A 24-year-old female is rushed to the emergency department by her roommates due to profoun… — USMLE Step 3

A 24-year-old female is rushed to the emergency department by her roommates due to profound lethargy and confusion. Her roommates report that she has type 1 diabetes mellitus and recently experienced a severe gastrointestinal illness that prevented her from eating or taking her usual insulin doses for the past 48 hours. On arrival, she is stuporous and responds only to deep pain. Vital signs reveal a blood pressure of $78/40 \text{ mmHg}$ , heart rate of $118 \text{ /min}$ , respiratory rate of $32 \text{ /min}$ with deep, sighing respirations, and a temperature of $36.4^\circ\text{C}$ ( $97.5^\circ\text{F}$ ). Oxygen saturation is $98\%$ on ambient air. Fingerstick blood glucose measurement indicates a value greater than $600 \text{ mg/dL}$ . A stat 12-lead electrocardiogram demonstrates absent P waves, significantly widened QRS complexes, and tall, peaked T waves. Two large-bore peripheral intravenous lines are immediately established. Which of the following is the single most urgent next step in the management of this patient?

Administer intravenous calcium gluconateAnswer
B
Administer a rapid infusion of 0.9% sodium chloride
C
Initiate a continuous intravenous regular insulin infusion
D
Obtain a stat comprehensive metabolic panel and arterial blood gas
E
Order a non-contrast computed tomography scan of the head

Answer

Administer intravenous calcium gluconate

The patient's presentation of hyperglycemia, Kussmaul respirations, and altered mental status is highly consistent with severe diabetic ketoacidosis (DKA) complicated by hypovolemic shock. However, the critical piece of clinical data dictating the immediate next step is the electrocardiogram (ECG). The presence of absent P waves, significantly widened QRS complexes, and tall, peaked T waves indicates severe, life-threatening hyperkalemia with imminent risk of cardiovascular collapse and cardiac arrest (ventricular fibrillation or asystole). In any patient with hyperkalemia accompanied by ECG changes (particularly QRS widening), the absolute most urgent intervention is cardiac membrane stabilization using intravenous calcium (gluconate or chloride). While aggressive fluid resuscitation is the cornerstone of DKA management and must be initiated concurrently, pushing calcium takes minutes and acts immediately to raise the threshold potential, thereby protecting the myocardium from fatal dysrhythmias.

Step-by-Step Solution

Analyze the clinical presentation and vital signs

The patient has signs of severe hypovolemic shock and diabetic ketoacidosis (hyperglycemia, Kussmaul respirations, altered mental status).

Establishing the overarching pathophysiologic state is necessary, but recognizing life-threats within that state is critical.

Interpret the 12-lead electrocardiogram findings

The ECG shows absent P waves, widened QRS complexes, and peaked T waves.

These are the classic, progressive electrocardiographic hallmarks of severe hyperkalemia, progressing toward a sine wave and imminent ventricular fibrillation or asystole.

Prioritize interventions based on time-to-death risk

Cardiac membrane stabilization is identified as the most time-critical intervention.

Although the patient desperately needs intravenous fluids for shock, a widened QRS from hyperkalemia dictates that calcium gluconate must be pushed immediately to prevent cardiac arrest while concurrent fluid resuscitation is initiated.

Key Concept

In patients presenting with severe hyperkalemia and consequential electrocardiographic changes (especially QRS widening), immediate administration of intravenous calcium is the absolute most urgent pharmacologic step to stabilize the cardiac membrane and prevent lethal arrhythmias.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic