A patient presents with stroke like symptoms in the
prehospital setting. Patient was last
seen normal about 3.5 hours ago. Prior
to that, family state patient was in his usual state of health - ambulating,
conversing - without any difficulty. You
perform a quick assessment His medical history is significant for HTN, DM, and
hypercholesterolemia. Blood sugar is
194. BP is 195/89 with a HR of 97. The closest primary stroke center is 20
minutes away. The closest comprehensive
stroke center is 45 minutes away. To
make matters worse, a snowstorm is occurring which potentially will further
delay transport. Where do you take him?
According to the Centers for Disease Control and Prevention
(CDC), stroke is a major cause of disability in the United States, with
approximately 795,000 adults suffering each year [9]. With therapeutic options such as tissue
plasminogen activator (tPA) and endovascular therapy, stroke is treatable -
given certain inclusion criteria. The
initial National Institute of Neurologic Disorders and Stroke (NINDS) study (1995)
found improvement in NIH Stroke Scale if tPA was given within 3 hours of
symptom onset [8]. The results of the
ECASS III trial (2008) extended the benefit to 4.5 hours [4]. In 2015 alone, multiple clinical trials (MR
CLEAN January 2015, EXTEND-IA February 2015, ESCAPE March 2015, Swift Prime
June 2015) found a reduction in disability when endovascular therapy was
performed within 6 hours of onset of symptoms [1, 2, 3, 12]. At present, acute stroke care is treated on a
time-based selection. When patients
exceed the time of symptom onset criteria (4.5 hours for tPA, 6 hours for
endovascular therapy), these interventions are not available and the patient is
left to suffer the natural progression of the disease.
The recently published DWI or CTP
Assessment with Clinical Mismatch in the Triage of Wake-Up and Late Presenting
Strokes Undergoing Neurointervention with Trevo (DAWN) trial revealed a significant improvement in functional
independence and disability at 90 days for patients who underwent mechanical
thrombectomy for large vessel occlusions despite presenting >6 hours after
onset of symptoms. The study found
benefit of treatment up to 24 hours with the median patient presentation being
12 hours [10]. With the possibility of
endovascular therapy, patients ideally should be brought to a center that can
perform such an intervention.
But should you delay transport to get a patient to a
comprehensive stroke center where mechanical thrombectomy can be performed?
Ideally you should get a patient to a center that has all the capabilities
of performing stroke management and treatment.
The DAWN Trial only applies to patients with large vessel
occlusions. The only option for patients
without a large vessel occlusion is tPA, which remains a time-based treatment
option. Because of this, patients should
be transferred to the nearest primary stroke center, especially if time and
distance are critical factors.
So you identify a patient with a stroke. How good are prehospital stroke assessments
in identifying large vessel occlusions anyway?
A
retrospective study in Berlin of 3,505 stroke patients (827 of which had a
large anterior vessel occlusion) analyzed the various prehospital scoring
scales: FAST, GFAST, C-STAT, PASS, and RACE.
The authors concluded that prehospital scoring systems performed
similar, if not better, when compared to the NIH stroke scale (in patients with
a score >= 6) for identifying large vessel occlusions (sensitivities over
90%) [13].
With an expanded time frame and potential for mechanical
thrombectomy, should you then perform a CTA/CT perfusion study on all patients
presenting to the ED with a stroke?
You will see arguments for both doing and not doing CTA/CT
perfusion, with the biggest detractors citing increased radiation, costs, and
contrast induced nephropathy. Several
studies have shown contrast induced nephropathy is minimal [5, 6, 7, 11]. Regarding radiation and costs, this can pale
in comparison to a lifetime of disability.
This may be beneficial especially to patients who present with a high NIH
stroke score who are outside the window for tPA. As with all things in
medicine, a risk versus benefit analysis should be performed to ensure that the
benefits outweigh the risks.
Ultimately, what does all this mean?
It is important to remain current on stroke literature to recognize
that an intervention exists for patients who present outside the traditional
stroke window of 4.5 hours (tPA) or 6 hours (endovascular therapy). The DAWN
study provides evidence that the treatment window can be extended up to 24
hours. If a large vessel occlusion can be identified, or is suggested based on
prehospital scoring tools, patients should be transported to a comprehensive
stroke center (time and distance permitting). Also, seeing how contrast induced
nephropathy is a minimal risk, it seems beneficial to get a CTA/CT perfusion
study on stroke patients with large deficits, especially if they present
outside the traditional treatment window.
REFERENCES:
[1] Berkhemer OA, et al. "A
randomized trial of intraarterial treatment for acute ischemic stroke".
The New England Journal of Medicine. 2015. 372(1):11-20.
[2] Campbell et al. “Endovascular
Therapy for Ischemic Stroke with Perfusion-Imaging Selection.” N Engl J Med
2015 Mar 12;372(11):1009-18.
[3] Goyal M et al. Endovascular
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patient data from five randomised trials. Lancet 2016. 387:1723-31.
[4] Hacke W, et al. "Thrombolysis
with Alteplase 3 to 4.5 Hours after Acute Ischemic Stroke". The New
England Journal of Medicine. 2008. 359(13):1317-1329.
[5] Hopyan JJ, et al. “Renal safety of CT angiography and
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[6] Krol AL, et al. “Incidence of radiocontrast nephropathy in
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[7] Lima FO, et al. “Functional
contrast-enhanced CT for evaluation of acute ischemic stroke does not increase
the risk of contrast-induced nephropathy.”
Am J Neuroradiol.
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[8] Marler JR, et al. "Tissue
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[9] Mozzafarian D, Benjamin EJ, Go AS,
Arnett DK, Blaha MJ, Cushman M, et al.
“Heart disease and stroke statistics—2016 update: a report from the
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[10] Nogueira, R.G., et al. “Thrombectomy
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doi:10.1056/NEJMoa1706442.
[11] Oleinik A, et al. “CT angiography
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[12] Saver JL, et al.
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stroke". The New England Journal of Medicine. 2015. 372(24):2285-2295.
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Patients With Large Anterior Vessel Occlusion.” Stroke, vol. 48, 2017,
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