Triage and Transport of Infants and Children with Cardiac Disease
2.4 Presentation and Stabilization
Stabilization is the shared responsibility of the referring facility, receiving institution, and transport team.
Stabilization always begins at the time of the initial transport request and is focused around procurement of a patent airway, establishing effective respiration, ensuring adequate circulation, and identifying hypo- glycemia or hypocalcemia.
For the purpose of this chapter, children with heart disease have been classified into four groups which are:
a. Defects with increased pulmonary blood flow b. Defects with decreased pulmonary blood flow c. Special considerations
d. Arrhythmias.
Each diagnosis will be discussed in terms of age of presentation and stabilization, following the ABC’s algorithm.
2.4.1 Defects with Increased Pulmonary Blood flow [1–4]
Congenital cardiac defects with increased pulmonary blood flow frequently present with signs of pulmo- nary overcirculation. These children present with the symptom of CHF around 3 months of age. Younger infants (less than 8 weeks of age) with CHF should be evaluated for left heart outflow tract obstruction as the symptoms may proceed the closure of a patent ductus arteriosus (PDA) and onset of shock. Other causes of CHF include cardiomyopathy, infectious myocarditis, and tachyarrhythmias.
2.4.1.1 Clinical Presentation
As mentioned before, patient assessment must begin with the ABC’s as recommended by the PALS and APLS curricula [6, 7]. Infants and children with lesions
resulting in CHF, present mainly with respiratory symptoms as a result of pulmonary edema or compli- cating infectious pneumonitis. A history from the parent(s) or care taker(s) will reveal a progressive increased work of breathing, poor feeding tolerance, and lack of weight gain. These children often appear Pale and thin but with normal length and head circumference.
A physical assessment reveals tachycardia, tachy- apnea with respiratory distress of varying degrees, and hepatomegaly. Auscultation of the lungs does not usu- ally reveal rales, more commonly found are wheezes;
however, some patients may present with clear breath sounds. These children rarely present with low cardiac output (CO) and shock, but more often are hypoxic and impending respiratory failure.
2.4.1.2 Chest Radiography
Chest radiograph will demonstrate cardiology with or without increased pulmonary vascular markings [9].
The lungs may be either atelectatic or hyperinflated secondary to airway obstruction from bronchial wall edema.
2.4.1.3 Stabilizing Intervention
The initial management of these patients should focus around alleviating hypoxemia, lessening respiratory distress, and preventing the need for endotracheal intubation. Oxygen should be administered immedi- ately to improve hypoxemia. Lowest concentrations, required to increase the arterial saturation level (SpO2) to an acceptable level, should be used, as oxygen is a potent pulmonary vasodilator and may worsen the left-to-right shunt. Infants with an increased work of breathing but maintaining adequate gas exchange should be administered intravenous diuretics such as furosemide [10]. If supplemental oxygen and diuretic therapy does not alleviate the respiratory distress or if the condition of the child worsens, endotracheal intubation should be considered.
In situations with poor cardiac function, an inotro- pic agent with peripheral vasodilatory properties should be initiated. Epinephrine and dopamine are useful; however, phosphodiesterase III inhibitors such as amrinone or milrinone may also be used [11].
If an infant requires high levels of inotropic support, other diagnosis such as sepsis should be considered.
• Atrial septal defects (ASD) and Ventricular septal defects (VSD) may result in pure volume overload of the right heart and lungs. If an infant or child presents with CHF, oxygen, inotropes, and diuresis are indicated. Moderate fluid restriction, mainte- nance fluid rates of 60–80 cc/kg/h/day may be help- ful in the absence of shock.
PDA refractory to Indomethacin therapy requires
•
transfer to pediatric tertiary care centers for surgical intervention. Oxygen should be used with caution in preterm infants with large PDA as it will further increase pulmonary overcirculation by decreasing PVR. If left untreated, the pulmonary overcircula- tion may result in pulmonary hypertension revers- ing the shunt thus resulting in hypoxia. A past medical history of a PDA may be associated with endocarditis in children.
• Truncus Arteriosus (TA) results in pulmonary over- circulation as the common “trunk” is exposed to systemic pressure causing a large left-to-right shunt.
Severe hypoxia is rare. Older children who are post- TA repair may present with CHF secondary to truncal insufficiency or conduit stenosis.
