In CPR time is of the essence and therefore it is important that all staff know what to do, how to do it and where everything is that is required in treating the patient. It is also important that staff know what is normal and what is abnormal in the patient. The emergency cart must be well stocked and checked regularly to ensure drugs and equipment is maintained. The definition of cardiac arrest is an abrupt cessation of spontaneous and effective ventilation and systemic perfusion (circulation) which leads to inadequate oxygen delivery to tissues.

In 2012 The Reassessment Campaign on Veterinary Resuscitation (RECOVER) was designed to systematically evaluate the evidence on the clinical practice of veterinary CPR with 2 overarching goals. First to devise clinical guidelines on how to best treat CPR in dogs and cats, and second to identify important knowledge gaps in veterinary CPR that need to be filled in order to improve the quality of recommendations, and thus the quality of patient care in the future. An advisory board of experts in the field as well as over 80 veterinarians were consulted throughout the process.

One of the findings in the guidelines was that delaying the start of CPR has shown significant reductions in survival to discharge and the neurological status of the patient. Agonal breaths can be misinterpreted as spontaneous breathing. In human studies less than 2% of patients on whom CPR is started when not completely confirmed are actually harmed as commonly the patients respond to the stimulation associated with CPR. If there is any doubt CPR should be started immediately.

Preparing for CPR

An organised, cohesive, knowledgeable and well trained team will lead to better outcomes in CPR. It was recognised that the factors that can affect the outcome of CPR are environmental and personnel factors.

Environmental factors that may impact performance include well-designed, straightforward checklists; algorithm charts; cognitive aids; and well-stocked, easy to access, organized crash carts.

Personnel factors include high-level team member training, specific leadership training, and appropriate intervals of retraining and debriefing. Improved outcomes require consistent improvement in resuscitation education and the implementation of support systems to allow the streamlined delivery of CPR in the clinic setting. Above all else the veterinary team should practice CPR in their clinic on a regular basis at least every 3–6 months so everyone knows what their role is and the techniques that will be used. This is simple to achieve by using a stuffed toy dog, cat or even teddy bear!

Crash Cart

An emergency box or “crash cart” is a vital part of emergency procedures as it contains all the vital equipment and drugs required to deal with an emergency in the one location. The emergency box can be as simple as a large tool box with the basic necessary items or a large storage cart on wheels with multiple draws. The emergency box should be located in the treatment area or surgery of the clinic and divided into sections of similar equipment.

On top of the cart would be all resuscitation equipment such as an Ambu bag, pulse oximeter, oxygen supply, suction unit and ECG unit. The top draw could contain airway equipment such as laryngoscope, endotracheal tubes, stylets, tracheostomy tubes, lubricating jelly, ties and swabs. The second draw could contain circulation equipment such as intravenous catheters, tape, tourniquet, feeding tubes, swabs and fluids. The bottom drawer could contain emergency drugs, syringes and needles. Carts may be divided into further sections with more drawers if available and to the specifications of the Veterinarians in the veterinary clinic.

Equipment and Usage

Ambu Bag

An Ambu bag is a self-inflating device that is used to provide artificial ventilation to the patient. An oxygen source is connected to the bag and the bag then attached to the endotracheal tube. Ambu bags are preferable to using an anaesthetic machine for assisted ventilations as there could be residual anaesthetic gases in the machine and the circuit must be closed. Using an Ambu bag also creates a shorter distance for the oxygen to travel to the patient.

Oxygen Supply

One hundred percent (100%) oxygen is ideally required for assisted ventilations. This may be via an anaesthetic machine or from a direct oxygen source (such as an Ambu bag) with a flowmeter attached.

Pulse Oximeter

A pulse oximeter is a vital piece of equipment in monitoring the percentage of arterial haemoglobin-oxygen saturation. This is important in assessing the need for supplemental oxygen and also when it is no longer required. It consists of an infrared sensor placed on the tongue, lip or paw to obtain a reading. Normal values are between 98–100%.

