CCM 205: Defibrillation Flashcards

1
Q

What is the mechanism of action of Defibrillation?

A

Electrical current causes simultaneous depolarization of the cardiac myocytes - forcing them into the refractory period

If enough myocytes enter the refractory period –> malignant rhythm stops propagating and underlying pacemaker rhythm can take over

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2
Q

Explain the difference between monophasic and biphasic defibrillators

A

Monophasic - single pulse of positive current (i.e., from one paddle to the other), unidirectional

Biphasic - first positive current, followed by negative current - the oppositve direction
* requires lower total energy - i.e., lower risk of myocardial damage
* case reports where monophasic currents were not successful but biphasic was - potential more effective as well

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3
Q

How do you perform internal defibrillation

A
  • requires access to chest - i.e., open chest
  • internal paddles - sterilized - wand-like with smaller surface area
  • placed on either side of the heart with saline soaked gauze inbetween heart and paddle - to prevent burn injury
  • ideally remove pericardium first
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4
Q

What is the current recommendation for timing of defibrillation during CPR in small animals?

A
  • if cardiac arrest witnessed and shockable rhythm present - defibrillate immediately
  • chest compressions while defibrillator is prepared
  • if malignant rhythm was present for >4 min - one cycle of CPR should be performed first
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5
Q

If a defibrillation attempt was unsuccessful, what do you increase the J/kg to?

A

Increase by 50%

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6
Q

What are the contraindications for Lidocaine in a dog with Vfib?

A

If only monophasic defibrillation is available –> has been shown to increased the defibrillaiton threshold (i.e., how much energy is needed)

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