Systems, devices, and methods for organ Retroperfusion along with regional mild hypothermia. One such system includes a hypothermia system including a hypothermia system outlet and a hypothermia system inlet； and a connector comprising a coolant inlet, a coolant outlet, a coolant reservoir, and a blood lumen, whereby the coolant inlet is configured to couple to the hypothermia system outlet and whereby the coolant outlet is configured to couple to the hypothermia system inlet； whereby a cooling product, when the hypothermia system is connected to the connector, can flow from the hypothermia system, through the hypothermia system outlet, into the coolant inlet, through the coolant reservoir, into the coolant outlet, and into the hypothermia system inlet, so that the cooling product can cool blood flowing through the blood lumen.
