Effect of Arterial Oxygen Partial Pressure on Mixed Venous Oxygen Saturation

Study Overview
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Brief Summary
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Mixed venous oxygen saturation is known to reflect oxygen delivery and, thus, is frequently monitored in patients undergoing cardiac surgery. Factors that affect mixed venous oxygen saturation include hemoglobin level, arterial oxygen saturation and arterial oxygen partial pressure. Among them, arterial oxygen partial pressure is known to have minimal effect on oxygen delivery compared to hemoglobin and arterial oxygen saturation. However, some argues that in certain clinical setting, such as anemia which is very common in cardiac surgery patients, the contribution of plasma (arterial oxygen partial pressure in this case) to oxygen delivery becomes more significant. Therefore, we planned to perform a pilot clinical trial to observe the change of oxygen delivery, which would be reflected in mixed venous oxygen saturation and cerebral regional oxygen saturation, according to hemoglobin level.

Official Title
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Effect of Arterial Oxygen Partial Pressure on Mixed Venous Oxygen Saturation and Regional Cerebral Oxygen Saturation During Cardiopulmonary Bypass in Patients Undergoing Cardiac Surgery: a Pilot Study

Conditions
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Anemia

Intervention / Treatment
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* Other: Change of the fraction of inspired oxygen


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients that scheduled to undergo cardiac surgery using cardiopulmonary bypass. Exclusion Criteria: Emergent surgery Symptomatic carotid artery stenosis or carotid artery stenosis of ≥50% Preoperative oxygen therapy that is equivalent to the inspired oxygen fraction of 0.5.

Ages Eligible for Study
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Minimum Age: 19 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Fraction of inspired oxygen setting change<br> | Other: Change of the fraction of inspired oxygen<br>* After the stabilization of cardiopulmonary bypass, in the first half of patients, fraction of inspired oxygen would be set at 0.5 and maintained for 5 minutes (T0), then it would be changed to 1.0 and maintained for 5 minutes (T1). Again, fraction of inspired oxygen would be resumed to be 0.5 and maintained for 5 minutes (T2). In the other half of patients, the direction of change in fraction of inspired oxygen will be reversed as follows. It will be set at 1.0 and maintained for 5 minutes (T0), then changed to 0.5 and maintained for 5 minutes (T1), and finally to 1.0 and maintained for 5 minutes (T2).<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Mixed venous oxygen saturation | Change of mixed venous oxygen saturation according to the fraction of inspired oxygen | From the beginning and the stabilization of cardiopulmonary bypass to 15 minutes thereafter. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cerebral regional oxygen saturation | Change of cerebral regional oxygen saturation according to the fraction of inspired oxygen | From the beginning and the stabilization of cardiopulmonary bypass to 15 minutes thereafter. |