Trousseau’s sign of latent tetany is a clinical sign that nurses and other healthcare professionals use to assess whether a patient has an electrolyte imbalance known as hypocalcemia, though this sign can present during hypomagnesemia as well. You’ll likely hear Trousseau’s sign mentioned in nursing school or medical school, especially when studying fluid and electrolytes.
What is Trousseau’s Sign of Latent Tetany?
Trousseau’s sign a specific type of muscle spasm that occurs in the hand and wrist due to neuromuscular irritability, which tends to be a definitive sign of hypocalcemia (low calcium level in the blood). This is not to be confused with Chvostek’s sign, which is a type of facial twitching that occurs when the masseter muscle is tapped.
Normal calcium level in the blood is 8.5-10.5 mg/dL so this typically occurs at a level less than 8.5 mg/dL.
How to Assess for Trousseau’s Sign
To assess for Trousseau’s sign of latent tetany, you’ll need a manual blood pressure cuff, as well as the patient’s most recent blood pressure reading – particularly the systolic number, which is the top number in the blood pressure reading.
Place the blood pressure cuff around the arm and inflate it to a pressure greater than the patient’s systolic blood pressure. Keep the pressure and cuff in place for around 3 minutes. During this time, you’ll want to monitor the hand and wrist of the patient’s extremity that has the blood pressure cuff on it.
As you monitor the patient and assess for Trousseau’s sign, you’ll want to determine whether the patient has a positive or negative sign.
Positive Trousseau’s Sign
When the patient has a positive Trousseau’s sign, the hand will slowly draw in toward the body, and flexion will occur at the wrist, thumb, and MCP (metacarpophalangeal) joints; but the fingers typically remain extended at the distal and proximal interphalangeal joints (DIP and PIP joints), as seen below.
Negative Trousseau’s Sign
The patient is considered to have a negative Trousseau sign if no spasm/response occurs during the assessment.
Why Does Trousseau’s Sign Occur?
When the cuff is inflated above the patient’s systolic pressure, the brachial artery that supplies the forearm and hand with blood is occluded. This decreases the blood flow to the hand and wrist’s muscles and nerves.
Consequently, since the patient is experiencing a low calcium level, the nerves and muscles are already irritated and too excited, so the lack of blood flow due to the blood pressure cuff causes them to spasm.
Electrolyte Imbalances that Can Lead to a Positive Trousseau’s Sign
Trousseau’s sign can occur during an electrolyte imbalance. Though it can occur with hypomagnesemia (low magnesium levels in the blood), it is primarily associated with hypocalcemia (low calcium levels in the blood).
Causes of Hypocalcemia
Below are some common causes of hypocalcemia, which may lead to a positive Trousseau’s sign.
- Low parathyroid hormone (removal or surgery of parathyroid gland or of the neck…thyroidectomy…damages structures that help support calcium levels)
- Low intake of calcium (lactose intolerance or dairy allergy)
- Low vitamin D intake
- Chronic kidney disease (wasting calcium)
In addition, the following medications can lead to hypocalcemia.
- Bisphosphonates (help make bones stronger: decreases the release of calcium from the bones into the blood, which can lower blood levels of calcium)
- Antibiotics…aminoglycosides (“mycin”)…waste calcium by the kidneys
- Anticonvulsants (phenobarbital, phenytoin) alters vitamin D levels