Defibrillation and Cardioversion

1. Defibrillation and Cardioversion EMS Professions Temple College

2. Defibrillation • Mechanism • Current depolarizes myocardium • Induces asystole temporarily • Allows one pacemaker to regain control

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

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

5. Defibrillation • Factors to consider • Heart size/body weight • Pedi requirement lower than adult • 2 J/kg initial shock • 4 J/kg repeat shocks • Direct size/energy relationship in adults unknown • 200 to 360 J

6. Defibrillation • Previous countershock • Repeated shocks lower resistance • Give three initial shocks in 30-45 sec • One quickly after another with little time between

7. Defibrillation • Factors to consider • Paddle size • Adults (large paddles) • 10-13 cm diameter • Pediatric (small paddles usually < 1 yr) • Children 8 cm • Infants 4.5 cm

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

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

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

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

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

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

14. Cardioversion • Indications • Tachyarrhythmias which: • Cause or worsen hemodynamic compromise • Cause or worsen ischemic heart disease • Are resistant to drug therapy

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

16. Cardioversion • Procedure • Activate synchronizer • Observe marking of complexes • May need to unsynchronize if: • Random synching occurs • Double-synching occurs

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

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