How does rewarming shock work with feedback mechanisms?

i'm not sure exactly what you mean by feedback loop (i mean, most physiological mechanisms are based on feedback, right?) but...

your vasculature (esp. peripheral/superficial) responds to changes in temperature, yes? add heat, vasodilation, reduce heat, vasoconstriction.

rewarming of a hypothermic patient can be done externally (ie hot baths, towels, etc) or internally (ie warmed intravenous fluids), yes? these cause vasodilation. the external methods will cause more PERIPHERAL v.dilation and contribute to hypotension, coupled with the low cardiac output of hypothermia (severely hypothermic people esp. have decreased HR, BP, RR, etc... i think it's the body's way of conserving heat expended mantaining those vitals?) precipitates shock

rewarming can also discourage heat production, but i'm not sure i understand that well enough to explain

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EDIT: note that current practice suggests risk of rewarming collapse is reduced when using IV methods