ReCCLAIM II Finds Systemic Cooling Feasible During Thrombectomy; Clinical Benefit Remains Uncertain

ReCCLAIM II assessed systemic hypothermia as an adjunct to mechanical thrombectomy at 10 US sites between May 2019 and May 2024. The phase II feasibility trial enrolled 95 patients: 29 in a roll-in phase and 66 randomized. Eligible patients had proximal middle cerebral artery or internal carotid artery occlusion, an Alberta Stroke Program Early Computed Tomography Score of 6–10, and symptom onset within 24 hours. Primary endpoints assessed cooling to <34 °C within one hour of arterial puncture, door-to-reperfusion times, and hemorrhagic conversion within 36 hours.

Among 33 patients assigned to intravascular cooling, 30 (91%) reached the temperature target within one hour and 23 (70%) before reperfusion. Median time to hypothermia was 10 minutes (IQR, 7–22). Median door-to-reperfusion times were 95 minutes with hypothermia and 94 minutes with standard care (P=0.70).

Final infarct volumes were numerically lower with hypothermia, at 11 versus 30 cm³ (P=0.13). Hemorrhagic conversion and pneumonia rates did not differ significantly. Serious adverse events were numerically more frequent with cooling: 45.5% versus 24.2% (P=0.12).

These findings support procedural feasibility, not established clinical benefit or safety equivalence. The trial was not powered to assess clinical efficacy or differences in serious adverse events. The infarct-volume findings and adverse-event imbalance require further investigation; this update is based on the published abstract.