Association Between Thyroid Dysfunction and Intensive Care Unit Acquired Weakness: A Case Control Study

Intensive care unit acquired weakness refers to muscle weakness encountered in the intensive care unit as a consequence of critical illness. It affects more than 50 % of patients in the intensive care and is related to many problems as difficult weaning from mechanical ventilation, prolonged hospital stay and increased mortality.

There are three distinct entities for ICUAW that can only be differentiated by neurophysiological studies. These are critical illness myopathy (CIM), critical illness polyneuropathy (CIP) and critical illness neuromyopathy (CINM).

Identification of risk factors responsible for the development of ICUAW is the first step in the prevention and management of this disorder. Till time septic shock, hyperglycemia, high dose steroid therapy, prolonged mechanical ventilation and the use of neuromuscular blocking agents are the main accused.

Thyroid disorders are also associated with neuromuscular abnormalities. Unfortunately, the prevalence of thyroid dysfunction in the intensive care is high reaching 90%. Moreover, patients with severe critical illness, who are typically prone to the development of ICUAW, show changes in their thyroid biochemistry namely low T3 levels (with or without low T4 levels) in the presence of normal TSH levels. These changes are collectively known as Non-Thyroidal illness syndrome (previously low T3 syndrome and Euthyroid sick syndrome) which is the most common form of thyroid dysfunction in the intensive care unit.