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The Effect of N2O Administration on Arterial Oxygenation

This study has been completed.
Monash University
La Trobe University
The Alfred
University of Melbourne
Information provided by:
Austin Health Identifier:
First received: September 6, 2005
Last updated: NA
Last verified: September 2005
History: No changes posted
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.

Condition Intervention Phase
Pulmonary Function Under Anaesthesia. Drug: Nitrous oxide Phase 4

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single
Primary Purpose: Treatment
Official Title: Relationship of Oxygenation During Anaesthesia in the Presence of N2O or N2 to Mode of Ventilation

Resource links provided by NLM:

Further study details as provided by Austin Health:

Primary Outcome Measures:
  • Measured change in PaO2 after a minimum of 30 minutes of general anaesthesia, following sternotomy, in the two groups.

Secondary Outcome Measures:
  • Change in pulmonary deadspace and shunt fractions, as calculated by the Bohr and shunt equations.

Estimated Enrollment: 20
Study Start Date: January 2005
Estimated Study Completion Date: August 2005
Detailed Description:

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.


Ages Eligible for Study:   18 Years and older   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Patients undergoing elective coronary artery bypass surgery

Exclusion Criteria:

  • Age under 18 years, emergency surgery
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its identifier: NCT00146250

Sponsors and Collaborators
Austin Health
Monash University
La Trobe University
The Alfred
University of Melbourne
Principal Investigator: Philip J Peyton, MD FANZCA Dept of Anaesthesia, Austin Health
  More Information Identifier: NCT00146250     History of Changes
Other Study ID Numbers: H99/00835
Study First Received: September 6, 2005
Last Updated: September 6, 2005

Additional relevant MeSH terms:
Nitrous Oxide
Anesthetics, Inhalation
Anesthetics, General
Central Nervous System Depressants
Physiological Effects of Drugs
Analgesics, Non-Narcotic
Sensory System Agents
Peripheral Nervous System Agents processed this record on September 18, 2017