Page 59 - Ultrasonography in Prehospital and Emergency Medicine - Rein Ketelaars
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                 US-guided pericardiocentesis under continuous visualization using a multi-angled needle guide was found to be effective, safe, and easy to perform.110
First described in 1954, resuscitative endovascular balloon occlusion of the aorta (REBOA) is a technique to stabilize patients suffering hemodynamic shock by temporarily interrupt- ing blood flow to non-compressible hemorrhage in the chest, abdomen, or pelvis.111,112 In animal studies, REBOA resulted in a 74% mortality risk reduction.113 After forty minutes of occlusion, however, the risks start outweighing the benefits.113,114 In 2014, the London HEMS was the first to report a prehospital performed REBOA in a patient with a pelvic fracture resulting in successful hemorrhage control.115
Chaudery found that the use of US improved the correct placement of REBOA catheters, shortened the time until correct placement, and improved the participants’ confidence in catheter placement of Zone III (infrarenal aorta) REBOA catheters in 20 porcine cadavers.116
These developments are promising for future prehospital US-guided REBOA hemorrhage control. However, future research is needed on prehospital feasibility, variations in body habitus, and zone I (intrathoracic aorta) placement.
Interventions - Disability
In the aforementioned disability section we highlighted the value of TCCS in diagnosing ischemic stroke. A therapeutic application of ultrasound in ischemic stroke patients is con- tinuous transcranial doppler (TCD) to enhance the thrombolytic activity of tissue plasmino- gen activator (t-PA).117 In a phase II multicenter randomized trial (CLOTBUST) transducers were applied over the temporal bone in a head frame. The investigators applied TCD (or placebo TCD) on maximum power output continuously for two hours and simultaneously started intravenous t-PA treatment in all patients. Two hours after starting thrombolysis recanalization or almost full recovery was observed in 49% in the continuous TCD group versus 30% in the control group. However, clinical recovery after 24 hours and outcome after three months was similar.117 In 2014, another analysis of the CLOTBUST trial, including more subjects, revealed 38.6% complete recanalization in the sonothrombolysis group and 17.1% in the intravenous t-PA group.118 A phase III trial is underway.119 Tsivgoulis concluded in a meta-analysis that high-frequency ultrasound (both TCD and TCCS) combined with t-PA was associated with a higher likelihood of complete recanalization (pooled OR = 2.99) than t-PA alone.120 They found no increased risk of symptomatic intracerebral hemorrhage.
Probably, transcranial US combined with microbubbles but without t-PA is effective as well.121,122 Microbubbles consist of an injectable aqueous suspension of small (1.5–4.7 μm)
ABCDE of prehospital ultrasonography 57
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