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A recent article has reported that CPB patients with nadir hematocrit values ≤19% had two times the mortality of patients with nadir hematocrit values ≥ 24%. Subsequently some perfusionists have suggested that an on-CPB hematocrit of 19% might be a good transfusion trigger point; although the article’s authors do not suggest this.
If 19% were used as a trigger point for transfusion to reduce the mortality rate from 4% to 2%, ninety low hematocrit patients is the number needed to treat (NNT) by transfusion to result in two additional survivors. That means that 88/90 patients would receive unnecessary transfusions and its associated risks. A transfusion trigger should be the plan of last resort; all other interventions such as hemoconcentration, hypothermia and hyperoxia being exhausted.

Perfusion Theory is an educational platform for the Oxygen Pressure Field Theory (OPFT). August Krogh’s theoretical concept of the oxygen pressure field is explained and then applied to clinical applications in perfusion practice.