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ObjectiveStress testing is commonly performed in emergency department (ED) patients with suspected acute coronary syndrome (ACS). We hypothesised that changes in N-terminal pro-B type natriuretic peptide (NT-proBNP) concentrations from baseline to post-stress testing (stress-delta values) differentiate patients with ischaemic stress tests from controls.MethodsWe prospectively enrolled 320 adult patients with suspected ACS in an ED-based observation unit who were undergoing exercise stress echocardiography. We measured plasma NT-proBNP concentrations at baseline and at 2 and 4  hours post-stress and compared stress-delta NT-proBNP between patients with abnormal stress tests versus controls using non-parametric statistics (Wilcoxon test) due to skew. We calculated the diagnostic test characteristics of stress-delta NT-proBNP for myocardial ischaemia on imaging.ResultsAmong 320 participants, the median age was 51 (IQR 44–59) years, 147 (45.9%) were men, and 122 (38.1%) were African–American. Twenty-six (8.1%) had myocardial ischaemia. Static and stress-deltas NT-proBNP differed at all time points between groups. The median stress-deltas at 2  hours were 10.4 (IQR 6.0–51.7) ng/L vs 1.7 (IQR −0.4 to 8.7) ng/L, and at 4  hours were 14.8 (IQR 5.0–22.3) ng/L vs 1.0 (−2.0 to 10.3) ng/L for patients with ischaemia versus those without. Areas under the receiver operating curves were 0.716 and 0.719 for 2-hour and 4-hour stress-deltas, respectively. After adjusting for baseline NT-proBNP levels, the 4-hour stress-delta NT-proBNP remained significantly different between the groups (p=0.009).ConclusionAmong patients with ischaemic stress tests, static and 4-hour stress-delta NT-proBNP values were significantly higher. Further study is needed to determine if stress-delta NT-proBNP is a useful adjunct to stress testing.

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Study Objectives: Emergency point-of-care ultrasound (POCUS) performed by non-physician out-of-hospital providers has shown promise in limited applications but is not widely utilized. No studies have examined the use of critical care ultrasound (US) by non-physician out-of-hospital providers in the out-of-hospital setting. Our objective was to evaluate whether critical care US performed by out-of-hospital providers can clarify the cause of symptoms or change management.Methods: Twenty aeromedical flight nurses completed a didactic and hands-on US curriculum focusing on critical care applications (cardiac, pulmonary, inferior vena cava, Focused Assessment with Sonography in Trauma [FAST]). To assess competency, all providers subsequently passed an objective structured US exam. Portable ultrasound devices (SonoSite iVIZ) were used during patient transports from both scene activations and referring hospitals when deemed clinically indicated by the provider. Post-transport surveys rated provider confidence on a 5-point Likert scale in initial assessment of patient cardiac function, intravascular volume status, cause of hypotension, and cause of respiratory distress when applicable. If US was performed, providers rated if US clarified the cause of symptoms or changed management on a 5-point Likert scale. Associations were evaluated with between-groups t-tests and contingency table analysis.Results: Providers completed 829 surveys over 14 months and reported US use during 102 (12.3%) patient transports. Of the transports in which US was used, ICU to ICU (58.8%) was the most frequent, followed by ED to ED (28.4%), ED to ICU (4.9%) and scene to ED (2.9%). Providers agreed or strongly agreed that US use clarified the cause of patient symptoms in 67.4% and changed management in 36.4% of transports. Transports in which US was used were more likely to involve a critically ill patient (92%) than flights in which US was not used (73%) (p < 0.001). Providers were significantly more likely to use US when less confident in initial assessment of patient cardiac function, intravascular volume status, and cause of respiratory distress (p < 0.05).Conclusions: Non-physician out-of-hospital providers can learn and perform critical care US. Non-physician performed US can clarify the cause of patient symptoms and change management in the out-of-hospital setting.