Basics
Description
Absence of ventricular electrical activity
Etiology
- An end-stage rhythm, sometimes degrading from:
- Prolonged bradycardia
- Prolonged ventricular fibrillation (VF)
- Prolonged pulseless electrical activity
- Patient is extremely unlikely to survive when asystole occurs outside the hospital:
- ~40% will have return of spontaneous circulation and survive to hospital admission, but <15% survive to hospital discharge.
- Prognosis is similarly poor for those patients who develop asystole after countershock for ventricular tachycardia/VF; <10% survive to hospital discharge.
- Potentially reversible causes include:
- Hypoxia
- Hypovolemia (blood loss)
- Acidosis
- Hyperkalemia
- Hypokalemia
- Drug overdose
- Hypothermia
- Pulmonary embolism
- Myocardial infarction
- Tension pneumothorax
- Cardiac tamponade
Diagnosis
Signs and Symptoms
- Unresponsive patient
- Pulseless
- Agonal or absence of spontaneous respirations
Essential Workup
- Confirm asystole in 2 limb leads to exclude VF.
- Confirm lead and cable connections.
- Confirm monitor power is on.
- Confirm monitor gain is up.
- Identify reversible causes (see above)
Diagnosis Tests & Interpretation
Lab
Arterial blood gas (potassium and hemoglobin)
Imaging
Cardiac US to exclude pericardial tamponade
Differential Diagnosis
"Fine" VF (which may be mistaken for asystole)
Treatment
Pre-Hospital
- No intervention should be made for a patient with a valid Do Not Resuscitate document.
- No intervention if patient can be verified as dead:
- Rigor mortis
- Dependent livedo
- Injury incompatible with life (e.g., decapitation)
Initial Stabilization/Therapy
- Initiate CPR, with emphasis on minimally interrupted, high-quality chest compressions
- Confirm asystole with cardiac monitor
- Place airway device (ETT preferred, but BVM acceptable), confirm placement, and provide 100% inspired oxygen and a slow ventilation rate (6-12 breaths/minute). Minimize interruption in chest compressions during airway placement
- Establish IV or IO access.
- Apply continuous waveform capnography to optimize quality of chest compressions (PETCO2 correlates with cardiac output and myocardial blood flow during CPR)
- Epinephrine every 3-5 min.
- Consider and treat potentially reversible causes (see above)
- Sodium bicarbonate if hyperkalemia or drug overdose suspected
- No proven benefit to an empiric single countershock
- No proven benefit to electrical pacing
- Provide defibrillation without delay, IF the patient develops VF or VT
Ed Treatment/Procedures
- Initiate induced hypothermia in comatose patients with return of spontaneous circulation
- Consider termination of resuscitation efforts if the following conditions are met:
- High-quality chest compressions performed for a period of time
- Tracheal intubation to ensure normal oxygenation
- Fine VF excluded
- Reversible causes corrected or excluded
- Bedside US without pericardial effusion
- No tension pneumothorax clinically
Medication
- Epinephrine: 1 mg (peds: 0.01 mg/kg) IV q3-5min
- Sodium bicarbonate: 1 mEq/kg IV only if:
- Pre-existing acidosis
- Hyperkalemia
- Tricyclic antidepressant overdose is suspected.
Follow-Up
Disposition
Admission Criteria
All patients with return of spontaneous circulation
Discharge Criteria
None-all patients with return of spontaneous circulation need admission to an ICU for post-arrest care
Followup Recommendations
A permanent pacemaker may be considered only if asystole is found to be due to primary heart block
Patient Monitoring
ICU for cardiac monitoring and induced hypothermia as appropriate
Pearls and Pitfalls
- Emphasis on high-quality, minimally uninterrupted chest compressions while considering reversible causes of asystole
- Resuscitation is likely to be successful only if reversible causes are found and corrected immediately
Additional Reading
- Aufderheide TP, Sigurdsson G, Pirrallo RG, et al. Hyperventilation-induced hypotension during cardiopulmonary resuscitation. Circulation. 2004;109:1960-1965.
- Bernard SA, Gray TW, Buist MD, et al. Treatment of comatose survivors of out-of-hospital cardiac arrest with induced hypothermia. N Engl J Med. 2002;346(8):557-563.
- Levine RL, Wayne MA, Miller CC. End-tidal carbon dioxide and outcome of out-of-hospital cardiac arrest. N Engl J Med. 1993;337;301-306.
- Neumar RW, Otto CW, Link MS, et al. Part 8: adult advanced cardiovascular life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010;122:S729-S767.
- Silvestri S, Ralls GA, Krauss B, et al. The effectiveness of out-of-hospital use of continuous end-tidal carbon dioxide monitoring on the rate of unrecognized misplaced intubation within a regional emergency medical services system. Ann Emerg Med. 2005;45:497-503.
Codes
ICD9
427.5 Cardiac arrest
ICD10
- I46.2 Cardiac arrest due to underlying cardiac condition
- I46.8 Cardiac arrest due to other underlying condition
- I46.9 Cardiac arrest, cause unspecified
- I46 Cardiac arrest
SNOMED
- 397829000 Asystole (disorder)
- 410429000 cardiac arrest (disorder)
- 423191000 cardiac arrest due to cardiac disorder (disorder)