The Effect of N2O Administration on Arterial Oxygenation
- Registration Number
- NCT00146250
- Lead Sponsor
- Austin Health
- Brief 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.
- 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.
Recruitment & Eligibility
- Status
- COMPLETED
- Sex
- All
- Target Recruitment
- 20
- Patients undergoing elective coronary artery bypass surgery
- Age under 18 years, emergency surgery
Study & Design
- Study Type
- INTERVENTIONAL
- Study Design
- PARALLEL
- Arm && Interventions
Group Intervention Description Nitrogen Nitrous oxide Nitrogen instead of nitrous oxide 70% as balance gas in inspired mixture Nitrous oxide Nitrous oxide Nitrous oxide 70% as balance gas in inspired mixture
- Primary Outcome Measures
Name Time Method PaO2 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 Outcome Measures
Name Time Method Change in pulmonary deadspace and shunt fractions Minimum of 30 minutes after induction of anaesthesia Change in pulmonary deadspace and shunt fractions, as calculated by the Bohr and shunt equations.