A 19-year-old man with type 1 diabetes mellitus is brought to the emergency department due… — USMLE Step 2 CK

A 19-year-old man with type 1 diabetes mellitus is brought to the emergency department due to lethargy, deep and rapid breathing, and a fruity breath odor. Laboratory results show a blood glucose of $580 \text{ mg/dL}$ , arterial pH of $7.12$ , serum bicarbonate of $10 \text{ mEq/L}$ , and a serum potassium of $5.6 \text{ mEq/L}$ . He is diagnosed with severe diabetic ketoacidosis (DKA).

Arrange the following management steps in the optimal chronological sequence for this patient.

1Administer a rapid intravenous bolus of $0.9\%$ normal saline
2Initiate a continuous intravenous regular insulin infusion
3Add potassium chloride to the intravenous fluids once serum potassium falls below $5.2 \text{ mEq/L}$
4Add $5\%$ dextrose to the intravenous fluids once serum glucose reaches $200 \text{ mg/dL}$
5Transition to a subcutaneous basal-bolus insulin regimen

Answer

The optimal sequence for managing diabetic ketoacidosis is: initial fluid resuscitation with

0.9\%

normal saline, followed by an intravenous insulin infusion, addition of potassium when levels drop into the normal range, addition of dextrose when glucose reaches

200 \text{ mg/dL}

, and finally transitioning to subcutaneous insulin when the anion gap closes.

Management of DKA requires a strict protocol to safely resolve the metabolic derangements. Initial fluid resuscitation with

0.9\%

normal saline restores intravascular volume. Once potassium is confirmed

>3.3 \text{ mEq/L}

, an intravenous regular insulin infusion is started to halt ketogenesis. As insulin therapy shifts potassium intracellularly, potassium must be added to maintenance fluids when serum levels drop

<5.2 \text{ mEq/L}

. Because blood glucose drops faster than ketones are cleared,

5\%

dextrose is added when glucose reaches

200 \text{ mg/dL}

to prevent hypoglycemia while maintaining the insulin drip. Finally, transition to subcutaneous insulin occurs once the anion gap closes and the patient can tolerate oral intake.

Step-by-Step Solution

Administer a rapid intravenous bolus of

0.9\%

normal saline

Restores intravascular volume and tissue perfusion

Severe osmotic diuresis leads to profound volume depletion. Reversing this shock state is the absolute top priority.

Initiate a continuous intravenous regular insulin infusion

Halts lipolysis and ketogenesis

Insulin drives glucose into cells and stops ketone production. It can be safely started because the initial potassium is well above the

3.3 \text{ mEq/L}

threshold.

Add potassium chloride to the intravenous fluids once serum potassium falls below

5.2 \text{ mEq/L}

Prevents severe hypokalemia

Despite total body potassium depletion, initial serum potassium is often high or normal due to acidemia. As insulin therapy drives potassium into cells, levels drop rapidly, requiring proactive supplementation.

Add

5\%

dextrose to the intravenous fluids once serum glucose reaches

200 \text{ mg/dL}

Prevents hypoglycemia while allowing insulin to continue

Blood glucose levels typically normalize faster than the ketoacidosis resolves. Dextrose must be given so the insulin drip can safely continue to close the anion gap.

Transition to a subcutaneous basal-bolus insulin regimen

Establishes long-term glycemic control

This transition is safe only when the acute crisis has resolved (evidenced by a closed anion gap) and the patient is able to eat.

Key Concept

Diabetic Ketoacidosis (DKA) Stepwise Management

Estimated Time:2m 0s

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