One study suggests delaying a second defibrillation attempt does not improve survival for cardiac arrest patients.
Cardiac arrest occurs when the heart suddenly stops beating, cutting off blood flow to the brain and other vital body organs. If not treated within minutes, cardiac arrest can kill.
According to the American Heart Association (AHA), there was around 209,000 in-hospital cardiac arrests in the US in 2013.
When a patient experiences cardiac arrest, they must be treated with a defibrillator - a device that delivers an electric shock to the heart - within minutes, with the aim of restoring heart rhythm.
Previous resuscitation guidelines in the US recommended that cardiac arrest patients should receive "stacked" shocks - that is, one defibrillation attempt after another within minimal delays in between.
However, the guidelines were updated in 2005 to recommend a time delay before delivering a second defibrillation attempt, allowing time to administer chest compressions.
But Steven M. Bradley, of the University of Colorado School of Medicine, and colleagues note that there is limited data on how this delayed defibrillation impacts patient survival.
Deferred second defibrillation attempt did not improve patient survival
To address this research gap, the team analyzed 2004-2012 data from a national registry, involving 2,733 adults over 172 hospitals in the US who experienced cardiac arrest.
As expected, the researchers saw an increase in the percentage of cardiac arrest patients whose second defibrillation attempt was delayed, rising from 26% in 2004 - before the guidelines were updated - to 57% in 2012.
However, the team found that the survival of cardiac arrest patients was not improved with a delayed second defibrillation attempt, compared with patients who received an early second defibrillation attempt.
Dr. Bradley and colleagues note that their study is observational, so it is unable to draw any firm conclusions relating to cause and effect.
Still, they say their findings "raise questions about the specific benefits of deferred second defibrillation attempts" for cardiac arrest patients in the hospital, adding:
"Further study is necessary to understand whether current guidelines, which recommend against immediate second defibrillation attempts for persistent VT/VF [ventricular tachycardia/ventricular fibrillation] in hospital, need reconsideration."
Large variation in adrenaline recommendations for cardiac arrest
Another form of treatment for cardiac arrest is the medication epinephrine, also known as adrenaline, which is used to increase blood supply to the heart.
In a second study, Lars W. Andersen, of the Department of Emergency Medicine at the Beth Israel Deaconess Medical Center in Boston, MA, and colleagues set out to assess compliance to current guidelines for adrenaline administration in cardiac arrest patients.
While adrenaline has been used for the treatment of cardiac arrest for many years, guidelines for its use vary greatly.
The AHA recommend that adrenaline be administered within 2 minutes of the second defibrillation attempt, but the European Resuscitation Council (ERC) say the drug should be administered after the third.
"In addition, clinical practice patterns could include the provision of epinephrine even earlier, such as after the first defibrillation, in patients with a persistently shockable rhythm," note the authors.
For their study, Anderson and colleagues analyzed national registry data of 2,978 cardiac arrest patients over 300 hospitals in the US.
Poorer survival with early adrenaline administration
The team found that 51% of these patients were given adrenaline within 2 minutes of the first defibrillation attempt, which opposes current AHA guidelines.
What is more, the researchers found that these patients had poorer outcomes and poorer survival than those who did not receive adrenaline within 2 minutes of the first defibrillation attempt.
While - like the previous study - the researchers are unable to establish cause and effect with their findings, they say the results "might be relevant to guideline developers, educators, and clinicians involved with the care of such patients."
In an editorial linked to both studies, Keith Couper and Gavin D. Perkins - of Warwick Medical School at the UK's University of Warwick - believe the results of these studies should be reflected in clinical practice for the treatment of cardiac arrest patients. They add:
"[...] the finding of widespread non-adherence with clinical guidelines should prompt those responsible for organizing or delivering advanced life support to review their practice and ensure that it is informed by the latest clinical guidelines.
While the jury remains out on the overall safety or effectiveness of adrenaline in cardiac arrest, these data suggest that if adrenaline is given, in accordance with current guidelines, it should be deferred until at least after the second shock has been delivered."
Last November, Medical News Today reported on a study suggesting lowering body temperature in cardiac arrest patients who have non-shockable heart rhythms can increase survival rates and brain function.