Cardiac Arrest in Dogs

A very small percentage of canines who fall ill due to cardiac arrest recover. The survival rate is less than 10%. If a dog suffers cardiac arrest while under anesthesia, the survival rate is a bit higher due to the fact that immediate intervention is available, and aids like oxygen and catheterization are already in place. Lack of oxygen to the brain results in brain death within four to six minutes without cardiopulmonary resuscitation CPR. There are three steps to CPR, basic life support, advanced life support and post-resuscitative care. These three components of revival include clearing the airway, giving fluid support and monitoring recovery. If your pet goes into cardiac arrest at home, chances of recovery are very slim.

Cardiac arrest, also known as cardiopulmonary arrest, is defined as the failure of the respiratory and circulatory systems in an acute manner. Resuscitation of your pet will depend on factors such as length of time under arrest before intervention and underlying cause of the event.

The symptoms of cardiac arrest can be very dramatic. Recognizing the signs and acting on them immediately is crucial. When a pet is under veterinary care, in particular under anesthesia, the monitoring of vital signs can alert the veterinary team to the incidence of cardiac arrest. Signs that you may see if the episode occurs at home are:

• Breathing abnormalities - difficulty breathing, decreased breathing, and respiratory distress
• Mucus membranes become white or blue due to lack of oxygen
• Pupils are dilated
• Obvious distress could be vocalized by your dog
• Collapse
• No response of any kind

Signs that are not obvious without the proper medical aids (like a stethoscope) are irregular heart beat, lack of heart sounds, changes in heart rate, and no pulse.

Cardiac arrest in canines can occur due to many circumstances. From end-stage disease, to arrhythmias, to different types of cancer, cardiopulmonary arrest is an unfortunate complication of many canine illnesses.

• Anesthetic error (for example overdose of anesthetic during surgery)
• Anesthetic equipment failure 
• Ventricular flutter
• Ventricular fibrillation
• Airway obstruction
• Electrical impulses to the vagal nerve
• Asystole
• Sinus bradycardia
• Decreased blood circulation
• Severe trauma such as to the chest
• Neoplasia
• Low oxygen levels
• Severe abnormalities of electrolytes
• Congenital heart failure

The presence of a pulse, the pattern of the respiratory action, and the ability of your pet to respond are main factors when checking for cardiac arrest. After assessing a cardiac arrest, the veterinary team, whether during a surgical procedure or evaluating an emergency admittance, will follow the ABC steps of cardiopulmonary resuscitation, in order to determine the status of your dog and attempt revival. Ensuring the airway is clear, ventilation with 100% oxygen through intubation, and compression to re-establish circulation of blood are the three steps normally followed.

Recovery from cardiac arrest is contingent on prompt action. The goal will be to regain a beating heart and thus, normal function for your pet. 

Basic life support is stage one of CPR

• Cleaning obstruction from airway if needed
• A tracheotomy could be necessary
• After clearing the airway, an endotracheal tube is placed
• Next is to restart the heart by chest compression, open-chest internal cardiac massage or defibrillation

Advanced life support is stage two

• Fluid resuscitation is carefully given depending on the stability of the pet
• An IV catheter or endotracheal tube are used for emergency medication
• An ECG will determine the type of arrhythmia (such as asystole or pulseless electrical activity for example), which guides the treatment

Post-resuscitative care is the third stage

• If your pet has been successfully resuscitated he will receive continued supportive care and will be assessed for complications like kidney and brain damage

If your pet has gone into cardiac arrest while you are at home, panic and distress on your part can make resuscitation difficult. Having a knowledge of pet CPR is something all pet owners could benefit from, but is rarely learned. However, if you have assistance and know for certain that your pet is in cardiac arrest you must clear the airway and begin chest compressions. 30 compressions (using one hand for a small dog and two hands for a medium to large dog) should be given and then two breaths into the nostrils. Again 30 compressions and two breaths. Continue. This is a very basic way to attempt CPR, with no guarantee of success. If you are fortunate, your pet may begin breathing again, or you may attempt to continue the CPR while someone drives to the emergency clinic. It is very important to note that CPR can be extremely dangerous for your pet if you have mistakenly identified his collapse as a cardiac arrest.

Even under the care of a veterinarian, the survival rate of a canine cardiac arrest is very low. Dogs who experience respiratory arrest as opposed to cardiopulmonary arrest have a better chance of survival, as do canine family members who go into cardiac arrest while under anesthesia. The survival of a dog with this condition will be highly contingent on how long he was in an arrested state, his condition when the event occurred, his age, and what exactly the underlying cause of the cardiac arrest was.