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Difficulty: MediumGeneral Internal Medicine

A 2222-year-old man with type 11 diabetes mellitus is brought to the emergency department with a 22-day history of nausea, vomiting, and abdominal pain. He recently had a respiratory infection and missed his last several doses of insulin. On presentation, he is lethargic. Vital signs show a heart rate of 122/min122/\text{min}, blood pressure of 90/60 mm Hg90/60 \text{ mm Hg}, and respiratory rate of 28/min28/\text{min} with deep, rapid breaths. Laboratory studies reveal:

- Serum glucose: 480 mg/dL480 \text{ mg/dL}
- Serum sodium: 132 mEq/L132 \text{ mEq/L}
- Serum bicarbonate: 12 mEq/L12 \text{ mEq/L}
- Arterial pH: 7.157.15
- Urinalysis: ++++++ ketones

A complete metabolic panel has been drawn, but the serum potassium result is currently pending.

Arrange the following critical steps in the management of this patient's diabetic ketoacidosis in the correct sequential order.

  1. 1Initiate rapid intravenous volume resuscitation with 0.9%0.9\% normal saline.
  2. 2Verify that the pending serum potassium level is ≥3.3 mEq/L\geq 3.3 \text{ mEq/L}.
  3. 3Start a continuous intravenous regular insulin infusion.
  4. 4Incorporate 5%5\% dextrose into the intravenous fluids once serum glucose falls below 200 mg/dL200 \text{ mg/dL}.
  5. 5Transition to subcutaneous insulin once the anion gap closes and the patient is tolerating oral intake.

Answer

The correct sequence for managing this patient's diabetic ketoacidosis is: 1) Initiate rapid intravenous volume resuscitation, 2) Verify the serum potassium is ≥3.3 mEq/L\geq 3.3 \text{ mEq/L}, 3) Start a continuous intravenous regular insulin infusion, 4) Incorporate 5%5\% dextrose into the intravenous fluids when glucose reaches the target threshold, and 5) Transition to subcutaneous insulin once the anion gap normalizes.
The standard of care for DKA management is a strict algorithmic sequence. Isotonic fluid resuscitation must happen immediately to correct hypovolemia. Because insulin drives potassium into cells, serum potassium must be verified as ≥3.3 mEq/L\geq 3.3 \text{ mEq/L} before starting the intravenous insulin infusion to avoid fatal arrhythmias. Once insulin is running and blood glucose falls below 200 mg/dL200 \text{ mg/dL}, dextrose is added to prevent hypoglycemia while allowing the insulin infusion to continue until the anion gap closes. Finally, the patient is transitioned to subcutaneous insulin once they can eat.

Step-by-Step Solution

1
Administer aggressive intravenous fluids (0.9%0.9\% normal saline).
Restores intravascular volume and organ perfusion.
Patients with DKA are severely dehydrated due to glucose-induced osmotic diuresis. Volume expansion is the most critical first step and helps lower glucose independently.
2
Wait for and verify that the serum potassium level is ≥3.3 mEq/L\geq 3.3 \text{ mEq/L}.
Prevents life-threatening insulin-induced hypokalemia.
Despite total body potassium depletion, initial serum potassium may be normal or high due to acidemia. Insulin drives potassium back into cells. If baseline potassium is low, insulin will cause severe hypokalemia and cardiac arrhythmias.
3
Initiate a continuous intravenous regular insulin infusion.
Halts lipolysis and ketoacid production.
Once potassium is confirmed to be safe, intravenous insulin is required to reverse the underlying pathophysiology of DKA, clear the ketones, and correct the anion gap acidosis.
4
Add 5%5\% dextrose to the intravenous fluids when glucose falls below 200 mg/dL200 \text{ mg/dL}.
Prevents hypoglycemia while insulin continues to clear ketones.
Serum glucose often normalizes before the ketoacidosis resolves. Insulin must be continued to clear ketones, so dextrose is added to prevent hypoglycemia during this period.
5
Transition to subcutaneous insulin once the anion gap is closed.
Safely transitions the patient to maintenance therapy.
Once the acidosis is fully resolved (anion gap <12 mEq/L< 12 \text{ mEq/L}) and the patient is tolerating oral intake, it is safe to overlap and then switch to a subcutaneous insulin regimen.

Key Concept

Algorithmic management of diabetic ketoacidosis (DKA) prioritizing fluid resuscitation and potassium verification prior to insulin therapy.
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Topics

General Internal Medicine

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