A patient with Myasthenia Gravis is admitted to the emergency department with complaints of respiratory distress. The patient's condition worsened, and he is likely to end up in?

1. A

   Metabolic acidosis

2. B

   Metabolic alkalosis

3. C

   Respiratory acidosis

4. D

   Respiratory alkalosis

Appeared in: SCTIMST Staff Nurse - 2015 (Set-B)

Explanation

• Myasthenia Gravis is a neuromuscular disorder that causes profound muscle weakness, including the muscles of respiration (diaphragm and intercostal muscles).
• This weakness leads to hypoventilation, which is the inability to breathe deeply and effectively enough to clear carbon dioxide (CO₂) from the body.
• The retention of CO₂ (hypercapnia) increases the level of carbonic acid in the blood, causing the blood pH to drop, which is the definition of respiratory acidosis.
• This situation, known as a myasthenic crisis, is a medical emergency requiring immediate intervention to support ventilation.

Why Other Options Were Wrong

• Option A: Metabolic acidosis is caused by an excess of acid (e.g., lactic acid, ketones) or loss of bicarbonate, which is not the primary problem in MG-related respiratory distress.
• Option B: Metabolic alkalosis results from a loss of acid (e.g., from severe vomiting) or an excess of bicarbonate. It is unrelated to the respiratory muscle failure seen in Myasthenia Gravis.
• Option D: Respiratory alkalosis is caused by hyperventilation, where the patient breathes too fast and blows off too much CO₂. This is the opposite of the hypoventilation that occurs in a myasthenic crisis.

Related Visual

Clinical Relevance

• Nursing practice connection: Prioritize focused assessment, early escalation, and real-time monitoring when managing Pathophysiology of respiratory failure in Myasthenia Gravis and resulting acid-base imbalance in acute care settings.
• Recognizing the risk of respiratory acidosis in patients with neuromuscular diseases like MG is a critical nursing skill. It is a life-threatening complication that requires prompt identification and intervention.
• Nurses must closely monitor respiratory parameters, including rate, depth, oxygen saturation, and signs of muscle fatigue. A decreasing vital capacity is a key indicator of impending respiratory failure.
• What if? If the patient with Myasthenia Gravis also had severe diarrhea, they could develop a mixed acid-base disorder. The respiratory acidosis from muscle weakness would be complicated by a metabolic acidosis from bicarbonate loss in the stool, leading to a more severe and complex acidemia.

How to Approach the Question

• First, identify the core disease process: Myasthenia Gravis (MG) is characterized by muscle weakness.
• Next, connect the disease to the clinical presentation: The patient has 'respiratory distress,' indicating the breathing muscles are affected.
• Analyze the effect on breathing: Severe muscle weakness will lead to ineffective, shallow breathing (hypoventilation).
• Determine the physiological consequence of hypoventilation: The body will be unable to exhale carbon dioxide (CO₂) effectively, causing it to build up in the blood.
• Finally, link the CO₂ buildup to the acid-base balance: Increased CO₂ is an acid in the blood, so its retention leads to acidosis. Since the cause is respiratory, the correct diagnosis is respiratory acidosis.

Concept Tested & Keywords

• Concept Tested: Pathophysiology of respiratory failure in Myasthenia Gravis and resulting acid-base imbalance.
• Stem keywords: Myasthenia Gravis, respiratory distress, worsened
• Lead-in keywords: likely to end up in
• Clinical cues: Myasthenia Gravis: This underlying condition is the key to understanding the cause of respiratory distress, pointing towards neuromuscular weakness.
• Clinical cues: Respiratory distress: This sign indicates a problem with ventilation or oxygenation, prompting an assessment of acid-base status.

Question ID

QJMk3-pl7eMv_ZeIpFJAkJ

Copy ID

Reference Book

E6 Medicine Harrison 22e Part 1 p. 416-418