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  1. 1. Defibrillators Use & How Dr.Imran
  2. 2. Definition ™Defibrillator is a device that deliver a therapeutic dose of electrical energy (electric shock) to the affected heart (fibrillated heart or other shockable rhythm) to force the heart to produce more normal cardiac rhythm.
  3. 3. First demonstrated on dogs in 1899 by Jean-Louis Prévost & Frederic Batelli, two physiologists from University of Geneva, Switzerland. The first use on a human was in 1947 by Claude Beck, professor of surgery at Case Western Reserve University. Transthoracic defibrillation was first used in humans using alternating current (AC) Bernard Lown and his coworkers introduced direct current (DC) defibrillators into clinical practice. History
  4. 4. Defibrillator Does not re-start the heart. Stops all electrical activity. If heart is still viable its natural pace maker will take over. It is an emergency life saving procedure. Probability decreases with time. Mechanism Current depolarizes the myocardium. Induces asystole temporarily. Allows SA node to take over coz it‟s the first to repolarize.
  5. 5. Indications - Pulse-less polymorphic VT/VF. - When unsure weather monomorphic or polymorphic VT in a un-stable patient.
  6. 6. Non Shockable rhythm’s - Asystole - Pulse less electrical activity (PEA)
  7. 7. Loss of synchronization in heart is called as fibrillation.  Types of fibrillation  Atrial fibrillation  Ventricular fibrillation Defibrillator……
  8. 8. ™Defibrillation is the definitive treatment for the life threatening cardiac arrhythmias ventricular fibrillation and pulseless ventricular tachycardia ™ Ventricular fibrillation results from: -Coronary occlusion -Electrical shock -Abnormalities of body chemistry ™ This irregular contraction of the muscle fibers causes non effectively blood pumping and that results in a steep fall of cardiac output. Need for a Defibrillator
  9. 9. ™Ventricular fibrillation can be converted into a more efficient rhythm by applying high energy shock to the heart. ™ This causes all muscle fibers to contract simultaneously, which may then respond to normal physiological pacemaking pulses Restoration of normal rhythm in fibrillating heart as achieved by direct current shock (arrow) across the chest wall. The horizontal line after the shock shows that the cardiograph was blocked or disconnected for its protection during the period of shock4 Ventricular fibrillation
  10. 10. This recommendation regarding CPR prior to attempted defibrillation is supported by 2 clinical studies JAMA. 2003;289:1389 –1395 JAMA. 1999;281:1182–1188
  11. 11.  Applying a brief(.25 to 1 sec) burst of 60 HZ ac at an intensity of around 6 A.  This application of an electrical shock to resynchronize the heart is sometimes called counter shock.  If the patient does not respond, the burst is repeated until defibrillation occurs. this method is known as ac defibrillation. AC DEFIBRILLATION
  12. 12. • It is cannot be successfully used to correct atrial fibrillation. • Successive attempts to correct ventricular fibrillation are often required. • Attempts to correct atrial fibrillation by this method often result more serious ventricular fibrillation. Disadvantage of using ac Defibrillator
  13. 13.  In this method a capacitor is charged to a high dc voltage and then rapidly discharged.  The amount of energy discharged by the capacitor may range between 2 to 400joules with peak value of current 20A.  A corrective shock of 750-800 volts is applied within a tenth of a second . DC Defibrillation
  15. 15. • Energy storage capacitor is charged at relatively slow rate from AC line. • Energy stored in capacitor is then delivered at a relatively rapid rate to chest of the patient. • Simple arrangement involve the discharge of capacitor energy through the patient’s own resistance. PRINCIPLE OF DEFIBRILLATOR
  16. 16. Cont….. The discharge resistance which the patient represents is roughly a ohmic resistance of 50 – 100 ohms for a typical electrode size of 80cm2. The particular wave form is called “Lown” wave form. The pulse width of this waveform is 10ms.
