Mild hypothermia improves outcome in patients with global cerebral ischemia after cardiac arrest. Hypothermia seems promising also in other acute hypoxic-ischemic or in brain swelling associated cerebrovascular disease. The narrow-time-frame is a major issue ("time is brain"). To provide immediate cooling without delay, easy to use, mobile and effective methods are needed. Cold infusions (4 °C) are an accepted standard worldwide. The RhinoChill (BeneChill, USA) is a new device. A comparison of these two induction methods has never been done before. Neither was the effect of cold infusions on brain-temperature measured. For the first time iCOOL 1 compares feasibility, safety and efficacy of the two methods.

Inclusion Criteria:

• Sedation, intubation and mechanical ventilation
• Combined ICP-temperature-probe
• Indication to lower body temperature
• Age ≥ 18 years

Exclusion Criteria:

• Body weight > 120 kg
• Fever > 38.5°C
• Chronic sinusitis
• Current or past fracture or surgery of the paranasal sinuses
• Severe infection with bacteremia or sepsis ≤ 72 h
• Severe renal insufficiency
• Severe liver insufficiency
• Acute pulmonary embolism
• Acute myocardial infarction
• Severe cardiac insufficiency (NYHA ≥ III)
• Threatening ventricular dysrhythmia
• Cardiac dysrhythmia with bradycardia (heart rate < 50 /min, QTc > 450 ms, sick sinus syndrome, AV-block II-III°).
• Known hematologic disease with increased risk of thrombosis (e.g. cryoglobulinemia, cold agglutinins, sickle cell anemia)
• Known vasospastic vascular disorder (e.g. Raynaud's phenomenon or thromboangiitis obliterans)