Effect of sevoflurane on P50 and on measurement of oxygen tension.

Fresh samples of heparinized human blood from 10 healthy nonsmoking volunteers were used to study the effect of the inhaled anesthetic sevoflurane on the oxygen half-saturation pressure of hemoglobin (P50) and on polarographic measurements of oxygen tension at low values. Control samples had a baseline P50 of 26.9 +/- 0.2 mm Hg. When the blood samples were exposed to 1.75% (1 minimum alveolar concentration, MAC), 2.75%, and 3.5% (2 MAC) of sevoflurane, the P50 values were 27.0 +/- 0.5 mm Hg, 27.1 +/- 0.4 mm Hg, and 26.9 +/- 0.5 mm Hg, respectively. Our present data show that 1 to 2 MAC sevoflurane has no significant effect on P50 (P greater than 0.05). Our data also show that sevoflurane did not interfere with polarographic measurements of oxygen tension (P greater than 0.05). Other inhaled agents--halothane, enflurane, and isoflurane--do interfere with these measurements, and we cannot explain the difference.