort, rales, hepatomegaly, and delayed capillary refill. Edema caused by CHF is rarely seen in neonates. Diaphoresis, feeding difficulties, and growth failure later become apparent. Finally, congestive heart failure may present acutely with cardiorespiratory collapse, particularly with obstructive defects. Birth asphyxia and anemia must also be considered as causes of congestive heart failure in neonates.
The common symptoms associated with congestive heart failure (see the Critical Findings box on p. 685) can be understood using the physiologic principles previously outlined.
Tachycardia
The heart attempts to compensate for the decrease in cardiac output (CO) by increasing either the heart rate (HR) or the stroke volume (SV) (CO = HR × SV). Because the fetal myocardium has fewer contractile elements and is poorly innervated by the sympathetic nervous system, capacity to increase stroke volume is very limited. Therefore increases in cardiac output are achieved mainly by increasing the heart rate.
Congestive Heart Failure
• Tachycardia
• Cardiac enlargement
• Tachypnea
• Gallop rhythm
• Decreased peripheral pulses and skin mottling in the extremities
• Decreased urine output and edema
• Diaphoresis
• Hepatomegaly
• Decreased activity
• Failure to thrive and feeding problems
• Diminished cardiac output
Cardiac Enlargement
Hypertrophy and dilation of the heart occur in response to the volume or pressure overload. This enlargement is evident on chest x-ray examination.
Gallop Rhythm
The gallop rhythm is an abnormal filling sound caused by dilation of the ventricles. It is heard as a triple rhythm on auscultation.
Decreased Peripheral Pulses/Mottling of the Extremities
Decreased cardiac output results in a compensatory redistribution of blood flow to vital tissues. Peripheral tissue perfusion is decreased, which results in mottling of the skin and decreased pulses.
Decreased Urine Output and Edema
Decreased renal perfusion results in decreased glomerular filtration. The body interprets this as a decrease in intravascular volume and begins to initiate compensatory mechanisms such as vasoconstriction and retention of fluid and sodium. Neonates manifest this as weight gain and periorbital edema.
Diaphoresis
Congestive heart failure leads to an increase in metabolic rate and increased activity of the autonomic nervous system, resulting in diaphoresis. This is representative of the increased workload of the heart in failure.
Hepatomegaly
The right ventricle in congestive heart failure is less compliant and does not adequately empty. This leads to elevated pressures in the right atrium, central venous system, and hepatic system. Hepatomegaly results from hepatic venous congestion.
Decreased Activity and Exercise Intolerance
The decreased perfusion to peripheral tissues and the increased energy needed by the heart in failure leaves little energy for activities such as feeding and crying. The infant in heart failure may sleep the majority of the time.
Failure to Thrive/Feeding Difficulties
Tachypnea compromises the infant’s ability to feed. The basal metabolic rate increases in neonates with congestive heart failure. This necessitates a higher caloric intake (150 kcal or more).
Dysrhythmias
Abnormalities of the cardiac rhythm and murmurs are discussed individually later.
CARDIAC EXAMINATION
See “Specific Conditions” section.
LABORATORY DATA
Arterial Blood Gases
The Pa co2 in cardiac disease is often normal. It is usually increased if a primary pulmonary disease is present. Frequent monitoring of blood gases is unnecessary, but the acid-base balance should be monitored closely.
Four-Extremity Blood Pressure
The measurement of blood pressure should be taken in both arms and both legs. A systolic pressure that is more than 10 mm Hg higher in the upper body compared with the lower body is abnormal and suggests coarctation of the aorta, aortic arch hypoplasia, or interrupted aortic arch. However, this is a highly specific test with low sensitivity; the lack of systolic blood pressure gradient does not conclusively rule out aortic arch abnormalities.
Chest X-ray Examination
Frontal and lateral views (if possible) of the chest should be obtained. In neonates, the size of the heart may be difficult to determine because of the overlying thymus. Chest x-ray examination may be normal even in the presence of life-threatening CHD. However, the degree of pulmonary vascularity helps define the type of CHD present and is characterized as being increased, normal, or decreased. Likewise, the heart size should be evaluated and is described as being increased, normal, or decreased.
Electrocardiogram
Neonatal electrocardiogram (ECG) reflects the hemodynamic relationships that existed in utero. Many forms of CHD have minimal prenatal hemodynamic effects, and therefore the ECG is frequently “normal for age” despite significant structural defects (e.g., transposition of the great arteries, tetralogy of Fallot).