Electrocardiogram (ECG)

An ECG may be used in advanced life support after basic life support has been established. An ECG shows the heart rate and rhythm and the presence of arrhythmias that may have developed and therefore appropriate therapy can be administered. Ventricular fibrillation is the most common arrhythmia and an electrical defibrillator if available may be used to help stimulate and regulate the electrical activity in the heart.

Suction Unit

A suction unit may be used to clear the airway of fluids and debris which may include mucous, blood, vomit or saliva and hence aid in endotracheal intubation.

Other Equipment

Endotracheal tubes, stylets, swabs and ties, lubricating jelly, IV catheters, loaded syringes (e.g., saline), feeding tubes or urinary catheters, tracheostomy tubes, chest drains and 3-way stopcock taps, bandage material and tape, gloves, syringes and needles.

Fluids

Fluid therapy is the primary method of circulatory support in the emergency patient. The goal of fluid therapy is to restore circulating volume, perfusion and oxygen to the tissues to a desired level (e.g., normal heart rate, mucous membrane colour and capillary refill time) without causing a volume overload. A volume overload could lead to pulmonary and cerebral oedema. The correct type of fluid and the rate of administration will depend on the patient’s condition. Crystalloid fluids are isotonic fluids (being of equal osmotic strength) that pass readily through cell membranes. These fluids will help to balance out between the extracellular space and intracellular space. Hartman’s and 0.9% sodium chloride are crystalloids and are given where there is a need to replace the extracellular fluid and for volume expansion. They are inexpensive and easily available. A downside to crystalloids, however, is that they do not remain in the vascular space for very long.

Colloids are also isotonic fluids but they contain higher molecular weight particles that will remain intravascular for a longer period of time. Therefore, the volume of fluid required will be less. Examples of colloids are Voluven and 5% Dextrose. Hypertonic saline draws fluid from the extracellular space into the intracellular space causing volume expansion. It is most commonly used in cases of hypovolaemic shock (decreased circulating volume) as it creates rapid volume expansion. It must always be followed by crystalloid fluid administration to restore equilibrium of the extracellular and intracellular fluid.

An example of hypertonic saline is dextrans. Mannitol is another fluid that may be used in the emergency situation. Mannitol is an osmotic diuretic and is used to treat cerebral oedema. It draws fluid from the extracellular space as hypertonic saline does. It helps by increasing cerebral blood flow and decreasing fluid and swelling of the brain therefore decreasing intracranial pressure. Fifty percent (50%) glucose should also be included in the emergency cart for use in cases of hypoglycaemia where the glucose level of the patient is extremely low. The rate of fluid administration will depend on the condition of the patient. In CPR fluid overload has been found to be a problem when there is circulatory compromise and the use of fluids will depend on the individual case. As a general guide slightly higher than maintenance rates at 5–10 ml/kg/h can be used, however, only if the patient is hypovolemic. Fluid may be given as a bolus in severe cases to rapidly restore circulating volume.

Therefore, the crash cart should contain both 500 ml and 1000 ml bags of Hartman’s, 0.9% sodium chloride and if possible Haemaccel or 5% dextrose. Hypertonic saline, mannitol and 50% glucose in 500 ml bags are required also. Infusion sets of 20 drops/ml and paediatric giving sets should also be included.

Emergency Drugs

Recommended route of administration for most emergency drugs is intravenous (IV) or intra-osseous for the fastest absorption rate, however, if these routes are not possible the intra-tracheal route can be used however there is not any evidence on optimal dose, volume or diluents. Any drugs administered during CPR via the IV route must be followed by a saline bolus of 20–30 ml to ensure the full effect. The following drugs, doses and routes of administrations are guides only and your veterinarian will decide on what may or may not be used and the dose and route of administration for each case.

