Metabolic acidosis is common in critical illness. It can be caused by shock, renal failure, ketoacidosis, toxins, diarrhea, lactic acidosis, or impaired tissue oxygen utilization.
The difficult question is deciding what the acidosis means.
Sometimes the pH is a marker. Sometimes the pH becomes part of the problem.
In shock, lactic acidosis often signals impaired oxygen delivery, increased adrenergic stimulation, mitochondrial dysfunction, or impaired clearance.
The solution is not simply to correct the number. The solution is to treat the underlying physiology.