Once an animal undergoes a cardiopulmonary arrest (CPA), their chance of surviving to discharge is greatly reduced. All cause survival rates post-CPA range from 6–18% (Hofmeister et al. 2009; Hoehne et al. 2019). However, when considering only those animals who experience CPA during the peri-anaesthestic period, survival rates up to 47% have been reported (Hofmeister et al. 2009; McMichael et al. 2012).

Risk factors identified for peri-anaesthetic arrest include patient factors; namely the severity of illness, human factors; failure of planning, insufficient monitoring or competence, and procedural factors; effect of drug administration or procedural intervention. In most cases of CPA, multiple risk factors can be identified, but the most common risk factors reported in one population of dogs and cats undergoing general anaesthesia were patient and human factors (Hofmeister et al. 2018). Having an intravenous catheter in place, alongside a witnessed CPR is associated with improved outcome and it is therefore essential that all animals undergoing anaesthesia have an intravenous catheter in place (Hoehne et al. 2019).

In light of the underlying disease process being one the most important risk factors for CPA, it is vital that these high-risk patients are recognised, their risk of arrest is communicated to the team and the underlying condition is stabilised as much as possible prior to any anaesthetic or procedural intervention. Underlying conditions most commonly associated with CPR include respiratory disease and associated hypoxemia, cardiovascular dysfunction including shock and arrythmia, neurological disease and severe systemic disease (Hofmeister et al. 2009; McIntyre et al. 2014). A thorough assessment of the three major body systems: respiratory, cardiovascular and neurological system is therefore recommended prior to any anaesthetic intervention. Surgical emergencies, such as gastric dilation volvulus, septic peritonitis, haemoabdomen and intussusception, require prompt surgical intervention; however, patient stabilisation should be performed prior to induction of anaesthesia. Resuscitation prior to surgery should aim to mitigate shock with intravenous fluids or blood products and treat severe electrolyte and/or glucose derangements. In animals with respiratory disease, pre-oxygenation is advised prior to induction, if upper respiratory tract disease is suspected, then equipment required for emergency airway access should also be available. Respiratory, neurological, ocular and gastrointestinal disease can be associated with an increase in vagal (parasympathetic) tone and this effect can be exacerbated by opioid analgesia. High parasympathetic tone to the heart may lead to bradycardia and cardiac arrest, as such in high-risk animals’ undergoing a procedure emergency drugs should be prepared prior to induction. Emergency drugs to consider include an opioid antagonist; naloxone or butorphanol and a vagolytic such as atropine (Rozanski et al. 2012). Atipamezole, the reversal agent for alpha 2 agonists should also be pre-drawn up in a syringe whenever alpha 2s are used in a sedation or anaesthetic protocol.

Human factors found to be associated with CPR not only include inadequate preparation of the patient but also ineffective monitoring under anaesthesia. The level of patient risk should be communicated to the person monitoring the anaesthetic prior to the procedure and the individual given the opportunity to ask questions as well as raise any concerns about their role. Surgical safety checklists have shown to reduce morbidity and mortality in both human and veterinary medicine and templates for checklists are freely available (WHO, 2009; RCVS Knowledge, n.d.). Adequate monitoring equipment should be in place during the anaesthetic period. Blood pressure and electrocardiography monitoring are particularly important in animals with cardiovascular disease, pulse oximetry in animals with underlying respiratory disease and a capnography is a useful piece of monitoring equipment in all animals under general anaesthesia. A sudden drop in end tidal carbon dioxide to near zero in an intubated animal undergoing positive pressure ventilation is highly suggestive of CPA (Brainard et al. 2012).

Communication of risk and close monitoring of the patient should continue in the post-operative period and throughout hospitalisation. Whenever the care of the patient is transferred to another individual, a verbal and written handover should be given and ideally include all veterinary staff involved in the care of the patient; again, with the opportunity for any individual to ask questions. A kennel sheet with regular monitoring and the associated alerts to notify the veterinary surgeon should be regularly updated and any changes communicated to the team.

Another important aspect in preventing an arrest is being prepared for the arrest. When dealing with a patient with severe disease, it is useful to consider the “worst case scenario” to ensure staff are prepared and necessary equipment available, should this occur. This includes having a centrally located, regularly audited pre-stocked arrest station including drugs and equipment that may be required peri-arrest, as well as visual aids to help determine drug and doses required in the emergency setting (McMichael et al. 2012). Debriefing should be performed after each arrest, but should also be considered in those cases deemed to be “near-misses.” Introducing a culture of reflection and analysis within the team will help improve practice, which will benefit the animal, owner and team as a whole.

Although the majority of cardiopulmonary arrests are a result of severe disease and this factor cannot be completely eliminated, the actions of the team can greatly decrease the chance of a CPR and influence patient outcome. Adequate planning and communication are the key to minimising the human and procedural risk factors associated with CPR. Documenting and reviewing cases that underwent a CPA will also help improve practice.

References

1.  Brainard BM, Boller M, Fletcher DJ; RECOVER Monitoring Domain Worksheet Authors. RECOVER evidence and knowledge gap analysis on veterinary CPR. Part 5: Monitoring. J Vet Emerg Crit Care (San Antonio). 2012 Jun;22 Suppl 1:S65–84.

2.  Hoehne, SN, Hopper K, Epstein SE. Prospective evaluation of cardiopulmonary resuscitation performed in dogs and cats according to the RECOVER guidelines. Part 1: Prognostic factors according to Utstein-style reporting. Front Vet Sci. 2019;6:S102–110.

3.  Hofmeister EH, et al. Prognostic indicators for dogs and cats with cardiopulmonary arrest treated by cardiopulmonary resuscitation at a university teaching hospital. J Am Vet Med Assoc. 2009;235(1):50–57.

4.  Hofmeister EH, Reed RA, Barletta M, et al. Critical incident technique analysis applied to perianesthetic cardiac arrests at a university teaching hospital. Vet Anaesth Analg. 2018;45:345–350.

5.  McMichael M, Herring J, Fletcher DJ, Boller M. RECOVER Preparedness and Prevention Domain Worksheet Authors. RECOVER evidence and knowledge gap analysis on veterinary CPR. Part 2: Preparedness and prevention. J Vet Emerg Crit Care (San Antonio). 2012 Jun;22(Suppl 1):S13–25.

6.  McIntyre RL, Hopper K, Epstein SE. Assessment of cardiopulmonary resuscitation in 121 dogs and 30 cats at a university teaching hospital (2009–2012). J Vet Emerg Crit Care (San Antonio). 2014 Nov–Dec;24(6):693–704.

7.  Rozanski EA, Rush JE, Buckley GJ, Fletcher DJ, Boller M; RECOVER Advanced Life Support Domain Worksheet Authors. RECOVER evidence and knowledge gap analysis on veterinary CPR. Part 4: Advanced life support. J Vet Emerg Crit Care (San Antonio). 2012 Jun;22 Suppl 1:S44–64.

8.  RCVS Knowledge Base (n.d.) Surgical checklist safety manual, available: https://knowledge.rcvs.org.uk [accessed 28th February 2021]

9.  World Health Organisation. 2009. Surgical safety checklists, available: www.who.int [accessed 28th February 2021].