Interpretation of Brain CT Scans in the Field by Critical Care Physicians in a Mobile Stroke Unit

Background and purpose: In acute stroke, thromboembolism or spontaneous hemorrhage abruptly reduces blood flow to a part of the brain. To limit necrosis, rapid radiological identification of the pathological mechanism must be conducted to allow the initiation of targeted treatment. The aim of the Norwegian Acute Stroke Prehospital Project is to determine if anesthesiologists, trained in prehospital critical care, may accurately assess cerebral computed tomography (CT) scans in a mobile stroke unit (MSU).

Methods: In this pilot study, 13 anesthesiologists assessed unselected acute stroke patients with a cerebral CT scan in an MSU. The scans were simultaneously available by teleradiology at the receiving hospital and the on-call radiologist. CT scan interpretation was focused on the radiological diagnosis of acute stroke and contraindications for thrombolysis. The aim of this study was to find inter-rater agreement between the pre- and in-hospital radiological assessments. A neuroradiologist evaluated all CT scans retrospectively. Statistical analysis of inter-rater agreement was analyzed with Cohen's kappa.

Results: Fifty-one cerebral CT scans from the MSU were included. Inter-rater agreement between prehospital anesthesiologists and the in-hospital on-call radiologists was excellent in finding radiological selection for thrombolysis (kappa .87). Prehospital CT scans were conducted in median 10 minutes (7 and 14 minutes) in the MSU, and median 39 minutes (31 and 48 minutes) before arrival at the receiving hospital.

Conclusion: This pilot study shows that anesthesiologists trained in prehospital critical care may effectively assess cerebral CT scans in an MSU, and determine if there are radiological contraindications for thrombolysis.