Small Animal Anaesthesia: Are we doing good (enough)?
We have come a long way in small animal anaesthesia when we look back at repetitive administrations of barbiturates for maintenance of anaesthesia even for longer anaesthetics or xylazine and ketamine (repetitive) bolus injections intramuscularly to produce short to intermediate duration anaesthesia. Today, European small animal practice consists mostly of an anaesthetic premedication (maybe intramuscularly), followed by simple combinations of one or two intravenously administered drugs and then maintenance of the anaesthetic state with an inhalant anaesthetic agent (almost exclusively isoflurane). This “happened” in a period of time of maybe three decades and constitutes a major advancement.
So, we can lean back and enjoy the view of our achievements or we look into the different aspects that this development may be put in context with:
A first context maybe the overall development of small animals’ role in human society. Dogs and cats during this period have evolved from fulfilling specific functions, for example being used as a guard dog on a farm or a farm cat keeping the mouse population under control, to being family members. The societal change that is underlying is very profound as is the requirement for a higher veterinary care level. The simple function farm animal had a very low individual importance and when sick in absence of many medical possibilities, was quickly disposed of (hopefully at least humanely euthanized) and maybe replaced. Today, this type societal standing is more and more discredited. Small animals are companions, even family members and the families in our societies often seek maximum possible level of care. They, however, sometimes have difficulties finding us veterinarians prepared for such intense and high-quality level of care. In a more drastic, maybe provocative wording consequently the question arises on whether or not we veterinary care givers are still in fulfilment of our societal task. In most cases, I believe, the question can be answered with a “yes”.
A second context is the overall medical care for small animals: Given the amount of internistic, laboratory and imaging diagnostic capabilities and the types and numbers of complicated surgeries, we can say: Veterinary medicine has catapulted itself to a high level of care that is close to that of human medicine. The companion animal population has grown much older and today we treat more geriatric animals and multimorbid patients than ever before. Some specialty areas, however, are lagging behind and among the more tragic situations are those of anaesthesia and analgesia.
At the same time, knowledge and expertise in veterinary anaesthesia and analgesia has increased much. Greek veterinarians were and are at the forefront of such global developments. Professor Dimitris Raptopoulos of Aristotle University of Thessaloniki was one of the earlier world-widely renowned veterinary anaesthesiologists in Europe and has invested endless efforts to pave the road for a safer and better anaesthesia and provision of good analgesia to companion animals in Greece and the world. His colleagues and successors walk and work in the same direction.
Unfortunately, the scissors are wide open between the high-level anaesthesia and analgesia care provided by trained anaesthetists to the average level of anaesthesia care in practice. The veterinary practitioner today finds her-/ himself in a classical dilemma when wanting to provide the best possible care on the one hand and being overwhelmed by the complexity of developments of all specialties on the other hand. Along the reasoning of Aristotle’s “Rhetorics”, the discrepancy between the three categories of Ethos (Phronesis, Arete and Eunoia) leads to fallacy of the argument. Exactly that feeling of discrepancy, of insufficient prestation, is described by the answers to the FVE’s Survey of the Veterinary Profession in Europe (Federation of Veterinarians of Europe) (FVE, 2018). Sixty-three percent of veterinarians in Europe feel that they are regarded very poorly, poorly or at maximum neutrally by society, but 73% of veterinarians spend between 30-70 hours (average 40) per year on continuing education (specialization not included) and virtually all vets work more hours than contracted (FVE, 2018). This dichotomy between providing all veterinary services by one veterinarian/in one practice and providing them at specialist level must lead to collapse. In fact, 26% of veterinarians in Europe experienced depression, burn-outs, exhaustion or compassion fatigue over a three-year period (FVE, 2018). One of the areas that demonstrate the difficulties that each veterinarian today is facing, is the lack of sufficient development in anaesthesia and analgesia and the resulting problems.
What are the reasons?
Anaesthesia is a “black-box-service”: It happens in the back of a practice, with no animal keeper/ owner present (mostly for good reasons). The outcomes of anaesthesia are not easy to measure and even more difficult to demonstrate. Other services, such as the ability to provide imaging or surgical techniques seem, at first glance, easier to communicate (and sell). Animal owners/keepers and consequently the society in general are less aware of the impact onto overall outcome (healing) in a disease state. To the “outside world” the animal goes into anaesthesia and comes out of it -or not. But what happens in between remains unknown and uncommunicated. Anaesthetic -actually better: intra-operative- mortality is the only “easy” parameter to measure.
Effectively, anaesthetic related mortality statistics represent impressive numbers. The CEPSAF study included ca. 100,000 dogs and 80,000 cats. The alarming mortality rates are 0.17%, 0.24% and 1.39% of fatalities among dog, cat and rabbit anaesthetics overall, respectively (Brodbelt et al. 2008). This study was performed in the United Kingdom. Other, smaller, studies on the European mainland show even higher mortality risks. A 2012 published cohort study that analysed quite practice-oriented 3,546 small animal mortalities retrospectively (Bille et al. 2012), showed even worse numbers: the overall dog and cat anaesthesia-related mortality was 1.35% (later mirrored by another study at 1.29%) (Gil & Redondo 2013). However, when analysed more in detail, mortality of healthy dogs and cats in anaesthesia (ASA 1 & 2) was low at 0.12%, but when looking at diseased animals the results are simply frightening: 2.9%, 7.58% and 17.33% in ASA 3-, 4- and 5-patients, respectively.
I think coming to the conclusion that we are NOT doing good enough is simple. Mortality, however we look at it, is an impossible-toaccept complication of anaesthesia and the only acceptable goal of our profession must be a zero percent anaesthesia mortality -despite an apparent impossibility to reach this goal in the foreseeable future.
If we look at less dramatic outcomes of anaesthesia complications, the statistics are less clear. This is assumingly so because most of such complications are not detected or not reported. However, in the few studies that estimate their incidences, they lay in the higher tens of percent. Hypotension is the most common intraoperative complication (Mazzaferro & Wagner 2001, Kronen 2007). It may have profound negative implications on later development of organ dysfunctions in brain, heart and kidneys. To diagnose it, we need specific small animal equipment -pulse palpation is insufficient. Hypotension may be tough to treat, and the presence of a trained anaesthetist may well decrease its incidence and impact.
Hypothermia is another complication that is not at all innocuous. According to a survey in Swiss veterinary practices the incidence is 93.4% (Kronen 2007, unpublished data) and consists of more than 1-2 °C decrease in body temperature in comparison to before-anaesthesia levels. While we have no clear data on longterm outcome of intraoperative hypothermia in companion animals, a comparison to humans as a thermoregulatory similar species seems adequate. Increased post-operative stress, slowed wound healing, temporary hypoxia, increased infection rates, tripled incidence of morbid cardiac outcome, prolonged recovery from anaesthesia and coagulopathies are just a few of the severe decrements that are caused by hypothermia and are long known (Sessler 2001). Diagnosis of hypothermia is too easy to mention, but prevention and therapy may be difficult. Here as well, a trained anaesthetist may prove helpful.
A complication of strong welfare impact is that of peri-operative pain, which per se has as well the capability of increasing stress, decreasing immune system function, leading to organ dysfunction, disabilities and even death (Gil & Redondo 2013). It requires expert intervention. Without adequate analgesia managing its peri-operative incidence can be very high.
This chapter just mentions three of the many possible intermediate- and long-term relevant anaesthesia complications. Other complications are important but beyond the scope of this editorial.
What can be done?
For a basic understanding: there are no safe drugs or safe anaesthesia protocols -only safe anaesthetists! This is a very important principle as many clinics work with standard protocols. A standard protocol is a possible starting point, but it must be understood that there is no one-size-fits-all anaesthesia. It rather needs to be tailored to each patient’s individual needs.
Pre-anaesthetic evaluation
NO patient should be anaesthetized without a pre-anaesthetic evaluation as this is a major pillar in reducing anaesthesia risk. The goal is, however, not only risk assessment, but also the anticipation and the prevention through preparation of possible complications. On the basis of the pre-anaesthetic evaluation the anaesthetic management is chosen and decided whether or not a standard protocol may be applied.
Drugs
A choice of different drugs, as well as variations of their doses, routes of application and combinations must be possible. We must have a variety of drugs to choose from for one patient. We furthermore need an understanding of the pharmacokinetics and pharmacodynamics to understand differential reactions by single patients.
Anaesthesia methods
A variety of different methods of application must be available to adapt to a patient, for example constant and variable rate infusions. Balanced anaesthesia techniques are to be considered a mainstay and mono-anaesthetics (using just one drug for anaesthesia like isoflurane) shall be the exception. Local anaesthetic techniques are to be considered for every painful intervention in addition to general anaesthesia.
Monitoring
Anaesthesia provision without adequate monitoring is similar to piloting a plane through foggy weather or storm without navigation instruments. The resulting high risk and mortalities simply do not fit our modern view of companion animals and provision of veterinary care. The apparative monitoring is an integral part and the more complex and the longer an intervention lasts, the most complex and intense the monitoring shall be.
Adjunctive therapies and recovery from anaesthesia
Generally, airway security, fluid- and heat-application therapies are integral parts of modern anaesthesia management as well as correct and careful positioning and padding. The necessity for adequate intra- and post-operative analgesia and its significant impact on outcome and survival shall be repeated here. The provision of a calm and quiet environment, safe monitoring and tender loving care during recovery from anaesthesia is of vital importance to the outcome and safety of the whole procedure, as a high percentage of anaesthesia related deaths occur during the recovery phase (Brodbelt et al. 2008).
Equipment
In modern practice it is unthinkable that anaesthetic equipment (machine, monitoring, syringe drivers, warming devices, infusion pumps, etc.) is not being checked before each use, adapted to the patient and found fully functional. Furthermore, the requirements to a high level of care pose the imperative that all necessary anaesthesia equipment is available for each procedure. The performance of thoracotomy without availability of ventilation possibilities is inappropriate and unless we deal with an emergency, equipment must be available, or the patient referred.
Anaesthetists
From analyses of human anaesthesia safety as well as from practical experiences in veterinary anaesthesia and common professional sense, it is obvious that engaging personnel with (formal) anaesthesia training strongly helps to reduce complication and mortality rates in companion animal anaesthesia. The two-tiered system in anaesthesia, employing trained veterinary nurses and veterinary anaesthesiologists is not only a mirror image of human anaesthesia, but also has proven successful in many countries of the world. In human anaesthesia, mortality has been decreased by a factor 16 when basic monitoring and the engagement of anaesthesia nurses and anaesthesiologists in such a two-tiered system was introduced in the 1980’s (Campling et al. 1995).
But trained anaesthesia professionals not only help to reduce mortality, but also complication rates, increase overall successful outcome (on healing), help provide best possible care and analgesia in the peri-operative period or even long-term (Mathews et al. 2014) and thereby help fulfil the societal task that companion animal practice has today.
In summary, in the average situation in practice, veterinary anaesthesia and analgesia has not sufficiently developed alongside the changes of the profession and the animal population. Apart from the principle that every anaesthesia death is one too many, the results are alarming mortality rates indicating a bad safety, even more alarming complication rates, indicating an even worse safety situation for complications and overall outcome.
Today, however, we have substantial information available as to how we can reduce risk. Drugs have been developed or researched for companion animal use, as well as safer doses, routes of application and anaesthetic techniques clinically introduced that provide better safety. Local anaesthetic techniques should be coadministered during every painful procedure as they increase analgesia provision and safety. Monitoring devices of all kinds are available and within reach of a veterinary clinics’ finances today and the same is true for the other anaesthesia equipment. It must be made available along investments on other clinical equipment (e.g. surgical or radiological). We know better how to provide effectively adjunctive therapy and safety during recovery. And we are finally at a turning point of being able to train personnel in anaesthesia and engage these people in clinics.
Anaesthesia remains a tool. Traditionally, it was a tool to decrease mortality from surgery, but we are not quite at the finish line of that path yet. Furthermore, within the reach of anaesthesia and analgesia care, lay not only avoidance of negative impacts (mortality, complications), but also positive impacts such as impact-free anaesthetics, freedom from (severe) pain, better healing, better immune responses, less stress, calmer patients and smooth transition during hospitalization.
Never in the history of the veterinary profession has the time been better to invest effort, knowledge and resources into a better anaesthesia care provision. As veterinary medical professionals, we should all together take that step now to fulfil our changed tasks in society and -maybe more importantly- towards our patients. It benefits all stakeholders, companion animals, owners/keepers, nurses and veterinarians and help us look into the future of veterinary medical care.
Let’s all together make anaesthesia and analgesia better! Now!
Peter W. Kronen, DVM, Dipl ECVAA, Dr med vet Veterinary Anaesthesia Services - International & Center for Applied Biomolecular Medicine, University of Zürich, Switzerland
References
- Bille Ch, Auvigne V, Libermann St et al. (2012) Risk of anaesthetic mortality in dogs and cats: an observational cohort study of 3546 cases. Vet Anaesth Analg 39, 59-68.
- Brodbelt DC, Blissit KJ, Hammond RA et al. (2008) The risk of death: the confidential enquiry into perioperative small animal fatalities. Vet Anaesth Analg 35, 365-373.
- Campling E, Devlin H, Hoile R (1995) Report of the Confidential Enquiry into Perioperative Deaths 1992/1993, British National Ministry of Health.
- FVE (2018) Survey of the Veterinary Profession in Europe, Federation of Veterinarians of Europe, www.fve.org.
- Gil L, Redondo JI (2013) Canine anaesthetic death in Spain: a multicenter prospective cohort study of 2012 cases. Vet Anaesth Analg 40, E57-67.
- Kronen PW (2007) Monitoring of Patients under Anaesthesia. Eur J Comp Anim Pract 17, 1-8.
- Sessler DI (2001) Complications and Treatment of mild Hypothermia, Anesthesiol 95, 531-543.
- Mathews K, Kronen PW, Lascelles D et al. (2014) Guidelines for recognition, assessment and treatment of pain. J Small Anim Pract 55, E10-68.
- Mazzaferro E, Wagner AE (2001) Hypotension during Anesthesia in dogs and cats: Recognition, Causes and Treatment. Compendium 28, 728-737.
