Tetralogy of Fallot

-Tetralogy of Fallot (TOF) is a congenital cardiac abnormality. The primary defects are pulmonary infundibular stenosis and ventricular septal defect (VSD). The VSD is sufficiently large for the pressure in both ventricles to be equal to that of the aorta. The tetralogy is completed by two secondary features, a variable degree of overriding of the aorta, and right ventricular hypertrophy.

-Dynamic right ventricular outflow obstruction may occur (infundibular spasm), which is accentuated by sympathetic stimulation. The fraction of the right to left-shunt depends primarily upon the relative resistances between the pulmonary (or right ventricular) and systemic outflows.

-If TOF is associated with patent foramen ovale (PFO) or atrial septal defect (ASD), it is a Pentalogy of Fallot.

-The aim of the surgery is to relieve the right ventricular outflow obstruction and to close the VSD. The traditional management by a two-stage repair has been replaced by definitive correction. Recent surgical advances include conduits to connect the RV to the PA and transatrial repair of the VSD.

The problems encountered during anesthesia will depend upon whether or not corrective surgery has been undertaken, and the functional result.

Preoperative Findings:

1. Dyspnea may occur on exertion and is hypoxia-related. Cyanosis and finger clubbing are variable, depending on the degree of pulmonary stenosis and the size of the shunt. Polycythemia (erythrocytosis) is common. There is a pulmonary stenotic murmur, but no murmur from the VSD because of the size of the defect. Squatting is thought to reduce the fraction of the shunt since kinking the large arteries increases systemic vascular resistance. Squatting is commonly seen in children with uncorrected lesions.

2. ECG shows right atrial and right ventricular hypertrophy, right axis deviation, and right bundle branch block.

3. Echocardiography shows right atrial and right ventricular hypertrophy, VSD, PFO or ASD, pulmonary hypertension, and overriding of the aorta.

4. Chest X-ray shows right ventricular hypertrophy and oligemic lungs. In the 2.6–6% of individuals who also have an absent pulmonary valve, aneurysmal dilatation of the pulmonary arteries may cause bronchial compression.

5. Initial surgery may have been undertaken to anastomose a systemic to a pulmonary artery, to improve the pulmonary blood flow, and reduce cyanosis. A definitive procedure is now more commonly undertaken in infancy.

6. In patients who have undergone shunt surgery without a definitive repair, there is chronic hypoxia and polycythemia. These patients have a high mortality, and an increased risk of bacterial endocarditis, thrombotic stroke, emboli, and intracerebral abscess.

7. In adults who have undergone repair there is an increased risk of arrhythmias, conduction defects, and sudden deaths, possibly related to mechanical events, such as ventricular dilatation and stretch, in the proximity of the conduction system. However, new approaches to surgery may result in a lower incidence of such problems in the future.

Anesthetic Problems:

1. In individuals with uncorrected lesions, the right to left shunt, and hence the cyanosis, is increased by a reduction in systemic vascular resistance produced by systemic vasodilatation. This may result from factors such as hypovolemia, drug effects, or pyrexia.

2. Cyanosis is also worsened by an increase in pulmonary vascular resistance or spasm of the right ventricular infundibulum. Right ventricular outflow obstruction is due to increased contractility which is produced by increases in catecholamine output or the administration of drugs with positive inotropic effects. Anxiety, pain, hypercarbia, hypoxia, and acidosis are all precipitating factors. These cyanotic attacks or ‘tet’ spells, which can occur when awake or under anesthesia, may initiate a cycle of increasing hypoxia that can result in cerebral damage or death. Direct intraoperative observations of shunt direction and flow have been made with Doppler color flow imaging using epicardial leads. Patients with severe life-threatening hypoxemic spells, refractory to other treatments, responded to phenylephrine (5 mcg/kg plus an infusion of 0.4–2 mcg/kg/min).

3. Dehydration in the presence of polycythemia and high plasma viscosity may combine to increase the incidence of cerebral thrombosis. Polycythemia may also be associated with coagulation defects.

4. In patients with an absent pulmonary valve, positional airway compromise occurred secondary to bronchial compression of dilated pulmonary arteries.

5. A significant incidence of tracheal anomalies has been found.

6. In adults who have undergone repair, ventricular and atrial arrhythmias are common, particularly during exercise. It has been suggested that patients scheduled for elective surgery should have Holter monitors, or undergo exercise testing, in case antiarrhythmic treatment is needed first.

