Literature Review of Large Patients Undergoing Cardio­ pulmonary Bypass: Concerns, Management and Future Considerations

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Appendix 1:
Body Mass Index formula:

BMI (kg/m2) = weight (kg) / Height (m*m)
Where kg is kilograms and m is meters.

Appendix 2:
CaO2: CaO2 mlO2/L = Hgb*1.36*SaO2

Delivery of Oxygen Index formula:
DaO2i = Hgb(gms/l) * 1.36(mlO2/gmHgb) * CI (l/min/m2) * SaO2 + paO2 * 0.03(mlO₂/mmHg/l) * CI

Where DaO2i is the delivery of oxygen index in mlO2/min/m2, Hgb is the hemoglobin in gms/l, the Hüfner factor is 1.36 mlO2/gmHgb, CI is the cardiac index in l/min/m2, the SaO2 is the arterial saturation as a fraction, and paO2 is the pressure of oxygen in mmHg.

For ease of calculation, the modified short form may be used during CPB: DaO2i = (Hgb*1.36* CI).

*Since this short form does not include the pO2s, the SaO2 is considered to be 1.

Appendix 3:
Dilutional hematocrit formula

TBV = dilutional HCT*(Volume preCPB+ Prime volume)/(drop in HCT)

TBV is Total Blood Volume in ml, dilutional HCT is the first hematocrit taken on CPB, volume pre-CPB is the volume given and volume lost pre-CPB, plus the prime volume in ml, and the drop in hematocrit is the difference between the HCT pre-CPB and the HCT on CPB.

Appendix 4:
Calculating cFiO2:150 mmHg:

Step 1) Convert PaO2 into a fraction (FaO2) by ­taking the PaO2 and dividing this by the ­barometric pressure (Pb) minus the water vapor pressure of 47 mmHg (713).

*Pb = Barometric pressure (taken as 760 mmHg).

PaO2 /(Pb–PH2O)

Step 2) The FiO2 minus the FaO2 gives the anoxic fractional difference (AFD). The AFD is the FiO2 at which the PaO2 is zero.

FiO2-FaO2 =AFD

Step 3) Add 0.21 to the AFD to obtain the cFiO2

Final formula: cFiO2:150 mmHg = FiO₂-(PaO2 /(713)+0.21

*The cFiO2 is referred to as the “cFiO2:150mmHg” so the standard of using a specific PaO2 is clearly stated.