From the Research
The patient's carpopedal spasms are most likely caused by respiratory alkalosis, and treatment should focus on addressing the underlying cause of hyperventilation, rather than calcium supplementation, as evidenced by the study 1 which found that short-term hyperventilation does not change the concentration of ionized serum calcium. The low bicarbonate (14 mEq/L) and low PCO2 (23 mmHg) with a near-normal pH (7.41) indicate chronic hyperventilation with renal compensation. Despite normal calcium levels, the alkalotic state has increased calcium binding to albumin, reducing ionized calcium and triggering neuromuscular irritability. Some studies suggest that tetany, which includes carpopedal spasm, is a series of symptoms characterized by painful muscle cramp that derives from enhanced neuromuscular excitability due to hypocalcemia, hypomagnesemia or alkalosis 2. However, the most recent and highest quality study 1 found that hyperventilation does not decrease ionized calcium levels. Immediate management involves controlled breathing techniques (breathing slowly into cupped hands or a paper bag) to increase CO2 levels. For severe symptoms, a short-acting benzodiazepine like lorazepam 0.5-1mg may help reduce anxiety-driven hyperventilation, as suggested by the case report 3. Correction of the respiratory alkalosis will normalize the ionized calcium fraction and resolve the carpopedal spasms. The patient should be evaluated for chronic causes of hyperventilation, including anxiety disorders, chronic pain, or pulmonary conditions that may require specific treatment, as recommended by the study 4. Key points to consider in management include:
- Addressing the underlying cause of hyperventilation
- Controlled breathing techniques to increase CO2 levels
- Short-acting benzodiazepines for severe symptoms
- Evaluation for chronic causes of hyperventilation
- No indication for calcium supplementation with normal total calcium levels, as supported by the study 5.