Questions about your pet's anaesthesia
Yes, it is crucial that your pet lies absolutely still in the scanner as any movement would result in having to repeat the image acquisition. An average MRI scan lasts for 45 min, which is obviously much too long for any animal to lie motionless.
Although the anaesthetists are rarely involved in initial consultations with pet owners, we spend most of our day in direct contact with animals before, during, and after anaesthesia, ensuring the highest standard of care However, should you wish to talk to an anaesthetist, please do not hesitate to ask. We will be happy to meet you and discuss your concerns.
We develop a pain control plan prior to the surgical procedure. When your pet returns to the ward after surgery, he or she will be assessed and the pain control protocol will be started. From that point onwards, each patient is assessed every 2 hours. If pain control is required beyond 24 hours, an anaesthetist will examine the ward records and decide the level of ongoing pain management required. In the majority of cases, patients are discharged only when we are confident that any residual pain can be controlled my mild generic pain killers or anti-inflammatory drugs.
Administration of sedatives and anaesthetics in animals with a full stomach presents an increased risk of complications. The drugs used may affect the function of the digestive system and we would prefer to keep any risk to an absolute minimum.
What are Anaesthesia and Analgesia?
The majority of diagnostic investigations and surgical operations performed at DWR will require the administration of a sedation or a general anaesthetic. Procedures that people would usually undergo conscious can require sedation or general anaesthesia in pets. After all, it is tricky to ask your pet to lie still, and hold their breath on command for an X-ray, or to open their mouth wide for us to get a good look inside!
Sedation is provided by the administration of sedative drugs that can make your pet calm and compliant, whereas general anaesthesia is a state of controlled unconsciousness obtained with the administration of anaesthetic agents. General anaesthesia is usually induced with the intravenous administration of an induction agent and, once the trachea is intubated, maintained with the administration of a mixture of anaesthetic gas and oxygen.
Analgesia is the provision of pain relief for your pet, which is an essential part of the perioperative management of hospitalised patients. Your pet may experience pain because of an underlying condition (for example osteoarthritis) or as a direct consequence of an elective surgery. A balanced analgesia is usually achieved with the use of different techniques and titrated to obtain the effect that is desirable for your pet. There are different tools to assess pain and guide analgesic treatments in pets, and Dick White Referrals continuously invest to guarantee that your pet receives the best possible care.
Our Anaesthesia Team
At DWR, we have one of the largest and experienced team of vets and veterinary nurses across Europe who have undergone further specialist training in veterinary anaesthesia and analgesia, or who are currently undertaking their specialist training here. The team is composed of Specialist anaesthetists (ECVAA or ACVAA Diploma holders), clinical anaesthetists, trainee anaesthetists and anaesthesia nurses.
An anaesthetist is usually assigned to all surgical and advanced imaging procedures (MRI and CT), as well as other diagnostic imaging procedures (X-ray and ultrasound) where procedures can be challenging and the patients more unwell, or with co-existing disease (for example: heart disease, or poorly controlled diabetes). Our anaesthetists also advise in unstable or challenging medicine and dentistry cases, and for hospitalised patients requiring additional help as the pain they are experiencing is more difficult to manage.
Anaesthesia and your Pet
The anaesthetist in charge of your pet will create a bespoke anaesthetic plan for them, taking into account:
- a pre-anaesthetic physical examination of your pet, focusing on their cardiovascular and respiratory systems;
- your pet’s medical history and current condition(s)
- medication(s) that your pet currently receives. Some medications may have an interaction with the anaesthetic drugs or dosages might be modified;
- results of blood tests and diagnostic imaging (X-ray, ultrasound, MRI or CT);
- the procedure your pet requires
Sometimes during a pre-anaesthetic examination, the anaesthetist may find an abnormality for which we suggest further investigation, for example further blood tests, or advice from a cardiologist for an abnormal heart rhythm or heart murmur. Anaesthetics affect the functioning of the cardiovascular and respiratory systems, whilst the liver and kidneys help metabolise and eliminate the drugs we give, so it is important to understand as best we can in cases where there might already be some impaired function, what effect our anaesthetic drugs could have and what choices we can make to avoid or lessen their impact. The anaesthetist would discuss any further tests with the vet responsible for your pet, who would keep you informed.
