A 22-year-old man with a history of type 1 diabetes mellitus is brought to the emergency d… — USMLE Step 2 CK

A $22$ -year-old man with a history of type 1 diabetes mellitus is brought to the emergency department due to severe abdominal pain, nausea, vomiting, and increasing lethargy over the past $24$ hours. His vital signs show a temperature of $37.2^\circ\text{C}$ ( $99.0^\circ\text{F}$ ), blood pressure of $90/60\text{ mm Hg}$ , pulse of $122/\text{min}$ , and respirations of $28/\text{min}$ with deep, sighing breaths. Physical examination reveals dry mucous membranes and poor skin turgor. Laboratory evaluation reveals the following:

Laboratory Test	Result
Serum glucose	$550\text{ mg/dL}$
Arterial pH	$7.15$
Serum bicarbonate	$10\text{ mEq/L}$
Serum potassium	$3.1\text{ mEq/L}$
Serum sodium	$132\text{ mEq/L}$
Urine ketones	Large

Arrange the following management steps in the correct, priority-based chronological order for this patient.

1Administer rapid intravenous fluid resuscitation with 0.9% normal saline
2Administer intravenous potassium chloride and withhold insulin
3Initiate a continuous intravenous regular insulin infusion
4Add 5% dextrose to the maintenance intravenous fluids
5Transition to a subcutaneous basal-bolus insulin regimen

Answer

The correct sequence for DKA management in this patient is: Intravenous 0.9% normal saline -> Intravenous potassium chloride (holding insulin) -> Intravenous regular insulin infusion -> Addition of 5% dextrose to fluids -> Transition to subcutaneous insulin.

The management of diabetic ketoacidosis follows a strict, priority-based physiological sequence. First, volume depletion must be addressed with rapid 0.9% normal saline. Second, and most critically in this specific patient, the serum potassium of 3.1 mEq/L dictates that potassium chloride must be given before insulin. Insulin therapy shifts potassium intracellularly; starting it when potassium is < 3.3 mEq/L can cause fatal arrhythmias. Third, after potassium is stabilized, an intravenous insulin infusion is started to halt ketogenesis. Fourth, as glucose falls below 200 mg/dL, 5% dextrose is added to the fluids to prevent hypoglycemia while allowing the insulin to continue closing the anion gap. Finally, once the acidosis resolves and the patient can eat, they are transitioned to subcutaneous insulin.

Step-by-Step Solution

Assess volume status and administer 0.9% normal saline

Restores intravascular volume and improves tissue perfusion

Patients with DKA have a massive free water deficit due to osmotic diuresis. The immediate priority is cardiovascular stabilization.

Evaluate serum potassium level and administer potassium chloride

Repletes total body potassium stores before starting insulin

The patient's potassium is 3.1 mEq/L. Insulin drives potassium into cells. Giving insulin before correcting potassium < 3.3 mEq/L can cause fatal hypokalemia.

Initiate continuous intravenous regular insulin

Halts ketone body production and lowers serum glucose

Once potassium is safe (> 3.3 mEq/L), insulin is required to reverse the metabolic acidosis and close the anion gap.

Monitor glucose and add 5% dextrose to IV fluids

Maintains blood glucose while continuing insulin therapy

When glucose reaches 200 mg/dL, adding dextrose prevents hypoglycemia, ensuring insulin can be continued to fully clear ketones.

Transition to subcutaneous insulin

Prepares patient for long-term maintenance therapy

Appropriate only when DKA is resolved (anion gap closed, pH > 7.3) and the patient is able to eat.

Key Concept

Diabetic ketoacidosis (DKA) stepwise management algorithm

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