Adrenalin 1:1000, 1 mg/ml

Dose rate of 0.01 mg/kg intravenously or double dose rate if given intratracheal for two doses on every other cycle of basic life support. If further doses are required then the dose is increased to 0.1 mg/kg. Administer on every other cycle of basic life support. Used in cases of ventricular asystole (No electrical activity present in the heart) and also in cases of severe bradycardia (slow heart rate). Adrenalin causes vasoconstriction and improves coronary and cerebral blood flow and venous return to the heart. It increases the heart rate and the force of contractions of the heart. It is most commonly administered intravenously but can also be given intratracheal through a feeding tube placed down the endotracheal tube. The dose rate does need to be doubled by this route and may already be made up as a 1:10000 solution (9 ml of saline to 1 ml of 1:1000 adrenalin). Lower doses are recommended to start with as high does may cause ventricular fibrillation. Its effect is immediate if given intravenously.

Vasopressin

Dose rate of 0.3 micrograms/kg (1 ml/25 kg) IV given instead of adrenalin for the first one or two doses then administer adrenalin for subsequent doses. May be given intra-tracheal at a dose rate 5 times the IV dose. Vasopressin is a nonadrenergic vasopressor that causes peripheral, coronary and renal vasoconstriction. This in turn increase cerebral and coronary blood flow and can be used instead of adrenalin to similar effects.

Current studies in human medicine do not find that vasopressin is superior to use of adrenalin, however, some studies have shown that it may be more effective in animals particularly those with severe hypovolaemia. The RECOVER guidelines recommend that vasopressin is used for only the first or second doses and that adrenalin is used thereafter.

Atropine Sulphate, 0.6 mg/ml

Dose rate of 0.02–0.05 mg per kg intravenously, intramuscularly or sub-cutaneously. Used in cases of bradycardia. It will increase the cardiac output and heart rate by blocking vagal stimulation in the heart. It is also used as an antidote in cases of organophosphate poisoning. Care must be taken not to overdose as this can cause sinus tachycardia. Its effect is at its peak 3–4 minutes after intravenous administration. Can be given intratracheal again at double the dose rate intravenously and should be followed with a few short breaths to enhance delivery into the patients system.

Lignocaine 2%, 20 mg/ml

Dose rate of 2–6 mg per kg equating to 1 ml/10 kg intravenously. Used in cases of severe tachycardia and ventricular fibrillation. It is a local anaesthetic and therefore suppresses the ventricular electrical activity of the heart. It can be given intratracheal at double the intravenous dose rate.

Frusemide (Furosemide), 50 mg/ml

Dose rate of 2–4 mg per kg in dogs and 1–2 mg per kg in cats intravenously or intramuscular. Used to treat cerebral and pulmonary oedema. It is a diuretic and hence helps to remove fluid. Care must be taken that the patient does not dehydrate and develop an electrolyte imbalance.

Dopamine, 40 mg/ml

Dose rate of 5–10 mg/kg/min for cardiac uses. Used for the treatment of acute heart failure and to correct the hemodynamic imbalances that can be present following shock. It increases cardiac output, organ perfusion and renal blood flow.

Dobutamine, 12.5 mg/ml

Dose rate of 5–15 mcg/kg/min. Used for the treatment of low cardiac output and myocardial failure. It can also be used in shock patients when fluid therapy alone has not restored arterial blood pressure, cardiac output or tissue perfusion. It is a short acting drug.

Visual aids such as dose rate charts, protocols and checklists will also improve the outcome for CPR. You do not have time to be working out the correct dose for that animal in CPR so having a dosage chart with the weight of an animal for the drugs adrenalin, atropine and lignocaine in particular is highly recommended.

References

1.  Journal of Veterinary Emergency and Critical Care 22 (s1) 2012 – Recover Emergency and Critical Care Guidelines on CPR.

2.  Lesley G. King, Amanda Boag - BSAVA Manual of Canine and Feline Emergency and Critical Care 2nd Edition.

3.  Donald C. Plumb - Plumbs Veterinary Drug Handbook 5th Edition.

4.  Animal Industries Resource Centre - Veterinary Nursing Technician Notes (CTVN L3) Emergency and Critical Care.

5.  Vetlearn Veterinary Technician - August 2012 Volume 33, Number 8 - “Cardiopulmonary Resuscitation: Administering fluids, oxygen and drugs” Amy Breton, CVT, VTS (ECC).