Introduction

What is tetany?

Tetany is a series of symptoms characterised by painful muscle cramps that derive from enhanced neuromuscular excitability due to hypocalcemia (ionised calcium <0.75 mmol/l), hypomagnesemia or alkalosis.^1,2 

Causes and complications of tetany

Tetanus is caused by a toxin secreted by Clostridium tetani, a Gram-positive, obligate anaerobic bacillus that forms a stable terminal spore.³ 

However, additional causes of tetany include alkalosis, hypokalemia, and hypomagnesemia, while the presence of hypocalcemia and alkalosis can act synergistically to cause tetany.⁴ 

Respiratory complications include laryngospasm and bronchospasm.⁵

Medications that induce tetany are bisphosphonates, denosumab, cisplatin, antiepileptics, aminoglycosides, diuretics, etc. Tetany is also encountered in acute pancreatitis, dengue, falciparum malaria, hyperemesis gravidarum, tumour lysis syndrome (TLS), massive blood transfusion, etc.⁶

Understanding laryngospasm and stridor

Laryngospasm involves spasm of all the muscles of the larynx such that the vocal cords are brought to the midline and will not allow air to enter or exit the lungs despite attempts by the patient to breathe. Inspiratory stridor is frequently audible immediately before laryngospasm. Here, air passing through a narrowed glottic chink during inspiration produces an eponymous sound audible to the examiner. Often, this stridor is followed by pure laryngospasm with complete occlusion of the larynx.⁷ 

Pathophysiology of tetany

Acidosis decreases calcium binding to albumin and thus increases ionised calcium. Thus, it protects against tetany. Conversely, alkalosis increases calcium binding to albumin and lowers the levels of ionised calcium. Hence, tetany may occur in alkalosis because of the low levels of ionised calcium, even in the presence of normal total serum calcium and both metabolic and respiratory alkalosis precipitate tetany, thus reducing the ionised calcium levels.⁶ Hypokalemia in the absence of alkalosis has also been reported to cause tetany,⁸

Diagnosis

Symptoms may be associated with circumoral numbness, muscle cramps, or paraesthesias of the hands and feet. Severe presentations are associated with laryngospasm, generalised muscle cramps, seizures, or even myocardial dysfunction.⁸  

Tetany can be diagnosed by observing bronchial contractions visible via bronchoscopy, indicating respiratory involvement.⁹ 

The electromyographic test is considered to be the most sensitive from the diagnostic spectrum at one's disposal and must be employed for proving or ruling out a tetany in indeterminate stenocardias, vasomotor circulatory disorders, in spastic disorders of the gastrointestinal tract, in indeterminate headache and in tetanic cataract and following thyroid gland operations.¹⁰ 

Chvostek and Trousseau signs are provocative tests for the diagnosis of latent tetany.¹ 

Management

Acute therapy

Infusion of calcium or magnesium is effective as an acute therapy for tetany.¹

Control respiratory alkalosis

In situations where hyperventilation is causing respiratory alkalosis, methods of calming anxiety and slowing the breath may be helpful. This can involve rebreathing methods or controlled breathing strategies.⁶

Electrolyte imbalance

Tetany tends to be caused by alkalosis of the respiratory and metabolic types, which will lower the ionised levels of calcium and cause manifestations like laryngospasm and stridor. Gitelman syndrome points to the need for electrolyte monitoring, as it can greatly affect tetany presentations

Medications

Benzodiazepines: These medications are widely used for their efficacy in relaxing muscle tension and muscle spasms. This may be particularly beneficial in patients in whom a patient's anxiety significantly increases or worsens pre-existing symptoms.^1,11

Positioning: Having the patient in a position of comfort can be incredibly vital in facilitating easier and more efficient breathing.

Tracheostomy or Intubation: In extreme laryngospasm resulting in severe airway obstruction, emergency intubation or tracheostomy may be necessary to keep the airway safe and patient.¹

Treat underlying conditions

Identification and treatment of any underlying condition causing tetany, like hypoparathyroidism or deficiency of vitamin D, plays a crucial role in long-term control.^{1, 6} 

Recent advancements

Rapid treatment and diagnosis 

Early detection of tetany is vital. A case report emphasised that immediate treatment with calcium gluconate markedly alleviated symptoms in 30 to 40 minutes, emphasising the urgency of early electrolyte correction.¹ Such a quick response can avoid serious respiratory complications like bronchospasm and laryngospasm.

