A 22-year-old man presents to the emergency department with a 2-day history of worsening n… — USMLE Step 2 CK

A 22-year-old man presents to the emergency department with a 2-day history of worsening nausea, diffuse abdominal pain, and profound fatigue. He has been excessively thirsty and urinating frequently. He has no significant past medical history. His temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $98/60\text{ mmHg}$ , heart rate is $118/\text{min}$ , and respiratory rate is $24/\text{min}$ with deep, rapid breaths. Mucous membranes are dry. The abdomen is diffusely tender but soft without rebound. Point-of-care testing reveals a capillary blood glucose of $480\text{ mg/dL}$ and large blood ketones. An arterial blood gas shows a pH of $7.18$ . The patient is diagnosed with an acute endocrine emergency.

Arrange the following management steps in the most appropriate algorithmic sequence for the acute stabilization and definitive therapy of this patient.

1Administer a rapid continuous infusion of isotonic crystalloid ( $0.9\%$ normal saline)
2Assess serum potassium concentration to ensure it is $>3.3\text{ mEq/L}
3Initiate a continuous intravenous regular insulin infusion
4Add $5\%$ dextrose to the intravenous hydration fluid
5Transition to a subcutaneous basal-bolus insulin regimen

Answer

The correct sequence for managing Diabetic Ketoacidosis is: 1) Administer intravenous isotonic crystalloid, 2) Assess serum potassium, 3) Initiate intravenous regular insulin, 4) Add dextrose to intravenous fluids when glucose falls to

200\text{-}250\text{ mg/dL}

, and 5) Transition to subcutaneous insulin once the anion gap is closed.

The exact algorithmic sequence for DKA ensures physiological safety. Fluid resuscitation immediately addresses life-threatening hypovolemia. Assessing potassium ensures insulin can be given safely without precipitating lethal arrhythmias. Insulin stops the underlying pathophysiology (ketogenesis). Adding dextrose prevents iatrogenic hypoglycemia while the insulin finishes clearing the acid load. Finally, transitioning to subcutaneous insulin represents the resolution of the acute crisis and return to maintenance therapy.

Step-by-Step Solution

Synthesize the clinical diagnosis based on the vignette.

The patient is experiencing Diabetic Ketoacidosis (DKA).

The clinical presentation of polyuria, polydipsia, abdominal pain, Kussmaul respirations, profound hyperglycemia (

480\text{ mg/dL}

), ketonemia, and severe metabolic acidosis (pH

7.18

) is diagnostic of DKA.

Determine the highest priority in acute stabilization.

Aggressive fluid resuscitation with

0.9\%

normal saline.

Patients with DKA have profound osmotic diuresis leading to severe total body water deficits (often

5\text{-}8\text{ L}

). Restoring intravascular volume is the absolute first step to prevent cardiovascular collapse and acute renal failure.

Identify the prerequisite safety check before starting specific medical therapy.

Check the serum potassium level.

Patients with DKA often have total body potassium depletion despite normal or high serum levels. Insulin drives potassium intracellularly. If baseline potassium is

<3.3\text{ mEq/L}

, insulin must be withheld until potassium is replaced to avoid lethal arrhythmias.

Establish the sequence of medication administration and subsequent fluid adjustment.

Start an intravenous regular insulin infusion, then add

5\%

dextrose when glucose reaches

200\text{ mg/dL}

Insulin is required to suppress lipolysis and resolve the ketoacidosis. Once glucose levels drop significantly, dextrose is added to prevent hypoglycemia while allowing the continuous insulin infusion to finish closing the anion gap.

Determine the criteria for transitioning to maintenance therapy.

Switch to subcutaneous insulin.

Once the anion gap closes, acidosis resolves, and the patient can eat, an overlapping transition to subcutaneous basal-bolus insulin is performed.

Key Concept

The algorithmic management of Diabetic Ketoacidosis requires strict sequential therapy: aggressive fluid resuscitation, potassium assessment prior to insulin initiation, fluid modification with dextrose, and eventual transition to subcutaneous insulin once the anion gap closes.

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