7. Cyanosed patients with Fallot’s rarely become pregnant. However, adults who have undergone corrective surgery are increasingly present during pregnancy with a favorable outcome.

Anesthetic Management:

1. Antibiotic prophylaxis against bacterial endocarditis.

2. A good premedication (morphine sulphate, or midazolam) to prevent excitement and anxiety.

3. In patients with cyanosis, measures are aimed at reducing the right to left shunt. Specific treatments for cyanotic attacks include:

a) Oxygen 100% to decrease PVR.

b) Pressor agents, such as phenylephrine (5-10 mcg/kg), to increase systemic vascular resistance.

c) Fluids to correct hypovolemia.

d) Propranolol (0.1 mg/kg) or Esmolol (0.5 mg/kg) to decrease outflow tract obstruction (decrease contractility and infundibular spasm).

e) Deepening of light anesthesia to reduce tachycardia associated with catecholamine output.

f) Compression of the femoral artery or the abdominal aorta against the vertebrae, sufficiently firmly to stop the femoral artery pulsations.

4. Techniques to avoid hypoxia and hypercarbia, and minimize vasodilatation and sudden increases in cardiac output. Ketamine, and Morphine sulphate (0.05-0.1 mg/kg), have been used.

5. Hydration is maintained in the perioperative period and, if there is severe polycythemia, venesection may be necessary.

6. Metabolic acidosis should be prevented or treated with sodium bicarbonate (1-2 mmol/kg).

7. In pregnancy, the outcome is satisfactory in patients whose ventricular function is good, and in whom no residual shunt occurs. However, close observation should be undertaken by an experienced team.

8. Venesection for erythrocytosis that is associated with cyanotic congenital heart disease should only take place if there are symptoms of hyperviscosity with a hematocrit >65%, and only provided volume replacement takes place at the same time.

9. Avoid muscle relaxants with histamine release e.g. atracurium, and use cisatracurium or rocuronium.

9. Mechanical ventilation:

-Increase FiO2

-Avoid increased airway pressure (< 15 cmH2O)

-Increase respiratory rate

-Avoid PEEP

Read More

 Eisenmenger’s Syndrome

-A rare syndrome of pulmonary hypertension associated with a reversed or bidirectional cardiac shunt, occurring through a large communication between the left and right sides of the heart. The defect may be interventricular, interatrial, or aortopulmonary.

-The development of Eisenmenger’s syndrome, from the initial left to right shunt, is usually a gradual process. Contributory factors to pulmonary hypertension are hypoxia, high pulmonary blood flow, and high left atrial pressure.

-Irreversible structural changes take place in the small vessels, causing pulmonary vascular obstruction and a reduction in the size of the capillary bed. The pulmonary artery pressure is the same as or sometimes exceeds, the systemic arterial pressure.

-The incidence of this syndrome is decreasing because of the more vigorous approach to diagnosis and treatment of congenital heart disease in childhood.

Preoperative Findings:

1. Presenting symptoms include dyspnea, tiredness, episodes of cyanosis, syncope, or chest pain. Hemoptysis may occur.

2. The direction of the shunt, and hence the presence or absence of cyanosis, depends on several factors. These include hypoxemia, pulmonary and systemic pressure differences, and intravascular volume. It can also be affected by certain drugs.

3. Sleep studies have shown that there is a nocturnal deterioration in arterial oxygen saturation, which seems to be related to ventilation/perfusion distribution abnormalities occurring in the supine position.

4. Chest X-ray shows right ventricular hypertrophy, and ECG indicates varying degrees of right ventricular hypertrophy and strain.

5. Complications include thrombosis secondary to polycythemia, air embolus, bacterial endocarditis, gout, cholelithiasis, and hypertrophic osteoarthropathy. A cerebral abscess may occur secondary to clot embolism.

Anesthetic Problems:

1. Reductions in systemic arterial pressure by myocardial depression or loss of sympathetic tone are potentially dangerous. Reversal of the shunt may occur, and sudden death has been reported.

Hypovolemia and dehydration are poorly tolerated. Syntocinon may cause a dramatic reduction in SpO₂ secondary to vasodilatation.

2. Sinus tachycardia results from exercise or emotion, and episodes of SVT are common after the age of 30. The onset of atrial fibrillation is associated with a sudden deterioration in the condition of the patient.

