Posted by: wockhardthospitals | June 29, 2009

MJ, Michael Jackson Dies of cardiac arrest. What is Cardiac Arrest?

cardiac arrestA cardiac arrest, also known as cardiopulmonary arrest or circulatory arrest, is the abrupt cessation of normal circulation of the blood due to failure of the heart to contract effectively during systole.

A cardiac arrest is different from (but may be caused by) a heart attack or myocardial infarction, where blood flow to the still-beating heart is interrupted (as in cardiogenic shock).

“Arrested” blood circulation prevents delivery of oxygen to all parts of the body. Cerebral hypoxia, or lack of oxygen supply to the brain, causes victims to lose consciousness and to stop normal breathing, although agonal breathing may still occur. Brain injury is likely if cardiac arrest is untreated for more than five minutes,although new treatments such as induced hypothermia have begun to extend this time. To improve survival and neurological recovery immediate response is paramount.

Cardiac arrest is a medical emergency that, in certain groups of patients, is potentially reversible if treated early enough. When unexpected cardiac arrest leads to death this is called sudden cardiac death (SCD).The primary first-aid treatment for cardiac arrest is cardiopulmonary resuscitation (commonly known as CPR) which provides circulatory support until availability of definitive medical treatment, which will vary dependent on the rhythm the heart is exhibiting, but often requires defibrillation.

Causes of cardiac arrest

Cardiac arrest is synonymous with clinical death. All disease processes leading to death have a period of (potentially) reversible cardiac arrest: the causes of arrest are, therefore, numerous. However, many of these conditions, rather than causing an arrest themselves, promote one of the “reversible causes” , which then triggers the arrest (e.g. choking leads to hypoxia which in turn leads to an arrest). In some cases, the underlying mechanism cannot be overcome, leading to an unsuccessful resuscitation.

Among adults, ischemic heart disease is the predominant cause of arrest. At autopsy 30% of victims show signs of recent myocardial infarction. Other cardiac conditions potentially leading to arrest include structural abnormalities, arrhythmias and cardiomyopathies. Non-cardiac causes include infections, overdoses, trauma and cancer, in addition to many others.

Reversible causes

Cardiopulmonary resuscitation (CPR), including adjunctive measures such as defibrillation, intubation and drug administration, is the standard of care for initial treatment of cardiac arrest. However, most cardiac arrests occur for a reason, and unless that reason can be found and overcome, CPR is often ineffective, or if it does result in a return of spontaneous circulation, this is short lived. As highlighted above, a variety of disease processes can lead to a cardiac arrest, however they usually boil down to one or more of the “Hs and Ts”.

