Lactic acidosis, oxygen carrying capacity, the Warburg effect!

Today in ICU report Jess Rubin talked about a case of occult GIB who developed severe lactic acidosis likely related to his anemia who also developed hypoglycemia. The patient was presumed to be septic and started on antibiotics, but there was a discussion of the Warburg effect given a history of cancer!

Oxygen carrying capacity:

Remember that the O2 content of blood of blood is heavily influenced by how saturated hemoglobin is with oxygen (the SaO2), and by the actual hemoglobin level of the blood. A small amount of O2 is dissolved in blood, but this plays a very minor role in the oxygen carrying capacity as a whole.

This relationship is explained in the O2 carrying capacity equation:

CaO2 = (SaO2 x Hb x 1.34) + .003(PaO2)

This equation can then be related to tissue perfusion and O2 delivery via the oxygen delivery equation:

DO2 = CO x CaO2 x 10 where CO = cardiac output

How this equation relates to our case is that in a patient with decreased cardiac output for whatever reason, oxygen delivery to the tissues will be much more heavily affected by reductions in O2 content of the blood, which as we have discussed, are heavily influenced by Hg levels. Cool!

Warburg effect!

As a bit of an aside, we also discussed the Warburg effect as a cause of hypoglycemia in cancer patients. The Warburg Effect is named after Otto Heinrich Warburn, Nobel Prize winning biochemist who noted that cancer cells tended to produced energy via glycolysis and then lactic acid fermentation via anerobic respiration given their high metabolic demands. This can present clinically as hypoglycemia and lactic acidosis in a cancer patient. According to Ben Davoren, the it is the malignancies with less blood supply to the interior of the cancer (pancreatic, non-small cell lung) that may be at most risk for this phenomenon.


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