What is the assessment and plan for a 30‑year‑old male who developed sudden carpopedal spasm, cold extremities, tinnitus, dry heaving, and severe shooting pain after vigorous exercise, with a normal neurologic exam and no past medical history?

Assessment and Plan for Exercise-Induced Carpopedal Spasm

Primary Assessment: Hyperventilation-Induced Tetany

This 30-year-old male experienced hyperventilation-induced tetany following vigorous exercise, manifesting as carpopedal spasm, paresthesias (tinnitus, "electrical shooting pain"), and autonomic symptoms (dry heaving, coldness). 1, 2, 3

The clinical presentation is classic for acute respiratory alkalosis from hyperventilation during intense physical exertion, causing decreased ionized calcium and subsequent neuromuscular hyperexcitability. 1, 2, 4

Immediate Diagnostic Workup

Essential Laboratory Tests

• Serum ionized calcium (most critical—can be normal in hyperventilation tetany due to alkalosis-induced protein binding changes) 1, 2
• Arterial or venous blood gas to document respiratory alkalosis (elevated pH, decreased PCO2) 4, 3
• Serum magnesium (hypomagnesemia can cause identical presentation) 1, 2
• Serum potassium (hypokalaemia can contribute to tetany) 2, 5
• Electrocardiogram to rule out cardiac causes given the severe pain and autonomic symptoms during exercise 6, 7

Critical Cardiac Evaluation Required

Given the syncope-equivalent symptoms (near-collapse with severe pain, autonomic instability) during vigorous exercise in a young adult, cardiac causes must be excluded before attributing symptoms solely to hyperventilation. 6

• 12-lead ECG is mandatory to screen for long QT syndrome, pre-excitation patterns, or other arrhythmogenic substrates 6, 8
• Echocardiography should be obtained if any ECG abnormalities or if symptoms recur with exercise 6, 8
• Exercise stress testing may be indicated if cardiac etiology remains a concern after initial workup 6

The American Heart Association/American College of Cardiology guidelines emphasize that syncope or near-syncope during exercise (not after) is a compelling symptom requiring thorough cardiovascular evaluation to exclude sudden cardiac death risk. 6

Immediate Management

Acute Treatment

• Reassurance and controlled breathing to normalize PCO2 (have patient breathe slowly into cupped hands or paper bag if still symptomatic) 4, 3
• Intravenous calcium gluconate 10% (10-20 mL over 10 minutes) if severe symptoms persist or ionized calcium is low 1, 2
• Magnesium supplementation if hypomagnesemia is documented 1, 2
• Rehydration with isotonic fluids given the exercise context and autonomic symptoms 6, 7

Observation Period

• Monitor for 4-6 hours to ensure symptom resolution and exclude evolving cardiac or metabolic complications 6
• Repeat ionized calcium and electrolytes after initial correction 2, 5

Differential Diagnoses to Exclude

Life-Threatening Causes

• Coronary artery spasm (can occur in young adults during exercise, though rare) 6
• Exercise-associated hyponatremia (presents with similar neurological symptoms if severe fluid overload occurred) 7
• Heat exhaustion progressing toward heat stroke (headache equivalent = tinnitus, nausea, severe pain) 6, 7
• Inherited arrhythmia syndromes (catecholaminergic polymorphic ventricular tachycardia, long QT) 6

Metabolic/Endocrine Causes

• Hypoparathyroidism (check PTH if hypocalcemia confirmed) 1, 2
• Vitamin D deficiency (contributing to hypocalcemia) 2
• Proton pump inhibitor use (can cause hypomagnesemia-induced tetany, though patient denies medications) 2

Common Pitfalls to Avoid

Do not dismiss severe exercise-associated symptoms as "just anxiety" without excluding cardiac and metabolic causes. 6, 7

• The American Heart Association explicitly warns that discomfort during exercise (including severe pain of any character) requires medical evaluation before exercise resumption 6
• Hyperventilation can be secondary to cardiac ischemia or arrhythmia rather than primary anxiety 6
• Syncope during exercise carries 75% risk of cardiac etiology in young athletes 6

Do not attribute all symptoms to a single diagnosis without comprehensive evaluation. 7, 9

• Multiple mechanisms may coexist: dehydration + hyperventilation + electrolyte shifts from exercise 6, 7
• Heat-related illness can present with neurological symptoms mimicking tetany 6, 7

Return-to-Exercise Criteria

Before Resuming Vigorous Activity

The patient should not return to competitive or vigorous exercise until:

1. Complete cardiovascular evaluation is normal (ECG, possibly echocardiogram and stress test) 6
2. All electrolyte abnormalities are corrected and stable 2, 5
3. Underlying cause is identified and addressed 1, 2
4. Patient demonstrates ability to exercise at moderate intensity without symptom recurrence 6

Prevention Strategies for Future Exercise

Implement structured exercise modifications to prevent recurrence: 6, 7

• Gradual warm-up and cool-down periods (minimum 5-10 minutes each) to avoid abrupt physiological transitions 6
• Adequate hydration before, during, and after exercise (but avoid excessive fluid intake that could cause hyponatremia) 6, 7
• Avoid exercising in extreme heat/humidity (temperature >70-80°F significantly increases risk) 6, 7
• Controlled breathing techniques during intense exertion to prevent hyperventilation 4, 3
• Avoid exercising within 2-4 hours of meals if gastrointestinal symptoms contributed 7, 9
• Progressive intensity increases rather than sudden maximal exertion 6

Education and Monitoring

Provide explicit warning signs requiring immediate exercise cessation: 6

• Chest discomfort, arm/neck/jaw pain during exercise 6
• Faintness or dizziness during (not just after) exercise 6
• Severe shortness of breath that prevents conversation 6
• Recurrence of carpopedal spasm or severe paresthesias 1, 2

Disposition

Admit for observation if:

• Cardiac workup reveals any abnormalities 6
• Severe electrolyte derangements requiring IV correction 2, 5
• Symptoms persist despite initial treatment 1, 2

Discharge with close outpatient follow-up if:

• Cardiac evaluation is completely normal 6
• Electrolytes normalize with treatment 2
• Symptoms fully resolve 1, 3
• Patient demonstrates understanding of warning signs 6

Mandatory outpatient cardiology referral for exercise stress testing and possible extended rhythm monitoring given the severity of symptoms during exertion. 6, 8