A 2-month-old infant diagnosed with tetralogy of Fallot (TOF) at birth is scheduled for repair of large, bilateral inguinal hernias. The parents report only occasional episodes of cyanosis with crying and feeding. The physical exam reveals hypertelorism, bulbous nose, small mouth, cleft palate, and mild retrognathia. Labs: Hematocrit (HCT) 40.
TOF is classically defined as follows: (1) right ventricular (RV) outflow tract obstruction (RVOTO) secondary to infundibular narrowing, valvar hypoplasia, and/or pulmonary artery hypoplasia; (2) RV hypertrophy; (3) ventral septum defect (VSD); (4) overriding aorta. Pathophysiology will depend on the degree and direction of shunting that occurs at the VSD level, which in turn is determined by the structural anatomy and by dynamic changes in pulmonary vascular resistance (PVR) and systemic vascular resistance (SVR).
“Blue tet”: stable blood oxygen saturations (SpO2; high 70s-low 80s), because the presence of severe RVOTO (eg, pulmonary atresia) requires major right-to-left (R-to-L) shunting across the VSD, mixing of oxygenated and deoxygenated blood in the left ventricle, and flow to the pulmonary arteries via a widely patent ductus arteriosus or aortopulmonary collateral.
“Pink tet”: anatomy favors near-normal flow across the RVOT with little R-to-L shunting, more prone to episodes of desaturation or “tet spells” during periods of infundibular spasming or fluctuations in PVR or SVR.
TOF is the most common cardiac lesion seen in children with chromosome 22q11 deletion, which is strongly associated with DiGeorge syndrome, velocardiofacial syndrome, and conotruncal anomaly face syndrome. These patients are at risk for endocrine (hypocalcemia); ear, nose, and throat (cleft palate, feeding and speech difficulties), neurologic (retardation, learning disabilities, motor and speech delays), renal (absent, dysplastic, or multicystic kidneys), hematologic (thrombocytopenia), and autoimmune (T-cell defects, immunodeficiency) abnormalities.
The patient described here appears to have dysmorphic features consistent with chromosome 22q11 deletion. Preoperative studies should include serum calcium, complete blood count, T-cell studies, immunoglobulins, renal ultrasound, electrocardiogram, chest x-ray, and echocardiogram. Feeding issues may be related to a cleft palate or cardiovascular instability. Although the parents report only occasional cyanosis, the relatively elevated HCT (at 2 months, HCT is often 28-30 due to physiologic anemia of infancy) may indicate more frequent episodes of cyanosis with a compensatory increase in hemoglobin production.
Minimize the nothing by mouth period and correct fluid deficits early. The hypertrophied and poorly compliant RV is sensitive to hypovolemia, which can lead to hypotension and increased R-to-L shunting.
Prepare for possible difficult intubation in patients with facial and/or airway dysmorphism consistent with chromosome 22q11 deletion.
Avoid agents or techniques that lower SVR and increase R-to-L shunting.
Avoid hypercarbia, hypoxemia, and acidosis, which can increase PVR and lead to increased R-to-L shunting.
Avoid hypothermia, as this may increase PVR and lead to increased R-to-L shunting.
Formulate and initiate an age-appropriate pain control regimen to avoid pain-induced increased PVR and subsequent R-to-L ...