Pediatric Anesthesia Week 3 Flash Cards
What is the most common cyanotic congenital heart disease? How common? What is its classification?
- Tetrology of Fallot
- Accounts for 6- 11% of congenital heart disease
- “Simple” Right- to- Left Shunt
What are 2 major characteristics of Tetrology of Fallot? What are the other characteristics?
- VSD
- RV-Outlet Tract Obstruction (infundibular obstruction/ spasm)
- Overriding Aorta
- RV Hypertrophy
What is an “Overriding Aorta”?
In TOF, the aorta is displaced to the right so that it appears to arise from both ventricles and straddles the VSD
What are “tet spells”?
In TOF, hypercyanotic spells occur when there is an increase in RIGHT-to-LEFT shunting (increase in PVR)
What relationship determines the degree of RIGHT-to-LEFT Shunting, ergo the degree of hypoxemia in a patient with TOF?
The relationship between RV-Outlet Tract Obstruction (RVOTO) AND Systemic Vascular Resistance (SVR)
What causes “tet spells”? What triggers “tet spells”?
Unclear, but they occur during:
- Crying -Feeding
- Anesthesia/surgical stimulation -Metabolic acidosis
- Increased PaCO2 - Circulating catacholamines
How do you treat TOF- Hypercyanotic “tet spells”?
- 100% O2
- Hyperventilation (decrease in eTCO2 will decrease PVR)
- Increase PRELOAD (IVF)- give fluid deficit early or give bolus of 10 ml/kg of crystalloid
- Sedation
- Vasoconstrict with Neosynephrie (to INCREASE SVR to reverse R-L shunt)
- Use a BETA-BLOCKER to relax infundibular spasm and reduce HR
When is surgical repair of TOF considered? What is done?
- Early
- Complete repair which involves closure of the VSD and relief of RV outlet tract obstruction (RVOTO)
What is the name of the surgical procedure to repair a TOF?
Modified “Blalock-Taussig (BT) Shunt” to improve systemic-to-pulmonary shunt and improve pulmonary blood flow
The Modified “Blalock-Taussig (BT) Shunt” shunts from the ______ ________ to the _______ _______, creating a _______ blood flow.
- Subclavian Artery
- Pulmonary Artery
- Passive
What are some anesthetic considerations for a TOF repair?
- PRESEDATE to prevent crying on induction increasing risk for “tet spells”
- A-Line is placed on the arm OPPOSITE to the side of the anastomosis ( Subclavian artery is going to be clamped).
- SNUG ETT with NO AIR LEAK
- Prepare for BLOOD TRANSFUSION potential
What is predominantly dependent on the size of PT shunts?
Postoperative pulmonary blood supply
How does post-operative blood supply effect the size of the BT shent?
- If the BT shunt is too small = Low saturation
- If the BT shunt is too large = Infant may develop heart failure/ pulmonary edema
- TEE intraoperatively will assess RV function
Pulmonary blood flow is also dependent on ? How?
- Systemic blood pressure
- The greater the blood pressure, the more blood flow toward the lungs, thus increase in saturation
*Postoperative ventilation may be required
Does blood shunt right-to-left or left-to-right through the VSD in Tetrology of Fallow (Cyanotic Heart Disease)?
Blood shunt RIGHT-to-LEFT, permitting unoxygenated blood to mix with oxygenated blood, resulting in CYANOSIS
What are goals of anesthetic management for the patient who has Tetrology of Fallot?
- Maintain intravascular volume and SVR
- AVOID increase in PVR
What pharmacologic agent decreases a right-to-left shunt?
Any drug that increases SVR, like Phenylnephrine, increases SVR and decreases right-to-left shunt
** An infant has Tetrology of Fallot (cyanotic heart disease). Which of the following arterial blood gas parameters will NOT typically be changed: PaO2, pH, PaCo2?
pH and PaCo2 typically maintain in the normal limits
PaO2 is usually markedly decrease (< 50 mmHg)
During the case, SpO2 decreases, apparently because of increased shunting. The patient has Tetrology of Fallot. What agents might be selected to decrease shunt and increase SpO2?
- Volume must be maintained with IV FLUID administration as hypovolemia increases the magnitude of the right-to-left shunt
- An alpha agonist, such as PHENYLNEPHRINE must be available
What change in SVR and PVR increase shunt in a patient with Tetrology of Fallot patient?
- Shunt increases when SVR decreases or PVR increases
- Volatile anesthetics, drugs that release histamine,
What drugs increase shunt in the patient with TOF by altering SVR or PVR?
Drugs that decrease SVR such as:
- Volatile anesthetics
- Histamine releasing drugs
- Ganglionic blockers
- Alpha blockers
- Vasodilators, like Nitroprusside, that decrease SVR
Drugs that increase PVR such as:
- Nitrous Oxide (N2O), detreimental to children with right-to-left shunts
List 3 conditions that increase right-to-left shunt (Tetrology of Fallot)?
- Acidosis
- Hypercarbia
- Hypotension
List 4 congenital heart defects involved with Tetrology of Fallot (cyanotic heart disease)?
- VSD
- Right Ventricular Outflow Tract (RVOT) Obstruction i.e. Pulmonary Stenosis
- RV Hypertrophy
- Overriding Aorta- Dextroposition (to the right) of the aorta with overriding of the VSD
What is a Complex Shunt? What are the 5 types?
Mixing of pulmonary and systemic blood flow with cyanosis
- TGA- Transposition of Great Arteries
- Truncus Arteriosus
- DORV- Double-Outlet Right Ventricle
- HLHS- Hypoplastic Left Heart Syndrome
- TAPVC- Total Anomalous Pulmonary Venous Connection