During morning rounds in the medical intensive care unit, a 24-year-old man is evaluated. … — USMLE Step 3

During morning rounds in the medical intensive care unit, a $24$ -year-old man is evaluated. He was admitted $18$ hours ago with severe diabetic ketoacidosis. He has received aggressive fluid resuscitation and a continuous intravenous regular insulin infusion. Currently, he is asymptomatic, alert, and requesting breakfast. His most recent basic metabolic panel demonstrates a serum bicarbonate of $21\text{ mEq/L}$ and an anion gap of $10\text{ mEq/L}$ . Venous pH is $7.34$ . Point-of-care blood glucose is $175\text{ mg/dL}$ . The care team decides it is time to transition him to a maintenance regimen of subcutaneous glargine and lispro insulin. Arrange the following steps in the most appropriate chronological sequence to safely accomplish this therapeutic transition.

1Administer the scheduled dose of subcutaneous basal and rapid-acting insulin
2Maintain the continuous intravenous regular insulin infusion for $1$ to $2$ additional hours
3Discontinue the continuous intravenous regular insulin infusion
4Assess the point-of-care blood glucose prior to the patient's next meal

Answer

The correct sequence for transitioning a patient off an insulin infusion is to first administer the subcutaneous insulin, continue the intravenous infusion for a 1- to 2-hour overlap, then discontinue the intravenous infusion, and finally resume standard pre-meal blood glucose monitoring.

The clinically correct and safe sequence for resolving diabetic ketoacidosis involves waiting until resolution criteria are met (anion gap

< 12\text{ mEq/L}

, pH

> 7.3

, tolerating PO), which this patient has achieved. At this point, subcutaneous insulin is administered. Because intravenous insulin clears the body within minutes and subcutaneous insulin takes

1

2

hours to onset, a mandatory overlap of

1

2

hours is required. After this overlap, the intravenous infusion is stopped, and standard routine blood glucose monitoring continues.

Step-by-Step Solution

Administer the scheduled dose of subcutaneous basal and rapid-acting insulin.

The patient receives the first dose of their home subcutaneous insulin regimen while still on the intravenous infusion.

Subcutaneous insulin requires time for absorption and onset of action, making it the necessary first step in the transition protocol.

Maintain the continuous intravenous regular insulin infusion for

1

2

additional hours.

Intravenous and subcutaneous insulin delivery overlap for a critical safety window.

Intravenous insulin has a half-life of only a few minutes. Without an overlap period, insulin levels will drop to zero before the subcutaneous insulin begins working, risking a rapid relapse into ketoacidosis.

Discontinue the continuous intravenous regular insulin infusion.

The intravenous line delivering insulin is stopped.

Once the subcutaneous insulin has reached sufficient systemic levels (after the 1-2 hour overlap), the intravenous infusion is no longer needed and can be safely stopped.

Assess the point-of-care blood glucose prior to the patient's next meal.

Routine glucose monitoring is established.

With the acute crisis resolved and the patient on a standard regimen, monitoring safely transitions to standard pre-prandial and bedtime checks.

Key Concept

Patients recovering from diabetic ketoacidosis require a 1- to 2-hour overlap between the administration of subcutaneous insulin and the discontinuation of the intravenous insulin infusion to prevent rebound ketoacidosis.

Estimated Time:1m 30s

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