Effect of Epidural Anesthesia and Surgery on Serum Thyroid Hormone and Cortisol Levels in the Gravid Ewe

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Abstract
The effects of epidural anesthesia and surgery on serum iodothyronine and cortisol levels were studied in 10 gravid ewes during the last trimester. The mean serum T3 concentration was significantly decreased 24 h after surgery, returning to the preanesthesia level at 48 h. The mean serum rT3 [reverse triiodothyronine] and cortisol levels were significantly increased after the start of anesthesia and surgery, returning to baseline levels after 48 h. There was a significant positive correlation between the rT3/T3 ratio and serum cortisol values. In the chronic ovine fetal-maternal model, studies which may be affected by corticosteroids or thyroid hormones should be delayed for at least 48 h following surgery to allow maternal serum iodothyronine and cortisol concentrations to return to baseline values.