Pre anaesthetic assessment: what to know before a sedation

A pre anaesthetic assessment is not paperwork: it exists to build a tailored protocol. A dog with a heart murmur, a cat with reduced renal function and a rabbit in gastrointestinal stasis need different drugs, fluids and timings. If that information only surfaces on the morning of the procedure, the options are to postpone or to proceed with a smaller margin. When the assessment happens a few days earlier there is time for an extra test, for a cardiology referral or for stabilising an ongoing treatment.

The conversation gathers three categories of information: clinical history, the medicines and supplements actually given, and previous anaesthetic experiences. The third is the one most often forgotten and it carries real weight: an agitated recovery, significant vomiting or an episode of hypothermia during a past procedure will change the protocol for the next one.

Before every anaesthetic the animal is placed in a risk class, using a scale applied worldwide in both human and veterinary medicine. It is not a prediction of what will happen but a snapshot of health status at the time of the procedure. It guides how much preparation and monitoring are required, and it should be explained to the owner in plain words.

Risk is not the same across classes and not the same across species. In the largest multicentre survey on this question, perioperative mortality within forty eight hours was around 0.05 per cent in healthy dogs and 0.11 per cent in healthy cats, rising to roughly 1.3 and 1.4 per cent respectively in animals with systemic disease. In rabbits the figures were higher in both conditions. These numbers explain why the same procedure is approached with different precautions in two different animals.

The recurring question is whether blood tests are truly needed in an animal that seems well. The honest answer is that it depends on age, species, known disease and type of procedure. In a healthy young adult a basic panel finds unexpected abnormalities in a minority of cases, but when it does it changes the protocol. In an older animal, in one with chronic disease or before a long surgery the informational value rises sharply.

• Complete blood count: detects anaemia, platelet abnormalities and signs of inflammation that alter fluid management and drug choice.
• Biochemistry with renal and liver values: liver and kidneys metabolise and clear most anaesthetics, so impairment calls for different doses and timings.
• Urinalysis with specific gravity: in cats it is often more sensitive than blood values alone for detecting early loss of renal function.
• Blood pressure: particularly useful in the older cat and in any animal with known renal or cardiac disease.
• Echocardiography: indicated when there is a murmur, an arrhythmia, a predisposed breed or a history of exercise intolerance, because a murmur alone does not tell you how severe the heart disease is.
• Clotting profile: reserved for cases with abnormal bleeding, suspected poisoning or liver disease, not required routinely.

Tests should be recent enough to be representative, usually within the preceding two to three weeks in a stable animal, and much closer to the date if the condition is changing. Keeping earlier reports adds value: a single value says little, while the same measurement repeated over time tells you whether something is deteriorating.

Fasting reduces the risk of regurgitation and aspiration during induction. The old habit of removing food the evening before and water at midnight has been revised: excessively long fasts increase reflux rather than reducing it, and in small patients they encourage hypoglycaemia. Current guidance has shortened the interval, but the final word always belongs to the clinic performing the procedure, because it varies with the type of intervention.

Ongoing chronic treatments need an explicit decision for each one: some are given as usual even on the morning of the procedure, others are suspended, others reduced. This is not a call to make on your own. It is worth asking, for every item on the list, whether it should be given or skipped, and writing down the answer rather than trusting memory.

A safe anaesthetic depends not only on drugs but on who is watching the animal while it sleeps. The widely shared minimum includes a person dedicated to monitoring, venous access, temperature control and instruments measuring oxygenation, rate and pressure. Asking which of these are in place is not suspicion: it is the question that reveals how the procedure is run.

• A dedicated person: someone whose only job during the procedure is to follow the anaesthetic and record parameters at regular intervals.
• Placed intravenous access: allows fluids and emergency drugs to be given in seconds rather than minutes.
• Pulse oximetry and capnography: measure oxygenation and ventilation, and flag a problem before it becomes visible to the eye.
• Blood pressure: hypotension is among the most frequent complications and among the most correctable when seen in time.
• Active temperature control: hypothermia slows drug metabolism, prolongs recovery and raises the risk of complications.

The most delicate phase is not induction but recovery. In the same multicentre survey cited above, roughly half of deaths in dogs and an even larger share in cats occurred in the postoperative period, mostly within the first three hours after the end of the procedure. This is why an animal should not be left alone in a kennel straight afterwards, and why discharge should follow stable parameters rather than the clock.

1. 1

   Prepare the medication list

   Write down every drug and supplement with dose and time of the last administration, including antiparasitic products applied in the preceding weeks. Bring the most recent weight too, measured on the scale you normally use.

2. 2

   Retrieve earlier test reports

   Even ones from several years ago. They allow values to be compared and show whether an abnormality is new or has been stable for a long time. An archive ordered by date makes the comparison immediate.

3. 3

   Describe past anaesthetics in detail

   Saying it went fine is not enough. Vomiting, agitated recovery, prolonged shivering, a slow return to normal or lost appetite in the following days are all useful inputs to the next protocol.

4. 4

   Ask three things explicitly

   Which risk class has been assigned and why, what monitoring will be used, and what the discharge criteria are. These are questions a professional expects and answers willingly.

5. 5

   Agree the pain plan and the return home

   Ask how pain will be managed in the following twenty four hours, which signs should make you call back and when the first check is due. Set the reminder before you leave the clinic.

Back home the rule is a quiet environment, a comfortable temperature, no stairs, no other animals climbing on top and water offered in small amounts once swallowing is normal again. Some drowsiness in the first twelve hours is expected; what is not expected is repeated vomiting, laboured breathing, pale gums, inability to stand or pain that does not respond to the agreed plan.