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Stroke management and the impact of mobile stroke treatment units

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IMPROVING TREATMENT TIMES

Studies have found that the major reason patients do not receive tPA is that they do not reach the hospital quickly enough to be assessed and treated within the treatment window.14,15 In essence, neurologists have the technology to treat most patients, but are waiting for the patients to arrive. Many factors contribute to this delayed arrival time. On the patient level, the primary factors are related to failure to recognize stroke symptoms as well as failure to understand their seriousness.

From the healthcare provider’s perspective, a major barrier to reducing the time-to-treatment window is the need to accurately assess patients with acute ischemic stroke who are eligible for thrombolytic therapy. This is difficult to achieve in clinical practice because it requires neurologic imaging primarily with computed tomography (CT) or magnetic resonance imaging (MRI) and laboratory analyses so that hemorrhagic stroke and other contraindications to thrombolysis can be excluded. Traditionally, this type of analytic equipment had been available only in emergency departments, requiring patients to be brought to those facilities.

Recent innovation in this area led to the development of specialized ambulances equipped with a CT scanner, point-of-care laboratory equipment, and telemedicine connection along with the appropriate treatment options/medications and trained healthcare personnel to provide prehospital stroke treatment. These specially equipped ambulances are known as MSTUs or stroke emergency mobile (STEMO) units. Their development has dramatically altered the strategy from one of taking the patient to the treatment to taking the treatment to the patient.

MOBILE STROKE TREATMENT UNITS

Two technological innovations have been fundamental to the creation and success of MSTU: portable CT scanners and high-speed wireless data transmission.

CT scanners. A key element was the development of a portable diagnostic-quality head and neck CT scanner that can be fit inside a typical-sized ambulance. This 8-slice CT scanner is capable of creating the same scan types and quality found in radiology department CT scanners, including axial imaging, helical angiography, and perfusion imaging. The resolution and slice thickness (1.25 mm) of the images are of suitable quality to enable neurologists and neuroradiologists to exclude hemorrhage in acute stroke, to assess the degree of brain injury, and to identify the vascular lesion responsible for the ischemic deficit. These technologies also enable diagnostic differentiation between brain tissue that is irreversibly infarcted from that which is potentially salvageable, thereby allowing more accurate patient assessment. The imaging data currently obtainable by CT scanners fitted on ambulances is only likely to improve with future technological advances.

Wireless data transmission. Cellular wireless providers have developed the technology and equipment to provide high-speed wireless broadband capable of transmitting high-quality CT and MRI images. It also enables encrypted feed of video telemedicine, data transmission, and download of patient data. This allows the MSTU to electronically sit inside the firewalls of healthcare facilities, providing access to the patients’ electronic health records and to on-site stroke experts.

The successes have been impressive. Studies have found that the deployment of an MSTU significantly reduces the median time from 9-1-1 alarm to intravenous thrombolysis without increasing adverse events.16–19 These data are primarily from the PHANTOM-S study, a pilot program conducted in Germany.18,19 Results showed a significant reduction in alarm-to-treatment times, from 76 minutes in the hospital control group to 52 minutes in the MSTU group (Table 2).17,19 Further, among patients who suffered an ischemic stroke, the proportion who received tPA within 1 hour of symptom onset was sixfold higher after MSTU deployment (Table 3).18 In a separate European study, prehospital stroke assessment using an MSTU significantly reduced the median time from alarm-to-therapy decision: 35 minutes versus 76 in the hospital group.16

The prehospital cerebrovascular diagnostic workup provided by an MSTU also can improve the emergency management of other stroke types. By providing more diagnostic data and higher quality imaging, the units improve the accuracy of the diagnosis. In turn, this enables emergency personnel to provide accurate therapy and to transfer patients to hospitals with the appropriate level of stroke care, decreasing the need for additional intrahospital transfers.20

Overall, it has been shown that an MSTU equipped with the necessary imaging and laboratory testing equipment can provide appropriate, accurate, and safe ambulance-based prehospital tPA administration, reduce the time to tPA administration, and increase the number of patients who receive tPA administration. All of these factors combine to improve outcomes in patients with acute ischemic stroke.

CLEVELAND CLINIC EXPERIENCE

Cleveland Clinic has a tradition of providing high-quality and innovative stroke care. Recognizing the importance of an appropriately equipped MSTU in reducing the time to stroke treatment, especially tPA administration, Cleveland Clinic instituted a plan to develop an MSTU for the care of patients in the Cleveland area. The development required several planning, funding, and development phases.

Planning. Establishing relations with both city planners and area hospitals was central to planning the MSTU startup. An agreement with the city of Cleveland included creating an emergency medical system (EMS) triage algorithm for the 9-1-1 dispatch center. When a call is received, the dispatcher uses a stroke checklist to perform an initial screening. If a stroke is suspected, the MSTU is dispatched along with a Cleveland EMS or other first-responder unit.

As part of the agreement, Cleveland officials required that the MSTU treat all patients, regardless of their ability to pay. This requirement has been beneficial to the MSTU mission as it allows for treating more patients with tPA as quickly as possible without concern for health insurance, which maximizes the potential for neurologic recovery.

Staffing and procedures. The MSTU staff is composed of a paramedic, a critical care nurse, a CT technologist, and an emergency medicine technician/EMS driver. They perform CT scans and point-of-care laboratory tests on patients who have stroke symptoms. The CT scans and laboratory results are wirelessly transmitted to Cleveland Clinic. A neurologist assesses the data, consults with the MSTU staff on history and neurologic examination, and diagnoses the patient remotely. Patients are then transported to the closest hospital with the resources to meet their clinical needs. If thrombolytic therapy is indicated, intravenous tPA is initiated immediately at the scene. If the patient has sustained a hemorrhagic stroke, reversal of anticoagulation therapy is initiated, if indicated.

Outcomes. The success rates also have been impressive, with dramatic reductions in time to treatment. On average, patients received tPA 40 minutes faster in the MSTU model than in the standard model of ambulance transport and in-hospital evaluation and treatment: 64 minutes versus 104 minutes. Further, more patients in the MSTU group received tPA: 26% versus 14%. Results also showed a 21-minute reduction in time-to-CT completion, an important aspect of providing more timely care.21–23 This CT scanner is also capable of CT angiography. This enables large-vessel occlusion strokes to be identified in the field. When these types of strokes are identified in the field, the patients are transported directly to a stroke center capable of endovascular therapy, even bypassing some primary stroke centers.

Using the MSTU to bring diagnostic and stroke care to the patient has shown that the time between the onset of stroke-like symptoms and the delivery of treatment can be reduced. Thus, an MSTU has the potential to minimize the mortality and long-term morbidity associated with strokes.

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