The effect of halothane/nitrous oxide/oxygen mask induction on arterial hemoglobin saturation in cyanotic heart disease.

The effect of a halothane/nitrous oxide/oxygen mask induction on arterial hemoglobin saturation (SaO 2 ) was studied in 25 patients with cyanotic congenital heart disease. During this induction the SaO 2 increased from 80%±2 (mean±SEM) in awake patients breathing room air to 86%±1 after induction of anesthesia, with an average increase of 6.8%±2 (absolute) (N=25; P 2 values of 76%±3 that increased significantly after induction to 86%±1, with an average increase of 10%±4 (absolute) ( P 2 of 83%±2, which rose insignificantly after induction to 87%±2, which rose insignificantly after induction to 87%±1, with an average increase of 4%±2 (absolute) ( P >.1). Thus, the significant increase in SaO 2 during induction for the entire group was primarily due to the large response of patients with PIS. No correlation was found between SaO 2 and systolic blood pressure for the entire study population as well as for groups A and B separately. The lack of correlation between systolic blood pressure and SaO 2 may indicate that relaxation of pulmonic infundibular stenosis is an important mechanism explaining the observed increase in SaO 2 during anesthetic induction in group A (PIS) patients. Six patients had clinically important decreases in SaO 2 during the induction of anesthesia, and airway obstruction was usually the cause. Anesthetic induction with halothane/nitrous oxide/oxygen leads to an increase in SaO 2 in patients with many forms of cyanotic heart disease, but especially those with the potential for variable pulmonary outflow tract obstruction.