2 The condition, current treatments and procedure
2.1 Acute ischaemic stroke is characterised by the sudden loss of blood circulation to an area of the brain and a corresponding loss of neurological function. This may lead to symptoms such as numbness or weakness of the face, arm or leg on 1 side of the body, and often problems with speech and swallowing. Stroke severity can be measured using scales such as the National Institutes of Health Stroke scale and the Modified Rankin scale. Broadly, strokes are classified as either haemorrhagic or ischaemic. Acute ischaemic stroke refers to a stroke caused by an arterial thrombosis or embolism. It is more common than haemorrhagic stroke.
2.2 Patients suspected to be having an acute ischaemic stroke should have rapid assessment and early intervention with specialist care according to NICE's guideline on stroke and transient ischaemic attack in over 16s. Recanalisation strategies, such as thrombolysis, attempt to re-establish blood flow so that cells starved of oxygen can be rescued before they are irreversibly damaged. Effective stroke care also includes specialised supportive care and rehabilitation when appropriate.
2.3 The timing, duration and degree of therapeutic hypothermia in trials has varied. Typically, however, cooling has been attempted as close to stroke onset as possible (usually within 6 hours) and continued for at least 12 to 24 hours, with body temperature maintained at 33°C to 36°C. This guidance only refers to the use of therapeutic hypothermia and not to other targeted temperature management approaches that treat or prevent pyrexia.
2.4 Before the procedure, the patient's temperature is measured and further temperature monitoring is done continuously with an internal (intravesical, rectal or oesophageal) probe connected to the cooling device. Cooling devices can be surface (ice-cold saline, surface cooling, cooling helmets and nasal cooling) or endovascular systems. After cooling, the body is slowly rewarmed, at a rate of 0.25°C to 0.5°C every hour. Rewarming takes about 8 hours. During cooling, patients need close cardiovascular monitoring in an intensive care environment, and may also need intubation and sedation. Drugs, including neuromuscular blockers, may be used to manage shivering.
2.5 The procedure may be used with thrombolysis (intravenous alteplase), mechanical thrombectomy or other vascular reperfusion techniques.
2.6 The aim of the procedure is to reduce the risk of secondary brain damage.