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Dog / cat narcosis and anesthesia: types and recommendations

Narcosis during the treatment of the dog

Narcosis - without it, it is hard to imagine any surgical intervention in a dog or cat.

The first mentions of painkillers come from antiquity - even then herbal extracts were used to relieve pain.

Virtually all surgical procedures are performed with the use of anesthetics.

They have many important tasks - in addition to relieving pain, they calm the animal, cause muscle relaxation and abolition of reflexes.

The frightened and stressed patient becomes calm and relaxed, unable to hurt himself and the doctor who tries to help him.

What are the types of anesthesia? Why are they used at all?

Why and how should your pet be prepared before the planned anesthesia?

I will try to dispel any doubts in the article below.

  • Types of anesthesia
  • Narcosis for surgery
    • Premedication
    • Induction
    • Maintaining anesthesia
    • Awakening the patient from anesthesia
  • How is anesthesia selected?
  • How to properly prepare a dog / cat for anesthesia?
  • Risks associated with anesthesia
  • How the doctor prepares the patient for anesthesia?
  • How much is anesthesia during the procedure?

Types of anesthesia

Types of anesthesia

Anesthesia can be divided into local and general.

Local anesthesia is painless and covers a specific area.

It is very often used for small, short procedures.

It is also used as an auxiliary, as an additional analgesic protection of the operated patient.

It works great, for example, in dentistry - anesthesia in the area of ​​the removed tooth significantly improves the patient's comfort after the procedure.

The duration of local anesthesia depends on the preparations used - it may provide an analgesic effect from several hours to one day.

The most commonly used methods of local anesthesia are:

  • infiltration anesthesia (administering small amounts of an appropriate agent to several places in close proximity to the place that should be excluded from feeling),
  • perineural anesthesia (administering anesthetics to the nerve area - then painlessness concerns the area from which the given nerve receives the stimuli),
  • local intravenous anesthesia (closing the vessel with a tourniquet and administering an anesthetic to it; then the preparation slowly seeps into the tissues supplied by the vessel).
  • Epidural anesthesia is one of the analgesia methods of the posterior parts of the animal's body; it is especially useful in farm animals, cows and horses - in dogs and cats additional pain relief is used if necessary after abdominal or pelvic procedures, but also in cases of caesarean section.
  • intra-articular anesthesia is also a type of local anesthetic; it is usually used during or immediately after orthopedic procedures - they maintain the analgesic effect of the agents administered generally; it is also worth using them for some injuries or degenerations.

General anesthesia is described as loss of consciousness coupled with loss of sensation.

This type of anesthesia should be combined with sleep, suppression or reduction in response to stimuli, suppression of pain sensation and muscle relaxation.

The types of general anesthesia are:

  • inhalation anesthesia,
  • infusion anesthesia,
  • mixed anesthesia.

The effect of anesthetics depends on many factors:

  1. Preparation dose - is calculated on the animal's body weight.
    The dose can be modified and adjusted to the mental state, agitation of the patient and the current medical conditions.
  2. Proper combining of drugs with each other - there are drugs that enhance their effect.
    In the case of some preparations, combining them with another substance can reduce the dose (and thus reduce the side effects associated with a specific drug).
  3. Route of administration:
    • intravenous administration usually produces a very quick effect.
      The drug or a mixture of drugs used to anesthetize the patient takes several seconds or several minutes.
      The dose of the preparations used should then be slightly lower than in the case of other routes of administration.
    • intramuscular administration of the preparation causes a noticeable effect after 10 - 20 minutes.
      The effectiveness of the action depends on the blood supply to the given muscle, the rate of drug absorption and the degree of its metabolism.
    • subcutaneous or intradermal administration - is rarely practiced when it comes to administering anesthetics.
  4. Concentration of the solution of the preparation used - the higher the concentration of the drug, the greater the intensity of its action.
    It may also affect the operating time. Unfortunately, it is usually associated with a greater likelihood of side effects.

Narcosis for surgery

Treatment for the dog

Surgical narcosis can be divided into the following phases:

  1. Premedication.
  2. Induction.
  3. Sustaining.
  4. Waking up.
  5. Post-anesthetic period.

Each of these phases has a different meaning and goals.

Each of them is important and it is difficult to ignore one in good patient care.

Different measures are used in different phases. I will try to discuss all of them in turn.

Premedication

Premedication is the first phase of anesthesia.

The purpose of premedication is to immobilize the animal, calm it down, reduce stress and relax the muscles. This makes it much easier to carry out further procedures.

In premedication, the first doses of painkillers are administered, preferably those that will work throughout the procedure.

It is also important to suppress sympathetic and parasympathetic reflexes.

Thanks to a properly conducted premedication, the doses of drugs used in subsequent stages of anesthesia can be reduced.

Four main groups of drugs are used in premedication:

  1. Cholinolitics - these are acetylcholine antagonists.
    They are antispasmodics, originally used to reduce salivation, reduce the secretion of glands in the respiratory tract and the digestive system, and increase the heart rate.
    Large doses of these drugs can cause seizures, lead to anxiety and confusion. They can cause lethargy.
    They are not recommended in patients with cardiological problems - they can cause ventricular arrhythmias, atrioventricular block.
  2. Phenothiazine-derived and butyrophenone transquilizers - cause relaxation and relaxation of muscles.
    After their administration, vomiting is not observed.
    They prevent cardiac arrhythmias, so they can be used in patients with cardiological problems.
    They work for quite a long time, up to 48 hours after administration.
    However, their use is associated with the risk of seizures, hallucinations and involuntary movements.
    Often there is hyperthermia and a significant reduction in blood pressure.
  3. Benzodiazepine derivatives - they cause the muscles to relax, but without the effect of calming the patient.
    They have an anticonvulsant effect and are recommended for use in patients with epilepsy.
    They are slightly stressful to the heart, but they cause agitation, especially in cats, they cause discomfort when administered intramuscularly.
  4. Alpha-2-agonists - cause drowsiness, sedation, muscle relaxation and painlessness after administration - therefore seem to be an ideal drug for premedication.
    Unfortunately, they do not work for every patient - they can cause atrioventricular block, reduce cardiac output, increase peripheral vascular resistance, so they must not be used in patients with cardiological problems.
    They can cause vomiting and respiratory depression.
  5. Opioids - cause severe painlessness, but without losing consciousness.
    They work very well in dogs, but in other species (such as cats), they can cause agitation.
    They can cause apnea, constipation and vomiting, but also diarrhea.

Drugs from these groups can be combined in an appropriate way, which increases the strength of their action and allows you to reduce the dose of individual drugs.

Induction

This phase of anesthesia deepens the effect achieved during premedication.

The animal relaxes, its muscles go limp, unconditional reflexes are abolished, it enters the sleep phase.

Preparations used for induction can be administered intramuscularly, but due to the effects they can cause, it is safer to administer them intravenously - a pre-applied cannula allows for quick administration of drugs in the event of an adverse reaction of the patient.

Drugs used in induction can also be used in the maintenance phase of anesthesia - however, using them in this way is associated with the inability to control their effects after administration.

The duration of action of drugs from this group varies - from a few minutes to 12 hours.

The main groups of drugs that are used to induce anesthesia are:

