Figure 51-7 Comparative changes in arterial oxygen saturation (SaO₂ ) and mean blood pressure (MAP) during mask halothane N₂ O (n = 7) and intramuscular ketamine (n = 7) inductions in children with tetralogy of Fallot at risk for right-to-left shunting. Note the maintenance of SaO₂ in the halothane group despite the significant drop in MAP. (From Greeley WJ, Bushman GA, Davis DP, Reves JG: Comparative effects of halothane and ketamine on systemic arterial oxygen saturation in children with cyanotic heart disease. Anesthesiology 65:666, 1986.)