Identifying an evidence-based model of therapy for the pre-hospital emergency management of supraventricular tachycardia

Abstract

This thesis provides a comprehensive reporting of the work undertaken to identify evidence supporting pre-hospital management of supraventricular tachycardia (SVT), delivering an evidence base for paramedic treatment of these patients. The literature search identified absences in evidence supporting therapies used within existing clinical guidelines. The vagal manoeuvres, the simplest and least invasive therapy to employ in the stable patient, were insufficiently evidenced regarding technique or a particular manoeuvre. The pharmacological agents (verapamil and adenosine) demonstrated equivalent reversion effectiveness, yet other pre-hospital suitability factors were not examined. The use of synchronised cardioversion for poorly perfused patients was without published evidence, yet advocated within international guidelines. There was little research into the overall effectiveness of pre-hospital treatment regimens for SVT, and this was compounded by an absence of epidemiological data regarding those pre-hospital patients with SVT attended by paramedics. A proposed model of pre-hospital evidence-based practice was constructed, drawing on existing evidence-based practice models, specifically identifying and examining the unique aspects of pre-hospital care that challenged the overlaying of a traditional model. Once defined, this theoretical model enabled exploration and definition of an evidence-based model of pre-hospital SVT management. The first study reported the epidemiology of SVT patients requesting ambulance attendance, and the effectiveness of paramedic treatment. This study identified that the majority of these patients lived in metropolitan Victoria, were aged around 57 years, and predominantly female. This study also identified that existing Clinical Practice Guidelines (CPG) were underutilised, and produced a less than effective model of care (with some 50% of patients arriving at hospital remaining in SVT). The second study quantified the most effective vagal manoeuvre (Valsalva manoeuvre (VM)), and demonstrated that supine posturing provided optimum vagal tone generation for performance. This study (an interventional trial), although limited in generalisability by using healthy participants, reported a performance technique that provided optimal vagal tone generation for clinical application. This study also identified the absence of a relevant clinically significant effect for vagal termination of SVT. Exploring this was not possible within the constraints of the PhD, yet has been highlighted for further research. The third project detailed the development and implementation of a revised CPG to more adequately reflect an evidence-based model of therapy. This CPG was subsequently adopted by Ambulance Victoria and the Tasmanian Ambulance Service to represent the current management of SVT across these Australian States. The fourth study examined the effectiveness of CPG change. Each aspect of therapy was examined, and the principal finding was that the VM was underutilised, despite expansion of authority to practice. The introduction of adenosine resulted in increased reversion success, with significant reduction in side effects. Overall the revised CPG provided improved pre-hospital reversion effectiveness, and demonstrated significant reductions in therapeutic side effects. The thesis examined the construct of an evidence-based model of therapy for pre-hospital SVT, and concluded that whilst significant work has been completed, further research is required to complete the process. This research is outlined at the end of the thesis, and centres on potential harm resulting from SVT.