[The effect of triiodothyronine (T3) and reverse triiodothyronine (rT3) on canine hemorrhagic shock].
The euthyroid sick ("low T3") syndrome occurs in circulatory collapse and could influence survival. To evaluate the role of T3 and rT3 in shock, 36 mongrel dogs were subjected to hemorrhagic shock. In 13 dogs 15 micrograms/kg of T3 was given after 60 min of hypotension and 15 micrograms/kg of rT3 was administered IV 30 min before hemorrhage in 10 dogs. An equal volume of saline was injected in 13 dogs for control study. These dogs were bled rapidly into a reservoir to a mean arterial pressure (MAP) of 40 mmHg. After 60 min of hypotension the reservoir line was clamped for 30 min. The shed blood was then reinfused over 30 min. T3 administration caused significant increases during the clamped period in cardiac output, stroke volume, MAP, right and left ventricular stroke work and systemic vascular resistance, with a decrease in pulmonary vascular resistance (PVR). In the group receiving rT3 the only significant hemodynamic-metabolic differences were PVR and mean arterial pH. In the control group, 6 of 13 dogs died, whereas 9 of 10 dogs given rT3 died (p less than 0.03) and only one of 13 T3 dogs died (p less than 0.05). This study strongly suggests that T3 improves survival by acting on cardiovascular receptors or via the hypothalamic-pituitary-thyroid axis and that exogeneous rT3 is detrimental during the stress of shock and may play a biologically causative role in the sick euthyroid syndrome.
Shigematsu
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First Department of Surgery, Faculty of Medicine, University of Tokyo, Japan.
Shatney
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CH
D000818:Animals; D004285:Dogs; D005067:Euthyroid Sick Syndromes / Q000209:etiology; D006439:Hemodynamics / Q000187:drug effects*; D012771:Shock, Hemorrhagic / Q000401:mortality / Q000503:physiopathology*; D014284:Triiodothyronine / Q000494:pharmacology*; D014285:Triiodothyronine, Reverse / Q000494:pharmacology*
D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse