Defibrillation by Basic Emergency Medical Technicians in Patients with out-of-Hospital Cardiac Arrest

A systematic review 1 including 10 studies with a total of 4,017 subjects with out-of-hospital cardiac arrest was abstracted in DARE. The study design was not reported - probably the studies were case series. There was an overall 9.2% increase in survival in those who received early fibrillation by an emergency medical technician.

Another systematic review 2 including 7 studies was abstracted in DARE. For all trials combined, defibrillation by BLS personnel significantly reduced the risk of mortality: p=0.0003. The overall relative risk was 0.915 (95% CI 0.876 to 0.955), a reduction in the risk of mortality for BLS using defibrillation relative to BLS teams without access to this treatment of 8.5%.

A third systematic review 3 including 36 studies with a total of 23,313 cases of cardiac arrest was abstracted in DARE. One-tier and two-tier systems were separately evaluated. In the one-tier system, a single provider and vehicle type responds to medical emergencies either with basic life support (BLS), basic life support plus defibrillation (BLS-D), or advanced life support (ALS). In a two-tier system, the firs respondent provides BLS or BLS-D, while a second responder then provides ALS.

After adjustment for other variables, survival was 5.2% in a one-tier system, compared to 10.5% in a two-tier system. A 1-minute decrease in mean response time was associated with an absolute increase in survival of 0.4% in a one-tier system and 0.7% in a two-tier system. A 5% increase in bystander CPR was associated with an absolute increase in survival of 0.1% in a one or two tier system.

A fourth systematic review 4 including 37 case series with a total of 33,124 subjects was abstracted in DARE. Four RCTs were also identified but they failed to meet all the inclusion criteria. Median survival for all rhythm groups to hospital discharge was 6.4%. Odds of survival were 1.06 (95% CI 1.03 to 1.09) per 5% increase in bystander cardiopulmonary resuscitation. Survival was constant if the defibrillation response time interval was < 6 minutes (OR = 1), decreased as the interval increased from 6 to 11 minutes (OR = 0.85, 95% CI 0.73 to 0.99) and levelled off at 11 minutes. Compared with basic life support plus defibrillation, the OR of survival for advanced life support was 1.71 (95% CI 1.09 to 2.70), basic life support plus advanced life support was 1.47 (95% CI 0.89 to 2.42), and BLS-D + ALS it was 2.31 (95% CI 1.47 to 3.62).

References

• Watts DD. Defibrillation by basic emergency medical technicians: effect on survival. Ann Emerg Med 1995 Nov;26(5):635-9. [PubMed][DARE]
• Auble TE, Menegazzi JJ, Paris PM. Effect of out-of-hospital defibrillation by basic life support providers on cardiac arrest mortality: a metaanalysis. Ann Emerg Med 1995 May;25(5):642-8. [PubMed] [DARE]
• Nichol G, Detsky AS, Stiell IG, O'Rourke K, Wells G, Laupacis A. Effectiveness of emergency medical services for victims of out-of-hospital cardiac arrest: a metaanalysis. Ann Emerg Med 1996 Jun;27(6):700-10. [PubMed][DARE]
• Nichol G, Stiell IG, Laupacis A, Pham B, De Maio VJ, Wells GA. A cumulative meta-analysis of the effectiveness of defibrillator-capable emergency medical services for victims of out-of-hospital cardiac arrest. Ann Emerg Med 1999 Oct;34(4 Pt 1):517-25. [PubMed] [DARE]