Pre-hospital stroke treatment
To obtain a real clinical benefit from active re-canalisation in the case of a brain infarction, the first 90 minutes are crucial (5). The number needed to treat (NNT) to achieve one improved outcome after treatment with intravenous recombinant human tissue plasminogen activator (r-tPA, alteplase) has been reported to be < 4 within 90 minutes, but as many as 45 after 271 – 360 minutes (5).
Pre-hospital thrombolytic treatment of heart infarction was introduced in Norway in the early 1990s (8). In the same way, use should be made of the pre-hospital space for diagnostics, high-quality triage and cause-oriented treatment for cases of stroke. Although the pathogenesis is near-identical for heart and brain infarctions, there are some material diagnostic and therapeutic differences indicating that the experience from the 1990s is not directly transferable. Pre-hospital treatment of cerebral ischaemia is wholly dependent on a precise diagnostic differentiation with regard to the nature of the cerebral haemorrhage. Furthermore, in the case of an acute cerebral ischaemia it must be clarified whether this involves a proximal or a distal arterial occlusion in order to select those that should be treated with invasive techniques.
Even though the further development of today’s diagnostic tools is based on the premise that stroke treatment takes place in-hospital, research and development efforts are underway in the field of pre-hospital diagnostics on the basis of biomarkers (9), microwaves (10), infrascanning (11) and ultrasound (12). This notwithstanding, diagnostics on the basis of brain scans has the largest potential at the pre-hospital stage. Walters and collaborators have shown that in an area with a short distance to a hospital, the time from the onset of symptoms to thrombolytic treatment can be reduced to < 90 minutes with the aid of an ambulance equipped with a CT scanner and staffed by a neurologist and a neuroradiologist (13). In comparison, rapid transport to a stroke unit for diagnostics and thrombolytic treatment required > 150 minutes. Moreover, it was shown that not only the stroke patients, but all the patients examined were faster and more correctly triaged, resulting in faster specific cause-oriented treatment (13, 14).
It is difficult to envisage that ambulances staffed by neurologists and neuroradiologists may be possible in Norway. In addition, a ground-based mobile stroke unit will have a limited operative range. The German project clearly demonstrated, however, that telemedical transfer of CT images for parallel diagnostics undertaken in the stroke unit of a hospital is possible (13).
In Norway, we have a well-developed air ambulance service staffed by anaesthesiologists, who with adequate diagnostic tools and with the aid of intravenous thrombolytic drugs will be able to minimise the time from the onset of symptoms to cause-oriented treatment for a large number of stroke patients. This presupposes telemedical diagnostic support from a neurological and neuroradiological medical institution and good procedures for triage of patients for intervention treatment or neurosurgery. The air ambulance has a maximum response time (time from alarm to take-off) of 15 minutes, and can reach the majority of the population in 30 minutes. With a quick alert, it will be realistic to initiate thrombolytic treatment and/or transport of the patient directly to invasive treatment within 90 minutes from the onset of the illness.
Norwegian Air Ambulance Foundation (SNLA) is engaged in the adaptation of a CT scanner to the current air ambulance fleet, and is preparing procedures for pre-hospital cause-oriented stroke treatment. Furthermore, a multi-centre study of pre-hospital diagnostics and thrombolytic treatment of stroke is being planned. This study will make use of ground-based CT-equipped ambulances staffed by an anaesthesiologist and a specialist nurse. The study is part of a comprehensive European research collaboration.
In the case of a stroke, the time elapsing before initiation of cause-oriented treatment is completely crucial for the outcome. In provision of treatment the concern for time must take precedence over the concern for hospital organisation. By including the pre-hospital space in the chain of treatment, the ambitions of the Minister of Health can be raised considerably – for the benefit of the stroke patient.