Nonthyroidal illness syndrome and prolonged mechanical ventilation in patients admitted to the ICU

The effect of the nonthyroidal illness syndrome (NTIS) on the duration of mechanical ventilation (MV) has not been extensively investigated. This study aims to determine whether the NTIS is associated with the duration of MV in patients admitted to the ICU.

We evaluated all patients admitted over a 6-year period to our ICU who underwent invasive MV and had measurement of serum free triiodothyronine (fT3), free thyroxine (fT4), and thyroid-stimulating hormone (TSH) performed in the first 4 days after ICU admission and, subsequently, at least every 8 days during the time they received MV. The primary outcome measure was prolonged MV (PMV), which was defined as dependence on MV for > 13 days.

Two hundred sixty-four patients were included. Fifty-six patients (normal-hormone group) had normal thyroid function test results, whereas 208 patients (low-fT3 group) had, at least in one hormone dosage, low levels of fT3 with normal (n = 145)/low (n = 63) levels of fT4 and normal (n = 189)/low (n = 19) levels of TSH. Patients in the low-fT3 group showed significantly higher mortality and simplified acute physiology score II, and significantly longer duration of MV and ICU length of stay compared with the normal-hormone group. Two of the variables studied were associated with PMV, as follows: the NTIS (odds ratio [OR], 2.25; 95% confidence interval [CI], 1.18 to 4.29; p = 0.01); and the presence of pneumonia (OR, 1.17; 95% CI, 1.06 to 3.01; p = 0.03).

The NTIS represents a risk factor for PMV in mechanically ventilated, critically ill patients.