Multifactorial approach: Management needs to treat different possible causes of tetany, such as hypocalcaemia, hypomagnesaemia, and alkalosis. When anxiety is also a contributing factor to hyperventilation and resulting respiratory alkalosis, behavioural management can also be useful.^5,12

Future directions

Research into breathing disorders: Further research into abnormal breathing patterns could shed light on the management of respiratory symptoms in tetany. How chronic alterations in breathing can generate dyspnoea is important to learn and understand to develop focused interventions for such affected patients.¹³

Summary

Respiratory distress in tetany, especially laryngospasm and stridor, is are life-threatening manifestation that can result in catastrophic airway obstruction and fatal outcomes if not identified and treated early. The pathophysiology underlying the condition, largely due to hypocalcemia and alkalosis, resulting in increased neuromuscular excitability, triggering spasms of the laryngeal muscles. Proper diagnosis includes identifying typical symptoms like inspiratory stridor, muscle cramps, and circumoral paraesthesia, along with verification of electrolyte derangements.

Treatment involves a multidimensional strategy, such as acute administration of magnesium or calcium, correction of the underlying electrolyte imbalance, and airway management in severe attacks. Prompt treatment, especially with calcium gluconate, can greatly reduce symptoms, highlighting the need for early diagnosis and intervention. Long-term treatment entails management of the underlying causes of alkalosis or hypocalcaemia and prevention of recurrent attacks.

Progress in appreciating the intricate interrelationship between electrolyte imbalances and respiratory complications in tetany has enhanced diagnostic and therapeutic approaches. Nevertheless, ongoing research into respiratory patterns and the effect on tetany symptoms is needed to enhance the development of effective, targeted therapies. Early diagnosis and effective management are imperative in avoiding morbidity and mortality from respiratory complications in tetany.

More research into preventive strategies, including educating high-risk patients and maximising long-term calcium and vitamin D supplementation, may improve patient outcomes. Also, creating standardised protocols for emergency treatment of laryngospasm and stridor may decrease complications and increase survival rates. Thorough patient education and follow-up are crucial to preventing recurrence and maintaining quality of life.

Innovative approaches for the future

• Point-of-care diagnostics:

Portable electrolyte analysers: Small, easy-to-use devices that can quickly measure serum electrolytes at the bedside or in the home, allowing for early intervention.

• AI-driven diagnostic tools:

Artificial intelligence software is embedded in diagnostic equipment to calculate the probability of respiratory complications using patient history, symptoms, and electrolyte concentrations.

• Advanced airway management techniques:

Smart airway devices: Design of intelligent laryngoscopes and endotracheal tubes with integrated sensors and cameras to improve visualisation and control of airway obstruction during laryngospasm.

Non-invasive airway support: Improved non-invasive ventilation devices to administer positive airway pressure, decreasing the necessity for intubation in moderate laryngospasm.

• Pharmacological developments:

Rapid-acting calcium formulations: Development of more rapid-acting intravenous or inhalable calcium supplements for immediate use in extreme hypocalcaemia-induced laryngospasm.

Targeted muscle relaxants: Creation of short-acting muscle relaxants that target specifically laryngeal muscles, minimising the risk of respiratory arrest.

FAQs

What is tetany?

Tetany is a disorder that involves painful muscle cramps and spasms due to elevated neuromuscular excitability. It is most often seen with low ionised calcium (hypocalcaemia), hypomagnesaemia, or alkalosis.

What causes respiratory complications in tetany?

Respiratory complications arise because of involuntary laryngeal muscle spasms that result in laryngospasm and stridor. These are most often initiated by hypocalcemia or alkalosis, which increase neuromuscular excitability.

What is laryngospasm, and how does it occur concerning tetany?

Laryngospasm is an involuntary, acute tightening of the vocal cords, causing partial or full airway closure. In tetany, it results from the low calcium content, which provokes nerve and muscle hyperexcitability.

What is stridor, and how does it occur in tetany?

Stridor is a wheezing, a high-pitched sound of breathing resulting from turbulent airflow in the upper airway. It results from tetany through partial airway obstruction from laryngospasm or laryngeal muscle spasms.

How does laryngospasm differ from stridor?

Laryngospasm is the true spasm of the vocal cords, resulting in airway obstruction, while stridor is the sound resulting from airflow through a constricted airway. Stridor tends to precede laryngospasm.

What are the tetany symptoms of laryngospasm and stridor?

Symptoms include acute breathing distress, stridor (high-pitched sound when breathing), cyanosis (a bluish colour due to insufficient oxygen), muscle spasms, circumoral paraesthesia (numbness around the mouth), and carpopedal spasms (spasmodic contraction of the hands and feet).