12.4 Pediatric Cardiovascular Crises: Palliated Congenital Heart Disease, Pulmonary Hypertensive Crisis, Pericarditis & Tamponade, Hypertensive Emergency & Anterior Mediastinal Mass

Pediatric Cardiovascular Crises Beyond Shock and Arrhythmia

Children With Palliated Congenital Heart Disease

Many children with single-ventricle hearts live between staged surgeries. They are frequent transport patients, and their physiology differs from a normal heart.

Shunt thrombosis is an emergency. A stage 1 infant who suddenly becomes profoundly cyanotic, with the continuous shunt murmur gone, may have a clotted shunt. Management includes:

• Heparin per cardiology
• Oxygen
• Support of systemic blood pressure, because higher systemic pressure pushes more flow through the shunt
• Avoiding dehydration
• Urgent catheterization or surgery

Vomiting and diarrhea in these infants are dangerous for the same reason: dehydration and hemoconcentration promote shunt thrombosis.

Positive pressure in Fontan patients: Every breath under positive pressure raises intrathoracic pressure and reduces passive venous return to the lungs. If a Fontan patient must be ventilated, use the lowest effective PEEP, short inspiratory times, and adequate preload.

Pulmonary Hypertension and Pulmonary Hypertensive Crisis

Children with pulmonary arterial hypertension (idiopathic, CHD-associated, BPD-associated, or related to Down syndrome) can develop a pulmonary hypertensive crisis. Pulmonary artery pressure rises abruptly, the right ventricle fails, cardiac output falls, and the child becomes hypoxemic and hypotensive.

Triggers: Hypoxia, acidosis, hypercarbia, pain, agitation, endotracheal suctioning, hypothermia, and interruption of pulmonary vasodilators.

Management:

1. 100% oxygen and inhaled nitric oxide (Section 5.3).
2. Deep sedation and analgesia (and paralysis if ventilated) to blunt catecholamine surges.
3. Correct acidosis and hypercarbia. Mild alkalosis helps, but avoid extreme hyperventilation.
4. Support the right ventricle and systemic pressure. Keep systemic pressure above pulmonary pressure so the right coronary artery stays perfused (for example, norepinephrine or vasopressin for pressure, epinephrine for inotropy, and milrinone carefully because it can lower systemic pressure).
5. Avoid excessive PEEP and lung overdistension, which raise pulmonary vascular resistance.

Never interrupt a continuous IV prostacyclin infusion (epoprostenol or treprostinil). These drugs have short half-lives, and stopping them can cause rebound pulmonary hypertension and death. Bring the patient's pump, backup cassettes, and dosing information. Do not flush or draw from the dedicated line.

Pericarditis and Cardiac Tamponade

Pericarditis in children is most often viral or idiopathic. It can also be bacterial (purulent pericarditis, often S. aureus), post-pericardiotomy after cardiac surgery, uremic, or related to cancer or rheumatologic disease.

• Sharp chest pain relieved by sitting forward, a friction rub, and diffuse ST elevation with PR depression on the ECG.
• Uncomplicated viral pericarditis is treated with anti-inflammatory medications. Purulent pericarditis needs drainage and antibiotics.

Tamponade occurs when fluid compresses the heart and prevents filling:

• Tachycardia, hypotension, muffled heart sounds, and distended neck veins (Beck's triad, which is often incomplete in children)
• Pulsus paradoxus greater than 10 mmHg (the systolic pressure drop with inspiration is exaggerated)
• Electrical alternans and low-voltage QRS complexes
• An echocardiogram or bedside ultrasound confirms the effusion and chamber collapse.

Transport management:

• Maintain preload with a fluid bolus. The filling-limited heart depends on high venous pressure.
• Avoid positive-pressure ventilation and heavy sedation when possible. Both reduce venous return and can cause arrest. If intubation is unavoidable, use ketamine, keep the fluid bolus running, and have drainage ready.
• Pericardiocentesis (subxiphoid approach, directed toward the left shoulder, ideally guided by ultrasound) is the definitive rescue. Avoid diuretics and vasodilators.

Hypertensive Emergency

In children, hypertensive emergency means severely elevated blood pressure with acute end-organ injury:

• Hypertensive encephalopathy or posterior reversible encephalopathy syndrome (headache, vomiting, visual changes, seizures)
• Heart failure or pulmonary edema
• Acute kidney injury

Common causes: Renal disease (post-streptococcal glomerulonephritis, hemolytic uremic syndrome, chronic kidney disease), coarctation of the aorta, drugs (stimulants, corticosteroids), increased intracranial pressure, and rarely pheochromocytoma. Cushing's triad (hypertension, bradycardia, irregular respirations) signals increased intracranial pressure, not primary hypertension, and must not be treated by lowering blood pressure alone (Section 13.2).

Treatment principles (2017 AAP clinical practice guideline):

• Lower blood pressure gradually. The AAP recommends reducing it by no more than 25% of the planned reduction over the first 8 hours. The remainder is commonly spread over the next 24–48 hours. Rapid normalization can cause cerebral, retinal, and renal ischemia.
• Use titratable IV agents: nicardipine infusion, labetalol (bolus or infusion), or esmolol. Hydralazine is an intermittent option.
• Treat seizures, and monitor with an arterial line when possible.

Anterior Mediastinal Mass

Anterior mediastinal masses in children are most often lymphomas or T-cell leukemia, and sometimes germ cell tumors. They can compress the trachea, bronchi, superior vena cava, pulmonary artery, and heart.

Warning signs: Orthopnea (the child cannot lie flat), stridor, wheeze, cough, facial swelling and plethora, distended neck veins (superior vena cava syndrome), and syncope.

The central transport rule: Sedation, general anesthesia, neuromuscular blockade, and the supine position can cause sudden complete airway or cardiovascular collapse. Muscle tone and negative-pressure breathing hold the airway open. Positive pressure and relaxation remove that support.

Transport management:

• Keep the child in the position of comfort, often sitting up, leaning forward, or lying on one side. Preserve spontaneous breathing.
• Avoid sedation if possible. If airway intervention becomes unavoidable, it should happen with experienced anesthesia and surgical help and, ideally, rigid bronchoscopy and ECMO backup.
• If collapse occurs, change position (lateral or prone) to shift the mass off the airway.
• Superior vena cava syndrome: Place IV access in the lower extremities when possible.
• Anticipate tumor lysis syndrome once treatment begins, and coordinate diagnostic tissue sampling with oncology before steroids when the child is stable enough (Section 15.2).