The anaesthetist will be with your pet from administering their anaesthetic drugs at the beginning, throughout their procedure, until they are suitably recovered to go back to their ward. Once anaesthetised, the anaesthetist will monitor your pet with the use of multiparametric modules to check the cardiovascular and respiratory systems and minimise the possible complications that may occur during the procedures. Mechanical ventilation and active warming can be required to support the respiratory functions and body temperature.
Sometimes the anaesthetist will need to perform blood tests during the procedure, for example, to monitor glucose. For painful procedures, an intra-operative analgesia plan specific for your pet is formulated. This can be via analgesic drugs given intravenously or by local anaesthetic techniques (see later). Your pet’s anaesthetist will also make an analgesia plan for the post-operative period to keep them comfortable as they recover from their procedure.
General Anaesthesia Risk and Adverse Events
The anaesthesia team at DWR uses state-of-the-art monitoring equipment appropriate for the level of risk of the procedure, the likely complications and the health of your pet. This is useful to help with monitoring your pet continually through their procedure. Monitoring has been shown to increase the safety of general anaesthesia and assists us in identifying complications and acting early, should they arise.
The safety of veterinary anaesthesia has been studied worldwide. Death associated with anaesthesia looking at all healthy and sick dogs ranges from 0.17% - 0.65% (1 to 4 cases in 600), and 0.24 % (1 in 419) in all sick and healthy cats. The risk has been shown to be associated with how healthy your pet is at the time of anaesthesia (as part of the pre-anaesthetic examination and planning, your pet’s anaesthetists assesses this according to the Association of American Anaesthesiologists physical status classification). Systemically unwell dogs are at 26 times increased risk of death (1 in 75, versus 1 in 1849 in healthier pets) and cats 12 times increased risk of death (1 in 71, versus 1 in 895) compared to the mortality rate in a healthy patient. In both cats and dogs, the risk is also increased in urgent procedures, major procedures and with older age (greater than 12 years old).
General anaesthesia is associated with other risks:
Low blood pressure (hypotension) – this is fairly commonly seen in pets under anaesthesia (38 in 100 dogs) and if it is a side effect of the anaesthetic drugs used, it is usually treatable. However, in patients with pre-existing organ dysfunction (for example, chronic renal insufficiency), low blood pressure can worsen the dysfunction. Low blood pressure can be harder to treat and be more severe in systemically unwell patients where its reason may be associated with co-existing medical conditions.
Regurgitation – this is where stomach fluid/content enters the oesophagus and mouth. Regurgitation can lead to inflammation of the oesophagus, and leakage of the fluid into the lungs (aspiration pneumonitis and/or pneumonia). In patients with pre-existing breathing difficulties or lung disease, or if the amount entering the lungs is large enough, aspiration can result in alteration of gas exchange which lead to hypoxaemia (low oxygen level in the blood). In healthy animals not prone to regurgitation, the risk is less than 1 in 100 patients (dogs). The endotracheal tubes (the tube placed into the patient’s trachea, or windpipe, to administer the anaesthetic gas and oxygen) are designed with sealing cuffs to minimise the risk of the fluid entering the lungs under anaesthesia, though regurgitation can also happen in certain conscious or immobile patients. This is also the reason why elective patients are starved on the day of their appointment in case a sedation or anaesthetic is scheduled for the same day as a full stomach increases the risk of regurgitation. However, in specific conditions affecting the ability of the pet to regulate their blood sugar, or in very young patients, the clinicians might advise to give a smaller meal, but you will be told if this is the case.
Worsening of heart disease – anaesthesia challenges the cardiovascular system, and patients with moderate or severe pre-existing heart disease are at risk of developing congestive heart failure in the perioperative period as their heart may have had to work at its maximum capability under the general anaesthetic.
Worsening of Canine Cognitive Dysfunction – post-anaesthetic cognitive dysfunction is recognised in some elderly human patients after general anaesthesia. Though not investigated in relation to anaesthesia in dogs and cats, these observed age-related changes in your pet’s routine and behaviour can worsen after general anaesthesia.
Allergic reaction to anaesthetic drugs used – this is quite rare. However, it is helpful to know if your pet has had any other reactions to previous anaesthetics they have experienced, as well as how they recovered from them. Your referring vet will provide us with your pet’s history, so the anaesthesia team should know which drugs have been used.
Whilst if sedated your pet remains more conscious though relaxed, and is able to swallow, for some pets and for specific procedures, a general anaesthetic is a safer option. We might be able to avoid the likelihood of some undesirable side effects related to the drugs used or the procedures.
After the Anaesthetic
If your pet returns home the same day as the anaesthetic, you might find they are more tired than usual, and might not want to eat a meal that day. This should disappear as the effects of the anaesthetic drugs wane. Make sure they have a quiet, safe and warm area to rest. Specific instructions dependent on your pet’s condition or procedure will be given to you by the vet looking after your pet. More often, and in the case of most surgical procedures, your pet will stay in the hospital for longer, dependent on their procedure, recovery and any further monitoring that they need. Whilst in hospital, their level of comfort is regularly assessed using pain-assessment scales, and pain relief administered based on their specific requirement.
Use of Locoregional Anaesthesia
Local anaesthetics interrupt painful impulses travelling along nerves : the area served by the nerve is “numbed”. This is performed by personnel of the anaesthesia team under close supervision with an experienced anaesthetist.
Local anaesthetic nerve block
Using anatomical landmarks, often with ultrasound or electrical nerve location guidance, local anaesthetic can be placed around different nerves serving different anatomical areas (for example, individual limbs, or areas of the thorax or abdomen), or between muscle layers therefore blocking the experience of pain. This is similar to having local anaesthetic for a tooth removal with your dentist. Use of local anaesthesia leads to increased comfort for your pet into the perioperative period, and helps to achieve a more stable anaesthetic. These techniques minimise the requirement of additional pain-relief drugs, limiting their side effects. Complications are possible but rare and include anaphylactic reaction to local anaesthetic; local anaesthetic toxicity; mis-injection into nearby structures; infection; nerve damage; the nerve block not working.
With this technique, local anaesthetic and other pain relief can be injected into the epidural space around the spinal cord within, to provide analgesia to large parts of the body, for example the entire abdomen. You may be familiar with this as a method of pain relief during childbirth. As with other nerve block techniques, it provides stability in addition to long-lasting analgesia (up to 24 hours depending on drug combination used). It will usually also affect the hindlimbs to some extent depending on the drugs used, and the injection site. Major complications are rare but include anaphylactic reaction to local anaesthetic; local anaesthetic toxicity; cardiopulmonary arrest; infection or abscess formation; nerve damage. Haematoma formation; mis-placement and injection into surrounding structures (muscles or closer to the spine); neurological deficits; pruritis; urinary retention are also minor complications that can be encountered.
For procedures where we would like to prolong the benefits of epidural analgesia, a specific catheter can be placed into the epidural space. This allows us to give repeated epidural injections, and also adjust the volume and interval of of drug administration based on your pet’s need. As well as the those with epidural anaesthesia above, complications arising from catheter placement include dislodgement of the catheter (most common); misplacement of the catheter or knotting or looping within the spinal canal causing entrapment of the catheter, both of which are rare.
We, the anaesthesia team at DWR, have your pet’s interests and welfare at the forefront of our work. We want your pet to be as comfortable as possible whatever they are visiting us for, to assist our colleagues in other departments to diagnose and treat your pet, and to keep your pet as safe and healthy as possible whilst we are caring for them.
Should you have any questions about anaesthesia and analgesia at Dick White Referrals, please email reception who can pass on your questions. For specific queries relating to your pet, please ask the vet responsible for your pet, who can put you in touch with the anaesthesia team.
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Royal College of Anaesthetists website: <https://www.rcoa.ac.uk/>