Echocardiogram
The echocardiogram is indispensable in the diagnosis of congenital heart disease. 4 Two-dimensional echocardiography, used to define cardiac anatomy, estimates pressures, measures gradients, and evaluates cardiac function21 and, supplemented with Doppler and color Doppler, has become the primary diagnostic tool in pediatric cardiology. Noninvasive transthoracic echocardiogram is the most commonly used approach. During the procedure, close monitoring is recommended with attention to vital signs, respiratory status, and temperature. Recently, three-dimensional echocardiograms (3D Echos) that offer real-time three-dimensional imaging with 2 Dx-matrix probe and reconstructed 3D imaging using spatiotemporal image correlation (STIC) techniques21 are being used.
Computed Tomography
More practitioners are finding 64-slice multidimensional computed tomography (64-MDCT) to be helpful in imaging some thoracic regions beyond the scope of echocardiograms, particularly after surgical revision. MDCT offers higher spatial resolution with shorter scan times. 31
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) offers three-dimensional reconstruction and high-resolution images of the heart and great vessels. The MRI is of particular use in evaluating extracardiac vascular abnormalities, such as arch anomalies, vascular rings, and pulmonary arteriovenous anomalies. MRI provides high spatial resolution, excellent soft-tissue definition, a large field of view, and unrestricted demonstration of cardiovascular morphology; however, it does require sedation and a stable patient, and it is expensive. 13
General Treatment Strategy
Optimal management of infants with heart disease requires specialized expertise. Infants are monitored closely for hypoxia, hypoglycemia, acidosis, and congestive heart failure.
The infant must be kept in an incubator or radiant heat warmer in which body temperature is maintained while color changes (pallor and increased cyanosis) may be observed. A cardiorespiratory monitor for continuous cardiac monitoring detects bradycardia, tachycardia, and dysrhythmias. Monitoring of oxygen saturations is helpful in determining adequacy of pulmonary blood flow and/or increased need for oxygen. Respiratory effort is assessed for tachypnea, shallow breathing, apnea, retractions, grunting, and nasal flaring. Observe and document activity level such as feeding behavior, muscle tone, spontaneous movement, and seizure activity.
MANAGEMENT OF CONGESTIVE HEART FAILURE
The medical management of congestive heart failure attempts to reverse the outlined process and helps the heart compensate with increased cardiac output.
Digoxin acts primarily as a positive inotropic (improves contractility) agent but decreases the heart rate and increases urine output (Box 24-3). Digoxin slows conduction at the atrioventricular (AV) node. This drug should be used with caution if acidosis, myocarditis, or obstructive lesions (e.g., tetralogy of Fallot, subvalvular pulmonary stenosis, asymmetric septal hypertrophy) are present. Diuretics such as furosemide (Table 24-4) help decrease total body water (which is increased as a result of congestive heart failure). In general, chronic fluid restriction and low-salt diets are not commonly used in newborns or infants with congestive heart failure.
BOX 24-3
| Digitalizing Schedule | |
|
Preterm infant
PO route: 20 mcg/kg total dose*
Term infant
PO route: 30 mcg/kg total dose*
|
Total dose is usually divided into three doses giving one half, then one fourth, then one fourth of the total dose q 8 hr. Check electrocardiogram rhythm strip for rate, PR interval, and dysrhythmias before each dose. |
| Maintenance Schedule | |
|
Preterm infant
PO route: 5-10 mcg/kg/day*
|
Total dose should be divided BID. Allow 12-24 hr between last digitalizing and first maintenance doses. It takes about 6 days to “digitalize” a patient with maintenance doses alone. The sign of digitalis effect is usually prolongation of the PR interval. The first sign of digitalis toxicity is usually vomiting, dysrhythmia, or bradycardia. |
|
Term infant
PO route: 5-10 mcg/kg/day
|
Drugs such as quinidine, amiodarone, and diuretics predispose to digoxin toxicity. The clearance of digoxin is directly related to renal function. Dosage must be reduced in patients with impaired renal function. |
