Emergency medical services bring a 21-year-old male university student to the resuscitatio… — USMLE Step 2 CK

Emergency medical services bring a $21$ -year-old male university student to the resuscitation bay after his roommate found him lethargic and vomiting in their dorm. The patient has a history of type 1 diabetes mellitus but ran out of his prescribed insulin three days ago. On initial assessment, he appears severely dehydrated and is taking deep, rapid breaths. Vital signs include a heart rate of $122/\text{min}$ , blood pressure of $90/60 \text{ mm Hg}$ , and respiratory rate of $28/\text{min}$ . A point-of-care capillary glucose reads $520 \text{ mg/dL}$ , and a venous blood gas reveals a pH of $7.12$ with a calculated anion gap of $22 \text{ mEq/L}$ . The clinical team establishes large-bore peripheral intravenous access. Arrange the following therapeutic steps in the most appropriate chronological order for managing this patient's metabolic decompensation.

1Initiate rapid fluid resuscitation with intravenous $0.9\%$ normal saline
2Review the initial basic metabolic panel to confirm serum potassium is $\geq 3.3 \text{ mEq/L}$
3Begin a continuous intravenous infusion of regular insulin
4Add $5\%$ dextrose to the maintenance intravenous fluids when serum glucose drops to $200$ to $250 \text{ mg/dL}$
5Transition to a subcutaneous basal-bolus insulin regimen once the anion gap normalizes

Answer

The correct chronological management of DKA begins with isotonic intravenous fluids, followed by verifying adequate potassium levels, initiating an intravenous insulin infusion, adding dextrose to fluids once blood glucose falls to 200-250 mg/dL, and finally transitioning to subcutaneous insulin when the anion gap closes.

The management of Diabetic Ketoacidosis (DKA) strictly follows an algorithmic approach to reverse metabolic derangements and prevent life-threatening complications. The very first step is aggressive fluid resuscitation with

0.9\%

normal saline to restore circulating volume and tissue perfusion. The second crucial step requires evaluating the serum potassium level; because insulin shifts potassium into cells, insulin therapy must be withheld if the potassium is less than

3.3 \text{ mEq/L}

. Once a safe potassium level is confirmed, the third step is initiating a continuous intravenous regular insulin infusion to suppress lipolysis and ketogenesis. As treatment progresses, blood glucose falls more rapidly than the ketoacidosis resolves. To prevent hypoglycemia while allowing insulin to finish closing the anion gap, the fourth step is adding

5\%

dextrose to the intravenous fluids when blood glucose reaches

200

250 \text{ mg/dL}

. Finally, the fifth step is the transition to a subcutaneous insulin regimen, which is performed only after the anion gap is closed (usually

\leq 12 \text{ mEq/L}

) and the patient is able to tolerate oral intake.

Step-by-Step Solution

Restore intravascular volume.

Administer an initial bolus of

0.9\%

normal saline.

Severe dehydration and osmotic diuresis cause profound volume depletion, which must be addressed first to prevent cardiovascular collapse.

Evaluate electrolyte status prior to insulin administration.

Check the serum potassium level.

Insulin administration causes intracellular shifting of potassium. Giving insulin to a patient with a potassium level below

3.3 \text{ mEq/L}

can trigger life-threatening arrhythmias.

Halt ketogenesis and reverse acidosis.

Start a continuous intravenous regular insulin infusion.

Insulin suppresses lipolysis and ketone production. It is initiated only after confirming potassium is safely above the critical threshold.

Prevent iatrogenic hypoglycemia during treatment.

Add

5\%

dextrose to the intravenous fluids when glucose reaches

200

250 \text{ mg/dL}

The blood glucose level normalizes before the ketoacidosis fully resolves. Dextrose allows continuous insulin administration to close the anion gap without causing hypoglycemia.

Transition to definitive maintenance therapy.

Switch to subcutaneous insulin.

Once the anion gap is

\leq 12 \text{ mEq/L}

and the patient can eat, subcutaneous insulin is administered. It is overlapped with intravenous insulin for

1

2

hours before the infusion is stopped to prevent rebound ketoacidosis.

Key Concept

The chronological management algorithm of Diabetic Ketoacidosis (DKA) prioritizes initial volume expansion, followed by potassium assessment, intravenous insulin infusion to resolve acidosis, dextrose supplementation to avoid hypoglycemia, and finally transitioning to subcutaneous insulin.

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