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NCT Number: NCT00146250

The Effect of N2O Administration on Arterial Oxygenation

Nitrous oxide is a standard part of most anaesthetic breathing mixtures. It has often been assumed that it reduces the amount of oxygen reaching the lower parts of the lung. However the results of previous studies and of some computer modelling suggests the opposite may be true, and that oxygen levels in the blood are actually higher with nitrous oxide. This study seeks to determine whether nitrous oxide increases or decreases blood oxygen levels in anaesthetized patients.

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Key information

Conditions

Anesthesia

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 4

About this study

The concentrating and second gas effects of nitrous oxide (N2O) uptake have been well described, and are produced by rapid uptake of N2O during the first several minutes of an inhalational anesthetic. This significantly increases alveolar and arterial O2 partial pressure. Theoretical modelling of alveolar gas exchange has predicted that these effects may not be transient but may be a persisting phenomenon. However, N2O is known to promote absorption atelectasis in poorly ventilated lung units.

This study, carried out pre-cardiopulmonary bypass in 20 patients undergoing coronary artery surgery, measures change in PaO2 after a minimum of 30 minutes of relaxant general anesthesia with a FIO2 of 30%. Patients are randomised to two groups. The intervention group has N2O introduced following baseline blood gas measurements, while the control group continued breathing an identical FIO2 in N2. The change in PaO2 in the two groups is the primary endpoint for comparison.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Patients undergoing elective coronary artery bypass surgery

Exclusion criteria

  • Age under 18 years, emergency surgery

Treatment and study plan

Nitrous Oxide

Drug

Substitution of Nitrous oxide for Nitrogen as balance gas in inspired gas mixture

Other names: N2O

Primary outcomes

  1. PaO2

    Time frame: Minimum of 30 minutes after induction of anaesthesia

    Measured change in PaO2 after a minimum of 30 minutes of general anaesthesia, following sternotomy, in the two groups.

Secondary outcomes

  1. Change in pulmonary deadspace and shunt fractions

    Time frame: Minimum of 30 minutes after induction of anaesthesia

    Change in pulmonary deadspace and shunt fractions, as calculated by the Bohr and shunt equations.

Sponsors and collaborators

Lead sponsor

Austin Health

Other Gov

Collaborators

  • La Trobe University
  • Monash University
  • The Alfred
  • University of Melbourne

Registry information

Official study title

Relationship of Oxygenation During Anaesthesia in the Presence of N2O or N2 to Mode of Ventilation

Important dates

Study start
2005
Primary completion
2005
Study completion
2005
First posted
Sep 7, 2005
Registry last updated
Jan 11, 2018

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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