Death of a clinical sign

To the Editor: Nothing is infallible in life. This fact further hammered itself in my mind when I recently took a ward round. There was a patient in the ward who had undergone total thyroidectomy with modified neck dissection for papillary carcinoma thyroid with cervical lymphadenopathy. A resident told me that the patient had not reported any symptom suggestive of hypocalcaemia and serum ionized calcium was normal. I asked if any of the residents had performed the Trousseau sign to look for subclinical hypocalcaemia. To my surprise, they replied that this sign could no longer be elicited as the mercury sphygmomanometer had been replaced with an electronic sphygmomanometer. It suddenly reminded me of the government drive to phase out mercury-based instruments. There has been a growing voice for mercury-free society and the World Health Organization issued a policy paper in 2005 calling for short-, medium-, and long-term measures to substitute mercury-based medical devices with safer alternatives.¹ So what about the Trousseau sign as it requires a few minutes of sustained inflation of a sphygmomanometer cuff above systolic blood pressure to cause a carpopedal spasm, as a feature of the increased excitability of the nerves in the arm and forearm, ostensibly caused by hypocalcemia.² I thought an aneroid sphygmomanometer would be there to demonstrate the Trousseau sign. However, the electronic sphygmomanometer has not left a role for the aneroid sphygmomanometer in wards in view of its simplicity, accuracy and trendy looks. An electronic sphygmomanometer is based on automatic inflation and deflation of the cuff, so cannot be used to demonstrate the Trousseau sign. It seems a simple and invaluable clinical sign will now be restricted to the books and will no longer be a part of clinical practice.