Asystole
Encyclopedia
In medicine, asystole is a state of no cardiac
electrical activity, hence no contractions of the myocardium and no cardiac output or blood flow. Asystole is one of the conditions that may be used for a medical practitioner to certify clinical
or legal
death
.
Asystole is treated by cardiopulmonary resuscitation
(CPR) combined with an intravenous vasopressor such as epinephrine
(adrenaline). Sometimes an underlying reversible cause can be detected and treated (the so-called 'H's and T's', an example of which is hypokalaemia). Several interventions previously recommended - such as intravenous atropine and defibrillation - are no longer part of the routine protocols recommended by most major international bodies.
Survival rates in a cardiac arrest patient with asystole are much lower than a patient with a rhythm amenable to defibrillation.
Out of hospital survival rates (even with emergency intervention) are less than 2 percent.
While the heart is asystolic, there is no blood flow to the brain unless CPR
or internal cardiac massage (when the chest is opened and the heart is manually compressed) is performed, and even then it is a small amount. After many emergency treatments have been applied but the heart is still unresponsive, it is time to consider pronouncing the patient dead. Even in the rare case that a rhythm reappears, if asystole has persisted for fifteen minutes or more the brain will have been deprived of oxygen long enough to cause brain death
.
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
electrical activity, hence no contractions of the myocardium and no cardiac output or blood flow. Asystole is one of the conditions that may be used for a medical practitioner to certify clinical
Clinical death
Clinical death is the medical term for cessation of blood circulation and breathing, the two necessary criteria to sustain life. It occurs when the heart stops beating in a regular rhythm, a condition called cardiac arrest. The term is also sometimes used in resuscitation research.Stopped blood...
or legal
Legal death
Legal death is a legal pronouncement by a qualified person that further medical care is not appropriate and that a patient should be considered dead under the law. The specific criteria used to pronounce legal death are variable and often depend on certain circumstances in order to pronounce a...
death
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
.
Asystole is treated by cardiopulmonary resuscitation
Cardiopulmonary resuscitation
Cardiopulmonary resuscitation is an emergency procedure which is performed in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person in cardiac arrest. It is indicated in those who are unresponsive...
(CPR) combined with an intravenous vasopressor such as epinephrine
Epinephrine
Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...
(adrenaline). Sometimes an underlying reversible cause can be detected and treated (the so-called 'H's and T's', an example of which is hypokalaemia). Several interventions previously recommended - such as intravenous atropine and defibrillation - are no longer part of the routine protocols recommended by most major international bodies.
Survival rates in a cardiac arrest patient with asystole are much lower than a patient with a rhythm amenable to defibrillation.
Out of hospital survival rates (even with emergency intervention) are less than 2 percent.
Cause
Possible underlying causes include the Hs and Ts.- HypovolemiaHypovolemiaIn physiology and medicine, hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma...
- HypoxiaHypoxia (medical)Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
- HydrogenHydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
ions (acidosisAcidosisAcidosis is an increased acidity in the blood and other body tissue . If not further qualified, it usually refers to acidity of the blood plasma....
) - HypothermiaHypothermiaHypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...
- HyperkalemiaHyperkalemiaHyperkalemia refers to the condition in which the concentration of the electrolyte potassium in the blood is elevated...
or hypokalemiaHypokalemiaHypokalemia or hypokalaemia , also hypopotassemia or hypopotassaemia , refers to the condition in which the concentration of potassium in the blood is low... - HypoglycemiaHypoglycemiaHypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...
- Tablets or toxins (drug overdoseDrug overdoseThe term drug overdose describes the ingestion or application of a drug or other substance in quantities greater than are recommended or generally practiced...
) - Cardiac TamponadeCardiac tamponadeCardiac tamponade, also known as pericardial tamponade, is an emergency condition in which fluid accumulates in the pericardium ....
- Tension pneumothorax
- ThrombosisThrombosisThrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...
(myocardial infarctionMyocardial infarctionMyocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
) - ThrombosisThrombosisThrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...
(pulmonary embolismPulmonary embolismPulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
) - TraumaPhysical traumaTrauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
(hypovolemiaHypovolemiaIn physiology and medicine, hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma...
from blood loss)
While the heart is asystolic, there is no blood flow to the brain unless CPR
Cardiopulmonary resuscitation
Cardiopulmonary resuscitation is an emergency procedure which is performed in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person in cardiac arrest. It is indicated in those who are unresponsive...
or internal cardiac massage (when the chest is opened and the heart is manually compressed) is performed, and even then it is a small amount. After many emergency treatments have been applied but the heart is still unresponsive, it is time to consider pronouncing the patient dead. Even in the rare case that a rhythm reappears, if asystole has persisted for fifteen minutes or more the brain will have been deprived of oxygen long enough to cause brain death
Brain death
Brain death is the irreversible end of all brain activity due to total necrosis of the cerebral neurons following loss of brain oxygenation. It should not be confused with a persistent vegetative state...
.