  • Hypovolemia – A lack of circulating body fluids, principally blood volume. This is usually (though not exclusively) caused by some form of bleeding, anaphylaxis, or pregnancy with gravid uterus. Peri-arrest treatment includes giving IV fluids and blood transfusions, and controlling the source of any bleeding – by direct pressure for external bleeding, or emergency surgical techniques such as esophageal banding, gastroesophageal balloon tamponade (for treatment of massive GI bleeding such as in esophageal varices), thoracotomy in cases of penetrating trauma or significant shear forces applied to the chest, or exploratory laparotomy in cases of penetrating trauma, spontaneous rupture of major blood vessels, or rupture of a hollow viscus in the abdomen.
  • Hypoxia – A lack of oxygen delivery to the heart, brain and other vital organs. Rapid assessment of airway patency and respiratory effort must be performed. If the patient is mechanically ventilated, the presence of breath sounds and the proper placement of the endotracheal tube should be verified. Treatment may include providing oxygen, proper ventilation, and good CPR technique. In cases of carbon monoxide poisoning or cyanide poisoning, hyperbaric oxygen may be employed after the patient is stabilized.
  • Hydrogen ions (Acidosis) – An abnormal pH in the body as a result of lactic acidosis which occurs in prolonged hypoxia and in severe infection, diabetic ketoacidosis, renal failure causing uremia, or ingestion of toxic agents or overdose of pharmacological agents, such as aspirin and other salicylates, ethanol, ethylene glycol and other alcohols, tricyclic antidepressants, isoniazid, or iron sulfate. This can be treated with proper ventilation, good CPR technique, buffers like sodium bicarbonate, and in select cases may require emergent hemodialysis.
  • Hyperkalemia or Hypokalemia – Both excess and inadequate potassium can be life-threatening. A common presentation of hyperkalemia is in the patient with end-stage renal disease who has missed a dialysis appointment and presents with weakness, nausea, and broad QRS complexes on the electrocardiogram. (Note however that patients with chronic kidney disease are often more tolerant of high potassium levels as their body often adapts to it.) The electrocardiogram will show tall, peaked T waves (often larger than the R wave) or can degenerate into a sine wave as the QRS complex widens. Immediate initial therapy is the administration of calcium, either as calcium gluconate or calcium chloride. This stabilizes the electrochemical potential of cardiac myocytes, thereby preventing the development of fatal arrhythmias. This is, however, only a temporizing measure. Other temporizing measures may include nebulized albuterol, intravenous insulin (usually given in combination with glucose, and sodium bicarbonate, which all temporarily drive potassium into the interior of cells. Definitive treatment of hyperkalemia requires actual excretion of potassium, either through urine (which can be facilitated by administration of loop diuretics such as furosemide) or in the stool (which is accomplished by giving sodium polystyrene sulfonate enterally, where it will bind potassium in the GI tract.) Severe cases will require emergent hemodialysis. The diagnosis of hypokalemia (not enough potassium) can be suspected when there is a history of diarrhoea or malnutrition. Loop diuretics may also contribute. The electrocardiogram may show flattening of T waves and prominent U waves. Hypokalemia is an important cause of acquired long QT syndrome, and may predispose the patient to torsades de pointes. Digitalis use may increase the risk that hypokalemia will produce life threatening arrhythmias. Hypokalemia is especially dangerous in patients with ischemic heart disease.
  • Hypothermia – A low core body temperature, defined clinically as a temperature of less than 35 degrees Celsius (95 degrees Fahrenheit). The patient is re-warmed either by using a cardiac bypass or by irrigation of the body cavities (such as thorax, peritoneum, bladder) with warm fluids; or warmed IV fluids. CPR only is given until the core body temperature reached 30 degrees Celsius, as defibrillation is ineffective at lower temperatures. Patients have been known to be successfully resuscitated after periods of hours in hypothermia and cardiac arrest, and this has given rise to the often-quoted medical truism, “You’re not dead until you’re warm and dead.”
  • Hypoglycemia or Hyperglycemia – Low blood glucose from overdose of oral hypoglycemics such as sulfonylureas, or overdose of insulin. Rare endocrine disorders can also cause unexpected hypoglycemia. Generally, hyperglycemia is itself not fatal, however DKA will cause pH to drop, and nonketotic hyperosmolar coma leads to a severely hypovolemic state. Hypoglycemia is corrected rapidly by intravenous administration of concentrated glucose (typically 25 ml of 50% glucose in adults, but in children 25% glucose is used, and in neonates 10% glucose is used.) However, the patient will often require a continuous intravenous drip until the causative agent is completely metabolized. In DKA, the goal is correction of acidosis. In NKH, the goal is adequate fluid resuscitation.
  • Tablets or Toxins – Tricyclic antidepressants, phenothiazines, beta blockers, calcium channel blockers, cocaine, digoxin, aspirin, acetominophen. This may be evidenced by items found on or around the patient, the patient’s medical history (i.e. drug abuse, medication) taken from family and friends, checking the medical records to make sure no interacting drugs were prescribed, or sending blood and urine samples to the toxicology lab for report. Treatment may include specific antidotes, fluids for volume expansion, vasopressors, sodium bicarbonate (for tricyclic antidepressants), glucagon or calcium (for calcium channel blockers), benzodiazepines (for cocaine), or cardiopulmonary bypass. Herbal supplements and over-the-counter medications should also be considered.
  • Cardiac Tamponade – Blood or other fluids building up in the pericardium can put pressure on the heart so that it is not able to beat. This condition can be recognized by the presence of a narrowing pulse pressure, muffled heart sounds, distended neck veins, electrical alternans on the electrocardiogram, or by visualization on echocardiogram. This is treated in an emergency by inserting a needle into the pericardium to drain the fluid (pericardiocentesis), or if the fluid is too thick then a subxiphoid window is performed to cut the pericardium and release the fluid.
  • Tension pneumothorax – The build-up of air into one of the pleural cavities, which causes a mediastinal shift. When this happens, the great vessels (particularly the superior vena cava) become kinked, which limits blood return to the heart. The condition can be recognized by severe air hunger, hypoxia, jugular venous distension, hyperressonance to percussion on the effected side, and a tracheal shift away from the effected side. The tracheal shift often requires a chest x-ray to appreciate (although treatment should be initiated prior to obtaining a chest x-ray if this condition is suspected. ) This is relieved in by a needle thoracotomy (inserting a needle catheter) into the 2nd intercostal space at the mid-clavicular line, which relieves the pressure in the pleural cavity.
  • Thrombosis (Myocardial infarction) – If the patient can be successfully resuscitated, there is a chance that the myocardial infarction can be treated, either with thrombolytic therapy or percutaneous coronary intervention.
  • Thromboembolism (Pulmonary embolism) – hemodynamically significant pulmonary emboli are generally massive and typically fatal. Administration of thrombolytics can be attempted, and some specialized centers may perform thrombolectomy, however, prognosis is generally poor.
  • Trauma (Hypovolemia) – Reduced blood volume from acute injury or primary damage to the heart or great vessels. Cardiac arrest secondary to trauma, particularly blunt trauma, has a very poor prognosis.