  1.  Barbiturates - this group includes long, medium and short-acting drugs.
    They are also used in the case of convulsions and strychnine poisoning.
    They significantly lower blood pressure, reduce blood flow through the brain and its neuronal activity - they are useful in neurosurgical procedures.
    They are metabolized by the liver, therefore they should not be used in patients with liver failure.
    Some drugs in this class can also cause the patient to agitate while awake.
  2. Etomidate - works practically immediately after intravenous administration, but the achieved effect lasts very shortly - about 15 minutes.
    It induces sleep, but has little analgesic effect.
    It is not recommended for use in patients with Cushing's disease and Addison's disease - it inhibits the adrenal function for up to 3 hours after administration.
    May cause vomiting and nausea, and animals that have been anesthetized with etomidate may experience seizures and involuntary muscle movements during recovery.
  3. Propofol - also has a very short duration.
    Similar to barbiturates, it has an anticonvulsant effect.
    He also has a weak analgesic effect.
    May cause respiratory depression and periodic apnea immediately after administration.
    It crosses the placenta and affects the fetuses in the uterus, it can be used with good effect in caesarean section.
    It accumulates in fat and is metabolized in the liver. It does not cause convulsions when awake.
  4. Chloral hydrate - was used to anesthetize horses, but due to a narrow margin of safety and respiratory depression, its use is being abandoned.
  5. Ketamine - causes deep unconsciousness, painlessness (but only superficial layers, not deep layers) and partial suppression of reflexes.
    It can cause excitement, fear and hallucinations, as well as salivation and tearing.
    Due to the numerous side effects, the use of ketamine is rather abandoned.

Maintaining anesthesia

Induction agents can be used to maintain anesthesia - they are then administered by slow continuous infusion or in a modified dose so that their duration of action covers the entire duration of the procedure.

Increasingly, however, to maintain anesthesia inhalation anesthesia.

This type of anesthesia is safe, it can be used in animals with various metabolic disorders, but also in species whose anesthesia is a challenge for a veterinarian - reptiles, birds, small mammals.

These agents are absorbed from the alveoli and are also excreted through the lungs.

The use of inhalation anesthesia requires the possession of appropriate equipment, as well as constant monitoring of vital signs, in the case of dogs and cats, the patient should also be intubated so that the anesthetic gas reaches only the patient's respiratory tract.

For small mammals and reptiles, special cages or containers for anesthesia are used.

The most commonly used preparation is isoflurane.

It anesthetizes the patient well, does not accumulate in the tissues, and its effect is quickly reversible.

Awakening the patient from anesthesia

After completion of the procedure or procedures, the patient should be awakened.

Not all drugs mentioned above have their antagonists.

You can reverse the action:

  • benzodiazepines,
  • alpha -2-agonists,
  • opioids.

Preparations used to wake up increase blood pressure and reduce drowsiness.

They are not used after each procedure - they can increase bleeding in the operated area.

They also put a strain on the heart, so they should not be used in patients with cardiological problems.

They are also not used in patients with epilepsy - they can trigger a seizure attack.

How is anesthesia selected?

How drugs are selected and the type of anesthesia?

The selection of anesthesia and anesthesia is a very individual matter.

The selection of drugs used for anesthesia is influenced by:

  • type,
  • race,
  • age and size of the patient,
  • health,
  • the presence of congenital or acquired diseases.

Chronic administration of drugs is very important as they may interfere with the effect of agents used for anesthesia.

In the case of unstable diseases, the doctor must take them into account - very carefully choose drugs, for example in the case of Cusching's disease, Addison's disease, problems with the thyroid gland or in patients suffering from diabetes.

The behavior, the patient's excitability and his resistance to pain are also a very important criterion in the selection of appropriate measures.

The expected duration of anesthesia and the assessment of the painfulness of the procedure are also very important.

The physician anesthetizing the patient should use drugs that he knows - knows from experience what dose will be appropriate for the patient and what side effects can be expected.

How to properly prepare a dog / cat for anesthesia?

First of all, you should absolutely follow the instructions of the doctor who will anesthetize your pet.

The standard recommendation is fasting before surgery.

Depending on the planned procedures, it is from 8 hours to even 18 hours without food before the procedure.

This is very important - even a small meal or light snack may disrupt the absorption of anesthetic preparations.

Additionally, after administration of some agents, vomiting or diarrhea occurs, even on the operating table, which makes the procedure difficult.

The exception is very young animals, miniature or small mammals - rabbits and guinea pigs should receive food until the procedure itself.

