BIPHASIC DEFIBRILLATION DOES NOT IMPROVE OUTCOMES

[FL_Medic]

BIPHASIC DEFIBRILLATION DOES NOT IMPROVE OUTCOMES COMPARED TO

MONOPHASIC DEFIBRILLATION IN OUT-OF-HOSPITAL CARDIAC ARREST

Kimberly Freeman, MD, Gregory W. Hendey, MD, Marc Shalit, MD, Geoff Stroh, MD

Abstract

Study Objective. To compare the outcomes of out-of hospital cardiac arrest (OHCA) victims treated with monophasic truncated exponential (MTE) versus biphasic truncated exponential (BTE) defibrillation in an urban EMS system. Methods. We conducted a retrospective review of electronic prehospital and hospital records for victims of OHCA between August 2000 and July 2004, including two years before and after implementation of biphasic defibrillators by the Fresno County EMS agency. Main outcome measures included: return of spontaneous circulation (ROSC), number of defibrillations required for ROSC, survival to hospital discharge, and discharge to home versus an extended care facility. Results. There were 485 cases of cardiac arrest included. Baseline characteristics between the monophasic and biphasic groups were similar. ROSC was achieved in 77 (30.6%, 95% CI 25.2-36.5%) of 252 patients in the monophasic group, and in 70 (30.0% 95% CI 24.5-36.2%) of 233 in the biphasic group (p = .92). Survival to hospital discharge was 12.3% (95% CI 8.8-17%) for monophasic and 10.3% (95% CI 7.0-14.9%) for biphasic (p = .57). Discharge to home was accomplished in 20 (7.9%, 95% CI 5.1-12.0%) of the monophasic, and in 15 (6.4%, 95% CI 3.9-10.4%) of the biphasic group (p = .60). More defibrillations were required to achieve ROSC (3.5 vs. 2.6, p = .015) in the monophasic group. Conclusions. We found no difference in ROSC or survival to hospital discharge between MTE and BTE defibrillation in the treatment of OHCA, although fewer defibrillations were required to achieve ROSC in those treated with biphasic defibrillation.

Not sure if you need a subscription but here is the link to the full article:

http://web.ebscohost.com.db07.linccweb.org...40sessionmgr102

[akroeze]

Can't view the main article

Where was this study done? That's a great survival to discharge.

[FL_Medic]

Department of Emergency Medicine, UCSF-Fresno, Medical Education Program, Fresno, California.

Source:

Prehospital Emergency Care (PREHOSPITAL EMERG CARE), 2008 Apr-Jun; 12(2): 152-6 (20 ref)

I will post the tables if interested. Obviously I can't post the whole article because of the copyright, but the abstract sums it up pretty well.

[triemal04]

Interesting study, and while it's good that someone finally did one, the results really aren't that surpising and just confirm something that most know: we may be able to get ROSC on someone in cardiac arrest, but getting them discharged home...we suck at that. It does confirm what I believe was the original reason for the push to change to biphasic; it takes fewer shocks to convert a rhythm with a biphasic defibrillator than a monophasic. Though that'd be a good thing for someone with a perfusing rhythm getting cardioverted; be curious to see a study on that and if there was any change in the results.

[CBEMT]

The study took place before the 2005 AHA update, meaning the three stacked shocks was still in effect, CPR was 15:2, ventilation was emphasized, but limiting hands-off time was not emphasized, ETI was still the be-all and end-all.... you get the idea.

Tell them to come back when they can publish a study in line with current practice.

Edited March 25, 2009 by CBEMT

[FL_Medic]

This one is from 1999, I know it's old. Hard to find one done after 2005, studies take a while so maybe they are doing one now.

External exponential biphasic versus monophasic shock waveform: efficacy in ventricular fibrillation of longer duration.

Yamanouchi Y; Brewer JE; Donohoo AM; Mowrey KA; Wilkoff BL; Tchou PJ

Abstract

Ventricular fibrillation (VF) duration may be a factor in determining the defibrillation energy for successful defibrillation. Exponential biphasic waveforms have been shown to defibrillate with less energy than do monophasic waveforms when used for external defibrillation. However, it is unknown whether this advantage persists with longer VF duration. We tested the hypothesis that exponential biphasic waveforms have lower defibrillation energy as compared to exponential monophasic waveforms even with longer VF duration up lo 1 minute. In a swine model of external defibrillation (n = 12,35 ± 6 kg), we determined the stored energy at 50% defibrillation success (E50) after both 10 seconds and 1 minute of VF duration. A single exponential monophasic (M) and two exponential biphasic (B1 and B2) waveforms were tested with the following characteristics: M (60 uF. 70% tilt), B1 (60/60 uF, 70% tilt/3 ms pulse width), and B2 (60/20 uF. 70% tilt/3 ms pulse width) where the ratio of the phase 2 leading edge voltage to that of phase 1 was 0.5 for B1 and 1.0 for B2. E50 was measured by a Bayesian technique with a total of ten defibrillation shocks in each waveform and VF duration randomly. The E50 (J) for M, B1, and B2 were 131 ± 41, 57 ± 18,* and 60 ± 26* with 10 seconds of VF duration, respectively, and 114 ± 62, 77 ± 45,* and 72 ± 53* with 1 minute of VF duration, respectively (*P < 0.05 vs M). There was no significant difference in the E50 between 10 seconds and 1 minute of VF durations for each waveform. We conclude that (1) the E50 does not significantly increase with lengthening VF durations up to 1 minute regardless of the shock waveform, and (2) external exponential biphasic shocks are more effective than monophasic waveforms even with longer VF durations.

[celticcare]

Isn't that the same sort of time as the international market started a big drive to dump the monophasic gear *which you can pick up cheap on ebay* and buy only biaphasic?

Been talking to a combination of medics and nurses and there seems to be a consensus that biaphasic is more successful in cardioversion of atrial arrythmias and vts however they found monophasic more successful for defibrillation.

Will see if I can find anything to back it up but sometimes just human experience is good too.

[FireMedic65]

I have a really good article on this, but it is in a pdf format, so I can't copy/paste it into the forum. If you would like it, let me know by sending a PM with your email and I will e-mail it to you.