3. General anesthesia tends to be favored since the reduction in systemic vascular resistance associated with regional blockade increases the shunt. However, successful use of epidural anesthesia for bilateral inguinal herniorrhaphy, and Cesarean section, have been reported.

4. Pregnancy is contraindicated because it carries considerable risks. Recent maternal mortality rates of 40% have been reported. A cesarean section may increase it to over 60%. Termination of pregnancy is usually recommended in the first trimester but is still associated with a mortality of 7%.

5. Patients are at risk from paradoxical air or clot embolism, and infective endocarditis.

Anesthetic Management:

1. Understanding the pathophysiology of the complex is essential, and both pregnancy and non-cardiac surgery require a multidisciplinary approach.

2. Maintenance of an adequate circulating blood volume is important. Myocardial depressants and peripheral vasodilators should be used with caution. Bradycardia must be prevented. If regional anesthesia is used, the block should be instituted with caution, and hypovolemia avoided.

3. It is unclear whether oxygen can cause pulmonary vasodilatation. Although the pulmonary vascular resistance was believed to be fixed in pulmonary hypertension, a high oxygen concentration has been shown to reduce it during cesarean section.

4. Maintenance of systemic vascular resistance is critical. The use of a norepinephrine infusion before induction has been described. Alpha-adrenergic vasopressors, such as methoxamine or phenylephrine, have also been used for the treatment of hypotension on induction of anesthesia.

5. Pulmonary ventilation should be performed with low inflation pressures and early tracheal extubation is advised, because of the deleterious effects of IPPV.

6. Air must be completely eliminated from all intravenous lines and the epidural space should be located with loss of resistance to saline, not to air.

7. Antibiotic prophylaxis against bacterial endocarditis.

8. Low-dose heparin may reduce the risk of emboli.

9. Patients are usually advised against pregnancy. If anesthesia is required either for termination of pregnancy or operative delivery, intensive cardiac care is indicated. It has been suggested that those reaching the end of the second trimester should be admitted to the hospital until delivery and given heparin 20000-40000 units daily and oxygen therapy. Successful epidural anesthesia has been reported for cesarean section.

Read More

 Goodpasture’s Syndrome

-A rapidly progressive syndrome of glomerulonephritis and pulmonary hemorrhage, in association with antibodies to glomerular basement membrane (anti-GBM) type IV collagen, detectable in plasma by radioimmunoassay and by immunofluorescence techniques on muscle biopsy.

-These antibodies cross-react with the alveolar basement membrane, although those individuals with lung hemorrhage are usually smokers, and those with isolated anti-GBM nephritis are non-smokers.

-The term is often applied more loosely, to any disease with pulmonary hemorrhage and glomerulonephritis, whether or not anti-GBM antibodies are present.

-Systemic vasculitides such as PAN and Wegener’s granulomatosis cause lung hemorrhage and renal failure, but without the antibodies.

Preoperative Findings:

1. Patient presents with cough, dyspnea, hemoptysis (that can be massive), and anemia.

2. The pulmonary lesions proceed to interstitial fibrosis, with hemosiderin deposits. Lung function tests show a restrictive type of abnormality.

3. Glomerulonephritis, which usually follows or coincides with pulmonary lesions, may produce proteinuria, hematuria, and casts. The end result is renal failure.

4. Treatment may be with corticosteroids (prednisone) for pulmonary hemorrhage, cytotoxic drugs (cyclophosphamide) to stop renal damage, and plasmapheresis to remove antibodies.

Anesthetic Problems:

1. Poor respiratory function with hypoxemia and respiratory alkalosis.

2. Pulmonary hemorrhage that may, on occasion, be life-threatening.

3. Impaired renal function and sometimes renal failure.

4. Hypochromic anemia and a high ESR.

5. Patients may be receiving immunosuppressives or steroids, or undergoing plasma exchange, to reduce the antibody titer. Plasma exchange may reduce levels of plasma cholinesterase.

Anesthetic Management:

1. Preoperative assessment of lung function and, in particular, blood gases. Elective pulmonary surgery should not be undertaken during periods of active hemorrhage.

2. Assessment of renal function and appropriate management.

3. The management of a successful pregnancy has been described. It requires regular assessment of pulmonary and renal function. The use of steroids was associated with hyperglycemia, which needed treatment with insulin. Plasmapheresis was required.

Read More