Conversion rates for prehospital paroxysmal supraventricular tachycardia (PSVT) with the addition of adenosine: a before-and-after trial.

OBJECTIVE: To determine whether the prehospital administration of adenosine to adults with stable and unstable paroxysmal supraventricular tachycardia (PSVT) influences conversion rate (CR) to sinus rhythm, scene time, use of synchronized electrical cardioversion (SEC), and accuracy of rhythm strip interpretation by paramedics.

METHODS: This before-and-after study compared a retrospective control group (CG) prior to the introduction of adenosine with a prospective treatment group (TG) following the addition of adenosine to the PSVT treatment protocol in a large urban advanced life support emergency medical services system. The population represented patients > or = 18 years of age with PSVT diagnosed by the paramedic (defined as spontaneous onset of a regular narrow-complex tachycardia between 140 and 250 beats/minute).

RESULTS: The CG comprised 74 calls and the TG 137 calls. The overall CR was higher in the TG (59% vs 32%, p < 0.001). The SEC and spontaneous conversion rates remained unchanged. The proportion of untreated patients with PSVT decreased from 26% CG to 12% TG (p < 0.01). Scene times were longer in the TG (26 vs 19 minutes, p < 0.001). Agreement between paramedic and physician rhythm strip interpretations was fair to moderate (CG kappa 0.43 [95% CI: 0.14, 0.72]; TG kappa 0.37 [95% CI: 0.13, 0.61]).

CONCLUSIONS: The introduction of adenosine was associated with a significant increase in the prehospital CR of stable and unstable PSVT, while the SEC and spontaneous conversion rates were similar in each group; however, scene times were longer in the TG and paramedic accuracy in rhythm strip interpretation remained fair to moderate.