Effect of nitrous oxide on the oxyhemoglobin dissociation curve and PO2 measurements.

Blood from 20 ASA physical status I patients collected before and after induction of anesthesia was used in vitro to reexamine the effects of nitrous oxide on the oxyhemoglobin dissociation curve and the response of the oxygen electrode. The preinduction P50 values with and without 70% N2O were 28.4 +/- 0.1 mmHg and 26.8 +/- 0.1 mmHg, respectively. The postinduction P50 values with and without N2O were unchanged, namely 28.4 +/- 0.1 mmHg and 26.8 +/- 0.1 mmHg, respectively. Our data confirm the observation that N2O causes a small elevation of P50 (P less than 0.001) and that this effect is both rapidly inducible and reversible. Our results also indicate that N2O has no effect on polarographic PO2 measurements.