Cardiopulmonary resuscitation (CPR) was first documented in the 1700s in Amsterdam where many people worked and travelled on canals. There was a high rate of drownings because people fell into the water, so the Society for Recovery of Drowned Persons dedicated their work to saving victims. In 1891 Dr Friedrich Maass documented the performance of chest compressions and by 1903 Dr George Crile reported a successful resuscitation.
There has been a lot of dispute over the best way to perform CPR and there remain large gaps in evidence. Historically in the veterinary field ideals have been extrapolated from human research, but in 2011 an evidence-based consensus was designed specifically for veterinary patients. The Reassessment Campaign on Veterinary Resuscitation (RECOVER) guidelines were published in 2012 and can be reviewed in full in The Journal of Emergency and Critical Care 22(S1): S102–S131 (Fletcher et al, 2012).
Causes of CPA
Cardiopulmonary arrest (CPA) is defined as a failure of effective circulation and ventilation. This leads to reduced tissue oxygenation and organ damage and emergency intervention can be life saving. Patients fall into two categories; those with reversible causes; those with irreversible causes.
The most common cause of CPA in humans is ventricular fibrillation either due to heart disease or secondary to severe systemic disease. McIntyre et al (2014) published common causes of CPA in veterinary patients which included: cardiac-related issues (hypotension, haemorrhage or anaemia), respiratory failure, neurological disorders or metabolic derangements. Anaesthetic-related CPA carries the best prognosis for survival (Maton and Smarick 2012). This may be because the patient is already intubated (therefore the airway is protected), is receiving supplemental oxygen and is being closely monitored which enables rapid CPA diagnosis and subsequent commencement of CPR. McIntyre et al (2014) published success rates of CPR to hospital discharge in animals of only 2–16%. If patients develop CPA as a result of irreversible disease the outcome of CPR is likely to be unsuccessful.
Preparedness
The likelihood of a survival is increased when the team is prepared. Research from human literature suggests that either equipment failure or poor supplies result in delay of CPR efforts in up to 18% of cases (McMicheal et al, 2012). There are several areas that need to be considered in terms of preparedness: the team; crash area; and crash trolley.
The team
There is no recommendation for the optimal team size (McMicheal et al, 2012). From personal experience it is beneficial to have 3+ persons: a chest compressor; a ventilator; and a drug administrator/timer. Team members can rotate tasks in order to switch chest compressors after 2 minute intervals. There is little evidence to support a more experienced team member (e.g. clinician) having a more successful outcome (McIntyre et al, 2014). The most important component of a successful resuscitation is that somebody takes the role of leader and directs the team by distributing tasks. Communication must be clear and concise. Closed loop communication is practised in some settings where the leader gives an instruction and the team member repeats the instruction back to the leader. This can help to reduce mistakes due to orders not being clear or an instruction not being heard due to the chaotic nature of the situation.
Training is another important factor. Personnel should receive effective and standardised training with the option of refresher sessions every 6 months (McMicheal et al, 2012). These should be practical sessions, using a mannequin, to ensure all team members are able to effectively carry out all tasks such as ventilation and chest compressions. Feedback should be given and technique critiqued so the team optimises their CPR efforts.
Crash area
Many busy emergency veterinary departments will have a dedicated crash area where the animal is taken in a crash situation. This may not be possible in smaller settings and so it may be more appropriate to resuscitate the animal where they are, e.g. ward area.
Ideally a crash area should have enough space for the team to be able to access the patient from all sides, good lighting and an oxygen supply. A suction unit should be kept plugged in and ready to use. If a specific crash area is utilised then a table with altering height is beneficial to maximise chest compression technique. If a static table is used then a foot stool should be supplied for shorter members of the team. A continuous electrocardiogram (ECG) machine and capnograph are the monitoring equipment of choice. A defibrillator can be a useful addition if working in an emergency setting.
Crash trolley
The crash trolley is likely to be stored in the crash area. If there is no crash area then several smaller crash boxes can be located in different areas such as theatre, prep room and radiography.
