1. Giuseppe Bello, MD; Mariano Alberto Pennisi, MD; Luca Montini, MD Serena Silva, MD; Riccardo Maviglia, MD; Fabio Cavallaro, MD Chest 2009;135;1448-1454

2.  The non-thyroidal illness syndrome (NTIS)  Abnormal thyroid function test in patients with acute or chronic systemic illnesses low serum levels of T3 high levels of rT3 normal or low levels of T4 normal or low levels of TSH

3.  The widespread changes in serum thyroid hormone levels in the critically ill patient (1) Alterations in the peripheral metabolism of the thyroid H (2) Alterations in TSH regulation (3) Alterations in the binding of thyroid hormone to thyronine- binding protein  Primary hypothyroidism  Causing abnormalities in the respiratory system  Alters respiration  The role of the NTIS on the duration of mechanical ventilation (MV) remains to be elucidated

4.  To evaluate the effect of the NTIS on the duration of MV in mechanically ventilated patients admitted to the ICU

5.  2001.1.1~2006.12.31  All patients admitted to18-bed general ICU  Invasive MV  Serum free T3 (fT3), free T4 (fT4), and TSH levels : in the first 4 days after admission(subsequently) at least every 8 days

6.  The two groups of patients (1) The normal-hormone group : serum levels of fT3, fT4, and TSH were normal throughout all the period of MV (2) The low-fT3 group : at least in one measurement  low serum levels of fT3, normal or low serum levels of fT4, normal or low serum levels of TSH patients with normal fT4 patients with low fT4  Prolonged MV (PMV) : dependence on MV for 13 days

7.  Exclusion criteria Intrinsic thyroid or pituitary-hypothalamic disease Use of iodine contrast agents in the previous 8 weeks Renal or hepatic failure Transfusion of plasma protein <48 h MV for 24 h Use of special drugs (to affect serum thyroid hormone concentrations) : IV glucocorticoids, amiodarone, moderate to high dose of vasopressors)

8. Underlying diseases (1) COPD (2) CNS disease (ischemic stroke, hypertensive intracerebral hemorrhage, subarachnoid hemorrhage, head trauma) (3) Acute respiratory failure (abdominal surgery, pneumonia, ARDS, sepsis, multiple trauma, heart failure, and acute GI bleeding)

9.  Thyroid profile, age, sex, reason for ICU admission  Duration of MV, length of stay (LOS) and mortality in the ICU  Serum albumin  The simplified acute physiology score (SAPS) II calculated 24 h after ICU admission

10. Results

11. 5285 866 751135 467 264 56 208 145 127 63

15.  The association of NTIS and PMV  remains controversial  Hypothyroid-like state  associated with the NTIS  Arem et al. : mean T3 concentrations NTIS patients < controls

16.  Hypothyroidism :The cause of ventilator-dependent respiratory failure Impairment of the normal ventilatory responses to hypercapnia and hypoxia Diaphragmatic and skeletal muscle dysfunction Pleural effusions Obstructive sleep apnea

17.  Pandya et al.: Correction of hypothyroidism was helpful in weaning from MV  Plikat et al - Patients with NTIS were found to receive MV more often in comparison with those with normal hormone levels  No report exists on the correlation between the NTIS and duration of MV in patients with respiratory failure

18.  Several limitations Regardless of the clinical suspicion of thyroid dysfunction The use of serum fT3, fT4, and TSH levels as a screening method  Insufficient to define the nature of the various abnormalities in thyroid function tests accurately Serum TSH levels : increase during recovery Serum fT4 concentrations : high in early phase of the NTIS

19.  NTIS represents a risk factor for PMV 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  Evaluating benefits in the respiratory function of these critically ill patients after a substitution treatment with thyroid hormones