Thyroid function in respiratory failure patients

Background: The non thyroidal illness syndrome (NTIS) represents a risk factor for prolonged mechanical ventilation in mechanically ventilated, critically ill patients admitted to the ICU. It is unclear, whether the NTIS is only a biochemical prognostic marker or it actually contributes to the development and progression of respiratory failure. Aim: To assess the thyroid function in patients with respiratory failure and to evaluate the impact of thyroid dysfunction as well as thyroid hormone replacement therapy on patients’ outcome. Patients and methods: The study was conducted on 100 patients (51 females and 49 males), they were divided into two groups, Group A (respiratory failure group), who were admitted to the Respiratory ICU (RICU) and group B (non-respiratory failure group) who were admitted to the Inpatient Chest Department of Zagazig University Hospitals Egypt. The respiratory failure group (Group A) included sixty-four (64) patients with respiratory failure (according to ABG parameters) 30 males and 34 females. They included 30 patients with acute exacerbation of COPD, 5 patients with acute severe bronchial asthma, 5 patients with severe pneumonia, 4 patients with acute pulmonary embolism, 8 patients with ARDS and 12 patients with acute exacerbation of IPF. This respiratory failure group included 43 patients who were on invasive mechanical ventilation and 21 respiratory failure patients who were non-mechanically ventilated. Group (B) included thirty-six (36) patients without respiratory failure according to ABG parameters as a control group (19 males and 17 females). There were 11 patients with acute exacerbation of COPD, 10 patients with exacerbated bronchial asthma, 6 patients with exacerbated IPF, 6 patients with pneumonia and 3 patients with acute pulmonary embolism. All patients were subjected to calculation of APACHE Π score, PaO2/FiO2 ratio and estimation of thyroid hormones (TSH, free T3 and free T4) at the 1st, 3rd and 10th day of admission. Those who were still having ESS at the 10th day (16 patients) and were not improving clinically, were subdivided randomly into two subgroups. Each of them comprised 8 patients. One group was given l-thyroxin replacement therapy (The replacement group) beside conventional appropriate management. The other group (8 patients) was followed by conventional appropriate management only without replacement therapy (The non-replacement group). l-Thyroxine 100 μg daily is administered for 7 weeks. At the 7th week, a fourth set of thyroid hormone estimation was done for the patients of the replacement and non-replacement groups. Patients’ outcome was assessed after 7 weeks of admission and labeled as the following: 1-death, 2-successfully treated and discharged. Results: Respiratory failure patients showed evidence of euthyroid sick syndrome (ESS) at the 1st, 3rd and 10th days of admission with a frequency of 31.2%, 79.6% and 43.7% respectively while none of the control group showed evidence of (ESS) and the difference was statistically significant. There were highly significant negative correlation between serum levels of free T3 and TSH and each of the duration of mechanical ventilation and length of ICU stay. There was significant negative correlation between APACHE Π score and serum level of freeT3 in the respiratory failure group. There was non significant impact of thyroid hormone levels on patients’ outcome. There was non significant difference in the levels of thyroid hormones between replacement and non replacement groups at the 7th week of the study. Conclusion: A state of hypothyroidism or euthyroid sick syndrome (ESS) is commonly found among patients with respiratory failure and this is related to the severity of the disease. ESS represents a risk factor for prolonged mechanical ventilation and length of ICU stay. l-thyroxin replacement therapy has no significant impact on patients’ outcome