Table 1. Intervention protocol when rSO2 values fall below the preoperative baseline.

PaCO₂ - Arterial carbon dioxide tension, SaO₂ - Peripheral oxygen saturation, FiO₂ - Fractional inspired oxygen, CPB - Cardiopulmonary bypass

Checklist if rSO2 falls below baseline		Intervention
1.	PaCO2 <5.3 kPa	Alter ventilation keeping PaCO2 at 5.3 kPa
2.	Mean arterial pressure <65 mmHg	Depending on situation vasoconstrictor, volume, or inotrope to keep MAP >65 mmHg
3.	SaO2 less than 94%	Increase FiO2
4.	Depth of anesthesia	Maybe appropriate to increase depth of anesthesia
5.	Haematocrit	Consider transfusion to hematocrit 27%
6.	Position of aortic cannula and head position.	Usually detected as soon as CPB is started
7.	Re-calculate pump flow on CPB	Check flow (2.4 l/m2/min) and venous return
8.	No response to above	Discuss surgical plan with surgeon