Anaesthesia Preparedness

Planning a patient’s anaesthetic involves three specific areas:

The Patient:

The American Society of Anaesthesiologists established a grading system for human anaesthetic patients based on patient risk. This has been modified for animals and is broken into five ASA classes:

Class 1: Normal risk. Normal healthy animal with no underlying diseases

Class 2: Slight risk with mild systemic disease present. Neonate, geriatric, obese animals.

Class 3: Moderate risk, obvious disease present. Moderate systemic disease with mild clinical signs. Anaemia, moderate dehydration, fever, low-grade heart murmur or cardiac disease.

Class 4: High risk. Severe systemic disease present. Severe dehydration, shock, uraemia, toxaemia, high fever, non-compensated heart disease or diabetes, pulmonary disease, emaciation.

Class 5: Extreme risk. Moribund, severe disease including heart, endocrine, renal disease, profound shock, severe trauma, pulmonary embolus, terminal neoplasia.

Patient preparation must consider risk, the procedure to be undertaken, pain management requirements, thermoregulation and anaesthetic duration.
Risk looks at patient age, physical condition and disease status. The very young or old are less capable of adapting to the demands of anaesthesia and surgery. Pregnant animals have dual risk because anaesthesia impacts both the dam and foetus. The foetus is directly affected by the anaesthetic agent(s) but is also affected by physiological changes in the dam associated with her anaesthetic.
Pain management will be dictated by the procedure or condition to be undertaken / addressed. Pain elevates catecholamine levels which increase cardiac and metabolic demand. Cardiac patients undergoing painful procedures benefit from appropriate pain management. This can greatly reduce cardiac workload and risk of arrhythmia.
The longer an animal is under anaesthesia the greater the loss of body heat. This can have a serious impact on anaesthetic safety and patient post anaesthetic recovery.
Patient Check List: 
  1. ASA assessment
  2. Appropriate drug selection
  3. Appropriate management prior to anaesthesia (fluids / pre oxygenation)
  4. Appropriate management during anaesthesia
  5. Appropriate management post anaesthesia

The Staff:

“Despair is most often the offspring of ill-preparedness.”
It is all too easy to bluster into a disaster. All it takes is too much haste, too little knowledge of the situation and no real planning.
In the article ‘Common Anaesthetic Mistakes’ , studies involving our human counterparts indicate 43% of surgical misadventures happen because of poor communication. The use of simple check lists have helped reduce mistakes by up to 50%.
Staff play a pivotal role in the anaesthetic process. They make all the decision, manage the patient and monitor the anaesthetic. This leaves ample room for things to go pear shaped. Before undertaking an anaesthetic the team should be able to answer the following questions:
  1. Who is in charge of the team?
  2. Who has assessed the patient and assigned an ASA risk rating?
  3. Who has made the decision on pre anaesthetic / anaesthetic / pain management selection?
  4. Who is responsible for preparing the anaesthetic drugs and equipment (for induction & maintenance)?
  5. Who is responsible for monitoring the patient during anaesthesia?
  6. What parameters indicate a potential anaesthetic problem?
  7. How will the team respond to an anaesthetic problem?
  8. Are emergency drugs available and does the team know dose volumes for that patient?
  9. How will the patient be kept warm?
  10. Who will monitor the patient’s anaesthetic recovery?
  11. Who will monitor the patient post recovery (where many anaesthetic deaths occur)?

Much of the above becomes automatic in veterinary practice. The problem is assumptions are made that someone has taken responsibility for various parts of the process. This may not actually be the case. I suspect many animals are anaesthetised without any real understanding of their true risk factors. That drugs are selected without considering if better choices could be made. What happens when key personnel are away or new staff start with the practice? Are systems in place to ensure staff are competent to complete the tasks they have been assigned?

Staff Check List:

  1. Assign responsibility
  2. Use check lists
  3. Provide good systems
  4. Maintain staff training levels


The Equipment:

Most modern anaesthetic circuits have ‘out of circuit’ vaporizers. This means they are not part of the breathing circuit but rather add inhalation gas at a controlled concentration. Oxygen can be added to the circuit directly from a cylinder attached to the machine or through an oxygen concentrator or liquid oxygen. Most practices tend to utilise oxygen cylinders.

Equipment maintenance is essential. Unless it is regularly checked the practice doesn’t really know where it stands in terms of patient and staff safety. Rubber or plastic hosing is exposed to volatile anaesthetic gases plus regular wear & tear. Over time it perishes or cracks leading to gas leaks. Soda lime can cause erosion of metal and rubber fixtures resulting in incomplete sealing of soda lime canisters. Pop off valves can become sticky with time making breathing more difficult for patients.

Having an equipment check list is a useful resource to help practices ensure equipment failure is minimised. This should include checking oxygen supplies to ensure you don’t run out at a critical time.

Anaesthetic monitoring equipment is common place. Staff should know how to accurately interpret results and what they mean for the patient. This equipment also needs to be maintained to ensure it is functioning properly and accurate.

Equipment Check List

  1. Use check lists (check for leaks, check O2 levels, check inhalation gas levels etc)
  2. Maintain equipment (daily / weekly etc)
  3. Use equipment correctly (have on hand appropriate circuits for individual patients)
  4. Train staff to use equipment to a high standard



Anaesthesia is an every day event in most veterinary practices. It is so common it tends to become second nature. Because adverse events are rarely recognised there is little pressure to put in place systematic patient processes. Many get treated in an identical fashion irrespective of the differences that do exist. So are there benefits in having a more systematic approach to patient anaesthesia? Compared to our human counterparts, veterinary anaesthetic death rates are much higher. I suspect ‘anaesthetic incidents’ are also more common? Having thorough systematic systems won’t stop anaesthetic deaths but they are likely to greatly reduce the current rate and ensure patient safety and care is improved.





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