DECREASED PULMONARY BLOOD FLOW
Overview
Decreased pulmonary blood flow results from the shunting of deoxygenated blood from the right side of the heart to the oxygenated left side of the heart (Nelson, Hirsch-Romano, Ohye, & Bove, 2015). Infants born with heart defects that cause a decrease in pulmonary blood flow present with cyanosis and hypoxemia because of a lack of blood flow to the lungs. The systolic and diastolic pressures on the right side of the heart exceed those on the left because of some form of obstruction to pulmonary blood flow, leading to this right-to-left shunting. Congenital heart defects (CHDs) that result in decreased pulmonary blood include tetralogy of Fallot (TOF), pulmonary atresia, tricuspid atresia, and pulmonary stenosis.
Background
TOF accounts for approximately 4% of CHDs (Nelson et al., 2015). The classic description of TOF includes (a) the presence of a ventricular septal defect (VSD), (b) some form of right ventricular outflow track obstruction, (c) overriding of the aorta, and (d) right ventricular hypertrophy (Hockenberry & Wilson, 2015). The degree of cyanosis is often determined by the severity of the right ventricular outflow tract obstruction. The obstruction to the right ventricular outflow tract in TOF patients can start below the pulmonary valve and extend all the way out to the branches of the pulmonary arteries. If the obstruction is severe and degree of cyanosis is significant in the neonatal period, a palliative or temporizing procedure is often performed to increase oxygen saturation and therefore increase pulmonary blood flow (Hockenberry & Wilson, 2015). Complete repairs are generally performed in the first year of life. The operative mortality for total correction of TOF is less than 3% (Hockenberry & Wilson, 2015).
Pulmonary atresia is a relatively rare defect and accounts for approximately 1% of all congenital heart lesions (Park, 2016). In this disorder, the pulmonary valve is absent or atretic and the intraventricular septum can be either intact, or accompanied by a VSD. This particular anatomy, where the intraventricular septum is intact, leads to an absence of blood exiting the right ventricle into the main pulmonary artery (Nelson et al., 2015). Patients born with this disorder must have an interatrial communication (either atrial septal defect or patent foramen ovale) or the presence of a patent ductus arteriosus (PDA) to allow for adequate pulmonary blood flow and cardiac output after birth. To maintain patency of the ductus arteriosus, intravenous prostaglandin E1 (PGE1) is administered (Park, 2016). The size of the right ventricle and pulmonary arteries determines the type and success of surgical repair. If the size of the right ventricle 136and pulmonary arteries is adequate, a two-ventricular repair can be performed. If the size or function of the right ventricle is inadequate, a single ventricle palliative approach may be necessary (Nelson et al., 2015). The survival rate of pulmonary atresia varies and is determined by a biventricular repair, single ventricle palliation, or cardiac transplantation.
Tricuspid atresia accounts for 1% to 3% of all CHDs (Park, 2016). Tricuspid atresia, a complete lack of a tricuspid valve, results in the absence of direct communication between the right atrium and right ventricle (Nelson et al., 2015). Pulmonary blood flow is achieved when deoxygenated blood flows or shunts across an atrial septal defect from the right atrium to the left atrium, then to the left ventricle, through a VSD and out to the lungs (Hockenberry & Wilson, 2015). The complete mixing of oxygenated and unoxygenated blood in the left atrium results in systemic desaturations and hypoxemia (Hockenberry & Wilson, 2015). This particular lesion is treated in three stages. The first-stage palliation for the majority of patients occurs in the newborn period and is the placement of a systemic to pulmonary artery shunt (modified Blalock–Taussig shunt) to maintain adequate pulmonary blood flow. The second procedure, referred to as the Glenn procedure, connects the superior vena cava directly to the pulmonary artery. In the third procedure, the Fontan, a direct connection between the inferior vena cava and pulmonary artery is created, thus completing the full separation of oxygenated and deoxygenated blood. All blood flow to the lungs is now passive and the single ventricle is solely responsible for pumping oxygenated blood to the body. The overall survival for tricuspid atresia is approximately 83% at 1 year, 70% at 10 years, and 60% at 20 years (Nelson et al., 2015).
Isolated pulmonary stenosis accounts for 10% of all CHDs and is defined as a thickening of the pulmonary valve at the entrance of the main pulmonary artery (Jone, Darst, Collins, & Miyamoto, 2016). This thickened pulmonary valve leads to variable levels of obstruction to pulmonary blood flow resulting in an increase in the right ventricular pressure that can be potentially life threatening (Jone et al., 2016). Neonates with severe pulmonary valve obstruction and minimal pulmonary blood flow present with cyanosis at birth (Jone et al., 2016). To minimize the patient’s degree of cyanosis, the patency of the ductus arteriosus must be established with prostaglandins. Then the decision to treat the patient with either a balloon angioplasty of the pulmonary valve or surgical treatment with the placement of a modified Blalock–Taussig shunt is made. Long-term outcomes after balloon valvuloplasty are favorable; however, restenosis or valve incompetence may occur later in life (Hockenberry & Wilson, 2015).
