defribrillation and cardioversion

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Defibrillation andDefibrillation and

CardioversionCardioversion

EMS Professions EMS ProfessionsTemple CollegeTemple College



DefibrillationDefibrillation

MechanismMechanism

Current depolarizes myocardiumCurrent depolarizes myocardium

Induces asystole temporarilyInduces asystole temporarily

Allows one pacemaker to regainAllows one pacemaker to regain

controlcontrol




Factors to considerFactors to consider

Duration of VFDuration of VF

The longer VF lasts, the harder it isThe longer VF lasts, the harder it isto cureto cure

The quicker the betterThe quicker the better

Shock earlyShock early--Shock oftenShock oftenLikelihood of resuscitation decreasesLikelihood of resuscitation decreases

77--10% with each passing minute10% with each passing minute





Myocardial environment/conditionMyocardial environment/conditionHypoxia, acidosis, hypothermia,Hypoxia, acidosis, hypothermia,

electrolyte imbalance, drug toxicityelectrolyte imbalance, drug toxicity

impede conversionimpede conversion

DoDo NOTNOT delay shock trying todelay shock trying to

correct problemscorrect problems





Heart size/body weightHeart size/body weight

Pedi requirement lower than adultPedi requirement lower than adult

± ± 2 J/kg initial shock 2 J/kg initial shock

± ± 4 J/kg repeat shocks4 J/kg repeat shocks

Direct size/energy relationship inDirect size/energy relationship in

adults unknownadults unknown

²² 200 to 360 J200 to 360 J



DefibrillationDefibrillationPrevious countershock Previous countershock

Repeated shocks lower resistanceRepeated shocks lower resistance

Give three initial shocks in 30Give three initial shocks in 30--45 sec45 sec²² One quickly after another with little time betweenOne quickly after another with little time between





Paddle sizePaddle size

Adults (large paddles)Adults (large paddles)²² 1010--13 cm diameter13 cm diameter

Pediatric (small paddles usually < 1 yr)Pediatric (small paddles usually < 1 yr)

± ± Children 8 cmChildren 8 cm

± ± Infants 4.5 cmInfants 4.5 cm



DefibrillationDefibrillationUse largest size that completelyUse largest size that completely

contacts chest without paddlescontacts chest without paddles

touchingtouching

Small paddles: concentrate current,Small paddles: concentrate current,

burn heartburn heart

Large paddles: reduce currentLarge paddles: reduce currentdensitydensity




Paddle placementPaddle placement

One to right of sternum below clavicle;One to right of sternum below clavicle;

Other to left of left nipple in anteriorOther to left of left nipple in anterior

axillary lineaxillary line

Reversing paddles marked ³apexReversing paddles marked ³apex----

sternum´ does NOT affectsternum´ does NOT affect

defibrillationdefibrillationAP placement can be used to defibAP placement can be used to defib

small children with adult paddlessmall children with adult paddles




PaddlePaddle--skin interfaceskin interface

Cream, paste, saline pads, gelled padsCream, paste, saline pads, gelled padsDecreases resistance to current flowDecreases resistance to current flow

Avoid smearing or running: ³bridges´Avoid smearing or running: ³bridges´

chargechargeNEVER use alcohol!!!NEVER use alcohol!!!




Paddle contact pressurePaddle contact pressure

Firm pressure of 25 poundsFirm pressure of 25 pounds

Deflates lungs; Shortens current pathDeflates lungs; Shortens current path

Do not lean on paddles; They slipDo not lean on paddles; They slip




DefinitionsDefinitions


Use of electrical shock to interruptUse of electrical shock to interrupttachycardiatachycardia

²² Used in NonUsed in Non--Arrest patients onlyArrest patients only

²² Only VF/VT (pulseless) can beOnly VF/VT (pulseless) can bedefibrillateddefibrillated




DefinitionsDefinitions

Synchronized cardioversionSynchronized cardioversion

Timing of shock to avoid peak of TTiming of shock to avoid peak of T--

wavewave

Prevents VF caused by deliveringPrevents VF caused by delivering

shock during vulnerable periodshock during vulnerable period



CardioversionCardioversionIndicationsIndications

Tachyarrhythmias which:Tachyarrhythmias which:

Cause or worsen hemodynamicCause or worsen hemodynamic

compromisecompromise

Cause or worsen ischemic heartCause or worsen ischemic heart

diseasedisease

Are resistant to drug therapyAre resistant to drug therapy




ProcedureProcedure

Oxygen, ECG monitor, IVOxygen, ECG monitor, IVPatient must be on leads to cardiovertPatient must be on leads to cardiovert

Sedate with Valium or VersedSedate with Valium or Versed

Do NOT make patient unresponsiveDo NOT make patient unresponsive




ProcedureProcedure

Activate synchronizerActivate synchronizer

Observe marking of complexesObserve marking of complexesMay need to unsynchronize if:May need to unsynchronize if:

Random synching occursRandom synching occurs

DoubleDouble--synching occurssynching occurs




ProcedureProcedure

Charge to desired energy settingCharge to desired energy setting

Depress buttons; Hold until dischargeDepress buttons; Hold until dischargeoccursoccurs

If VF occurs, unsynchronize beforeIf VF occurs, unsynchronize before

defibrillatingdefibrillating




If a patient is in VF, why might theIf a patient is in VF, why might the

defibrillator not discharge if thedefibrillator not discharge if the

synchronizer is on?synchronizer is on?

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defribrillation and cardioversion