What is the likely state of a patient's serum potassium level if they are in diabetic ketoacidosis (DKA)?

Serum Potassium in Diabetic Ketoacidosis

In diabetic ketoacidosis (DKA), serum potassium is most likely increased (option B) despite total body potassium depletion.

Pathophysiology of Potassium in DKA

Patients with DKA typically present with normal to elevated serum potassium levels despite having significant total body potassium deficits. This paradoxical finding occurs due to several mechanisms:

• Acidosis-induced extracellular shift: The severe acidosis in DKA causes potassium to shift from the intracellular to the extracellular space, raising serum potassium levels 1
• Insulin deficiency: Lack of insulin prevents potassium movement into cells 2
• Hyperosmolality: High serum osmolality from severe hyperglycemia draws water and potassium out of cells
• Tissue catabolism: Breakdown of tissues releases intracellular potassium

The American Diabetes Association guidelines specifically note that "despite total-body potassium depletion, mild to moderate hyperkalemia is not uncommon in patients with hyperglycemic crises" 1.

Clinical Implications

This initial hyperkalemia masks a significant total body potassium deficit that becomes apparent during treatment:

• Insulin therapy drives potassium back into cells, rapidly lowering serum levels 1, 2
• Correction of acidosis further promotes potassium movement into cells
• Volume expansion dilutes extracellular potassium concentration

Important Treatment Considerations

1. Always measure serum potassium before starting insulin:

   • The American Diabetes Association recommends obtaining serum potassium levels before initiating insulin therapy 2, 3
   • This is critical as insulin will rapidly lower serum potassium levels

2. Potassium replacement protocol:

   • Begin potassium replacement when serum K+ falls below 5.5 mEq/L 1, 2
   • Ensure adequate urine output before starting replacement
   • Use a combination of KCl (2/3) and KPO₄ (1/3) at 20-30 mEq/L 2
   • Withhold insulin if K+ <3.3 mEq/L until potassium is repleted 2, 4

3. Monitoring requirements:

   • Check potassium levels every 2-4 hours during initial treatment 2
   • Adjust replacement based on serial measurements

Special Considerations

While hyperkalemia is typical in DKA, there are exceptions:

• Rare cases of severe hypokalemia at presentation have been reported 5, 4
• A prospective study found hypokalemia in 5.6% of DKA patients before treatment 3
• Patients with renal failure on hemodialysis may develop extreme hyperkalemia during DKA due to anuria 6

Conclusion

The comatose patient with a glucose of 724 mg/dL most likely has increased serum potassium if they are in DKA, despite having a total body potassium deficit. This hyperkalemia will rapidly change to hypokalemia once insulin therapy is initiated, making close monitoring and appropriate potassium replacement essential to prevent life-threatening arrhythmias.