Preoxygenation by 8 deep breaths in 60 seconds using the Mapleson A (Magill), the circle system, or the Mapleson D system.

STUDY OBJECTIVE: To investigate the efficacy of preoxygenation by eight deep breaths in 60 seconds with the Mapleson A (Magill) system, the circle anesthesia system, or the Mapleson D system at an oxygen flow of 5 L/min or 10 L/min. DESIGN: Randomized, clinical study. SETTING: Operating room of a university hospital. SUBJECTS: 10 healthy volunteers. INTERVENTIONS: Volunteers underwent 6 preoxygenation trials consisting of 8 deep breaths in 60 seconds using the Mapleson A, Mapleson D, and the circle anesthesia systems at an oxygen flow of 5 L/min and 10 L/min. MEASUREMENTS: Fractional end-tidal oxygen concentration (F(ET)O(2)) was measured at 15-second intervals during preoxygenation. RESULTS: At an oxygen flow of 10 L/min, mean F(ET)O(2) values at 60 seconds of preoxygenation were comparable among the Mapleson A, Mapleson D, and the circle anesthesia systems (87 +/- 2.1%, 87 +/- 1.6%, 87 +/- 1.6%, respectively). Using an oxygen flow of 5 L/min, mean F(ET)O(2) values at 60 seconds were similar among the Mapleson A, Mapleson D, and circle anesthesia systems (74 +/- 4.1%, 75 +/- 2.6%, 74 +/- 4.4%, respectively); however, they were significantly lower than the corresponding values achieved at an oxygen flow of 10 L/min. CONCLUSIONS: The 8-deep-breaths in 60 seconds technique at an oxygen flow of 10 L/min can achieve adequate preoxygenation with the Mapleson A (Magill), Mapleson D, and circle anesthesia systems. Suboptimal preoxygenation is obtained with the three systems when the oxygen flow used is 5 L/min.

Prophylactic methylene blue in a patient with congenital methemoglobinemia.

PURPOSE: To report the beneficial effect of prophylactic methylene blue administration before induction of anesthesia in a patient with congenital methemoglobinemia. CLINICAL FEATURES: A 26-yr-old male patient known to have congenital methemoglobinemia was scheduled for turbinectomy under general anesthesia. The patient was clinically cyanotic with a pulse oximetry of 91%. Arterial blood gas analysis showed a partial pressure of oxygen (PaO(2)) of 81.3 mmHg associated with a fractional oxyhemoglobin of 80.7%, and a methemoglobin fraction of 0.159. Preoperative iv administration of 1 mg.kg(-1) of methylene blue resulted, within five minutes, in a decrease of methemoglobin fraction down to 0.05 associated with an increase of the fractional oxyhemoglobin saturation up to 94.7%. After two hours, the methemoglobin fraction decreased to 0.01 and the fractional oxyhemoglobin concentration increased to 97.7%. Induction of anesthesia as well as intraoperative and postoperative course were uneventful without any episode of hypoxemia. Postoperatively, the methemoglobin fractions remained low for 24 hr, to be followed by a gradual increase up to 0.02 on the second day to reach 0.094 on the fifth day. CONCLUSION: The prophylactic preoperative methylene blue administration in a patient with congenital methemoglobinemia significantly decreased the methemoglobin level and increased the fractional oxygen saturation with a consequent increase of the safety margin against perioperative hypoxemia.