| BID, Twice daily. | |
| *Intravenous (IV) dose is 75% of oral (PO) dose. |
|
| Standard Concentrations: Each institution’s concentration may vary; NOT to exceed maximum concentration per pharmacy reference manuals. | ||||
| Neonatal Drug Guidelines Updated May 7, 2002. | ||||
| BID, Twice daily; BP, blood pressure; BUN, blood urea nitrogen; CNS, central nervous system; ETT, endotracheal tube; GI, gastrointestinal; IHSS, idiopathic hypertrophic subaortic stenosis; IV, intravenous; IM, intramuscular; KCl, potassium chloride; kg, kilograms; Maint., maintenance; max, maximum; mcg, micrograms; mg, milligrams; min, minutes; NEC, necrotizing enterocolitis; NS, normal saline; PO, per os; PRN, as needed; q, every; QID, four times a day; TID, three times a day. | ||||
| Drug | Route | Dose | Onset of Action | Comments |
|---|---|---|---|---|
| Atropine | IV | 0.01-0.03 mg/kg/dose PRN (max 0.4 mg) | Seconds | May cause tachycardia, urinary retention, or hyperthermia |
| PO | 0.01-0.03 mg/kg/dose q 4-6 hr (max 0.4 mg) | Minutes | May cause tachycardia | |
| ETT | Give 2-3 times the IV dose followed by NS flush | Minutes | May cause tachycardia | |
| Calcium chloride (10% solution) | IV | 0.2-0.3 mL (20-30 mg)/kg/ dose q 10 min PRN (max 500 mg) | Minutes | Slow infusion; must be IV; potentiates digoxin, bradycardia |
| Calcium gluconate (10% solution) | IV | 1-2 mL/kg/dose (100-200 mg/kg/dose) q 10 min PRN (max 500 mg) | Minutes | Slow infusion (over 10-30 min); must be IV; potentiates digoxin, bradycardia/dysrhythmias |
| Captopril (Capoten) | PO | Younger than 2 months:
Initial dose: 0.1-0.25 mg/kg/dose q 8-24 hr
Titrate: up to 0.5 mg/kg/dose
Older than 2 months:
Initial dose: 0.3 mg/kg/day
Titrate: up to 6 mg/kg/day in 1-4 divided doses
|
15 min + | Hypotension, tachycardia, increased BUN and serum creatinine, hypercalcemia |
| Diazoxide (Hyperstat) | IV | 5 mg/kg/dose q 30 min PRN | 1-2 min | May cause hypotension or hypoglycemia |
| Dobutamine (Dobutrex) | IV | 2-10 mcg/kg/min | Minutes |
Do not use if IHSS or tetralogy of Fallot, may cause ventricular ectopy, tachycardia, or hypertension
Incompatible with alkaline solutions
|
| Dopamine (Intropin) | IV | 5-10 mcg/kg/min | Minutes | Tachydysrhythmia, vasoconstriction, gangrene of extremities, anginal pain, and palpitations can occur; inactivated in alkaline solution |
| Epinephrine (1:10,000) | IV/ETT | 0.1-0.3 mL/kg/dose (max 5 mL/dose) q 3-5 min PRN | Seconds | May cause tachycardia, dysrhythmias, or hypertension; not effective if acidosis is present |
| Esmolol (Brevibloc) | IV |
Loading dose: 500 mcg/kg/min
Continuous infusion: titrate 50-200 mcg/kg/min
|
Minutes | May cause bradycardia, hypotension, bronchoconstriction |
| Furosemide (Lasix) | IV | 1-2 mg/kg/dose | 5-15 min | May cause metabolic alkalosis and hypokalemia; monitor electrolytes—may need KCl supplementation; renal calcification |
| PO | 1-4 mg/kg/dose | 30-60 min | ||
| Hydralazine (Apresoline) | IV PO |
0.1-0.5 mg/kg q 3-6 hr 0.1-0.5 mg/kg q 6 hr; may increase to max of 2 mg/kg/dose q 6 hr |
15-30 min Often days until titrated effect achieved |
May cause lupus-like syndrome, tachycardia, or hypotension |
| Hydrochloro-thiazide (HydroDIURIL) | PO | 1-2 mg/kg q 12 hr | 1-2 hr | May cause electrolyte imbalance, may need KCl supplementation |
| Ibuprofen lysine (NeoProfen) | IV | 10 mg/kg first dose; then 5 mg/kg second and third dose (q 24 hr) |
Most effective in first 3 days of life
Monitor urine output and creatinine levels; discontinue drug if dramatic decrease in urine output
Significantly fewer adverse effects (compared with indomethacin) on renal and mesenteric blood flow; less oliguria and increase in serum creatinine levels
|
|
| Indomethacin (Indocin) | IV | 0.1-0.2 mg/kg/dose; may be repeated q 8 hr for a total of 3 doses |
Less effective if administered after 7 days of age; probably will have no effect after 14 days
Monitor urine output and creatinine levels; discontinue drug if dramatic decrease in urine output
Contraindications: severe renal impairment, active bleeding in the CNS or GI tract, and NEC10
|
|
| Isoproterenol (Isuprel) | IV | 0.1-0.4 mcg/kg/min | 30-60 seconds | May cause tachycardia/ventricular tachydysrhythmia; may also cause subendocardial ischemia |
