Infusion warm during selective hypothermia in acute ischemic stroke

Mechanical thrombectomy (MT) has dramatically improved the prognosis for acute ischemic stroke (AIS) patients. Despite high recanalization rates, up to half of the patients will not present a good neurological outcome after MT. Therapeutic hypothermia is perhaps the most robust neuroprotectant studied preclinically.

We explored various warming effects that can reduce the effectiveness or potency of selective hypothermia during AIS under conditions similar to actual clinical care. Four different selective hypothermia layouts were chosen. Layouts 1 and 2 used a single catheter without and with an insulated IV bag. Layouts 3 and 4 used two catheters arrange coaxially, without and with an insulated IV bag. Independent variables measured were IV bag exit temperature, catheter inlet temperature, and catheter outlet temperature at four different flow rates ranging from 8 to 25 ml/min over an infusion duration of 20 min.

Dominant warming occurs along the catheter pathway compared to warming along the infusion line pathway, ranging from 66% to 72%. Coaxial configurations provided an approximate 4°C cooler temperature benefit on delivered infusate over a single catheter. Brain tissue temperature predictions show that the maximum cooling layout, Layout 4 at maximum flow provides a 1°C within 5 min.

Significant rewarming effects occur along the infusate flow path from IV bag to site of injury in the brain. Previous selective hypothermia clinical work, using flow rates and equipment at conditions similar to our study, likely produced rapid but not deep tissue cooling in the brain (~ 1°C).