• In anomalous pulmonary venous return (APRV) clinical presentation depends on the number, loca- tion, and presence of obstruction within the anoma- lous connection(s). In infants with a total anomalous venous return (TAPVR), cyanosis may present in the neonatal period due to the elevated PVR limiting pulmonary blood flow. As the PVR drops, pulmo- nary blood flow increases and the SpO2 rises to the upper 80’s lower 90’s %. These infants usually present during first of age with right heart failure, unless there is an obstructed anatomic form, TAPVR, with venous obstruction usually presents in the first few days of life and requires urgent sur- gical intervention. Fluid overload must be avoided and initiation of prostaglandin E1 (PGE1) may not improve hypoxia in these infants as mixing occurs at the atrial and ventricular levels. However, PGE1 should still be started as some infants may have restricted mixing at the atrial level requiring a PDA for systemic blood flow (see chapter Anomalous Pulmonary Venous Return, by Tsifansky M, Munoz R, Kazmerski T, Kreuter J, Morell V). This lesion is difficult to differentiate from primary pulmonary hypertension (PPHN) in the transport environment.
2.4.2 Left Heart Outflow Tract Obstruction
Obstruction to systemic output is the most common cause of cardiogenic shock in infants less than 1 month of age. These infants may present with symptoms of CHF prior to ductal closing. Once ductal patency is lost, the infant appears “septic” due to low CO and profound metabolic acidosis. For this reason, septic shock is the principal differential diagnosis and the infant should be treated for both conditions until further diagnostic elucidation. Infants with left heart outflow tract obstruction often become symptomatic over hours, however, they may present as late as 8 weeks of age.
2.4.2.1 Clinical Presentation
Physical examination reveals tachyapnea with increas- ing respiratory distress or apnea, tachycardia, lethargy, irritability, hepatomegaly, and severe shock. Pulses may be weak or absent. Arterial blood gas analysis will reveal a severe metabolic acidosis (pH <7.20) with a low PaCO2, and mild hypoxia with a PaO2 between 50 and 70 torr. Hypoxemia is a result of pulmonary edema and/or right-to-left shunting across the PDA;
however, the addition of oxygen may constrict the PDA limiting systemic blood flow and should be used with caution in these patients.
2.4.2.2 Chest Radiography
Chest radiograph will reveal cardiomegly with pulmo- nary edema.
2.4.2.3 Stabilizing Intervention
The emergency stabilization of left heart obstruction focuses around re-establishing ductal patency and increasing systemic blood flow. PGE1 infusions are critical for reopening the ductus arteriosus providing a pathway for this to occur. When systemic blood flow is improved, peripheral pulses will return, urine output will increase, and the metabolic acidosis will slowly clear. Severe acidosis will decrease myocardial function and should be buffered with sodium bicarbonate (NaHCO3−). In cases where poor cardiac function is
present, intravenous inotropic support with dopamine and/or dobutamine should be initiated [11]. Amrinone or milrinone may be useful for increasing CO, peripheral vasodilatation, and lusitropic properties [11].
Endotracheal intubation is indicated in infants who have apnea, refractory shock, altered mental status (GCS
<8 or 3 less than baseline), or in those who’s respiratory status posses a risk of decompensation while en route.
Advanced airway management should also be consid- ered in infants receiving high dose PGE1 infusions as clinically significant apnea may occur [12]. Ventilator management should be aimed at preventing pulmonary overcirculation by maintaining a pulmonary to systemic perfusion (Qp:Qs) ratio of 1:1. [9, 12]. Maintaining arterial oxygen saturations between 80% and 85%, and a PaO2 in the 35–40 mmHg range is recommended [10].
• Aortic stenosis (AS) may present either during the immediate newborn period or childhood. Critical AS presents in the neonatal period when ductal patency is lost limiting systemic blood flow through a stenotic aortic value. Blood pressure in all four extremities will be low as the obstruction is below the root of the subclavian arteries.
Undiagnosed AS in the older child presents with a history of fatigue, dyspnea on exertion, and less commonly syncope. These children rarely require interfacility transport. However, children in this age group may suffer from restenosis following repair leading to severe aortic insufficiency and ultimately left heart failure.
• Coarctation of the aorta (CoA) may present as late as 8 weeks of age and should be considered in any infant within this age group who has signs of cardio- genic shock. Assessment of pulses will reveal signifi- cant difference in the carotids and upper extremities compared to the femoral and lower limbs. Blood pressure measurements should be performed and recorded in all four extremities. The blood pressure will be greater above the obstruction (right arm) and lower below the obstruction (legs). In the setting of an aberrant right subclavian artery, the pressure gra- dient may not be present.
• Hypoplastic left-sided heart syndrome (HLHS) commonly presents within the first 7 days of life.
Rapid deterioration occurs as the only source of systemic blood flow (PDA) closes resulting in profound cyanosis, hypotension, and metabolic acidosis. Endotracheal intubation and immediate initiation of PGE1 are indicated. These infants often
require inotropes and multiple boluses of Na HCO3− for pH buffering. Maintaining Qp:Qs ratio at 1:1 is essential for survival. Arterial blood gases should be in the ranges of pH 7.40, PaO2 35–40 mmHg, PaCO2 35–40 mmHg, HCO3− 24 mmol/L, and FiO2 should be set to achieve a SpO2 in the 70’s [10].
