Hypothyroidism and failure to wean in patients receiving prolonged mechanical ventilation at a regional weaning center

Objective: Hypothyroidism is cited as an uncommon cause of ventilator-dependent respiratory failure. The objective of this study was to determine the incidence of hypothyroidism in patients with respiratory failure, receiving prolonged mechanical ventilation (PMV) with failure to wean, referred to a regional weaning center (RWC) for weaning. Setting: RWC. Design: Retrospective. Methods: Medical records were reviewed of 173 patients admitted to this RWC between January 1999 and March 2002. One hundred forty patients were noted to have had screening serum thyroid stimulating hormone (TSH) levels obtained at admission. Records of these patients were further evaluated. The following data were abstracted: age, sex, body mass index, serum TSH levels, number of patients with previously diagnosed hypothyroidism, and number of patients with hypothyroidism diagnosed clinically and by laboratory tests following admission to the RWC. Primary outcome was liberation from PMV, which was defined as being off ventilatory support for > 1 week. Univariate analysis was performed to determine relation between serum TSH levels and outcome; p < 0.05 was deemed statistically significant. Results: Of 140 patients studied, 67 were male (48%) and 73 were female (52%), with a mean age of 66 + 15 years (+/-SD). Only one patient had a history of previously diagnosed hypothyroidism. A clinical diagnosis of hypothyroidism was made in 4 of 140 patients (3%) following admission. Serum TSH levels ranged from 0.19 to 121 mU/L in the studied subjects. Seventeen of 140 patients (12%) had elevated serum TSH levels. Serum tri-iodothyronine and/or thyroxine levels confirmed diagnosis of hypothyroidism in four of these patients (3%). Patients with newly diagnosed hypothyroidism were treated with thyroid supplements, and three patients were liberated from PMV while one patient died from other medical causes. Of the 140 patients, 92 patients (67%) were liberated from PMV while 48 patients (33%) could not be weaned. Mean serum TSH levels were 4.2 + 13 mU/L in the liberated patients and 4 + 4.7 mU/L in the patients who could not be weaned (p = 0.25). Conclusion: Hypothyroidism is an uncommon cause of failure to wean in patients receiving PMV (with an incidence of 3%). However, it is a potentially treatable cause and should be considered in all patients who fail to wean. Serum TSH level does not appear to affect successful weaning from PMV.