Defibrillation

As an ambulance service, we should be industry leaders in the quality of CPR we deliver to our patients. HP-CPR is the ‘new’ way of thinking about CPR, going back to basics and focusing on delivering excellent quality basic life support (BLS) with elements of advanced life support (ALS) introduced where required. Be prepared for lots of practical sessions in your upcoming practical sessions! The Quest to Reverse Sudden Death - History of CPR and Defibrillation [42:00 minutes] (Requires login to YouTube) A great reminder of how far we have come in terms of both in-hospital and pre-hospital resuscitation.

Defibrillation is the delivery of lifesaving electrical energy to the heart of the unresponsive patient who is in a VT or VF rhythm. SAAS Volunteers were one of the Australian pioneers in the use of Automated External Defibrillators (AED). SAAS introduced AEDs to the AO level in 1994. What was once considered an advanced care skill is now taught to all SAAS AAs/ARs/AOs at basic recruit training. Modern-day devices are now much cheaper to purchase and simpler to maintain and use, allowing for workplace first aiders and members of the public to access and use. AED electrodes/pads placed on the patient’s chest to serve as the conduit for delivering a measured electrical shock to the heart to restore natural rhythm. AEDs are small computerized devices that analyse heart rhythms and provide the shock needed for defibrillation. Through adhesive pads placed on a patient’s chest, a processor inside the AED analyses the victim’s heart. The machine will not shock unless it is necessary; AEDs are designed to shock only when VF or VT, common causes of cardiac arrest, is detected. After the processor analyses the heart rhythm and determines a shock is required, an electric current is delivered to the heart through the patient’s chest wall through the adhesive electrode pads. The shock delivered by a cardiac defibrillator aims to interrupt the chaotic rhythm and allows it to return to normal. Defibrillation pad placement is VITAL to successful defibrillation. We know EARLY defibrillation saves lives. Every minute delay = 10% reduction in survival from VF rhythm. If our pads aren’t in the right place or the current is impeded by anything, we may delay effective defibrillation. Studies suggest, for defibrillation to be successful, 75-90% of the myocardium mass needs to be defibrillated at the same time. Hence pad placement is vital to successful defibrillation. We practice often on manikins with training leads that connect directly to the manikin, so it is important to remind ourselves of the patient preparation and actual defibrillation pad/electrode application.

Standard Adult defibrillator pad placement

Essentially, we want to “sandwich” the heart between the two pads as the current runs between them. According to ANZCOR guidelines, pads need to be placed on the exposed chest; one pad slightly below the collarbone on the right chest and one pad on the person’s left side below the armpit (lateral to left breast in large-breasted individuals). In large-breasted patients, if defibrillator pads are placed over the breast tissue this may increase impedance and decrease defibrillation efficacy. An alternative adult pad placement the EOC Clinician may advise is Anterior/Posterior, which is the upper back between shoulder blades and front of the chest and slightly to the left (ANZCOR guideline 7). Refer to the actual pads and pad packaging for pad placement guidance.

Adult Defibrillator - Alternative pad placement - Anterior/Posterior

For paediatric and infant patients <8 years, the adult defibrillator pads are uses in SAAS but are placed in the Anterior/Posterior placement. Keep ‘defib’ pads at least 8cm away from visible ICD and pacemaker devices, due to possible interference (ANZCOR guideline 11.4). Do not place defib pads over medication patches that may be on the patient’s chest. Typically shocks ranging from 150 joules to 360 joules (varied between brands/manufacturers) are necessary for successful defibrillation when pads are placed on the body surface. However, only 4-20% of the delivered current ever reaches the myocardium. The method outlined in the ANZCOR guidelines allows for optimal joules to be delivered to the greatest area of the myocardium.

Successful pad placement will ensure good contact with the pad on the patient’s bare skin. Hair, moisture, breast tissue, bone can all reduce the effectiveness of the shock and are essential to avoid as much as possible. These things will all create an impedance of the electrical current getting to the myocardium. Make sure your vehicle’s defibrillator has a razor and either a small hand towel or combine dressing. In the unit’s soft pack. Use the razor if the chest is excessively hairy and dry chest with a towel or combine dressing, otherwise, defibrillation pad connection will not be optimal. If you aren’t getting anywhere with your shocks after multiple attempts, we need to reassess. It may be appropriate to apply new pads or reassess their position. Taking the time to dry and shave the chest should occur when needed. At the ten-minute mark when you consult with the EOC Clinician, discuss the possibility of changing pad position from standard to anterior/posterior positioning with a new set of pads.