Why does my pet need to be sedated/anaesthetised?

Hospitalised pets experience some degree of stress, which can relate to separation anxiety, being in a new environment, seeing other animals and being unwell. Physical restraint will add a further source of stress, and this will affect your pet's behaviour. Some non-invasive procedures require uncomfortable positioning (x rays, for example), or pressure on parts of the body (eg ultrasound). It is not possible to explain to an animal that this discomfort is temporary and necessary in order to investigate and treat its condition. Sedation will decrease the stress experienced by the animal, result in a diagnostic investigation of better quality.

It is not possible for owners to be present to manually restrain their pet for imaging procedures, both because of strict laws protecting humans from exposure to even small doses of radiation and simply because this interferes with / distracts veterinary personnel from doing their job.

Why is it necessary to starve my pet?

Administration of sedatives and anaesthetics in animals with a full stomach presents an increased risk of potentially serious complications. This does not mean that the animal will encounter the complication but, in view of the potential gravity of complications, it is generally not worth taking this risk. Sedation and anaesthesia may affect the emptying of the stomach and the function of the gastrointestinal system, and it is also possible that the food and fluids in the stomach may reach the mouth, and enter the airways, reaching the lungs. This complication, although rare, is very serious and will result, in the best case scenario, in a considerably longer hospitalisation, to treat pneumonia. In some patients the risk of prolonged starvation is more significant than the likelihood of this complication occurring. Therefore we may advise only a short fasting period or none at all. You will be instructed about starving your pet before your appointment.

What is the risk of serious complications?

The risk of fatality caused by anaesthesia alone is extremely low in dogs and cats, and it is difficult to quantify, due to the possible complications related to the procedure. Generally speaking, the more unwell the patient, the greater the risk related to anaesthesia and the procedure. If your pet is considered to be at an increased risk of anaesthetic complications, you will be informed about this.

What does sedation consist of?

We will administer a combination of drugs to your pet. In order to achieve a rapid and predictable onset of the effect, we will administer the drugs intramuscularly (usually in the back muscles) or intravenously. In the latter case, we will clip the hair on top of a vein, place a cannula inside the vein and administer the drug. We will try to minimise the size of the clipped patch but please remember that clipping is necessary to allow proper disinfection of the skin and prevent infections. Positioning of an indwelling venous cannula will also allow prompt administration of other treatments, if necessary. The choice of the sedative drug to be administered and its dose will be based upon the temperament of the animal, the presence of medical conditions and the desired duration of sedation. The most appropriate sedation for your pet will minimise possible side effects and result in a prompt recovery. Before administration of the sedative drug, the animal will undergo a thorough physical examination by a veterinary surgeon and, if necessary, blood tests will be performed. A record of the drugs used for the sedation and their effect will be added to the clinical notes of the patient, for future reference.

What if my pet hates vets/may be aggressive?

This is a good question! We will try to do our best to examine your pet thoroughly, even if it is not very 'friendly'. However, in some cases this will not be possible and we will have to proceed with sedation in order to allow physical examination and blood sampling. In this event we will rely on the history of the patient to identify conditions that may represent a contraindication to administration of certain drugs. Aggressive patients are notoriously difficult to sedate, as they 'fight' the sedation. Although more time consuming, we will try to use the minimal dose of sedative that we deem likely to allow management of the patient, even if this means still using a muzzle to prevent injuries to our staff. Sometime it will be necessary to administer a second dose of the drug. Generally speaking, extremely aggressive patients are slightly more at risk of presenting side effects after administration of sedatives and anaesthetic, because we cannot perform a thorough physical examination and we may have to use higher doses of the drugs. Please consider, however, that genuinely aggressive patients are relatively rare, and most of the time aggression is caused by stress, fear, anxiety or simply guarding the owner.

What does general anaesthesia consist of?

Anaesthesia in a pet is very similar to that of human beings. Every patient, before undergoing anaesthesia, will be examined thoroughly. This usually happens in the ward, and the purpose of this physical examination is to rule out presence of conditions that may require particular attention during anaesthesia. Generally speaking, we will establish the level of fitness of our patients and assign them a score from 1 to 5, one being a healthy animal, and 5 a moribund one. We will also consider the temperament of the animal, as this may affect the choice of anaesthetic drug or the need for post operative sedation. We will then administer a drug (pre-anaesthetic medication) to calm the patient, provide some pain relief and allow placement of an intravenous cannula for drug and fluid administration. The animal will still be able to walk, and behave nearly normally. However, it will be less interested in its environment. After about 20-30 minutes the patient will be brought to the theatre preparation area. We will perform a physical examination to assess the impact of pre-anaesthetic medication of the cardiovascular and respiratory system, then we will proceed with the intravenous administration of a drug that will cause the animal to loose consciousness, and relax the muscles. We will then place a specially designed tube in the trachea (windpipe). This will allow administration of oxygen and anaesthetic vapours in a very controlled way. We also will be able to take over breathing of the animal, to ensure optimal respiration. Physiological monitoring will be instituted, including electrocardiography, blood pressure, composition of the gas inspired/expired and temperature. In the theatre preparation area the part to be operated will be prepared for surgery. Local anaesthetic techniques will be used whenever possible (it depends on the type of the surgery) to reduce intra and post operative discomfort. If locoregional techniques cannot be used, one or more strong pain killers will be administered during surgery. The animal will then be transferred to theatre and undergo surgery. During the operation we will use purpose-designed devices to prevent the animal becoming cold, as hypothermia (low temperature) is one of the most common complications after anaesthesia and surgery. Monitoring of the cardiovascular and respiratory function will continue until recovery is complete and, in some animals undergoing major procedures, in the ward after recovery, until we are sure that the risk of complications is negligible. Careful monitoring will ensure that the anaesthesia is sufficiently deep to maintain unconsciousness and prevent pain from causing changes in blood pressure and heart rate. The anaesthetist will keep a detailed record of the anaesthetic procedure, and this will be filed in the clinical notes of the animal.