Sedation and paralysis may be useful in controlling the aforementioned parameters. If SpO2 rises and the metabolic acidosis worsens there is excessive pulmonary blood flow (Qp) and if the SpO2 drops there is too little pulmonary blood flow. Blood glucose and calcium level should be followed throughout transport.
2.4.3 Defect with Decreased Pulmonary Blood Flow
Cyanosis in the newborn presenting to a local community hospital without pediatric cardiology poses a significant diagnostic problem as the cause may be pulmonary, cardiac, or a combination of both. In a resource limited environment such as transport, distinctions must be made by obtaining an accurate familial and prenatal history, conducting a thorough physical exam, and utilizing specific lab data.
2.4.3.1 Clinical Presentation
Familial and prenatal history: Upon arrival, the trans- port team should quickly evaluate the family history for congenital heart defects, birth defects, syndromes, and early deaths [10]. A prenatal history should be reviewed for a maternal history of diabetes, or for any exposure to rubella, Coxsackie, or radiation. The onset of cyanosis and/or respiratory distress should also be noted as it may give important clues to whether the symptoms are related to the closure of the ductus arte- riosus or the development of sepsis.
Physical Examination: The physical assessment should begin with the appearance and level of respira- tory distress. Agitation, irritability, tachypnea, nasal flaring, grunting, and retractions suggest pulmonary pathology. Infants with cyanotic heart disease, usually have central cyanosis, appear comfortable with little to no increased work of breathing which is generally referred to as “quiet tachypnea.” Pre and post-ducal pulse oximetry is extremely useful in identifying the
presence of ductal shunting [13]. Evaluating the presence of differential cyanosis is also useful since blue upper extremities and pink lower extremities are highly suggestive of congenital heart disease.
2.4.3.2 Imaging and Laboratory Data
A chest X-ray with any of the following is suggestive of cyanotic heart disease: clear lung fields, cardiomegaly (cardiothoracic ratio >0.50), and decreased pulmonary vascular markings.
If any of the following are present, a hyperoxia test may be useful in identifying the etiology of the cyanosis.
A right to left shunt is likely when the PaO2 is
<200 mmHg in 100% oxygen [10].
Immediate intervention is indicated in any cyanotic infant whose arterial blood gas reveals a pH <7.28 or a PaCO2 >50 mmHg or a PaO2 <50 mmHg on a FiO2
³0.5 [10, 14].
2.4.3.3 Stabilizing Intervention
Prostaglandin E1 should be initiated in any situation where there is a high suspicion of cyanotic heart disease. Some have recommended intubation prior to transport in all infants who require PGE1 infusions to avoid clinically significant apnea and lessen the risk of severe hypoxia [10]. Further control in the respiratory status of the infant may be facilitated with the use of sedation and neuromuscular blockade.
• Tetralogy of fallot (TOF) in the newborn period may have little right-to-left shunting, occasionally referred to as “pink tetralogy.” A chest X-ray in this period may reveal a “boot shaped” heart. As the infant grows, the infundibular obstruction function- ably becomes more significant, increasing right-to- left shunting resulting in hypoxia. Sudden onset of severe hypoxia or “tet spells” commonly occur between 2 and 4 months of age for reasons includ- ing fever, dehydration, anxiety, pain, and manipula- tion of an artificial airway, as for example suctioning.
Tet spells are treated with supplement oxygen, administration of morphine sulfate and beta-block- ers, administration of volume, initiation of vasoac- tive agents to increase the systemic vascular resistance, or simply placing the child in the knee–
chest position [10]. Intubation may be indicated
which depends on the degree of cyanosis, acidosis, and the frequency of these hypercyanotic spells (see chapter Tetralogy of Fallot, by Chrysostomou C, Domnina Y, Kazmerski T, Morell V, Munoz R).
Endocarditis should be considered in febrile chil- dren with a history of TOF.
• Critical pulmonary stenosis (PS) and pulmonary atresia with intact ventricular septum cause obstruc- tion of forward flow across the pulmonary valve resulting in profound cyanosis. These infants require PGE1 infusions to ensure adequate pulmo- nary blood flow, and in the presence of ventricular dysfunction may require inotropic support [11].
Older children with progressive PS rarely present with cyanosis; if present, its usual cause is an ASD with a right to left shunt [10].
• Transposition of great arteries (TGA) is the most common cyanotic heart defect [10]. It should be sus- pected in any infant with isolated, central, and pro- gressive differential cyanosis: blue upper extremities and pink lower extremities. In the event there is little response from the administration of fluids, supple- mental oxygen, then the initiation of PGE1 is indi- cated; however, older infants may be unresponsive to the later and may require an urgent atrial septostomy to facilitate adequate mixing. Time to reach a pediat- ric tertiary center, where a emergent septostomy can be performed, is an important factor in the survival of these infants. Infants with an associated VSD may present in CHF. Inotropic support and diuresis are often indicated. Calcium should be monitored, keep- ing in mind the possibility of a DiGeorge syndrome.
