Important

Question 1

General anaesthesia

Answer 1

Loss of consciousness and reduction of motoric and sensory functions to a level, where any operation can be done
o Unconsciousness + analgesia + muscle relaxation
o Retained respiratory and cardiovascular functions!

Question 2

Neuroleptanalgesia

Answer 2

(superficial sleep with analgesia)

tranquilizer + opiate

Question 3

Procedure of anaesthesia

Answer 3

1. Premedication (before surgery): sedatives + analgesics
   o Sedatives: tranquilizers, benzodiazepines, alpha2-agonists
   o Analgesics: opiates, NSAIDs, ketamine
   o Post narcotic excitation: treatment, as inhibitory parts of the brain are still inhibited. F.e. Diazepam before surgery, prevent animals waking up screaming.
2. Induction: injectable anesthetics (barbiturates, propofol, etomidate, steroids, ketamine)
   (rarely inhalational anesthetics (sevofluran) – e.g. rodents)
3. Maintenance:

   a. inhalational anesthetics
   b. injectable anesthetics (propofol, ketamine)

Question 4

Injectable anesthetics

Answer 4

-Barbiturates:
• Long Acting: Phenobarbital
• Short acting: Pentobarbital
• Ultrashort Acting: Thiopental, Thiamylal, Methohexital
-Propofol
-Imidazoles: Etomidate, Metomidate
-Dissociative anaesthetics: Ketamine, Tiletamine
-Steroid anaesthetics: Alfaxlon, Alfadolon

Question 5

Propofol

Answer 5

-Mechanism of effect: binds to GABAA receptors, Cl-ion channel opening delayed, hyperpolarization
-Pharmacological effects:
o Unconsciousness
o Good muscle relaxation
o NO analgesic activity (NSAIDs, opiates)
o Anticonvulsant effect
o Duration: Dogs recover fully after 20 mins, Cats 30 mins
o Quick and smooth recovery (“good dream”)
o Bronchodilation (asthma, pneumonia, ideal when operating on animals with resp. disease)
o ICP (during head trauma or due to heat shock), IOP (glaucoma)
-Side effects:
o Resp. dep., apnea (30-40%) (NB! Adm. slowly, until effect)
o Negative inotropic –> hypotension
o Postnarcotic excitation (pre-narcotic: rare)
o Septicaemia
o Pancreatitis
o Increased appetite
-Pharmacokinetics:
o Administration: IV
o Distribution: crosses placenta but safe if operation is completed within 18-20 minutes
o Metabolism: slower in cats
o In hepatic and renal failure extrahepatic metabolism (e.g. lung) contributes to elimination!
-Dose:
o Alone: 6-8mg/kg bolus (repeat)
o Continuous infusion: 0,2-0,4 mg/kg/min
o Can be combined with: ACP (4-5 mg/kg), Medetomidine (3-4 mg/kg)
-Indications:
o Simple surgical interventions
o Induction
o Antiepileptic
o TIVA: if combined with analgesic drug (medetomidine, midazolam) (bradycardia can be controlled with atropine)

Question 6

Ketamine, Tiletamine

Answer 6

Dissociative anaesthetics - NMDA antagonists
•Only anaesthetic group with analgesic properties!
•DOA: 60-90 min
•Mechanism of effect:
o Dissociation by acting on NMDA-receptors (others act on GABA receptors!)
o Dissociates connection bw Limbic and Thalamic systems.
•Pharmacological effects:
o Dissociation from environment, causing hallucinations, but NOT total unconsciousness.
o NMDA receptors play important role in pain perception, so blocking them causes analgesia, but mainly for body surfaces not serosa. (not enough for abd. surgeries - combined w. morphine derivative if cutting serosa)
o Prevent sensitization to pain (balanced anaesthesia)
o NO muscle relaxation, NO unconsciousness
o Moderate anaesthetic
•Side effects:
o Pronounced catalepsy (incr. tone of muscles) –> hallucination (bad dreams), hypotonic muscles, tremors, convulsions, sometimes seizures (counteracted if using benzodiazepines or α2-agonsits)
o Resp. muscles dyspnoe (laboured breathing)
o Mild stimulant of CV system (dose dep.): incr. HR and BP
 Incr. sympathetic tone (sensitize heart to: adrenaline, noradrenaline, dopamine) – causing hypertension and arrhythmias! NOT to heart problem patients!
• Do not give to a dog that already has arrhythmias!
• Useful in risk patients (after accident, shock, dehydrated, old)
o Incr ICP and IOP (head trauma: do NOT use)
o Protective reflexes retained (coughing reflex) – Can’t intubate
o Eye, jaw tone maintained (eye remains open – hydrate/lubricate eye surface to protect the cornea) (jaw tone: not good to clean teeth – can be bitten)
o “Bad dream” - hallucinations
o Very delayed recovery (6-7 hours), can be screaming, staggering, vomiting some hours later
•Pharmacokinetics:
o IV. & IM. (mild tissue irritation - painful) or nasal mucosa
o Elimination: dog: metabolises in liver and eliminates quickly in kidney, cat: low grade metabolism & kidney excretion of active compound primarily
o Contradicitons: head trauma (ICP), glaucoma (IOP), liver failure (dog), kidney failure (cat), cardiac failure/stenosis, hypertyhroidism (older cats, can cause arrythmias)

Question 7

Combinations of Ketamine

Answer 7

-Anaesthesia in combinations: used alone in amphibians, reptiles & cats – not sensitive to hypotonicity of muscles
-Analgesia during surgery in very low dose!
-Xylazine, medetomidine, demotidine (a2-agonist): dog, cat, horse (middle aged, healthy patients)
 Total anaesthesia: Unconsciousness, analgesia, muscle relaxation
 Contraindicated in heart failure patients
-Diazepam, midazolam, zolazepam (Zoletil®): unconsciousness, analgesia (not so pronounced), muscle relaxation
 Use in risk patients, very old/young animal, animals in bad shape
 Very safe
-Acepromazine: unconsciousness, analgesia

Question 8

Alfaxalon+alfadolon (3:1) (Saffan®), Alfaxalon (Alfaxan®)

Answer 8

-Steroid anaesthetics
-Mechanism of effects: GABA agonists
-Pharmacological effects:
o Unconsciousness
o Dose dep. narcosis and muscle relaxation
o NO analgesia
o Decr. cerebral BP and oxygen consumption –> good for head trauma
• Side effects:
o Saffan: contains cremophor as vehicle - cause histamine release in dogs (hypotension and shock), ONLY used in cats!
*Ear oedema, rarely necrosis in cats
*Pulmonary oedema - rarely (1:1000)
o Alfaxan:
*Cyclodextrine in an aqueous solution - does not cause histamine release - used in BOTH dogs and cats
*Hypotension for both products
*Pre and post narcotic excitation if stimulated
*Vascularization is frequent with steroid anaesthetic use
*Sensitivity to loud environments
-Pharmacokinetics:
o Administration: IM, IV
o Distribution: excellent, crosses BBB
o Metabolism: in liver, excretion: via kidney
*Careful usage in liver and kidney failure

Question 9

Sulphonamides - carefullness

Answer 9

• Never give IV to horses (death!)
• Never combine w. a-2-agonists (lethal cardiac toxicity)
• Never give vit.C/methionine (precipitates)
• Never give to dehydrated patients