Weak link in resuscitation
In a recent opinion piece in The Guardian, the author says that our pre-hospital cardiac arrest survival rate is far worse than in more progressive countries, such as Australia, the U.S. and the UK. Really? According to a recent meta-analysis, published in the American Heart Association’s journal “Circulation,” survival from out-of-hospital cardiac arrest (OHCA) worldwide has not significantly improved in almost 30 years.
The aggregate survival rate [those who make it through their hospitalization and get discharged home, mostly intact, is between 6.7 per cent and 8.4 per cent. This lack of progress, despite enormous increases in resuscitation research, the introduction of new drugs and devices, and periodic revisions to clinical guidelines may be explained, in part, by declining numbers of ventricular fibrillation cardiac arrests, increasing age of the population, and longer EMS response times.
Seattle, Phoenix, Minneapolis and Tokyo have survival rates two to three times higher than average. Such centres of excellence have many things in common: high population densities, geographically small response coverage zones, high percentage of CPR-trained adults, tiered EMS response and sophisticated notification systems, including use of social media.
All Seattle firefighters are trained as Emergency Medical Technicians (EMTs) and act as first responders; there are nearly 300 fully trained paramedics and 26 ambulances on duty; there are automated external defibrillators in multiple public locations, including many police cars and all dental offices.
Seattle EMS responds with at least three vehicles to each cardiac arrest, giving a minimum of seven EMTs on-scene, providing a highly organized ‘pit crew’ response. Resuscitated patients who regain a palpable pulse (ROSC) are rapidly transported to hospitals which are set up to provide immediate access to angiography and angioplasty, lifesaving procedures not available on P.E.I..
The same study found that OHCA victims who receive CPR from a bystander or an EMS provider, and those who are found in ventricular fibrillation (VF) or ventricular tachycardia (VT), rhythm disturbances amenable to application of an automated external defibrillator (AED), are much more likely to survive than those who do not. Chances of survival were significantly increased when a defibrillator was available at public sites. It is noteworthy that only 40 per cent of patients with OHCA were found in VF/VT, and only 22 per cent of them achieved return of spontaneous circulation (ROSC).
To put these observations in context, approximately one of every five patients with VF/VT survives to hospital discharge, compared to one of every 250 patients found in asystole. Prompt initiation of CPR can delay the degradation of VF and VT to asystole, which may explain why bystander CPR and pre-hospital defibrillation have such a positive impact on survival. Future efforts to boost OHCA survival should focus on immediate initiation of CPR and early defibrillation. Targeted CPR training will have its greatest effect in communities with currently low rates of survival.
Good outcomes depend on an interlocking series of events occurring rapidly and effectively. When even one link is weak or missing, it can’t be compensated for elsewhere. Advanced life support and rapid access to a cardiac centre are of no use to a patient who has been in cardiac arrest without basic life support for more than ten minutes. We know that every minute without CPR before defibrillation means an almost 10 per cent decrease in survival, and that we get the biggest bang for our buck from immediate and effective CPR followed by defibrillation.
In most cardiac arrests, the weak link is prompt bystander CPR. Unfortunately, intervention only helps if the cardiac arrest is witnessed. Un-witnessed cardiac arrests are almost always fatal. If high-quality bystander CPR is started immediately, chances of successful defibrillation increase significantly.
Realistically, successful resuscitation from pre-hospital cardiac arrest is limited to witnessed cardiac arrest, where the victim is in ventricular fibrillation or ventricular tachycardia, the witness is trained to perform and promptly initiates effective CPR, there is application of an AED within 10 minutes, circulation is restored and rapid transfer to a cardiac centre occurs. In a mostly rural province with only 165 pre-hospital cardiac arrests a year, less than half of whom have a reasonable shot at successful resuscitation and meaningful survival, improving on the norm will be a monumental challenge.