Farzaneh Faraji Shahrivar - Department of Physiology, School of Medicine, Iranshahr University of Medical Sciences, Iranshar, Iran.
Samira Khani - Department of Physiology and Pharmacology, School of Medicine, Qom University of Medical Sciences, Qom, Iran
Aida Mehdipour - Department of Pediatric dentistry, School of dentistry, Saheli St, Qom University of medical sciences, Qom, Iran.
Hamid Farahani - Molecular & Cellular Research Center, School of Medicine, Qom University of Medical Sciences, Qom, Iran.

Background and Aim: Hemorrhagic shock (HS) is one of the most important causes of death. In this study, we investigated the benefits of therapeutic hypothermia (۳۲°C) during HS on blood pressure (BP) and the role of thyroid hormones during HS. Materials and Methods: Twenty-four male Wistar rats were divided into two normothermic hemorrhagic (NH) and hypothermic hemorrhagic (HH) groups (۳۲°C during shock); the animals were then anesthetized, a microcatheter was inserted into the femoral artery, and one into the femoral vein. The arterial samples were centrifuged, and plasma was isolated to measure thyroid hormones later. The microcatheter was fixed to a physiograph to record BP. Animals were exposed to HS for ۹۰ minutes by withdrawing blood from the femoral vein and BP was assessed during HS. Results: The BP of HH animals was significantly higher in most times of HS and at ۴۰ minutes (۵۶.۸±۴.۲ mmHg) in comparison to NH rats (۴۵.۴±۳.۸ mmHg) (P<۰.۰۵). In addition, the amount of BP in HH animals at the end of the shock period at ۹۰ minutes (۶۳.۸±۵.۵ mmHg) was significantly (P<۰.۰۰۱) higher in comparison with the NH groups (۳۹±۳.۲ mmHg). Levels of thyroid hormones T۴ and T۳ at the end of shock were lower in the HH group compared to the NH group (P<۰.۰۰۱). Conclusion: Therapeutic hypothermia indirectly reduces the level of thyroid hormones and directly reduces the metabolism of non-vital tissues, preserves blood in the central arteries, and increases BP.

Shock, Hemorrhagic, Hypothermia, Induced, Thyroid hormones