Best 2017 Cardiac and Respiratory arrest for Medical Doctor

Signs and symptoms

 

Cardiac arrest is sometimes preceded by certain symptoms such as fainting, fatigue, blackouts, dizziness, chest pain. shortness of breath, weakness, and vomiting.

The arrest may also occur with no warning.When the arrest occurs, the most obvious sign of its occurrence will be the lack of a palpable pulse in the person experiencing it (since the heart has ceased to contract, the usual indications of its contraction such as a pulse will no longer be detectable).

Certain types of prompt intervention can often reverse a cardiac arrest, but without such intervention the event will almost always lead to death. In certain cases, it is an expected outcome of a serious illness where death is expected.

Also, as a result of inadequate cerebral perfusion, the patient will quickly become unconscious and will have stopped breathing. 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. Near-death experiences are reported by 10–20% of people who survived cardiac arrest.

 


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Causes

Coronary artery disease is the leading cause of sudden cardiac arrest. Many other cardiac and non-cardiac conditions also increase one’s risk.

Coronary artery disease often results in coronary ischemia and ventricular fibrillation (v-fib).Cases have shown that the most common finding at postmortem examination of SCD is chronic high-grade stenosis of at least one segment of a major coronary artery, the arteries that supply the heart muscle with its blood supply. Left ventricular hypertrophy is thought to be the leading cause of sudden cardiac death in the adult population. This is most commonly the result of longstanding high blood pressure which has caused secondary damage to the wall of the main pumping chamber of the heart, the left ventricle.


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Although the most frequent cause of sudden cardiac death is ventricular fibrillation, other causes include the following:

Coronary heart disease
Physical stress
low levels of magnesium
low levels of potassium
major blood loss
lack of oxygen
severe physical activity which triggers adrenaline
Inherited disorders
Hypertrophic cardiomyopathy
Enlarged heart due to increased blood pressure
Commotio cordis

 

Coronary artery disease

 

Approximately 60–70% of SCD is related to coronary artery disease, also known as ischemic heart disease. Among adults, it is the predominant cause of arrest, with 30% of people at autopsy showing signs of recent myocardial infarction.

 

Non-ischemic heart disease

A number of non-ischemic cardiac abnormalities can increase the risk of SCD, including cardiomyopathy, cardiac rhythm disturbances, myocarditis, hypertensive heart disease, and congestive heart failure.

In a group of military recruits aged 18–35, cardiac anomalies accounted for 51% of cases of SCD, while in 35% of cases the cause remained unknown. Underlying pathology included coronary artery abnormalities (61%), myocarditis (20%), and hypertrophic cardiomyopathy (13%).Congestive heart failure increases the risk of SCD fivefold.

Many additional conduction abnormalities exist that place one at higher risk for cardiac arrest. For instance, long QT syndrome, a condition often mentioned in young people’s deaths, occurs in one of every 5000 to 7000 newborns and is estimated to be responsible for 3000 deaths each year compared to the approximately 300,000 cardiac arrests seen by emergency services. These conditions are a fraction of the overall deaths related to cardiac arrest, but represent conditions which may be detected prior to arrest and may be treatable.

 

Non-cardiac causes

 

About 35% of SCDs are not caused by a heart condition. The most common non-cardiac causes are trauma, bleeding (such as gastrointestinal bleeding, aortic rupture, or intracranial hemorrhage), overdose, drowning and pulmonary embolism.Cardiac arrest can also be caused by poisoning (for example, by the stings of certain jellyfish).

 

Risk factors

The risk factors for SCD are similar to those of coronary artery disease and include smoking, lack of physical exercise, obesity, and diabetes, as well as family history. A prior episode of sudden cardiac arrest also increases the risk of future episodes.

 

Mechanism

 

Ventricular fibrillation
The mechanism of death in the majority of people dying of sudden cardiac death is ventricular fibrillation. Structural changes in the diseased heart as a result of inherited factors (mutations in ion-channel coding genes for example) cannot explain the suddenness of SCD. Also, sudden cardiac death could be the consequence of electric-mechanical disjunction and bradyarrhythmias

 

Diagnosis

 

Cardiac arrest is synonymous with clinical death.

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 result from other conditions (e.g. shock), or simply an error on the part of the rescuer. Studies have shown that rescuersoften make a mistake when checking the carotid pulse in an emergency, whether they are healthcare professionals 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. Another method is to use molecular autopsy or postmortem molecular testing which uses a set of molecular techniques to find the ion channels that are cardiac defective.

 

Classifications

Clinicians classify cardiac arrest into “shockable” versus “non–shockable”, as determined by the ECG rhythm. This refers to whether a particular class of cardiac dysrhythmia is treatable using defibrillation. The two “shockable” rhythms are ventricular fibrillation and pulseless ventricular tachycardia while the two “non–shockable” rhythms are asystole and pulseless electrical activity

 

Prevention

With positive outcomes following cardiac arrest unlikely, an effort has been spent in finding effective strategies to prevent cardiac arrest. With the prime causes of cardiac arrest being ischemic heart disease, efforts to promote a healthy diet, exercise, and smoking cessation are important. For people at risk of heart disease, measures such as blood pressure control, cholesterol lowering, and other medico-therapeutic interventions are used. A Cochrane review published in 2016 found moderate-quality evidence to show that blood pressure-lowering drugs do not appear to reduce sudden cardiac death.

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