From the Guidelines
Tetany is directly related to respiratory alkalosis caused by hyperventilation, as the decrease in carbon dioxide levels leads to an increase in blood pH, which in turn increases the binding of calcium to albumin, reducing free calcium ions and causing neuromuscular excitability 1.
Pathophysiology of Tetany and Respiratory Alkalosis
The relationship between tetany and respiratory alkalosis due to hyperventilation is rooted in the physiological changes that occur when an individual hyperventilates. Hyperventilation leads to the excessive exhalation of carbon dioxide (CO2), which is a crucial component in maintaining the acid-base balance in the blood. With less CO2 in the blood, the pH level increases, leading to respiratory alkalosis. This condition affects the balance of ions in the blood, particularly calcium.
Effect on Calcium Levels and Neuromuscular Function
As noted in the context of hyperventilation syndrome, the increase in blood pH due to respiratory alkalosis enhances the binding of calcium to albumin, thereby reducing the levels of free, ionized calcium in the blood 1. Ionized calcium is essential for the proper functioning of nerves and muscles. A decrease in its levels leads to increased neuromuscular excitability, which manifests as tetany. Tetany symptoms can include carpopedal spasm, paresthesias, muscle cramps, and in severe cases, laryngospasm.
Clinical Presentation and Diagnosis
Subjects with hyperventilation syndrome may present with several symptoms, including exertional dyspnea, chest pain, and light-headedness, which can be attributed to unrecognized hyperventilation due to anxiety and stress. The diagnosis of hyperventilation syndrome and its relation to tetany involves identifying abnormal breathing patterns at rest and during exercise, which can be almost diagnostic. Cardiopulmonary exercise testing (CPET) often reveals impressive hyperventilation, as evidenced by abnormal increases in ventilation (Ve), Ve/Vco2, and respiratory frequency, and respiratory alkalosis (decreased PetCO2 and PaCO2) 1.
Management and Treatment
The management of tetany due to hyperventilation focuses on normalizing breathing patterns. Techniques such as breathing into a paper bag or cupped hands can help retain carbon dioxide and restore normal pH levels, thereby alleviating tetany symptoms. Reassurance and addressing underlying anxiety disorders through cognitive behavioral therapy are also crucial for preventing recurrent episodes. In severe cases where tetany persists, intravenous calcium gluconate might be considered, although this is rarely necessary as symptoms typically resolve once breathing normalizes.
Importance of Early Recognition and Intervention
Understanding the physiological mechanism behind tetany and respiratory alkalosis due to hyperventilation empowers patients to recognize the connection between their breathing pattern and physical symptoms. Early recognition and intervention can significantly improve the quality of life for individuals experiencing these symptoms, reducing morbidity and the risk of complications associated with severe or prolonged tetany episodes.
From the Research
Relationship between Tetany and Respiratory Alkalosis due to Hyperventilation
- Tetany can be caused by various electrolyte disturbances, including alkalosis, which can result from hyperventilation 2, 3, 4, 5, 6.
- Hyperventilation syndrome (HVS) leads to respiratory alkalosis, which is a frequent cause of tetany 5.
- Respiratory alkalosis caused by hyperventilation can lead to reduced ionized calcium levels, resulting in tetany 5.
- Hyperventilation-induced tetany can also be seen after spinal anesthesia and in respiratory disorders like asthma 5.
- Latent tetany or spasmophilia, which involves hyperventilation and magnesium deficiency, is a common type of tetany that affects particularly young women 4.
- Hyperventilation is a common symptom of tetany, and it can be accompanied by other symptoms such as shortness of breath, palpitation, dizziness, nausea, and carpopedal spasm 2.