Case

A 62-year-old patient complains of rapid onset of severe left abdominal pain that has been increasing over the past 3 hours. The patient indicates they has had nausea and vomiting associated with the pain. On examination, their abdomen has normal bowel sounds. Blood is present in a stool specimen. Bloodwork shows a pronounced low bicarbonate level with a matching increase in serum lactate level. They has a history of myocardial ischemia and vascular disease, including extensive calcifications of their aorta and a thoracic aortic aneurysm repair several years ago.

Question 2/3 - What is the significance of the electrolyte bicarbonate/lactate levels?

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Correct.  This pattern of low bicarbonate with matching elevated lactate is lactic acidosis (aka, metabolic acidemia) indicating mitochondrial dysfunction.

If you recall from Foundations, this occurs when there is reduced oxygen and mitochondria are upregulating glycolytic pathways in the setting of reduced ATP production.

This can be seen with a variety of conditions from genetic disorders (inborn errors of metabolism) through to what we have in this patient, an ischemic event (also occurs acutely with hypoxia, cardiac insufficiency, patient decompensating, and other conditions).

The presence of pronounced lactic acidosis suggests the patients problem is generalized ischemia (ischemic colitis) rather than a localized ischemic region of the gastrointestinal tract (which might not cause as pronounced systemic lactic acidosis). 

Incorrect. While an inborn error of metabolism from any of several hundred genes could result in mitochondrial disease and the resulting electrolyte levels in the patient, these would be present throughout life and not acutely manifest over several hours. 

Incorrect. Infection would result in changes to cytokine levels and white blood cell counts, not specifically in bicarbonate/lactate levels.

Incorrect. Severe blood loss would trigger the release of immature red blood cells into the circulation, so an increase would be expected in reticulocytes (the immature red blood cells) and not specifically in bicarbonate/lactate levels.

Incorrect. Absence of food does not induce these electrolyte changes. In general, the liver is capable of buffering intermittent nutrient intake to maintain stable blood nutrient levels, particularly across a short gap of hours such as in this patient.