Examkin

Question

Difficulty: MediumCardiovascular System

An emergency response team brings a 54-year-old male to the resuscitation bay after he experienced sudden, crushing central chest pain while working in his garden. The pain radiates to his jaw and is accompanied by profuse sweating. En route to the hospital, the transport personnel administered 325 mg of chewable aspirin and one dose of sublingual nitroglycerin. Shortly after receiving the nitroglycerin, the patient developed profound lightheadedness.

Currently, his blood pressure is 78/48 mmHg, and his pulse is 52/min. His respiratory rate is 16/min, and oxygen saturation is 96% on room air.

Physical examination reveals clear lung fields bilaterally. The jugular veins are markedly distended while the patient is positioned at a 45-degree angle.

A 12-lead electrocardiogram demonstrates 3-mm ST-segment elevations in leads II, III, and aVF, as well as ST-segment depressions in leads I and aVL.

Which of the following is the most appropriate initial step to manage this patient's hemodynamic instability?

  1. A
    Intravenous furosemide administration
  2. B
    Repeated administration of sublingual nitroglycerin
  3. C
    Transfer to the radiology department for a contrast-enhanced chest scan
  4. Isotonic intravenous fluid bolusAnswer
  5. E
    Endotracheal intubation and positive pressure ventilation

Answer

Administration of an isotonic intravenous fluid bolus.
The patient is experiencing an acute inferior ST-elevation myocardial infarction (STEMI) complicated by right ventricular (RV) involvement. RV infarction is characterized by the triad of hypotension, clear lung fields, and elevated jugular venous pressure. Because the ischemic right ventricle loses its contractility, it becomes highly dependent on adequate filling pressures (preload) to maintain forward flow to the left ventricle. The administration of sublingual nitroglycerin (a potent venodilator) abruptly reduced this patient's preload, precipitating profound hypotension. The most appropriate initial step is to administer an isotonic intravenous fluid bolus to augment right-sided filling pressures, thereby increasing forward flow and restoring systemic blood pressure.

Step-by-Step Solution

1
Identify the primary diagnosis based on the clinical presentation and electrocardiogram.
The ST-segment elevations in leads II, III, and aVF indicate an acute inferior myocardial infarction.
Inferior wall STEMIs often involve the right ventricle, which is supplied by the right coronary artery.
2
Correlate the physical exam findings with the mechanism of hypotension.
Clear lung fields combined with jugular venous distention and hypotension following nitroglycerin administration confirms right ventricular (RV) infarction.
The stunned right ventricle cannot effectively pump blood to the left heart, making it heavily dependent on venous return (preload) to maintain cardiac output.
3
Select the appropriate intervention to restore hemodynamic stability.
The correct intervention is to maximize preload by administering an isotonic intravenous fluid bolus.
Increasing intravascular volume physically pushes blood through the impaired right ventricle, thereby restoring left ventricular filling and systemic blood pressure.

Key Concept

Right ventricular myocardial infarction presents with hypotension, clear lungs, and jugular venous distention. The stunned right ventricle is highly preload-dependent; therefore, therapies that reduce preload (nitrates, diuretics) are contraindicated, and hypotension should be managed with isotonic fluid boluses.
Estimated Time:1m 15s
Rate this question

Topics

Cardiovascular System

More questions from this topic