| Lidocaine (Xylocaine) | IV |
IV bolus: 1-3 mg/kg
IV drip: 30-50 mcg/kg/min
|
May cause dysrhythmia, CNS agitation or depression | |
| Milrinone (Primacor) | IV |
Loading: 50 mcg/kg over 15 min
Maint.: 0.25-0.75 mcg/kg/min
|
May cause ventricular dysrhythmias, ventricular fibrillation, or hypotension | |
| Nitroprusside (Nipride) | IV | 1-10 mcg/kg/min over 10 min to control BP; chronic infusion: 2 mcg/kg/min (protect from light; change solution q 4 hr) | Seconds | May cause hypotension and reflex tachycardia; may cause thiocyanate toxicity, especially if decreased renal function is present |
| Phentolamine (Regitine) | IV | 1-20 mcg/kg/min | 5-10 min | May cause hypotension; commonly used with an inotropic agent |
| PO | 5 mg/kg/day QID | |||
| Phenytoin (Dilantin) | IV |
Load: 10-15 mg/kg over 5 min (slow infusion)
Maint.: 3-5 mg/kg/day BID
|
5-10 min | May cause cardiac depression |
| PO | 3-5 mg/kg/day BID | 2-4 hr | Therapeutic blood levels (5-20 mcg/mL) | |
| Procainamide (Pronestyl) | IV |
Load: 10-15 mg/kg/dose over 5 min (max 100 mg)
Maint.: IV 30-80 mcg/kg/min
|
1-5 min | May cause hypotension or lupus-like syndrome |
| IM | 5-8 mg/kg q 6 hr | 15-30 min | Same as for IV | |
| Propranolol (Inderal) | IV |
Dysrhythmias: 0.01-0.15 mg/kg/dose slow IV q 6-8 hr PRN (max single dose, 10 mg)
Hypercyanotic spell: 0.15-0.25 mg/kg/dose slow IV push q 15 min (max dose 10 mg)
|
2-5 min | May severely decrease cardiac output |
| PO | Dysrhythmias: 0.5-1 mg/kg/dose TID-QID (max daily dose 60 mg) Hypercyanotic spell: 1-2 mg/kg/dose QID | 30-60 min | Same as for IV | |
| Prostaglandin E 1 (Prostin VR) | IV |
Initial dose: 0.05-0.1 mcg/kg/min cont. IV infusion
Maint.: 0.01-0.05 mcg/kg/min cont. IV infusion
|
30 min | May cause apnea, fever, or hypotension |
| Spironolactone (Aldactone) | PO | 1-2 mg/kg/day | 3-5 days | Hyperkalemia, drowsiness, GI upset |
| Tolazoline | IV |
Test: 1-2 mg/kg slow IV push
Maint.: 1-2 mg/kg/hr
|
Minutes | May cause hypotension, GI or pulmonary hemorrhage |
| Adenosine | IV | 30-250 mcg/kg | Slows the spontaneous heart rate and prolongs the PR interval; may cause transient complete heart block and hypotension; half-life is only 9.3 seconds so its effects quickly dissipate | |
Infants with congestive heart failure may be difficult to feed, and the process is often frustrating. They may have trouble sucking, swallowing, and breathing simultaneously. They may have to rest frequently during a feeding, thus prolonging feeding times, and they may fall asleep exhausted before adequate caloric intake is achieved. Because caloric requirements are higher in infants with CHD, the use of higher caloric formulas may be of benefit. Adequate nutrition must be ensured by the following:
• Observing the infant’s ability to nipple feed (a soft, free-flowing [premature] nipple offers the least resistance to sucking and helps the infant conserve energy)
• Providing adequate calories for growth and, if necessary, using alternative feeding methods (i.e., gavage or continuous nasogastric drip) if the infant is sucking poorly
• Anticipating the infant’s hunger and offering feedings before the infant uses energy by crying
• Positioning the infant in a semi-erect position for feeding
• Burping the infant after every half ounce consumed to help minimize vomiting
• Weighing the infant daily and checking for appropriate weight gain
Before discharge from the nursery, the infant should be in stable condition (e.g., feeding well and gaining weight appropriately).
An important fact for families to understand is that many infants gain weight very slowly because of their cardiac defects, regardless of the method of feeding used. The family of an infant in congestive heart failure needs support and teaching. Explanation of the term congestive heart failure should be given early, because it is a frightening term for parents. The term “heart failure” is often interpreted as “heart attack” or “cardiac arrest.” Parents must understand that saying an infant is in heart failure does not imply that the infant’s heart will stop beating. A simple explanation describing heart failure as a condition in which the heart shows signs of being less able to pump sufficient blood to meet all the needs of the body helps decrease anxiety for the family.
