Anaesthesia

Fortunately, anaesthetics these days are extremely safe – especially compared to the “bad old days” of ten to twenty years ago, when monitoring equipment was less widely used and anaesthetic agents were less advanced. All anaesthesia carries risk; there is no escape from that fact, even for us humans! However, the risk is very minor, and adverse anaesthetic reactions are extremely rare, especially in young healthy patients.

Owners of older pets are often concerned about having them undergo anaesthesia. This is where modern anaesthetic agents, monitoring equipment and indeed the skill of the veterinarian come into their own. Anaesthetic risk does increase with age and ill-health, but the risks are very minor nevertheless. We will run through the basic anaesthesia protocol that is normal for most patients, then we will discuss the various extra options that are available for clients that wish to provide additional care to their pets, and especially for aging or ill patients.

Standard Quality Protocol

• Patients are given a “pre-anaesthesia” sedative injection about half an hour before the operation. At Southern Animal Health we use a combination of Acepromazine and Buprenorphine. Buprenorphine is an opioid analgesic (similar to morphine) that reduces the required dose  – and, therefore, the risks – of the anaesthetic agent required, as well as calming the patient and providing greater pain relief post surgery.
• When ready for surgery, the patient is “induced” into a state of general anaesthesia using an intravenous agent. There are many different types available. One of the most modern and safe induction agents is Alfaxan, which we use in both cats and dogs. The patient is asleep within five to ten seconds of Alfaxan being administered directly into the vein. Induction agents have a short duration of action; for example, a patient given Alfaxan will be awake again within five minutes. Hence we use this opportunity to place an endotracheal tube in the airway and connect the patient to a flow of oxygen and Isoflurane gas. Gaseous anaesthetics are the safest way to maintain ongoing general anaesthesia for as long as needed, and Isoflurane is one of the most modern of those available. Once surgery is complete, the Isoflurane is turned off and patients awake within five minutes. Having been given the analgesic Buprenorphine prior to surgery, and anti-inflammatory pain relief during the procedure, they awake calmly and comfortably.
• Throughout anaesthesia, the patient’s ongoing condition is assessed with monitoring equipment. This includes an ap-Alert machine which registers every breath the patient takes, and a Pulse Oximeter which monitors heart rate and blood oxygen levels, enabling anaesthesia to be modified as needed. In times past, gaseous maintenance anaesthesia and monitoring equipment were not commonly employed. These days they are available at most clinics, but if you’re concerned always feel free to ask what the protocol is used for your pet. Not all clinics follow the same protocols.
• All patients at Southern Animal Health are given Buprenorphine and Metacam pain relief injections to provide the smoothest post-surgical recovery possible. These are not standard across all clinics, so feel welcome to ask what your pet will be given, and how they will be anaesthetised.

The above regime describes very modern and safe anaesthetic practice which ensures very little risk of adverse reactions, even in old and sick patients. There are however, extra precautions that can be added to this regime for concerned clients, and especially for old and sick patients. We will describe these options, then explain the actual advantages of each.

Pre-Anaesthetic Blood Screen

A blood test prior to surgery may detect underlying conditions that don’t necessarily cause visible symptoms, but can affect an animal’s response to anaesthetic. Hence, a pre-anaesthetic blood screen is important in either sick patients, or geriatric patients. In young to middle aged patients who are well, we feel this screen is extremely unlikely to be rewarding, therefore we tend not to recommend these in such patients. The analogy we often use is one from head veterinarian Dr Marcus Hayes who cites: “I’ve had 10 anaesthetics in my life, and not once been offered a pre-anaesthetic blood screen”. So either us humans are not as important as our pets, or pre-anaesthetic blood screens they are largely over rated. We do feel these are a little on the retail marketing side of upselling items unlikely to be rewarding in 99.9% of cases. For our clients who still wish to have them however, you can ask on the day and they will be done ($110).

Intra-Operative Fluids

Intra-operative fluid therapy has a two-fold benefit. Firstly, it helps to counteract the drop in blood pressure that tends to occur during anaesthesia. Maintaining blood pressure reduces this risk factor and can help to protect against potential organ failure in sick and elderly patients. Secondly, young and old patients alike generally experience a better recovery from surgery if they are not in a state of dehydration. It’s amazing how patients that have had fluids are often quite bouncy and active even a few hours after anaesthesia.

Bottom Line

For older and sick patients, don’t be scared of anaesthesia to the point that a patient’s health may be more compromised by not performing a surgical procedure. Consider fluids as the main extra, and we, as clinicians, will advise whether a pre-anaesthetic blood test should be considered more strongly, but the choice is still there for you if costs are of no concern.