The Norwegian Acute Stroke Prehospital Project

Background Stroke is the third leading cause of death in most western countries, and the major cause of adult disability leaving two thirds of stroke survivors struggling with moderate to severe disability. Stroke affects approximately 15 million people worldwide each year.

Up to 90% of all strokes are ischemic (cerebral infarction), mostly due to an acute thromboembolic obstruction of a cerebral artery, whereas around 10 % of strokes are cerebral hemorrhages. Acute ischemic stroke must be considered as a medical emergency, and early recanalization of the obstructed artery must be attempted. The intravenous drug alteplase (Actilyse®), a recombinant human tissue type plasminogen activator, is approved for use within 4.5 hours after symptom start of an ischemic stroke. The earlier treatment is initiated, however, the better odds for of a good outcome.

A cerebral infarction cannot be differentiated from a cerebral hemorrhage without neuroradiological investigation. If a patient with acute cerebral hemorrhage is treated with thrombolysis it may be fatal. Therefore, and contrary to the setting of a cardiac infarction, intravenous thrombolysis of cerebral infarction has to be performed in-hospital after computer tomography (CT), or magnetic resonance imaging (MRI), scanning of the brain. The consequence of this obligatory radiological examination is an unavoidable time delay and very few ischemic stroke patients are actually treated within "the golden 90 minutes" after symptom onset. The only way to avoid this, for the brain, detrimental time delay is logical; to establish the diagnosis of ischemic stroke outside the hospital and in time as near symptom onset as possible. Subsequently this will open the possibility for very early prehospital thrombolytic treatment for a much higher number of patients.

Minimizing prehospital time delay has been proven to positively influence thrombolytic rates in acute ischemic stroke. However, a recent study with a telemedicine-equipped ambulance (telestroke ambulance) has shown that prehospital real-time stroke severity assessment by hospital-based stroke physicians during ambulance transport does not have a technical acceptable stability for clinical use. In this Berlin study using "actor stroke patients" in a moving ambulance, an acceptable clinical evaluation of only 40% of the patients was achieved. A recent clinical stroke study from the University Saarland, Germany has, however, demonstrated that the concept of prehospital stroke diagnosis is feasible. Using a specially designed mobile stroke unit (MSU), a car ambulance equipped with a stroke neurologist, a CT scanner and a point of care biochemical laboratory, time from symptom onset to diagnostic therapeutic decision for thrombolysis was reduced from 76 to 35 minutes. The CT scanner in the MSU was shown to provide brain scans of high quality in 95% of cases allowing differentiation of cerebral infarction and cerebral hemorrhage. No safety radiation issues occurred for either staff or patients.

The time delay in stroke diagnostics may be reduced with early radiological diagnosis, but there is also need of reliable clinical recognition of stroke symptoms. The reliability of the National Institutes of Health Stroke Scale (NIHSS) is established by several clinical trials when performed by trained neurologists. Dewey et al proved in a 1999 trial "Inter-rater reliability of the National Institutes of Health Stroke scale: Rating by Neurologists and Nurses in a Community-Based stroke Incidence study" that the overall agreement in NIHSS scoring between trained nurses and a trained neurologists were no different from the agreement between neurologists. The study suggested that trained nurses could administer the NIHSS with reliability similar to stroke- trained neurologists.