SPECIFIC CONDITIONS
Patent Ductus Arteriosus
PHYSIOLOGY
The ductus arteriosus is a normal pathway in the fetal circulatory system and allows blood from the right ventricle and pulmonary arterial system to flow into the descending aorta for ultimate delivery to the placenta (Figure 24-3). Functionally, the patent ductus arteriosus (PDA) closes within a few hours to several days after birth, but this closure is often delayed in premature infants. After birth, as a result of a decrease in the pressure of the pulmonary circulation and an increase in the pressure of the aorta, the blood flow through a PDA is predominantly from the aorta to the pulmonary artery (left-to-right shunt). The hemodynamic changes and the resultant clinical manifestations of a PDA depend on the magnitude of the pulmonary vascular resistance and the size of the ductal lumen.
 |
| FIGURE 24-3
(Modified from Hockenberry MJ, Wilson D: Wong’s essentials of pediatric nursing, ed 8, St Louis, 2009, Mosby.)
|
Approximately 15% of infants with PDAs have additional cardiac defects (e.g., VSD, coarctation of the aorta, aortic stenosis, pulmonary stenosis). PDA can be associated with known syndromes, most commonly rubella.
DATA COLLECTION
History
Asphyxial insult or respiratory distress syndrome (RDS), inability to wean from a ventilator, and an increasing F io2 demand usually accompany PDA.
Physical Findings
Increased flow to the pulmonary circulation and volume overload of the left ventricle are the two major physiologic abnormalities in a PDA.
Cyanosis
Generally, cyanosis is not present in an isolated PDA, because the predominant shunt is from left to right.
Heart Sounds
Infants with a PDA may have an audible murmur as a result of the left-to-right shunting through the ductus during systole. A grade I through III systolic murmur is best heard at the upper left sternal border with radiation to the left axilla and faintly to the back. Although this murmur occasionally may spill into diastole, the classical continuous machinery-like murmur is an unusual occurrence in the newborn period. It is often helpful to briefly disconnect the newborn from the ventilator before auscultating. There are cases of large PDAs in which no murmur is audible.
Pulses
Because of the rapid upstroke and wide pulse pressure, the peripheral pulses are bounding. Pulses are hyperdynamic and easily palpated. Assessment of the pulses should include palpation of palmar, plantar, and popliteal pulses. The presence of an easily palpated pulse in these areas suggests the presence of an aortic run-off lesion, which is most commonly a PDA.
Congestive Heart Failure
Because of the volume overload of the left ventricle, the infant may show signs of congestive heart failure and pulmonary edema (see “Congestive Heart Failure” section).
Laboratory Data
Arterial Blood Gases
Arterial blood gas values are normal.
Chest X-ray Examination
Chest x-ray examination is normal in small shunts. Cardiomegaly is present with increased pulmonary vascularity in large shunts.
Electrocardiogram
The ECG may be normal, demonstrate left ventricular hypertrophy, or demonstrate combined ventricular hypertrophy.
Echocardiogram
Direct imaging is the preferred method both to diagnose patency and to determine the significance of the ductus arteriosus. An increased left atrial/aortic ratio suggests a moderate to large left-to-right shunt (i.e., PDA, VSD). An echocardiogram should be performed before medical or surgical closure of the PDA to rule out a ductal-dependent lesion or other associated anomalies. Color-flow Doppler mapping allows visualization of the PDA and aids in determining the size and direction of the shunt across the PDA (i.e., left to right, right to left, bidirectional).
Cardiac Catheterization
If the echocardiogram has eliminated a ductal-dependent lesion, cardiac catheterization is usually not necessary before treatment.
TREATMENT
Medical Management
Asymptomatic infants with PDAs generally do not require medical management or surgical ligation. These infants should be monitored for evidence of congestive heart failure, failure to thrive, increasing oxygen requirement, or other complications.
Symptomatic infants require ductal closure by either pharmacologic management with prostaglandin inhibitors such as indomethacin or ibuprofen lysine therapy (both are Food and Drug Administration [FDA]–approved cyclo-oxygenase [COX] inhibitors) or surgical ductal ligation. Medical management such as fluid restriction, watchful waiting, and ventilator support is rarely successful, especially in low-birth-weight infants. The current trend is to treat early presymptomatic therapeutic PDA at 2 to 3 days of age after a confirmed echocardiogram.30 Although indomethacin was first reported in the 1970s and became first-line therapy for the treatment of PDA, ibuprofen lysine has been shown to be equally effective in closure rates and may be preferable because of its better toxicity profile. 25Table 24-4
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