  17. 17. 1. Manual external defibrillator 2. Manual internal defibrillator 3. Semi-Automated External Defibrillator 4. Automated external defibrillator (AED) 5. Implantable cardioverter-defibrillator (ICD) {automatic internal cardiac defibrillator (AICD)} 6. Wearable cardiac defibrillator Types of Defibrillators
  18. 18. Manual external defibrillator Electrodes placed directly around the heart area of chest. Higher Voltage required than internal defibrillator. Classified as - Monophasic Biphasic
  19. 19. Monophasic waveform Defibrillators • Deliver current of one polarity. • Current travels in one direction through the patients heart from one paddle to another. 2 types :- • The monophasic damped sinusoidal waveform (MDS) returns to zero gradually • Monophasic truncated exponential waveform (MTE) current is abruptly returned to baseline (truncated) to zero current flow
  20. 20. MDS v/s MTE wave form
  21. 21. Biphasic waveform Defibrillators Current travels towards the +ve paddle & then reverses back. Reversing of polarity, depolarizes all cells – called “burping” response. Classified into – Biphasic truncated exponential waveform (BTE) Rectilinear biphasic waveform (RLB) RLB is better than BTE.
  22. 22. Biphasic truncated exponential waveform (BTE) v/s Rectilinear biphasic waveform (RLB) RBL BTE
  23. 23. Advantages of Biphasic over Monophasic Less power – Less trauma – Less battery. Defibrillation more effective at low energy. Fewer burns. Less myocardial damage. 1st shock success rate in cardiac arrest due to shockable rhythm – Monophasic 60% Biphasic increases to 90%
  24. 24. Manual internal defibrillator Just like normal defilbrillator. Electric charge is usually pumped in by internal paddles in close or direct contact with the heart. These devices are mainly used in operating theatres, where the chest can be opened or being treated by a surgeon
  25. 25. Semi-Automated External Defibrillator Carries features of both full-manuated as well as automated units of defibrillator. Has an ECG display and manual override in it. Generally used by paramedics and emergency medicine technicians.
  26. 26. Implantable cardioverter-defibrillator (ICD) {automatic internal cardiac defibrillator (AICD)} A implanted device that detacts and terminats life threatning episodes of VF / VT in high risk patients.
  27. 27. Wearable cardiac defibrillator - Life vest
  28. 28. • AED is a portable type of external defibrillator that automatically diagnoses the ventricular fibrillation in a patient. • Automatic refers to the ability to autonomously analyze the patient's condition. • AED is provided with self-adhesive electrodes instead of hand held paddles. AUTOMATIC EXTERNAL DEFIBRILLATOR
  29. 29. Automated external defibrillator (AED) cont… Use does not require special medical training. Found in public places – offices, airport, shopping mall. The electrodes transmit information about the person's heart rhythm to a controller in the AED. The controller examines the electrical output from the heart and determine if the patient is in a shockable rhythm or not and whether shock is needed. The AED uses voice / visual prompts to tell user when to give the shock, and the electrodes deliver it.
  30. 30. Paddle placement 4 Positions ---- Anterior-lateral > most convenient Anterior-posterior Anterior-left infrascapular Anterior-right infrascapular Anterior-lateral position ---- one – right of sternum below clavicle (2nd & 3rd ICS) other – left 4th or 5th ICS mid axillary line Reversing paddle markings “sternum & apex” does not affect defibrillation Paddles placed along axis of heart. AP- placement used in children with adult paddles.
  31. 31. Position of electrodes in pregnant patients :- -One on right of sternum below the right clivcle -Other left mid-axillary line avoiding breast Paddle Size - Adult – large paddles 10-13 cm diameter - Pediatric – small paddles <1yr Infant <10kgs – 4.5cm Children >10kgs – 8cm
  32. 32. Steps of Defibrillation Give 2min CPR before analysis. Power on ADE Attach electrode pad. Check rhythm. CLEAR. Give shock(120-200J) Resume CPR for 2mins before analysis cardiac rhythm again. Consider giving – vasopressors / anti-arrhythmic‟s during subsequent shock.
  33. 33. Defibrillation Success Termination of VF into an organized rhythm or asystole for atleast 5secs after shock. Regardless of haemodynamic response Start with – 150-200J Bisphasic truncated waveform 120J Rectilinear biphasic waveform
  34. 34. Monitoring Monitor that patient stay in converted rhythm. Keep patient well oxygenated.(SPO2 >98%) Check serum K+ & Mg+ levels. Maintain acid base balance. Get 12 lead ECG after procedure. Check for chest pain & access. Get CPK & Troponin done. Access patients skin.