2.4.4 Special Considerations
• Cardiomyopathy is a common etiology of pediatric heart failure. Dilated and hypertrophic cardiomyopa- thies are two types which pose a significant challenge to the transport team. Delineation of the two is based on clinical, hemodynamic, and structural features, of which there is some degree of overlap [14].
2.4.4.1 Clinical Presentation
Infants and children with either type present with symp- toms of CHF. However, in more seriously ill children, it
presents as cardiovascular failure and shock. Children with poor cardiac function will appear anxious with tachycardia, tachypnea, possibly with grunting, prolonged capillary refill, and hypotension. Hypotension results from low cardiac output and in the most severe cases, ful- minant pulmonary edema may be present. Stabilization is focused around decreasing myocardial workload on the failing heart while increasing its function.
2.4.4.2 Stabilizing Intervention
The level of cardiopulmonary compromise dictates the extent of stabilization. Noncritical patients may require only supplemental oxygen and diuretics to improve fluid homeostasis. In the most severe cases, airway control and work of breathing must be removed from the patient and controlled by the team. Removing the work associated with breathing will decrease the metabolic demands of both the respiratory muscles and heart, thus decreasing stress on the already failing cardiopulmonary system. In addition, a higher mean airway pressure will decrease intrapulmonary shunting created by the fluid filled alveo- lus. High levels of positive end-expiratory pressure (PEEP) should be used with caution as it may limit venous return to the heart. Following stabilization of the airway and breathing, continuous infusions of inotropic agents should be initiated. Sympathomimetic agents such as dopamine, dobutamine, and epinephrine have been advo- cated [15]. High doses of dopamine will amplify cardiac action but will also increase peripheral vasoconstriction, and may be proarrhythmogenic [15]. Amrinone or milri- none may also be useful in improving CO, promoting peripheral vasodilatation, and increasing systolic and possibly diastolic function [10]. Peripheral vasodilators such as nitroprusside and hydralazine may be useful in decreasing afterload [15]. In the presence of a metabolic acidosis, buffering with Na HCO3− is indicated, as severe acidosis further compromises myocardial function.
• Dilated cardiomyopathy (DCM) is the most common form of cardiomyopathy and a major reason for cardiac transplantation, with 31% of patients either succumbing to the disease or receiving transplanta- tion within 1 year of diagnosis [16]. This type of cardiomyopathy is characterized by ventricular dila- tion and systolic dysfunction. A chest radiograph will show cardiomegaly often with pulmonary venous congestion [14].
• Hypertrophic cardiomyopathy is primarily a disease of the myocardium which is distinguished by left
ventricular hypertrophy without ventricular dilation [14]. Typically, a chest radiograph is normal [14, 17].
This type of cardiomyopathy is the leading cause of sudden death in children and adults.
2.4.5 Arrhythmias
The transport team’s management of arrhythmias should be focused around those which may potentially, or at the time, be compromising hemodynamic stabil- ity. It is essential to assess and support the ABC’s, since, often the underlying cause of the arrhythmia is related to compromise of the airway, breathing, circu- lation, or hypoglycemia (Table 2.1) [6, 7, 18].
Most transport monitors used today have the capacity to record and print rhythm strips which are potentially useful in diagnosing the exact arrhythmia which occurred.
All strips should be saved in the presence of a suspected arrhythmia for a later evaluation by a pediatric cardiol- ogist. A continuous ECG strip should also be obtained during any attempt at converting the arrhythmia by noninvasive methods such as vagal maneuvers or infu- sions of antiarrhythmics agents. Recording the onset and/or termination of an arrhythmia offers vital clues in identifying the most successful method of management.
2.4.5.1 Tachyarrhythmias
• Supraventricular tachycardia (SVT) most com- monly occurs in infants under the age of 4 months and often presents as poor feeding, inconsolability, tachypnea, prolonged capillary refill time, and mot- tling [19]. It should be considered in any infant with a sudden onset narrow complex (£0.08 s) tachycar- dia with a heart rate 220 or more or in any child with a heart rate 180 or more. SVT is associated with Ebstein’s anomaly and with pre-excitation syn- dromes (i.e., Wolff-Parkinson-White syndrome).
Table 2.1 Treatable causes of arrhythmias: The four H’s and four T’s concept
Hypovolemia Toxins
Hypoxia Tamponade, cardiac
Hydrogen Ion (acidosis) Tension pneumothorax
Hypo-/Hyper-kalemia Thrombosis (coronary or pulmonary) Hypoglycemia Trauma (hypovolemia)
Hypothermia
Adapted from references [6, 7, 19]