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Cardiac output (CO) monitoring is often required for clinical evaluation and management in critically ill patients and during anesthesia. There are many methods to measure CO. Fick-based CO estimation (Fick-CO) is one of the most commonly used methods, while thermodilution (TD-CO) is viewed as golden standard. But Fick-CO is still widely used, especially in catheterization laboratories and pediatric cardiologic department, whose patients often with congenital heart disease. Multiple studies from the 1960s find a strong correlation between TD-CO and Fick-CO. However, more recent studies reject the conclusion. Since Fick-CO is the ratio of oxygen consumption (V'O2) to the arteriovenous difference in oxygen content, many parameters are included in the Fick equation, such as V'O2, hemoglobin (Hb), arterial oxygen saturation (SaO2), mixed venous oxygen saturation (SvO2), partial pressure of arterial oxygen (PaO2), and mixed venous oxygen tension (PvO2). Any changes of each parameter may influence the accuracy of Fick-CO calculation. This may be the reason why it remains controversial whether Fick-CO and TD-CO are interchangeable or not. Although there are lots of studies comparing Fick-CO and TD-CO, discussing the impact of V'O2 on Fick-CO, how the other parameters influence the final CO estimation are rarely focused. Therefore, the purpose of this study was to assess the influence of FIO2 on PaO2, SvO2, PvO2, and the accuracy of Fick-CO in cardiac surgery patients.
Patients who are aged ≥20 years, are undergoing planned elective cardiac surgery, and provided signed informed consent are included in the present study. Any patients with cardiac arrhythmia or an intra-cardiac shunt are excluded.
The patients are randomly assigned to 2 groups: FIO2 <70% or FIO2 >90%. And during the surgery, the oximeter values are kept ≥98%. Intra-operatively, FIO2, PaO2, SvO2, PvO2, Hb, and TD-CO are recorded.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| FIO2 >90% group | Experimental | This group receives FIO2 >90% during the surgery. |
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| FIO2 <70% group | Active Comparator | This group receives FIO2 <70% during the surgery. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| fraction of inspired oxygen (FIO2) | Other | Different group receives different (70% vs. 90%) fraction of inspired oxygen (FIO2) during the surgery. |
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| Measure | Description | Time Frame |
|---|---|---|
| The Hemoglobin Values in Different FIO2 Groups during Cardiac Surgeries | The patients were divided into two FIO2 groups (FIO2 >90% or <70%) during the surgery. We will collect hemoglobin data in each patient. | 5 minutes before surgical incision |
| The Hemoglobin Values in Different FIO2 Groups during Cardiac Surgeries | The patients were divided into two FIO2 groups (FIO2 >90% or <70%) during the surgery. We will collect hemoglobin data in each patient. | 5 minutes after finishing protamine infusion |
| The Oxygen Consumption in Different FIO2 Groups during Cardiac Surgeries | The patients were divided into two FIO2 groups (FIO2 >90% or <70%) during the surgery. We will calculate oxygen consumption in each patient. | 5 minutes before surgical incision |
| The Oxygen Consumption in Different FIO2 Groups during Cardiac Surgeries | The patients were divided into two FIO2 groups (FIO2 >90% or <70%) during the surgery. We will calculate oxygen consumption in each patient. | 5 minutes after finishing protamine infusion |
| The SaO2 in Different FIO2 Groups during Cardiac Surgeries | The patients were divided into two FIO2 groups (FIO2 >90% or <70%) during the surgery. We will record SaO2 data in each patient. | 5 minutes before surgical incision |
| The SaO2 in Different FIO2 Groups during Cardiac Surgeries | The patients were divided into two FIO2 groups (FIO2 >90% or <70%) during the surgery. We will record SaO2 data in each patient. |
| Measure | Description | Time Frame |
|---|---|---|
| The Precision of Fick-based Cardiac Output in Different FIO2 Groups during Cardiac Surgeries | After collecting the elements data included in the Fick eqaution (oxygen consumption, hemoglobin, SaO2, SvO2, PaO2, and PvO2), we can calculate the Fick-based cardiac output in each patient. And the pulmonary artery thermodilution is adopted as the standard cardiac output monitoring method. We will calculate the correlation and level of agreement between Fick-based cardiac output and pulmonary artery thermodilution in the two groups. |
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Inclusion Criteria:
Exclusion Criteria:
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| 5 minutes after finishing protamine infusion |
| The SvO2 in Different FIO2 Groups during Cardiac Surgeries | The patients were divided into two FIO2 groups (FIO2 >90% or <70%) during the surgery. We will record SvO2 data in each patient. | 5 minutes before surgical incision |
| The SvO2 in Different FIO2 Groups during Cardiac Surgeries | The patients were divided into two FIO2 groups (FIO2 >90% or <70%) during the surgery. We will record SvO2 data in each patient. | 5 minutes after finishing protamine infusion |
| The PaO2 in Different FIO2 Groups during Cardiac Surgeries | The patients were divided into two FIO2 groups (FIO2 >90% or <70%) during the surgery. We will record PaO2 data in each patient. | 5 minutes before surgical incision |
| The PaO2 in Different FIO2 Groups during Cardiac Surgeries | The patients were divided into two FIO2 groups (FIO2 >90% or <70%) during the surgery. We will record PaO2 data in each patient. | 5 minutes after finishing protamine infusion |
| The PvO2 in Different FIO2 Groups during Cardiac Surgeries | The patients were divided into two FIO2 groups (FIO2 >90% or <70%) during the surgery. We will record PvO2 data in each patient. | 5 minutes before surgical incision |
| The PvO2 in Different FIO2 Groups during Cardiac Surgeries | The patients were divided into two FIO2 groups (FIO2 >90% or <70%) during the surgery. We will record PvO2 data in each patient. | 5 minutes after finishing protamine infusion |
| 5 minutes before surgical incision |
| The Precision of Fick-based Cardiac Output in Different FIO2 Groups during Cardiac Surgeries | After collecting the elements data included in the Fick eqaution (oxygen consumption, hemoglobin, SaO2, SvO2, PaO2, and PvO2), we can calculate the Fick-based cardiac output in each patient. And the pulmonary artery thermodilution is adopted as the standard cardiac output monitoring method. We will calculate the correlation and level of agreement between Fick-based cardiac output and pulmonary artery thermodilution in the two groups. | 5 minutes after finishing protamine infusion |