A 21-year-old woman with type 1 diabetes mellitus is brought to the emergency department d… — USMLE Step 2 CK

A 21-year-old woman with type 1 diabetes mellitus is brought to the emergency department due to lethargy, abdominal pain, and vomiting. She stopped taking her insulin two days ago because she was unable to eat. Her blood pressure is $88/55 \text{ mm Hg}$ , heart rate is $132\text{/min}$ , and respiratory rate is $26\text{/min}$ with deep, sighing breaths. Mucous membranes are markedly dry. Laboratory studies reveal:

Laboratory Study	Result
Serum glucose	$520 \text{ mg/dL}$
Serum sodium	$132 \text{ mEq/L}$
Serum potassium	$2.9 \text{ mEq/L}$
Serum bicarbonate	$10 \text{ mEq/L}$
Arterial pH	$7.15$

Arrange the following targeted management steps in the most appropriate chronological sequence according to standard diabetic ketoacidosis (DKA) protocols.

1Administer a rapid intravenous bolus of $0.9\%$ sodium chloride.
2Initiate intravenous potassium chloride supplementation.
3Start a continuous intravenous infusion of regular insulin.
4Add $5\%$ dextrose to the maintenance intravenous fluids.

Cevap

The correct chronological sequence for this patient's management is: 1) Administer a rapid intravenous bolus of 0.9% sodium chloride, 2) Initiate intravenous potassium chloride supplementation, 3) Start a continuous intravenous infusion of regular insulin, and 4) Add 5% dextrose to the maintenance intravenous fluids.

The initial priority in diabetic ketoacidosis (DKA) is restoring intravascular volume with

0.9\%

normal saline to reverse hypovolemic shock and improve renal perfusion. Next, serum potassium must be evaluated. Although patients with DKA have total body potassium depletion, serum levels are often falsely normal or elevated due to extracellular shifts from acidosis and insulin deficiency. In this patient, the serum potassium is already severely low (

2.9 \text{ mEq/L}

). Because insulin drives potassium into cells, insulin therapy MUST be delayed until serum potassium is restored to at least

3.3 \text{ mEq/L}

to avoid fatal arrhythmias. Once potassium is appropriately replaced, an intravenous regular insulin infusion is started to halt ketogenesis. Finally, when blood glucose levels fall to approximately

200 \text{ mg/dL}

5\%

dextrose is added to the intravenous fluids. This prevents hypoglycemia while allowing the continuous insulin infusion to remain active until the anion gap successfully closes.

Adım Adım Çözüm

Assess hemodynamic status and establish immediate priorities.

Patient is in hypovolemic shock (BP

88/55 \text{ mm Hg}

). The first step must be fluid resuscitation with

0.9\%

normal saline.

Restoring intravascular volume improves renal perfusion and begins the process of lowering serum osmolality.

Evaluate the initial serum potassium level before giving insulin.

Potassium is

2.9 \text{ mEq/L}

, which is below the critical threshold of

3.3 \text{ mEq/L}

Insulin drives potassium intracellularly. Giving insulin now would cause life-threatening hypokalemia. Potassium repletion is the immediate next step.

Determine the timing for insulin administration.

Intravenous regular insulin can only be started after serum potassium is confirmed to be

> 3.3 \text{ mEq/L}

Insulin is required to halt ketogenesis and close the anion gap, but must be timed safely relative to potassium correction.

Plan for the transition phase of DKA management.

Dextrose (

5\%

) must be added to the intravenous fluids once serum glucose falls below

200 \text{ mg/dL}

To prevent hypoglycemia while continuing the insulin drip required to resolve the underlying ketoacidosis.

Anahtar Kavram

The acute management sequence of Diabetic Ketoacidosis (DKA) strictly prioritizes fluid resuscitation, followed by assessment and correction of severe hypokalemia prior to the initiation of insulin therapy.

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