A case of congenital heart disease: tetralogy of fallot.

dibesh87

The patient, a 13 year old female, diagnosed with tetralogy of fallot, came to the operating room with spo2 at 70-80 and bradycardia. Blood pressure was also low at the range of 80/50 mm Hg. It was observed that the spo2 was directly related to the blood pressure (i.e. when blood pressure decreased the spo2 also decreased). Clinical case record was unremarkable for coexisting pathologic conditions. Two questions arised when about to start induction of general anesthesia.
1. Why is sp02 directly related to blood pressure?
2. Can we use sevofluorane (inhaled general anesthetic) in this patient?

shenxiu2

1. The SpO2 is directly related to the blood pressure in TOF , this is probably due to the increase in mixing of deoxygenated blood to the oxygenated blood across the VSD when the systemic blood pressure goes down..  We know that  in TOF , it is the balance between the systemic vascular resistance & the pulmonary vascular resistance that maintains the oxygenation to the body.
2. Sevoflurane induction is fine , as long as you maintain the systemic vascular resistance . It is advisable to draw out noradrenaline in the syringe & dilute into the correct dilution before induction , in case the SVR drop too much & patient desaturates.