Clinical Aspects
ASSESSMENT
Patients born with TOF can either present with cyanosis at birth, or develop it over time as the subvalvular obstruction increases (Jone et al., 2016). The patient’s physical examination is positive for a grade II to IV/VI systolic ejection murmur that is heard best at the left sternal border in the third intercostal space 137and radiates to the lungs. Extreme cyanosis or hypoxic episodes occur causing severe “blue spells” or “tet spells.” Hypercyanotic spells are defined as a sudden onset of cyanosis or deepening of cyanosis. Infants have dyspnea, alterations in consciousness, from irritability to syncope with a decrease or disappearance of the systolic murmur (Jone et al., 2016).
Infants with pulmonary atresia present with cyanosis at birth and as the ductus arteriosus closes, they will become more cyanotic (Jone et al., 2016). These patients have a continuous murmur because of the PDA (Park, 2016). To maintain pulmonary blood flow, patency of the ductus must be achieved with infusion of prostaglandins until surgery can be performed (Jone et al., 2016).
Infants with tricuspid atresia usually present with cyanosis at birth as well as tachycardia, tachypnea, and increased work of breathing (Hockenberry & Wilson, 2015). If there is a significant increase in pulmonary blood flow, they may develop symptoms of congestive heart failure, such as sweating, tachypnea, poor oral intake and increased time to orally feed, resulting in poor weight gain (Jone et al., 2016). A grade III/VI systolic murmur from the VSD is often heard at the lower left sternal border (Park, 2016).
Patients with pulmonary stenosis have variable presentations. Those with mild pulmonary stenosis are usually asymptomatic. Infants with severe pulmonary stenosis present often with hypoxic spells, failure to thrive, and right-heart failure (Nelson et al., 2015). The murmur of valvular pulmonary stenosis is an ejection click heard best at the upper left sternal border. A low-pitched murmur indicates less severe pulmonary stenosis (Park, 2016). Those patients may be followed symptomatically with mild to moderate pulmonary stenosis. Catheter-based intervention or surgical intervention should be considered for a gradient higher than 50 mmHg, progressive ventricular hypertrophy, or new tricuspid regurgitation.
NURSING INTERVENTIONS, MANAGEMENT, AND IMPLICATIONS
Nursing-related issues for infants with decreased pulmonary blood flow can vary depending on the lesion. These infants can experience cyanosis, dyspnea, tachycardia, irritability, and feeding difficulties.
It is important to become informed about the infant’s cardiac anatomy and baseline clinical presentation in order to intervene when changes occur. The nurse should assess and record heart rate, respiratory rate, breath sounds, blood pressure, and pulse oximetry readings. Oxygen administration and nasopharyngeal suctioning may be required to maintain appropriate pulse oximetry and reduce respiratory distress. Any prescribed cardiac medications need to be given at the scheduled time and monitored for any side effects or signs and symptoms of toxicity, which should be reported and documented (Hockenberry & Wilson, 2016).
The nurse can decrease cardiac demands by minimizing unnecessary stress and stimulation. Nursing interventions must focus on providing maximum rest and comfort care such as offering nonnutritive sucking and swaddling. In order to promote energy conservation, nursing must organize activities that allow for uninterrupted sleep (Hockenberry & Wilson, 2016). In order to provide adequate 138nutrition, infants should be fed in a semi-upright position and be offered small, frequent feedings.
Cyanotic infants must be well hydrated in order to maintain good cardiac output and to minimize their risk for cerebral vascular accidents because of polycythemia (Hockenberry & Wilson, 2016). Infants with decreased pulmonary blood flow are at risk for hypercyanotic spells, which occur suddenly and are typically observed in the setting of extreme agitation or painful stimulation. The interventions to reverse hypercyanotic spells center around promoting an increase in pulmonary blood flow and include the following: place infant in a knee–chest position, calm the infant with comfort measures, administer 100% oxygen, give intravenous morphine, begin fluid replacement and volume expansion (Hockenberry & Wilson, 2016).
In any patient born with a cardiac defect, alteration in parenting related to the perception of the infant as vulnerable may be present. These families experience periods of shock, followed by tremendous anxiety and oftentimes fear that their child may die (Hockenberry & Wilson, 2016). Nurses are instrumental in dealing with parental stress; providing support and education; and participating as an interdisciplinary team member in order to care for both the infants and their families.
OUTCOMES
Patients with congenital heart disease have outcomes specific to evidence-based nursing practice that focus on assisting the patient to demonstrate an improvement in cardiac function, a decrease in cardiac demands, and optimal blood flow to the lungs (Hockenberry & Wilson, 2016). Improvement in cardiac function occurs when there is a decrease in the afterload of the heart, thereby increasing the overall cardiac output.
Summary
Infants born with TOF, pulmonary atresia, tricuspid atresia, and pulmonary stenosis are at increased risk for decreased pulmonary blood flow because of an interruption of blood flow leaving the right side of the heart and entering the lungs. They may experience cyanosis, feeding issues, and inadequate weight gain. Many of these infants undergo palliative or corrective surgery within the first few weeks of life. Understanding each specific patient’s cardiac anatomy is imperative to caring for the infant effectively. Providing efficient and holistic nursing care to hospitalized infants with congenital heart disease results in increased survival and quality of life in this vulnerable patient population.
Hockenberry, M., & Wilson, D. (2015). Wong’s nursing care of infants and children (10th ed.). St. Louis, MO: Elsevier Mosby.
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