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.

Cardiovascular safety of high doses of inhaled fenoterol and albuterol in acute severe asthma.

BACKGROUND: It has been suggested that overuse of fenoterol metered-dose inhalers (MDIs) may increase the risk of death from asthma due to cardiac arrhythmias. Our primary objective was to compare the cardiovascular safety of fenoterol and albuterol MDIs when administered in maximal bronchodilating or maximal tolerated doses to an absolute maximum of 16 puffs, for the emergency department (ED) treatment of acute severe asthma. METHODS: Asthmatic patients presenting to the ED with acute severe asthma (FEV1 less than 50% of predicted) were enrolled in a multicenter, randomized, double-blind, parallel-group study. Following baseline measurements, (medical history, physical examination, determination of serum potassium and serum theophylline levels, oximetry, 12-lead ECG, and spirometry), each patient received 4 puffs of either fenoterol, 200 micrograms per puff, or albuterol, 100 micrograms per puff, 1 puff every 30 s via an MDI attached to a holding chamber. Additional doses of inhaled beta 2-agonist were administered by dose titration, 2 puffs every 10 min to a maximal cumulative dose of 16 puffs of albuterol or fenoterol, side effects were intolerable to the patient, or an FEV1 plateau (i.e., < 10% improvement for 2 consecutive doses) occurred. ECG was recorded continuously via Holter monitor, and respiratory rate, BP, dyspnea (Borg scale), and FEV1 were assessed after each dose. RESULTS: 128 patients were randomized to receive fenoterol and 129 to receive albuterol. Overall, fenoterol increased FEV1 160 mL more than albuterol. The mean (SEM) FEV1 increase from baseline was 0.75 +/- 0.06 L in the fenoterol group and 0.59 +/- 0.06 L in the albuterol group (p < 0.03). Both beta 2-agonists caused a decrease in serum potassium level that was significantly greater in the fenoterol (0.23 +/- 0.04 mmol/L) than in the salbutamol (0.06 +/- 0.03 mmol/L) group (p = 0.0002). There was also a greater increase in the Q-Tc interval in the fenoterol group, 0.011 +/- 0.003 s compared with 0.003 +/- 0.003 s in the albuterol group (p < 0.05). Differences in hypokalemia and Q-Tc prolongation associated with fenoterol and albuterol were significantly different only after 8 puffs of fenoterol had been given. 32 patients exhibited ventricular premature beats, 14 in the fenoterol group and 18 in the albuterol group. There were 34 patients with episodes of supraventricular premature beats, 17 in each group. No episodes of sustained ventricular tachycardia were detected in either group. CONCLUSIONS: In adequately oxygenated patients, using dose titration of fenoterol, in a formulation of 200 micrograms per puff by MDI valved holding chamber and mask, to a total dose of 3,200 micrograms and salbutamol (100 micrograms per puff) to a total dose of 1,600 micrograms over 90 min, showed cardiovascular safety in acute severe asthma. This was evidenced by absence of cardiovascular mortality or clinically significant arrhythmias in either group. The 100% greater dose of fenoterol improved FEV1 significantly more than salbutamol and was associated with a relatively small but significantly greater prolongation of the Q-Tc interval and decrease in serum potassium level. This study does not exclude the possibility that adverse cardiac events could occur with severe hypoxemia.

Prehospital interventions.

This article examines a number of areas in emergency prehospital care that the authors view as important and controversial. It offers a Canadian perspective on international research done in the field of prehospital care, and it is not intended to suggest recommendations for the American prehospital care environment. The discussion is not encyclopedic. The authors believe that the areas discussed merit further research and analysis.

Update on trauma care in Canada. 5. Trauma and hypothermia.

Trauma may be accompanied by hypothermia in all climates. Because of the associated increased death rate due to hypothermia (core body temperature less than 35 degrees C), traumatized patients must be protected from it. The body maintains heat balance by hypothalamic regulation of endogenous heat generation and heat loss. Decreased core temperature causes generalized physiologic deceleration and homeostatic disturbances in all organ systems. To prevent hypothermia in polytraumatized patients a number of methods may be used: warming crystalloid, increasing ambient temperature, the use of warming devices, irrigation of body cavities with warmed fluids, heating of inspired gases and, in severe cases when there is circulatory instability, the use of extracorporeal membrane oxygenation.

Two cases of accidental immersion hypothermia with different outcomes under identical conditions.

Two cases of accidental immersion hypothermia are presented, both occurring during the same aircraft ditching. One victim survived while the other patient died despite identical immersion time and environmental conditions. Pertinent literature is reviewed to attempt to explain the different patient outcomes. The most important discriminating factor appears to be skinfold thickness, which reflects body fat.