Cardiac Arrest Rhythms - Resuscitation Emergency Management

Cardiac Arrest Rhythms

·        Due either to:

o  Disordered electrical activity (arrhythmia) such as following an MI, or 

o  Impaired mechanical performance: Pulseless Electrical Activity (PEA) or Electro-Mechanical Dissociation (EMD) – primary (damaged myocardium, e.g. ischaemia) or secondary (e.g. hypovolaemia, pneumothorax, anaphylaxis ® ¯afterload, pulmonary embolus). EMD has worst prognosis. ECG may be normal but patient is still arresting

Ventricular Fibrillation (VF)

·        Most non-traumatic arrests are ventricular fibrillation.  Only effective treatment is defibrillation

·        No organised depolarisation ® doesn‟t contract as a unit.  But still contracting Þ still using O2

·        Coarse VF: irregular, large amplitude ECG waves ® onset recent. Responds well to defibrillation (if given within 5 – 8 minutes). CPR not sufficient to maintain the coronary artery perfusion necessary to offset O2 consumption ® rapid ischaemia. Precordial thump MAY revert VF

·        Fine VF: progressively lower amplitude VF until indistinguishable from asystole. 5-10% decrease in likelihood of successful defibrillation per minute

·        Treatment:

o   Defibrillation 

o   CPR and adrenaline help maintain diastolic BP and thus ­ cardiac perfusion

o   If failing, consider sodium bicarbonate and lignocaine (antiarrhythmic)

o   Discontinue after 30 minutes

Ventricular Tachycardia

·        Fast (100 – 220/minute) and wide QRS complexes (> 0.12 sec)

·        Causes: ischaemia, K or Mg disturbances, PE, etc

·        Can be confused with supraventricular tachycardia with bundle branch block

·        Dangerous precursor of VF

·        Treatment: 

o   If stable (i.e. still sufficient cardiac output ® pulse):

§  Oxygen

§  Lignocaine (1 mg/kg) stat plus 0.5 mg/kg every 8 minutes up to 3 mg/kg

§  If this fails then cardioversion

§  If little cardiac output/no pulse: same as for VF

o   If pulse but unstable:

§  Sedation 

§  Cardioversion: starting at 50J, then 100 then 200 then 300. If recognisable regular rhythm then synchronised 

§  If recurrent, give lignocaine, then procainamide 20 mg/min up to 1000 mg then bretyllium 5 – 10 mg/kg and magnesium

Torsade de Pointes

·        ECG like VT – but QRS amplitude changes due to rotating electrical axis

·        May be self-limiting for periods of 5 – 10 secs

·        May be due to anti-arrhythmics prolonging the QT interval (if so, stop them)

·        Treat by correcting electrolyte abnormalities and by increasing basic heart rate (i.e. over-pacing)

·        Magnesium sulphate 1-2gms given over 1 – 2 minutes may reverse drug induced torsade

·        Defibrillate for sustained episodes or use over-drive pacing

Asystole

·        Complete absence of ventricular electrical activity

·        Usually end result of major disturbance/myocardial damage

·        Usually a wandering straight line (if completely flat check ECG)

·        Invariably fatal after 15 minutes

·        Atropine + CPR may bring back rhythm