  35. 35. Efficacy of Defibrillation Trans – thoracic resistance is the major factor : Which depends upon Chest width & configuration Ventilatory phase Electrode skin interface Electrode position Electrode size Force of electrode application Energy level Time between & no. of shocks
  36. 36. Factors to consider during defibrillation 1) Duration of VF - the longer VF lasts, the harder it is to cure - the quicker the batter - shock early, shock often - likelihood of resuscitation decrease by 7-10% with every passing minute (Ann Emerg Med. 1993;22:1652–1658 )
  37. 37. 2) Myocardial environment / condition Hypoxia, acidosis, hypothermia, electrolyte imbalance, drug toxicity – impede conversion. DO NOT DELAY SHOCK trying to correct these problems.
  38. 38. 3) Heart size / Body type Pediatric requirement lower than adult 2J /kg initial shock 4J /kg repeat shock Higher dose (upto 10J/kg) Or adult maximum dose Direct size / energy relationship in adults unknown
  39. 39. 4) Use largest size paddles - completely contact chest without paddles touching each other - In pediatric minimum of 3cm distance between pads. NOTE :- - Small paddles : concentrate current, burn heart. - Large paddles : reduces current density
  40. 40. 5) Previous counter shock - repeated shocks lower resistance - give one shock at a time & then continue CPR - subesquent shock either equal or higher energy 6) Paddle size ( as discussed before)
  41. 41. 7) Paddle placement - In pacemaker / ICD atleast 12cm from generator 90 degree to AICD electrode avoid placing pads directly over no delay in defibrillation - for other as described before…….
  42. 42. 8) Paddles – Skin interface - only gel should be used (ECG gelly) - cream, paste, saline pads etc.- not recommended - gel decreases resistance to the flow of current - never use alcohol 9) Paddle contact pressure - firm pressure of 25 pounds - in child <10kgs --- 3kg pressure - in large children >10kgs --- 5kg pressure - deflate lung, shortens the path of current - do not lean on paddles : they slip
  43. 43. CARDIOVERSION Cardioversion is the delivery of energy that is synchronized to the large R waves or QRS complex. It uses energy less than that used for defibrillation in shockable SCA Avoids delivering shock during repolarization period (T wave on ECG)
  44. 44. Indications - Atrial flutter - Atrial fibrillation - Re entry SVT - Mono morphic VT - Poly morphic VT - Wide complex tachycardia of uncertain type
  45. 45. Contraindications - Digitalis induced dysrythmias - refractory to cardioversion - may precipitate to more serious ventricular dysarythmias - Junctional tachycardia or ectopics / multifocal atrial tachycardia - automatic foci not reverted by cardioversion
  47. 47. Cardioversion can be Elective or Emergency
  48. 48. Elective Cardioversion > Pre procedure conciderations - History & physical examination (neurological) - Concurrent illness - Current medication including anticoagulation - Fasting 6hrs - Correct electrolyte imbalance - Obtain 12 lead ECG - Shaving at site if nessacery - Digoxin to be withheld for 48hrs - Continue other medications - Transthoracic Echo or TEE
  49. 49. Cardioversion Anaesthetic Technique Cardioversion is almost always performed under induction or sedation (short-acting agent such as midazolam) exceptions : if patient is hemodynamically unstable or if cardiovascular collapse is imminent - Amnesia / Sedation / GA – may be required - Premedication – Midazolam 1 to 2 mg - Pre oxygenation - Airway maintained & supported
  50. 50. Cardioversion Anaesthetic Drugs -- IV sedation – Propofol, Etomidate, Thiopentone, Benzodiazepines -- Etomidate haemodynamically more stable myoclonus 40%- interferes with ECG interpretation -- Propofol hypotension (boluses) slow induction can attenuate this drop
  51. 51. Steps - Check environment at procedure site - Turn on defibrillator - Anaesthetic technique as required - Apply electrodes - Press SYNC control - Select applicationenergy level - „3 clear‟ shout & look - Deliver shock
  52. 52. Post Procedure Monitoring - Record delivery energy & result - Continuous ECG monitoring - 12 lead ECG - If successful response check for peripheral pulses, BP, Airway patency & LOC - Inspect skin under the padds - If not successful, check & reassess
  53. 53. Complications of Cardioversion - Systemic embolization - Post shock cardiac arythmias asystole heart block atrial / ventricular ectopics ventricular tachyarrythmias - Trasient ST & T wave changes
  54. 54. Cardioversion Defibrillation Elective planned procedure Emergency life saving procedure Synchronized shock Un-synchronized shock Low energy shock High energy shock There can be some delay No delay, immediate Anti-coagulation needed No anti-coagulation needed Less damage to myocardium More damage to myocardium Used in most of the arrhythmias except VT /VF Used in VT / VF