All crash carts within the practice should be standardised (Figure 1). They should contain the same items in the same places to minimise wasted time looking for resources. All personnel who are likely to be involved in CPR efforts should know where to locate the crash trolley/box and where items are kept within it. It is useful to access these during training refreshers so they act as a visual reminder.
Equipment should include airway equipment (laryngoscope, a range of endotracheal (ET) tubes and tracheostomy tubes, Intubeaze®, urinary catheter), intravenous (IV) access (short peripheral catheters of multiple sizes, intraosseous catheters, surgical blade for cutdown), emergency drugs (adrenaline and atropine — large settings may contain other drugs such as drug antagonists, i.e naloxone, calcium gluconate, propofol), ventilation equipment (anaesthetic circuits or Ambu bags), surgical kit for cut down or open chest CPR, needles and syringes.
The crash trolley should be sealed so people do not ‘borrow’ equipment that may be required urgently. It should be audited monthly and restocked after each crash. The RECOVER initiative have devised a CPR algorithm and drugs chart (Figure 2) that can be kept alongside the crash trolley as a quick reference guide. A standardised CPR recording form can be useful for recording the times and events of actions during the CPR efforts.
Recognising a crash
Identification of a CPA includes the unconscious/unresponsive patient with absent or agonal respiration. If there is concern that a patient is rapidly deteriorating and it is felt that a crash situation may be imminent then call for assistance and move the patient to the crash area. Airway, breathing and circulation (ABC) should be rapidly assessed and if there is concern regarding CPA then CPR should be commenced immediately. The alarm should be raised for help by shouting ‘CRASH’. In large hospital settings it can be extremely useful to have a crash alarm installed. If a patient experiences CPA, the alarm can be sounded making staff aware of an emergency in a certain area of the hospital so help can be provided and CPR started. Time should not be wasted trying to feel for a pulse or auscultating a thorax as this will delay CPR efforts. There is some evidence to suggest that the benefit of starting CPR in a patient not in CPA outweighs the risks associated with not starting CPR (Hopper et al, 2012).
Basic life support (BLS)
BLS consists of ABC — airway, breathing and circulation. Rapid initiation and effective technique are associated with return of spontaneous circulation (ROSC) and survival. It may be more appropriate to use the pneumonic CAB — circulation, airway and breathing as chest compressions should not be delayed until an airway is obtained.
Circulation
During CPA there is no cardiac output, therefore chest compressions should be used to generate pulmonary blood flow in order to eliminate CO2 and increase oxygen uptake. Efficient compressions will increase tissue perfusion and oxygen delivery. Establishing blood flow can be done via external chest compressions (closed chest) or cardiac massage (open chest) with the latter being considered an advanced life support technique.
Technique for external chest compressions:
Airway and breathing
Hypercapnia and hypoxia both increase the likelihood of an unsuccessful outcome so it is essential to obtain and secure an airway and provide adequate ventilation. This should be performed with the patient in lateral recumbency as chest compressions will have already been initiated and should continue uninterrupted. The use of a laryngoscope can aid in ET tube placement. A rigid urinary catheter can be used as a stylet in difficult airways. Suction may be required if there has been reflux from the stomach or fluid from the lungs causing upper airway obstruction. ET tubes should be tied in place as they are easily dislodged due to movement during CPR. The cuff should be inflated to improve ventilation and due to the risk of gastric reflux during CPR. Breaths should be delivered to the patient via an anaesthetic circuit (Ayres T–piece/Bain) or an Ambu bag (Figure 5) at a rate of 10 breaths/minute with a tidal volume of 10 ml/kg and an inspiratory pressure of 15 cmH20. A common mistake is to increase ventilation as chest compressions are happening so be careful to time ventilation efforts to avoid decreasing oxygen delivery.
Conclusion
BLS is the steps taken in an emergency situation when a patient is experiencing CPA. These steps can be life saving and if started immediately are more likely to be associated with a ROSC. Preparedness and training are key features that can be easily achieved by ensuring that the crash trolley/box is fully stocked and that all staff members are familiar with how to deliver chest compressions and manually ventilate the patient.
Key Points
Conflict of interest: none.