Effect of Arterial Oxygen Partial Pressure on Mixed Venous Oxygen Saturation

Seoul National University Hospital40 enrolled

Overview

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.

Study Type

INTERVENTIONAL

Allocation

Purpose

TREATMENT

Masking

NONE

Enrollment

Conditions

Anemia

Interventions

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).

Eligibility

Sex: ALLMin age: 19 Years

Medical Language ↔ Plain English

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.

Outcomes

Primary Outcomes

Mixed venous oxygen saturation

Change of mixed venous oxygen saturation according to the fraction of inspired oxygen

Time frame: From the beginning and the stabilization of cardiopulmonary bypass to 15 minutes thereafter.

Secondary Outcomes

Cerebral regional oxygen saturation

Change of cerebral regional oxygen saturation according to the fraction of inspired oxygen