A post-CABG patient shows sudden decrease in chest drain output (80 mL/hr → 10 mL/hr) along with hypotension, raised JVP, and tachycardia. What is the most likely cause?

1. A

   Hypovolemic shock due to bleeding

2. B

   Tube blockage due to clot leading to cardiac tamponade

3. C

   Myocardial infarction

4. D

   Pulmonary embolism

Appeared in: NORCET 10 Mains

Explanation

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• The sudden decrease in chest tube output in a post-cardiac surgery patient strongly suggests an obstruction, most commonly a blood clot.
• When the tube is blocked, blood that is still oozing post-surgery accumulates in the pericardial space, leading to compression of the heart (cardiac tamponade).
• This compression impairs the heart's ability to fill and pump, causing a drop in cardiac output.
• The clinical signs presented—hypotension (low output), raised JVP (venous backup), and compensatory tachycardia—are the direct result of this mechanical obstruction.

Why Other Options Were Wrong

• Option A: Hypovolemic shock results from significant blood loss. This would manifest as high or increasing chest tube output, not a sudden decrease. The JVP would be low or flat due to volume depletion, which contradicts the patient's raised JVP.
• Option C: A myocardial infarction (heart attack) is a failure of the heart muscle due to ischemia. While it can cause hypotension and tachycardia, it does not explain the primary mechanical problem indicated by the sudden drop in chest tube drainage.
• Option D: A pulmonary embolism is an obstruction in the pulmonary artery, typically causing acute respiratory symptoms like dyspnea, hypoxia, and pleuritic chest pain. It does not directly cause a blockage of the mediastinal chest tube.

Related Visual

• Visual 1: Diagram - A diagram illustrating the pathophysiology of cardiac tamponade, showing fluid accumulation in the pericardial sac compressing the heart chambers.
• Visual 2: Infographic - An infographic of Beck's Triad (Hypotension, Jugular Venous Distention, Muffled Heart Sounds) to help memorize the classic signs of cardiac tamponade.

Clinical Relevance

• Nursing practice connection: Use the key finding related to Assessment of postoperative complications following cardiac surgery, specifically cardiac tamponade to guide bedside assessment, documentation, and the next nursing action.
• Recognizing cardiac tamponade is a critical nursing skill in the care of post-cardiac surgery patients. A blocked chest tube is a surgical emergency that can lead to cardiac arrest if not identified and treated promptly.
• The nurse is the first line of defense. Meticulous monitoring of chest tube drainage—noting not just the amount but also the character and any sudden changes—is essential for patient safety.
• What if? If the patient's chest drain output suddenly increased to over 200 mL/hr with hypotension and tachycardia, the priority diagnosis would shift from tamponade to active hemorrhage (hypovolemic shock), requiring immediate volume resuscitation and potential surgical re-exploration to control the bleeding.

How to Approach the Question

• First, identify the patient context: a post-CABG patient, who is at high risk for bleeding and tamponade.
• Next, analyze the most critical piece of data: the sudden change in chest tube output from a significant amount (80 mL/hr) to almost nothing (10 mL/hr). This points towards an obstruction.
• Correlate this primary finding with the other vital signs: hypotension, raised JVP, and tachycardia. These are signs of the heart failing as a pump due to an external pressure.
• Synthesize the information: An obstruction (blocked tube) is causing blood to build up and compress the heart (tamponade), leading to obstructive shock.
• Evaluate the options based on this synthesis. Only 'Tube blockage due to clot leading to cardiac tamponade' explains all the findings cohesively.

Concept Tested & Keywords

• Concept Tested: Assessment of postoperative complications following cardiac surgery, specifically cardiac tamponade.
• Stem keywords: post-CABG, sudden decrease in chest drain output, hypotension, raised JVP, tachycardia
• Lead-in keywords: most likely cause
• Clinical cues: The sudden drop in chest drain output from 80 mL/hr to 10 mL/hr is the key diagnostic clue, pointing to an obstruction rather than a resolution of bleeding.

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