The Effect of N2O Administration on Arterial Oxygenation

Anesthesia Clinical Trial

Official title:

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

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT00146250
• Other study ID #: H99/00835
• Status: Completed
• Phase: Phase 4
• First received: September 6, 2005
• Last updated: January 9, 2018
• Start date: March 1, 2005
• Est. completion date: September 30, 2005

Study information

• Verified date: January 2018
• Source: Austin Health
• Contact: n/a
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial Summary

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.

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.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 20
• Est. completion date: September 30, 2005
• Est. primary completion date: July 20, 2005
• Accepts healthy volunteers: No
• Gender: All
• Age group: 18 Years and older

Eligibility

Inclusion Criteria:

• Patients undergoing elective coronary artery bypass surgery

Exclusion Criteria:

• Age under 18 years, emergency surgery

Related Conditions & MeSH terms

• Anesthesia

Intervention

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

Locations

Country	Name	City	State
n/a

Sponsors (5)

Lead Sponsor	Collaborator
Austin Health	La Trobe University, Monash University, The Alfred, University of Melbourne

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	PaO2	Measured change in PaO2 after a minimum of 30 minutes of general anaesthesia, following sternotomy, in the two groups.	Minimum of 30 minutes after induction of anaesthesia
Secondary	Change in pulmonary deadspace and shunt fractions	Change in pulmonary deadspace and shunt fractions, as calculated by the Bohr and shunt equations.	Minimum of 30 minutes after induction of anaesthesia