Thyroid hormone response to moderate hypothermia in severe brain injury.

Abstract

To examine the effect of controlled moderate hypothermia on thyroid response in head-injured patients. Prospective, controlled, randomized study. University hospital intensive care unit (ICU). Twenty-eight patients with severe blunt head injury (Glasgow Coma Scale < or =9). Patients were randomly assigned to a hypothermia or a normothermia group. Hypothermia (32-33 degrees C) was induced within 8 h after trauma and maintained for a mean of 36 h. All patients were sedated and mechanically ventilated. Thyroid-stimulating hormone( TSH), free and total triiodothyronine (FT3/TT3), reverse triiodothyronine (RT3) and thyroxine (FT4/TT4) were measured during the hypothermia or corresponding normothermia period, after regaining normothermia and 4-6 days later. Of 28 patients included in the study, 11 subjects were treated with hypothermia and 13 patients with normothermia. Four patients had to be excluded. In both groups, serum concentrations of TT3 and FT3 were just below the lower normal range whereas RT3 serum concentrations were near the upper limit of the normal range. TSH serum concentrations were not increased. No statistically significant intra- or inter-group differences were observed. Thyroid hormone patterns during moderate hypothermia in head-injured patients did not differ from the well known "low T3 state" which is observed in other forms of severe illness.