What about pain relief?

Control of perioperative pain (analgesia) is an important part of our work. We will begin planning analgesia from the pre-anaesthetic physical examination. Depending upon the procedure, the temperament of the patient and the presence of medical conditions, we will establish which drugs or techniques are the most suitable to control perioperative pain. Because the use of locoregional anaesthetic techniques is known to provide the best intraoperative control of pain and also decrease post operative pain, we try to use them whenever possible. Once in the ward, the level of comfort of the patient will be assessed at least every 2 hours by a fully qualified nurse or a vet for 12-24 hours. An anaesthetist will then examine the ward records and the patient and decide how to plan pain management, if still necessary. Since pain is a subjective experience in animals, as it is in human beings, we will administer pain killers according to the individual needs of the patient. Some animals need pain killers every 2 hours, others every 4 hours and others do not need them at all. In order to avoid unnecessary or insufficient administration of pain killers, we use a dedicated pain scoring system that will indicate when the animal requires administration of a pain killer. Although time consuming, we assess the patients every 2 hours, to allow early intervention and minimise the risk of breakthrough pain. In some cases we will use a patch to deliver strong pain killers. If this is the best option for your pet, you will be instructed on how to manage it. With some rare exceptions, your pet will be discharged only when we are confident that pain will not be an issue and mild generic pain killers (anti inflammatory drugs) will be able to control it.

What does ‘locoregional’ techniques mean?

The term 'locoregional techniques' encompasses a variety of interventions aimed at selectively "numbing" the part of the body undergoing surgery. Most commonly these techniques involve administration of a drug (local anaesthetic) in the proximity of a nerve or the spinal cord. While systemic administration of pain killers will make the pain bearable, locoregional techniques will completely remove any type of sensation from the part of the body undergoing surgery for the duration of surgery and for some time afterwards. This will result in better pain control after surgery and studies performed in people have also demonstrated a positive effect on outcome and a more rapid discharge. Locoregional techniques will allow us to use less anaesthetic drugs to keep the patient asleep, resulting in less depression of the cardiovascular and respiratory systems.

What if my pet has had a ‘funny’ reaction before?

Reactions are very uncommon with modern anaesthetic and sedative drugs, but they are still possible. We will try to establish, from the history of the patient, the referral letter from your vet and, in certain cases, by talking with your vet, which drug(s) or event caused the incident. We will then try to avoid the suspected drugs. Veterinary surgeons specialised in anaesthesia have a great familiarity with a large number of anaesthetic drugs and their possible complications. With their experience they can choose the combination of anaesthetics that is less likely to cause an adverse reaction and put in place all the necessary steps to identify and treat possible complications.

What is a veterinary anaesthetist? Can I discuss concerns?

Just as veterinary surgeons can specialise in such areas as medicine, neurology or surgery, a small proportion of veterinary surgeons dedicate their professional life to anaesthesia, pre-operative care and pain management. We are rarely involved in initial consultations with pet owners but we spend most of our day in direct contact with animals before, during, and after anaesthesia, ensuring the highest standard of care by using the most advanced equipment and techniques available. As with other disciplines, we undergo lengthy training and examinations to become a specialist. We have to keep up to date with the evolution of anaesthesia, analgesia and perioperative care, as our specialists status is re-assessed every 5 years.

Don't worry. It is normal to be concerned when your pet is sick, and needs to be sedated or anaesthetised. If you wish to talk to an anaesthetist, do not hesitate to ask. We will be happy to meet you and discuss your concerns.

Selected publications

• Wheeler DW, Thompson AJ, Corletto F, Reckless J, Loke JC, Lapaque N, Grant AJ, Mastroeni P, Grainger DJ, Padgett CL, O'Brien JA, Miller NG, Trowsdale J, Lummis SC, Menon DK, Beech JS (2011) Anaesthetic impairment of immune function is mediated via GABA(A) receptors.
  PLoS One. 24;6(2):e17152.
• Sarotti D, Rabozzi R, Corletto F. Efficacy and side effects of intraoperative analgesia with intrathecal bupivacaine and levobupivacaine: a retrospective study in 82 dogs (2011)
  Vet Anaesth Analg. 38(3):240-51
• Corletto F.(2011) Oxygen: when less may be more. Vet Rec. 169(17):437-8.
• Aprea F, Vettorato E, Corletto F (2011) Severe cardiovascular depression in a cat following a mandibular nerve block with bupivacaine. Vet Anaesth Analg 38: 614-618.
• Vettorato E, Corletto F (2011) Gabapentin as part of multi-modal analgesia in two cats suffering multiple injuries. Vet Anaesth Analg 38: 518-520.
• Vettorato E, Bacco S (2011) A comparison of the sedative and analgesic properties of pethidine (meperidine) and butorphanol in dogs. J Small Anim Pract 52: 426-432.
• Vettorato E, Chase-Topping ME, Clutton RE (2010) A comparison of four systems for scoring recovery quality after general anaesthesia in horses. Equine Vet J 42: 400-406.
• Vettorato E, Zonca A, Isola M et al. (2010) Pharmacokinetics and efficacy of intravenous and extradural tramadol in dogs. Vet J 183: 310-315.