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Title: Magnitude of the second gas effect on arterial sevoflurane partial pressure.
Austin Authors: Peyton, Philip J ;Horriat, Maryam;Robinson, Gavin J B;Pierce, Robert J;Thompson, Bruce R
Affiliation: Department of Anaesthesia, Austin Hospital, Heidelberg, Melbourne, Australia
Issue Date: 1-Mar-2008
Publication information: Anesthesiology; 108(3): 381-7
Abstract: A number of studies have demonstrated a faster rate of increase in end-expired partial pressure as a fraction of inspired (Pa/Pi) for volatile agents in the presence of high concentrations of nitrous oxide, consistent with the second gas effect. However, no study has demonstrated a similar effect on arterial blood concentrations.The authors compared arterial and end-tidal partial pressures of sevoflurane (Pa/Pisevo and Pa/Pisevo) in 14 patients for 30 min after introduction of either 70% nitrous oxide or nitrous oxide-free gas mixtures to determine the magnitude of the second gas effect. Blood partial pressures were measured using a double headspace equilibration technique.Both Pa/Pisevo and Pa/Pisevo were significantly higher in the nitrous oxide group than in the control group (P < 0.001 on two-way analysis of variance). This difference was significantly greater (P < 0.05) for Pa/Pisevo (23.6% higher in the nitrous oxide group at 2 min, declining to 12.5% at 30 min) than for Pa/Pisevo (9.8% higher in the nitrous oxide group at 2 min) and was accompanied by a significantly lower Bispectral Index score at 5 min (40.7 vs. 25.4; P = 0.004).Nitrous oxide uptake exerts a significant second gas effect on arterial sevoflurane partial pressures. This effect is two to three times more powerful than the effect on end-expired partial pressures. The authors explain how this is due to the influence of ventilation-perfusion scatter on the distribution of blood flow and gas uptake in the lung.
Gov't Doc #: 18292675
DOI: 10.1097/ALN.0b013e318164caf3
Type: Journal Article
Subjects: Aged
Aged, 80 and over
Anesthesia, Inhalation.methods
Blood Gas Analysis.methods
Catheters, Indwelling
Exhalation.drug effects.physiology
Methyl Ethers.blood
Middle Aged
Nitrous Oxide.blood.pharmacokinetics
Partial Pressure
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