Prevention

With positive outcomes following cardiac arrest so unlikely, a great deal of effort has been spent in finding effective strategies to prevent cardiac arrest.

As noted above, one of the prime causes of cardiac arrest outside of hospital is ischemic heart disease. Vast resources have been put into trying to reduce cardiovascular risks across much of the developed world. In particular schemes have been put in place to promote a healthy diet and exercise. For people considered to be particularly at risk of heart disease, measures such as blood pressure control, prescription of cholesterol lowering medications, and other medico-therapeutic interventions, have been widely used. A magnesium deficiency, or lower levels of magnesium, can contribute to heart disease and a healthy diet that contains adequte magnesium may help prevent heart disease. Magnesium can be used to enhance long term treatment, so it may be effective in long term prevention.

Extensive research has shown that patients in general wards often deteriorate for several hours or even days before a cardiac arrest occurs. This has been attributed to a lack of knowledge and skill amongst ward based staff, in particular a failure to carry out measurement of the respiratory rate, which is often the major predictor of a deterioration and can often change up to 48 hours prior to a cardiac arrest. In response to this, many hospitals now have increased training for ward based staff. A number of “early warning” systems also exist which aim to quantify the risk which patients are at of deterioration based on their vital signs and thus provide a guide to staff. In addition, specialist staff are being utilised more effectively in order to augment the work already being done at ward level. These include:

  • Crash teams (also known as code teams) – These are designated staff members who have particular expertise in resuscitation, who are called to the scene of all arrests within the hospital.
  • Medical emergency teams – These teams respond to all emergencies, with the aim of treating the patient in the acute phase of their illness in order to prevent a cardiac arrest.
  • Critical care outreach – As well as providing the services of the other two types of team, these teams are also responsible for educating non-specialist staff. In addition, they help to facilitate transfers between intensive care/high dependency units and the general hospital wards. This is particularly important, as many studies have shown that a significant percentage of patients discharged from critical care environments quickly deteriorate and are re-admitted – the outreach team offers support to ward staff to prevent this from happening.

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