Defibrillation and Cardioversion Terry White, RN

Defibrillation u Mechanism v Current depolarizes myocardium v Induces asystole temporarily v Allows one pacemaker to regain control

Defibrillation u Factors to consider v Duration of VF u The longer VF lasts, the harder it is to cure u The quicker the better u Shock early-Shock often u Likelihood of resuscitation decreases 7-10% with each passing minute

Defibrillation u Factors to consider v Myocardial environment/condition u Hypoxia, acidosis, hypothermia, electrolyte imbalance, drug toxicity impede conversion u Do NOT delay shock trying to correct problems

Defibrillation u Factors to consider v Heart size/body weight u Pedi requirement lower than adult –2 J/kg initial shock –4 J/kg repeat shocks u Direct size/energy relationship in adults unknown – 200J bi-phasic or 360 J mono phasic

Defibrillation v Previous countershock u Repeated shocks lower resistance u Give one initial shocks in sec

Defibrillation u Factors to consider v Paddle size u Adults (large paddles) – cm diameter u Pediatric (small paddles usually < 1 yr) –Children 8 cm –Infants 4.5 cm

Defibrillation u Use largest size that completely contacts chest without paddles touching u Small paddles: concentrate current, burn heart u Large paddles: reduce current density

Defibrillation u Paddle placement v One to right of sternum below clavicle; Other to left of left nipple in anterior axillary line v Reversing paddles marked “apex-- sternum” does NOT affect defibrillation v AP placement can be used to defib small children with adult paddles

Defibrillation u Paddle-skin interface v Cream, paste, saline pads, gelled pads v Decreases resistance to current flow v Avoid smearing or running: “bridges” charge u NEVER use alcohol!!!

Defibrillation u Paddle contact pressure v Firm pressure of 25 pounds v Deflates lungs; Shortens current path v Do not lean on paddles; They slip

Cardioversion u Definitions v Cardioversion u Use of electrical shock to interrupt tachycardia –Used in Non-Arrest patients only –Only VF/VT (pulseless) can be defibrillated

Cardioversion u Definitions v Synchronized cardioversion u Timing of shock to avoid peak of T- wave u Prevents VF caused by delivering shock during vulnerable period

Cardioversion u Indications v Tachyarrhythmias which: u Cause or worsen hemodynamic compromise u Cause or worsen ischemic heart disease u Are resistant to drug therapy

Cardioversion u Procedure v Oxygen, ECG monitor, IV v Patient must be on leads to cardiovert v Sedate with Valium or Versed u Do NOT make patient unresponsive

Cardioversion u Procedure v Activate synchronizer v Observe marking of complexes v May need to unsynchronize if: u Random synching occurs u Double-synching occurs

Cardioversion u Procedure v Charge to desired energy setting v Depress buttons; Hold until discharge occurs v If VF occurs, unsynchronize before defibrillating

Cardioversion If a patient is in VF, why might the defibrillator not discharge if the synchronizer is on?