6. Defibrillation for first responders – June 2015
Three decades ago, use of a defibrillator belonged to doctors, a handful of trained nurses and intensive care paramedics. Move forward a decade and these devices had become common amongst all paramedics. The devices were still relatively heavy to carry. They were also used manually requiring the operator to be trained in attaching and using them if they were to work properly.
Move forward some more and the defibrillator has continued its evolution. It is now smaller and lighter. More importantly though, many are work automatically requiring little more than the operator to attach them now. They don’t have to be in the hands of trained professionals anymore. Now they hang on walls in shopping centres and airports for anyone to use.
Evidence shows that the two big actions that can resuscitate patients in cardiac arrest are effective chest compressions and early defibrillation. So what is defibrillation?
The heart is a muscle. Like all muscles, there must be a nerve cell tell it when to contract. The heart has its own built in set of nerve like cells to take care of this. When plugged into the body this allows the heart to speed up or slow down as needed. However when things go wrong, the normal electricity controlling the heart beat can be greatly disturbed. It can fire too fast. It can fire too slowly. It can stop completely. In some of these cases the result will be that the heart will stop beating leaving the patient in cardiac arrest.
In some cases though the nerve cells can fire off excessively or bizarrely. The result is that the normal heart beat cannot occur until this excessive nerve firing stops. In most cases this excessive firing is called fibrillation because it results in the heart muscle quivering or trembling instead of beating. The patient will have no pulse and will be in cardiac arrest.
Enter the defibrillator. All of these devices essentially work the same. A wave of electricity is passed through the heart, stopping the excessive nerve firing and allowing the nerves that cause normal heart beats to then take over. This is caused defibrillation. Defibrillation only works in this situation. It won’t start a heart that has totally stopped nor do anything for a heart that is too slow. This means that a defibrillator will not be helpful at all cardiac arrests, only this type.
The automatic external defibrillator (AED) is able to determine what sort of heart beat problem exists and decide if electricity will help or not. The rescuer attaches it to the chest of the patient, turns it on then allows the machine to analyse and decide.
The first step is to attach the defibrillator. Electrode pads are used for this. One is attached on the upper right side of the chest, the second on the lower left side right around in line with the armpit. In this position a direct line between one and the other goes straight through the heart. That is the line the electricity is needed to go. To attach the pads like this the patient’s upper clothing must be removed or opened. Since this must also be done to perform chest compressions it will happen quickly and right at the start. The pads must also be kept away from the breastbone (sternum) as this will be where the chest compressions have to be done. Pushing on the pads could damage them causing them to not discharge the electricity properly.
With an AED the device will call out instructions. Generally the first step is to turn the device on. The device will then direct attaching the pads, plugging them in and deciding if the electricity is needed or not. If electricity is needed the AED will instruct when to push the button. The electricity will pass through the electrodes.
There are some rules with using an AED. Firstly, since the patient is in cardiac arrest, chest compressions must be kept going until the pulse returns. The compressions should only be briefly stopped to allow the AED to analyse the patient’s heart and then to deliver the electrical shock. Currently this happens every two minutes during a cardiac arrest. If the patient is moved whilst the AED is analysing the heart the movement can confuse the device and cause it to make mistakes. No touching or moving the patient whilst the AED is making up its mind. Then, if the device instructs to make it discharge, again nobody must be touching the patient. It is possible for the electricity to provide a shock to anyone touching the patient.
This isn’t the only safety concern. The electricity is meant to pass through the patient. If the patient is wet the electricity might pass over the skin as electricity finds it easy to move through water. The AED should not be used in the rain and, if the patient is wet, the skin should be dried. Electricity also likes passing through metal. If the patient is lying on a metal surface, the rescuer can also be exposed. Move the patient away or slide a board beneath as insulation.
One interesting piece of metal when using an AED is body piercing. These are usually metal and the nipple is a popular piercing point. For safety, the pads should not be placed closer than a few centimetres from the piercing. The piercings do not have to be removed first.
When applied, the pads need to stick fully to the patient’s skin. If there are folds or parts not attached the electricity in the pad can cause a burn or spark at that point. Pads may not stick to hairy chests. They can rise up and away from the skin. Hairy chests should be clipped with scissors first to stop this happening. The hairs can be shaved with a razor but this often causes cuts and scratches. When this happens the electricity can burn the area and not pass through the pads properly.
Finally, as is so often the case, there are some differences for children. A child in cardiac arrest is rare compared to an adult. When this does happen to a child, it often follows not being able to breathe, such as drowning, or loss of body fluid in trauma or illness. This means the heart usually slows down and stops rather than fibrillates. Defibrillation then is not usually needed in children. Very occasionally it might be such as where the child has been born with a heart defect. Adult AEDs should only be used on children if there is a proper adaptor to reduce the electricity. A lot less electricity is usually used on children. About eight years of age is the maximum where an adult device can be safely used on a child. Only devices meant for children can be used below this.
Not only is the electricity a problem with children, so too can be the pads. The pads on the AED are fairly big. This is on purpose to allow the electricity to be delivered across a bigger area. If it all went through one little spot it would likely cause an electrical burn there. Pads cannot simply just get smaller then for little children. Pads meant for children should be used. Where they look fairly big compared to the size of the child, they have to be applied as best as possible to the body in the same places as on an adult.
Jeff Kenneally www.prehemt.com
Jeff is the author of the 2014 – 2016 Ambulance Victoria First Responder clinical practice protocols and accompanying education program.