Cardiac Arrest

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Introduction

Cardiac arrest, also called cardiopulmonary arrest or circulatory arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively. Without timely CPR and defibrillation, cardiac arrest signifies death. When in the hospital, the response to cardiac arrest is a 'code' or 'code blue'.

The cardiac rhythms accompanying cardiac arrest may be called 'shockable' and 'non-shockable', depending on their potential responsiveness to defibrillation:

shockable rhythms

pulseless ventricular tachycardia
ventricular fibrillation
unstable tachydysrhythmia

non-shockable rhythms

pulseless electrical activity
asystole

The Case of Will Regan

Will Regan is a 78 year-old man who suffers cardiac arrest at the mall. CPR is started within seconds, and he is unsuccessfully resuscitated with the mall's AED. An ambulance crew brings him into the emergency department, intubated and with an IV in place, with his wife beside him.

As team leader, what do you do?

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Causes and Risk Factors

The majority of cardiac arrest is caused by ischemic heart disease. Other predisposing conditions include:

7 H's and 5 T's: pnemonic for mechanisms

hypoxia
hypovolemia
hyperkalemia
hypokalemia
hypoglycemia
hypothermia
hydrogen ions (acidosis)

thrombosis (MI)
tension pneumothorax
tamponade
toxins/therapeutics
thromboembolism
trauma

cardiomyopathy
arrhythmias
congestive heart failure

Non–cardiac SCDs causes include:

trauma
non-trauma related bleeding (such as gastrointestinal bleeding, aortic rupture, and intracranial hemorrhage)
overdose
drowning
pulmonary embolism

Sudden cardiac death appears to be due to ischemic heart disease, leading to fatal ventricular arrhythmias.

Other causes are involved, particularly in younger people:

congenital structural or arterial abnormalities
aortic valve stenosis
mitral valve stenosis
myocarditis
dilated or hypertrophic cardiomyopathy
pulmonary hypertension
systemic hypertension and resulting hypertrophy
problems with electrical conduction system
isolated hypertrophy

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Pathophysiology

Ventricular fibrillation represents the loss of coordinated contraction of the ventricles. A rapid loss of cardiac output will result in death if it is not quickly reversed by defibrillation. VF can be caused by ventricular tachycardia on top of electrolyte imbalances, hypoxemia, or acidosis. Reentry circuits are thought to break up into smaller wavelets which wander throughout the ventricles.

VF or rapid, pulseless VT, which rapidly detiorates into VF. VF will become asystole if untreated.

Pulseless electrical activity (PEA) is a group of rhythms that are organized or semi-organized, but lack a discernible pulse. Examples include:

idioventricular rhythms
ventricular escape rhythms
postdefibrillation idioventricular rhythms
bradysystolic rhythms

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Signs and Symptoms

history
physical exam

History

Due to inadequate cerebral perfusion, the patient will be unconscious and will have stopped breathing.

If the arrest is witnessed, collateral history should be obtained.

Cardiac arrest is an abrupt cessation of pump function in the heart (as evidenced by the absence of a palpable pulse). Cardiac arrest can usually be reversed with prompt intervention, but without such intervention, it will almost always lead to death.

In certain cases, it is an expected outcome to a serious illness.

Physical Exam

The main diagnostic criterion to diagnose a cardiac arrest, (as opposed to respiratory arrest which shares many of the same features), is lack of circulation, however there are a number of ways of determining this.

A cardiac arrest is usually diagnosed clinically by the absence of a pulse. In many cases lack of carotid pulse is the gold standard for diagnosing cardiac arrest, but lack of a pulse (particularly in the peripheral pulses) may be a result of other conditions (e.g. shock), or simply an error on the part of the rescuer. Studies have shown that rescuers often make a mistake when checking the carotid pulse in an emergency, whether they are healthcare professionals[16] or lay persons. Owing to the inaccuracy in this method of diagnosis, some bodies such as the European Resuscitation Council (ERC) have de-emphasised its importance. The Resuscitation Council (UK), in line with the ERC's recommendations and those of the American Heart Association, have suggested that the technique should be used only by healthcare professionals with specific training and expertise, and even then that it should be viewed in conjunction with other indicators such as agonal respiration.

Various other methods for detecting circulation have been proposed. Guidelines following the 2000 International Liaison Committee on Resuscitation (ILCOR) recommendations were for rescuers to look for "signs of circulation", but not specifically the pulse. These signs included coughing, gasping, colour, twitching and movement. However, in face of evidence that these guidelines were ineffective, the current recommendation of ILCOR is that cardiac arrest should be diagnosed in all casualties who are unconscious and not breathing normally.

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Investigations

lab investigations
diagnostic imaging

Lab Investigations

Diagnostic Imaging

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Treatments

The interval from collapse to defibrillation, the only effective treatment for VF, is one of the most critical determinants of survival. CPR cannot directly restore an organized rhythm, but does provide a small amount of blood flow to the brain and heart. For every minute that passes, survival declines by 7-10% per minute, or by 3-4% per minute if CPR is provided (ref).

The following provide further information on treatment of cardiac arrest:

Breaking bad news is unfortunately often required following cardiac arrest.