The losses of potassium via urine are severe in diabetic coma. Despite severe potassium depletion, the concentration of potassium in serum can be normal or even be increased initially. The combination of hyperosmolality, acidosis and insulin deficiency leads to a shift from intracellular potassium to the extracellular space (29). This is accompanied by normal or hyperkalemic values in the laboratory analysis although the patient is kaliopenic. In cases of chronic or acute prerenal insufficiency this discrepancy can be even more evident. After insulin application there is a dramatic decrease of potassium concentration.
The potassium deficit must be counterbalanced by substituting potassium in the infusion solution, e.g., isotonic saline solution with 20 mmol/L potassium. If potassium in serum is below 3.3 mmol/L the amount should be increased to 40 mmol/L. Furthermore, one can provide a continuous infusion of potassium chloride with 10 to 40mmol/hr under control of heart rhythm by a monitor. Potassium infusion of more than 20 mmol/hr is reserved for severe hypokalemia and needs closely controlled potassium levels. In addition, one should consider that changes in serum pH can lead to shifts of potassium: an increase of the pH-value of 0.1 leads to a decrease of serum potassium by about 0.4 to 1.2 mmol/L.
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