Page 54 - Ultrasonography in Prehospital and Emergency Medicine - Rein Ketelaars
P. 54
52
Chapter 2
C – Abdominal aortic aneurysm
US is feasible and suitable to assess for an aneurysm of the abdominal aorta in symptomatic patients. An ED study showed a sensitivity and specificity of 100% and 98%.83 Prehospital- ly this is also feasible, reported Heegaard et al. Trained ambulance paramedics performed PHUS scans of the abdominal aorta in twenty symptomatic patients. A blinded expert also judged the images and agreed in 100% with the paramedics’ judgment.84
D – Central nervous system
Stroke – transcranial US
Reducing the interval between ischemic stroke and intravenous thrombolysis is associated with reduced mortality, reduced symptomatic intracranial hemorrhage, and higher rates of independent ambulation at discharge and discharge to home.85,86 Unfortunately, prehospital delays lead to missed opportunities to initiate treatment within the preferred 90 minutes af- ter the onset of symptoms.87 For instance, in an American study, only 38% of patients arrived within two hours of the onset of their symptoms.88
Early prehospital detection of ischemic stroke may be beneficial to a favorable outcome. Pre- hospital caregivers could allocate patients to the most appropriate hospital, provide a prear- rival notification, and initiate stroke-specific therapies such as sonothrombolysis and neu- roprotective strategies.87,89,90 Intravenous thrombolysis, however, is only administered safely after a CT or magnetic resonance imaging (MRI) scan excludes an intracranial hemorrhage.
Herzberg et al. evaluated the diagnostic accuracy of prehospital neurological examination supported by transcranial color-coded sonography (TCCS).89 The TCCS consisted of col- or-mode visualization and flow measurements in the proximal M-1 segment of both middle cerebral arteries (MCA) to find an occlusion. When desired, they scanned the anterior and posterior cerebral arteries or administered an intravenous ultrasound contrast agent (UCA). Sensitivity and specificity were 95% and 48%; PPV and NPV were 82% and 77% for the pre- hospital diagnosis of ‘any stroke’ compared to in-hospital CT angiography (CTA) and mag- netic resonance angiography (MRA). With appropriate training, telemedicine, and UCAs, these results might still improve.89
In their prehospital study, Schlachetzki found that 36% of the physicians used microbubbles as a UCA to save time or to increase the diagnostic confidence when temporal window anatomy did not allow an optimal visualization of the MCAs. Sensitivity and specificity of ultrasound for MCA occlusions were 90% and 98%. PPV and NPV were 90% and 98%.90
