The 'critical hematocrit': a figure differing from patient to patient.

In my opinion, the problem of a 'critical hematocrit' can be summarized in five contentions: First, it is inadmissible to label any single hemoglobin or hematocrit value as being generally acceptable, the reason being, second, that the adequate values differ between patients and sometimes also between various stages of their individual course--for instance during the intra- and the postoperative period. Third, a hemoglobin or hematocrit within the normal range constitutes a natural buffer against encroachments upon the oxygen supply from non-Hb causes. Intentional manipulation of this buffer requires a careful assessment of potential benefits vs. risks. Fourth, a patient in otherwise perfect condition tolerates a hemoglobin or hematocrit below 10 g/dl or 30%, respectively, down to approximately 8 g/dl or 25%- but tolerance is not necessarily equivalent to an optimum. And fifth, the patient most dependent on his 'hemoglobin buffer' is the individual who has to overcome troubles without the monitoring facilities of an intensive care unit, for instance in the peripheral hospital equipped only for primary care.