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Asystole: Definition, Causes, Treatment and ECG Example

Asystole, otherwise known as a flatline, is a state of cardiac standstill in which all electrical activity has ceased. It is diagnosed following a physical examination where no pulse is detected in conjunction with ECG monitoring.On an ECG tracing, asystole appears as a flatline:

Identifying Asystole

Confirmation that the rhythm is indeed a flatline, and not a false positive, is an important part of the asystole treatment algorithm. For most patients, true asystole is the result of a prolonged illness or cardiac arrest, and prognosis is very poor.

The few patients that have a positive outcome following a diagnosis of cardiac arrest with asystole will usually result from the identification and correction of an underlying cause of the asystole. Because of this, we need to be sure the result is legitimate.

Apparent asystole may be the result of a user or technical error. If you believe the rhythm may be incorrect, ensure patches have good contact with the individual, leads are connected, the gain is set appropriately, and the power is on.

If all equipment appears to be functioning normally, and you still see a rhythm that appears to be asystole, quick action is imperative.

Treating Asystole

Standard asystole treatment involves cardiopulmonary resuscitation, or CPR, and intravenous administration of epinephrine given every three to five minutes as needed. When a reversible underlying cause is found, that cause should be treated directly to reverse asystole.

Some theoretically reversible causes of asystole include:

Because asystole is not a shockable rhythm, defibrillation is not an effective asystole treatment. Researchers estimate that less than two percent of people who suffer asystole outside of the hospital will survive - even with trained emergency intervention.

ACLS Asystole Treatment Algorithm

  1. Conduct an initial patient assessment, checking for respirations and pulse
  2. If the patient is not breathing and has no pulse, start CPR
  3. Establish an airway and administer oxygen to keep oxygen saturation above 94%
  4. Attach monitor/defibrillator to confirm asystole in at least two leads
  5. Continue CPR at 100-120 compressions per minute being sure to change emergency team members every 2 minutes to sustain quality CPR
  6. Establish IV or IO access while someone else on the team continues CPR, and administer 1mg epinephrine every 3 to 5 minutes as needed
  7. Check for heart rhythm after 2 minutes of CPR
  8. Check for reversible causes of asystole and treat those
  9. As soon as the return of spontaneous circulation (ROSC) occurs, begin Post Cardiac Arrest Care

Vasopressor Usage

Vasopressors are drugs that produce vasoconstriction, leading to a rise in blood pressure which helps to increase blood flow to the brain and heart. For asystole, the standard medication to use is epinephrine. 

While treating asystole, epinephrine should be administered as soon as possible without delaying the start or continuation of CPR. Following the initial dose, epinephrine is given every 3-5 minutes as needed.

During CPR, a rhythm check should be done every 2 minutes (5 cycles). These rhythm checks should be kept to less than 10 seconds, in order to prevent meaningful interruptions in CPR.

Pulse checks should be performed when a rhythm check reveals a change in the rhythm to a rhythm that is organized and could be generating a pulse.

Epinephrine Dosage for Asystole Treatment

Previous versions of the AHA guidelines have suggested that higher doses of epinephrine (greater than the standard 1mg dose), or an alternative vasopressor, called vasopressin, could be more effective alternatives to the standard dose of epinephrine.

However, subsequent research has failed to demonstrate a clear benefit of vasopressin or higher doses of epinephrine over the standard dose. Thus, the standard dosage of 1mg epinephrine every 3-5 minutes while CPR continues is still the recommended approach.

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