Cardiopulmonary bypass temperature does not affect postoperative euthyroid sick syndrome?

Area of Science:

• Cardiology
• Endocrinology
• Anesthesiology

Background:

• Thyroid function is crucial for metabolic regulation.
• Cardiopulmonary bypass (CPB) is a complex procedure with potential systemic effects.
• The impact of CPB temperature on thyroid hormone levels requires further investigation.

Purpose of the Study:

• To investigate the effect of hypothermic versus normothermic cardiopulmonary bypass (CPB) on perioperative and postoperative thyroid function.
• To determine if maintaining normothermia during CPB mitigates changes in thyroid hormone levels.

Main Methods:

• Prospective study comparing hypothermic and normothermic CPB in 12 cardiac surgery patients.
• Serum concentrations of total thyroxine (TT4), total triiodothyronine (TT3), free T3 (fT3), reverse T3 (rT3), and TSH were measured preoperatively and at multiple time points post-CPB.
• Patients were grouped into hypothermic (26°C ± 5°C) and normothermic (35°C ± 1°C) CPB.

Main Results:

• Both hypothermic and normothermic CPB led to significant reductions in TT4 and TT3 levels postoperatively.
• Free T3 levels decreased for up to 3 days, while reverse T3 levels increased on postoperative days 1 and 3 in both groups.
• Thyroid stimulating hormone (TSH) levels remained unchanged throughout the study period.
• Patient demographics, CPB duration, and postoperative outcomes were comparable between groups.

Conclusions:

• Normothermic CPB does not prevent the development of the "euthyroid sick syndrome" during and after cardiac surgery.
• Despite observed thyroid function alterations, patients generally experienced normal postoperative recovery regardless of CPB temperature.
• These findings suggest that transient thyroid hormone changes during CPB may not significantly impact short-term clinical outcomes.