During induction of anesthesia, a 6-month-old female with Tetralogy of Fallot becomes increasingly hypercyanotic. Appropriate management could include all the following EXCEPT:
a) Increasing preload to the right ventricle
b) β-blockade to reduce right ventricular infundibular spasm
c) Elevation of the lower extremities
d) Phentolamine bolus
e) Morphine bolus
Answer d.
Hypercyanotic “tet” spells are caused by right-to-left shunt, and can occur during induction of anesthesia due to RV infundibular spasm causing subpulmonary obstruction. Treatment includes deepening anesthesia, improving preload, increasing SVR, morphine boluses and β-blockade to reduce infundibular spasm. Phenylephrine may provide benefit by increasing SVR; phentolamine is an α-antagonist that will decrease SVR and increase right-to-left shunting and cyanosis.