Congenital Heart Defect (CHD) – Acyanotic

Anesthesia Implications

Anesthesia Implications

Get a detailed medical history – understand all you can about what defect the patient has and how severe the symptoms are. Get surgical history, daily medications, hemodynamic status, and cardiac and lung function.

Reduce left-to-right shunt flow – Limit stress or anything that would stimulate sympathetic response. Opioids are often used to reduce/eliminate sympathetic responses to pain, laryngoscopy, etc. Use a slow/cautious induction. Volatile anesthetics, propofol, etomidate, and barbiturates all decrease SVR – so use cautiously.

Maintain MAP and SVR – Arterial lines and/or central lines are ideally employed to keep tight controls. These patients will not have optimal cardiac reserve.

Avoid airway obstruction, hypoventilation, hypoxia, and pulmonary hypertension – These create greater pressures on the right side of the heart and reverse the shunt (making it a cyanotic shunt). This is otherwise called Eisenmenger Syndrome.

Debubble – avoid any bubbles in venous lines. These can lead to a paradoxical embolus.

Cardiac bypass – complex congenital defects sometimes require this. Be aware that this may result in hemodilution!

Endocarditis prophylaxis – for 6 months post-surgical repair of the cardiac defect.

Pathophysiology

Acyanotic heart diseases – Ventricular Septal Defect (VSD) is the most common (20-25%). Others include Atrial Septal Defect (ASD), Atrioventricular Septal Defect (AVSD), Patent Ductus Arteriosus (PDA), Pulmonic Stenosis (PS), Aortic Stenosis (AS), and Coarctation of the Aorta (CoA)

Many of these conditions are managed medically (digoxin, diuretics, ACE inhibitors, adequate nutrition, etc). If medical management is unsuccessful, surgical repair is considered.

Disease characteristics – Acyanotic congenital heart diseases are characterized by a left to right intracardiac shunt or obstructive lesions (stenosis).

These defects lead to an increased pulmonary blood flow that puts extra strain on the right side of the heart. This leads to right atrial and ventricular enlargement and pulmonary hypertension.

If an acyanotic CHD is not caught in the early phases, pulmonary hypertension can become so severe that it leads to Eisenmenger Syndrome, which is a right-to-left, cyanotic shunt.

Risk factors for acyanotic CHD – maternal diabetes, maternal systemic lupus erythematosus (SLE), folic-acid deficiency during pregnancy, advanced maternal age, previous history of stillbirths and abortions, and maternal drug abuse.

Presenting problems – typically these defects are caught when the infant demonstrates feeding/exercise intolerance, poor weight gain, and delayed recovery from minor respiratory infections. Symptoms may include crackles on auscultation of the lungs, tachypnea, tachycardia, grade 3 holosystolic murmur with a thrill at the lower left sternal border, decreased urinary output, diaphoresis with feedings, failure to thrive, and cardiomegaly (right ventricular hypertrophy and a large pulmonary artery).

Diagnosis – Echocardiography, CXR, MRI, and cardiac catheterization

References

Nagelhout. Nurse anesthesia. 5th edition. 2014.
Yen. ASD and VSD flow dynamics and anesthetic management. Anesthesia Progress. 2015.
American Heart Association. Atrial Septal Defect. 2021. link
Centers for Disease Control. Facts about atrioventricular septal defects. 2019 link