ON CARDIAC ARRESTS
There is nothing we can philosophise about when discussing cardiac arrests. Here it is - life at its most penetrating, the moment of truth. Without assistance, the souls of all victims will rise to their maker. With assistance and in the correct setting (i.e. hospital, rather than on the street or at home), and type of arrest (patients with VF/VT have 10-15 times more chance of surviving than if pulseless electrical activity or asystole because they are sensitive to defibrillation, whereas asystole and PEA are not), on average only 15% survive, and often not without very serious complications, such as permanent brain damage.
The term “cardiac arrest” implies a sudden interruption of cardiac output, which may be reversible with appropriate treatment. It does not include the cessation of heart activity as a terminal event in serious illness; in these circumstances the techniques of basic life support are usually inappropriate. Survival after cardiac arrest is most likely to be the outcome in the following circumstances:
Event is witnessed
Bystander summons help from the emergency services and starts resuscitation; when the heart arrests in ventricular fibrillation
Defibrillation and advanced life support are instituted at an early stage.
Basic life support is one link in this chain of survival. It entails assessment followed by action—the ABC: A is for assessment and airway, B is for breathing, and C is for circulation.
There are three main causes:
1) Ventricular fibrillation / Ventricular tachycardia (pulseless) – commonest rhythm
2) Pulseless electrical activity (PEA)
Basically, the heart is a pump with an electrical controlling system. Its power supply comes from burning fuel with oxygen. It stops functioning in three main ways:
1. Failure of oxygen supply – causing extreme bradycardia or asystole; there is no electrical activity and no pumping
2. Failure of electrical control causes VF or pulseless VT; there is no effective electrical activity and no effective pumping
3. Failure of the pumping mechanism causes electromechanical dissociation (EMD or PEA); there is electrical activity but no pumping.
The reversible causes of cardiac arrest can be remembered by the 4H & 4T:
Hypo & hyperkalaemia Tamponade
Thromboembolism (coronary or pulmonary)
JAMES BOND’S CARDIAC ARREST
Because of the sensationalism that is associated with cardiac arrests, they are a frequent feature of many movies, most of which are over-dramatized.
I am not a very active pursuer of TV and cinema, finding the advice, wit and wisdom of Graucho Marx very useful in this regard, “I find television very educational. Every time someone switches it on, I go into another room and read a good book”. Nevertheless, American movies do occasionally give us some excellent educational points – such as the very interesting and well managed cardiac arrest that James Bond endured in the movie ‘Casino Royale’ (2006) – probably the most intriguing aspect of the film.
The cardiac arrest happened, “while playing a game of poker in the casino was due to digoxin poisoning. He was resuscitated with intravenous lignocaine and defibrillation by his glamorous female partner. The tuxedo-clad Agent 007 then coolly wipes his brow, straightens his bow-tie, and returns to the table to beat up the bad guy in a high-stakes game of Texas Hold ’em.”
Believe it or not, there are at least three medical lessons given in this short sketch. Firstly, it makes us aware that, although digoxin poisoning is generally associated with heart block and bradycardia, it can cause tachycardia and fibrillation. Secondly, it teaches that the drug of choice in digoxin induced VF is not amiodarone, because the latter can worsen the arrhythmia. The second choice drug lidocaine (100mg) is therefore used. Thirdly, it highlights a very interesting point – that overall survival from cardiac arrests in casinos is actually better than hospitals! In the article, ‘Outcomes of rapid defibrillation by security officers after cardiac arrest in casinos’, Valenzuela et al showed (N Engl J Med. 2000 Oct 26;343(17):1206-9) that 53% of people who had ventricular fibrillation in casinos survived to discharge. By contrast, the percentage of people who survive in-hospital ventricular fibrillation to discharge is only 34%, according to 2003 data from the National Registry of CPR (NRCPR). This is extremely interesting, and may have been known to the script writers of the movie.
THE MANAGEMENT OF CARDIAC ARREST
The management of cardiac arrest is done according to the ALS algorithm, beginning with basic life support. If the scene is safe, assess responsiveness by gently tapping/speaking loudly. Activate emergency response system if unresponsive. Then assess:
Airway - open airway, look, listen, and feel for breathing in <10 seconds. Use appropriate C-spine precautions if trauma is present / suspected.
Breathing - If not breathing adequately, give 2 rescue breaths, 1 second each.
Circulation - Carotid pulse check, 5-10 seconds. If pulseless, begin chest compressions at 100/min. Push hard, allow full chest rebound (30:2 CPR ratio)
Defibrillation - Analyze rhythm (AED/quick-look paddles). Shock VF/PVT once, immediately resume CPR for 2 minutes starting with chest compressions. Defibrillation is appropriate only in VF or pulseless VT, delivering one 360 J shock followed immediately by 2 minutes of CPR. CPR should never be interrupted for >10 seconds except to defibrillate.