Before performing the planned procedure, it is worth performing a control blood test, including morphology and basic biochemical parameters.

Thanks to this, the anaesthesiologist has an understanding of the capacity of internal organs (liver, kidneys) and can select the dose and preparations for anesthesia in a way that will not burden the animal's body.

If some parameters differ from the established norms, it is worth conducting additional tests to determine the cause of the disorders and implement appropriate treatment.

Sometimes, when the procedure is not a life-saving procedure, it is worth postponing it to stabilize your pet's health.

A urinalysis is often recommended prior to anesthesia.

The urine test allows you to determine the quality of kidney function - the presence of a large amount of protein, sediment composed of crystals, red blood cells or a change in pH will indicate abnormalities.

This is very important because the metabolites of some of the drugs used for anesthesia are excreted by the kidneys - it can overload their work.

If any abnormalities are noticed in the urine test, the doctor who will anesthetize the patient, select drugs that will not burden the kidneys and will not affect their work.

In the case of middle-aged or older animals, it is worth carrying out a cardiological examination.

Patients with evidence of heart murmur in a clinical examination should also be referred for a cardiological consultation.

Panting with exertion, fatigue quickly and coughing at night should prompt the pet's guardian to carry out detailed examinations.

Assessment of myocardial function, contractility and valve function is very important when considering drugs used for anesthesia.

Cardiological problems mean that the doctor cannot use, for example, alpha-2-agonists, so it is worth determining before the procedure whether the pet's heart is healthy.

Depending on the procedure being performed, you may need additional tests.

Abdominal ultrasound, chest X-ray (with particular emphasis on the trachea or lung parenchyma), computed tomography are just some of the procedures that may be ordered by the doctor performing the procedure.

Risk related to anesthesia

Every preparation, from vitamins and supplements to anesthetic agents, has a list of side effects that it can cause.

The list of contraindications to use is just as long.

Therefore, it is important to check the health of your pet before the planned treatments.

The more information and test results the doctor has, the safer the anesthesia is.

How the doctor prepares the patient for anesthesia?

How the doctor prepares the patient for anesthesia?

After premedication, the dog or cat is also prepared for anesthesia by an anaesthesiologist or auxiliary staff.

First, a cannula is put on.

On the basis of previously performed blood tests, additional drugs or a drip with an appropriate infusion fluid are administered - depending on the results of the ionogram, the deficiencies of ions or the volume of circulating fluids are replenished.

Slow infusion of properly selected fluid affects the functioning of the kidneys and prevents dehydration.

If the decision to use inhalation anesthesia has been made, the patient is intubated.

This procedure involves anesthesia of the larynx and insertion of a tube into the trachea through which a mixture of anesthetic gases will enter the respiratory system.

Intubation is necessary in dental and thoracic procedures, but also in patients with tracheal collapse, laryngeal deformity and in brachycephalic breeds.

How much is anesthesia during the procedure?

The price of anesthesia depends on many factors.

First of all, on the amount of preparations used.

The price of anesthesia for a small cat is different than for an adult Great Dane.

It also depends on the type of medication used.

Newer generation agents, much safer and with fewer side effects after use, are usually more expensive.

The use of inhalation anesthesia usually has an additional cost associated with the use of patient monitoring equipment.

The price of anesthesia usually ranges from PLN 70 to PLN 300, added to the price of the procedure.

Another issue is the presence of an anesthesiologist in the operating room.

He will take care of the safety of the anesthetized patient, will monitor vital signs (number of heartbeats, blood pressure) and will take care of the pet during awakening.

It increases the chances of a safe course of anesthesia at every stage.

It is very important, especially in the case of prolonged procedures, or in patients with health problems - liver failure, kidney failure, diabetes, cardiological problems.

For the assistance of an anesthesiologist during the procedure, however, you must pay extra - an hour of work costs from 100 to 400 PLN.

Before the procedure, the caregiver should be informed about all forms of sedation offered by a given clinic or office and about the best method for a specific patient.

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