The effect of therapeutic hypothermia on plasma levels of thyroid hormones during hemorrhagic shock in adult male Wistar rats

Hemorrhagic shock (HS) is one of the most important causes of death. In this study, was investigated the benefits of therapeutic hypothermia (32 °C) during HS on blood pressure (B.P), and the role of thyroid hormones during HS.

Twenty-four male Wistar rats were divided into two groups of normothermic (NH) and hypothermic (HH) (32 °C during shock); the animals were then anesthetized, and a microcatheter was inserted into the femoral artery and one into femoral vein. The arterial sampels centrifuged, and plasma were isolated to measure thyroid hormones later. The microcatheter was fixed to a physiograph to record B.P.  Animals were involved to HS for 90 minutes by withdrawing blood from the femoral vein. B.P was assessted during HS.

The amount of B.P of hypothermic animals was significantly higher in most times of HS and at 40 minutes (56.8​ ± 4.2 mmHg) than in normothermic rats (45.4​ ± 3.8 mmHg) (p <0.05). In addition, the amount of B.P in hypothermic animals at the end of the shock period at 90 minutes (63.8 ± 5.5 mmHg) was significantly (P <0.001) higher in comparisoin with the normotormic groups (39 ​​± 3.2 mmHg). Levels of thyroid hormones T4 and T3 at the end of shock were lower in the hypothermic group than in the normothermic group (p <0.001).

Therapeutic hypothermia indirectly by reducing the level of thyroid hormones and directly reduces the metabolism of non-vital tissues, and preseves blood in the central arteries and increases B.P.