Ventricular fibrillation (VF)

Features: always associated with absent pulse and loss of consciousness

ECG

• chaotic disorganised broad complex rhythm with rate of 300-600 bpm
• initially high amplitude (coarse)
• amplitude becomes less with time and eventually becomes asystole after 1 – 3 minutes
  • approx. 3% of asystole is really VF (either unipolar or fine)

Differential diagnosis

• shivering artefact: native rhythm still usually visible
• severe tremor: usually regular and low amplitude
• loose lead connection: high amplitude spiking pattern

Management: Electrical cardioversion

• non synchronised
• energy setting
  • monophasic
    • adults 360 J
    • children: 4 J/kg (although little evidence that 4J/kg is more effective than 2J/kg)
  • biphasic
    • 150 J to 200 J for a biphasic truncated exponential waveform
    • 120 J for a rectilinear biphasic waveform
  • repeated shocks should be given following drug therapy

Management: Drug therapy

• only after failed electrical cardioversion and CPR
• adrenaline
  • dose of 1 mg IV after 2nd DCR then after every second 2 minute CPR cycle
• amiodarone
  • may improve outcome

Special circumstances

• active core rewarming if T < 30^o C
• HCO3 if Na channel blocker toxicity present
• K+ replacement if significant hypokalaemia present