Definitions + Injectable anaesthetics Flashcards
(49 cards)
Requirements for general anaesthesia.
1 - Unconsciousness
2 - Analgesia
3 - Muscle relaxation
4 - No cardiovascular effect
What is neuroleptanalgesia and why is it used?
Tranquilliser + opiate
(acepromazine) + (morphine/fentanyl)
More superficial state = safer
1 - Superficial sleep
2 - Analgesia
3 - Muscle relaxation
What is ataranalgesia?
The safest anaesthetic combination, but with the most superficial state.
Benzodiazepine + opiate
(diazepam) + (morphine/fentanyl)
Procedure of anaesthesia.
- Premedication (injectable)
- Induction (injectable or inhalational)
- Maintenance (usually inhalational, sometimes injectable)
What is the purpose of premedication?
3
- Decrease the dose of anaesthetic
- Analgesia
- Decrease pre- and post-narcotic excitation (because narcotics first inhibit all inhibitory pathways of brain)
Name three groups of sedatives.
- Tranquillisers
- Benzodiazepines
- a2-agonists
Name three groups of analgesics.
- Opiates
- NSAIDs
- Ketamine
What is the purpose of induction?
Allows for introduction of the tracheal tube for inhalational anaesthetics.
Indication/use of injectable anaesthetics.
4
- Simple procedures
- Induction
- Total intravenous anaesthesia (TIVA) (acepromazine+diazepam or propofol+fentanyl)
- Animals with seizures (barbiturates, propofol)
What is the treatment course for convulsions?
4
- Diazepam
- Pentobarbital/phenobarbital
- Propofol
- Inhalational anaesthetic
Name 1 long acting-, 1 short acting-, and 3 ultrashort acting barbiturates.
Long acting - Phenobarbital (30-40 min)
Short - Pentobarbital (10-20 min)
Ultrashort - Thiopental, thiamylal, methohexital (5-8 min-)
Barbiturate mechanism of action.
Agonist of GABAa-recetors → opens Cl- ion channel → hyperpolarisation → inhibition of nerve → sleep
Barbiturate pharmacological effects.
4
- unconsciousness
- muscle relaxation
- anti-convulsion
- NO analgesic effect (cannot be used alone)
Barbiturate side effects.
5
1) respiratory depression!!! (depress. of CNS resp. centre)
+
2) cardiovascular depression → hypotension
= life-threatening
3) Severe tissue irritant effect (only IV!)
→ must be given slowly IV (20 sec), stop if decreased resp.
4) Pre- and post-narcotic excitation
5) Delayed recovery in greyhounds and slim animals
Barbiturate pharmacokinetics.
administration, distribution, metabolism
Administration: Only given IV (only inject once!!)
Distribution: Excellent, crosses BBB very quickly
Redistribution! (Leaves brain→blood→muscle+fat→animal wakes up) Animal wakes up due to redistribution, NOT excretion!!
- do not readminister bc muscle+fat already saturated, so all goes to brain (esp. Thiobarbital) Accumulation can last for days.
Metabolism: in liver
Barbiturate indication/use.
Pentobarbital
- seizures
- euthanasia
Thiopental, methohexital (faster elimination, can be readministered)
- only for induction
- most often used in horses bc propofol v expensive
Propofol dosage.
alone, continuous infusion, premed
Can be readministered
Alone:
Once (high dose)
→ 6-8 mg/kg, 5-10 min duration
Continuous infusion:
→ 0.2-0.4 mg/kg/min
Premed:
+ACP → 4-5 mg/kg
+ medetomidine → 3-4 mg/kg
Propofol pharmacological effects.
8
1) unconsciousness
2) good muscle relaxation
3) Ø analgesia (combined with NSAIDs or opiates)
4) quick and smooth recovery (good dream, infrequent excitation)
5) bronchodilation
6) decreased intracranial pressure (ICP) - imp during head trauma surgery + heat shock
7) decreased intraocular pressure - imp in glaucoma patients
8) anti-convulsive
Propofol side effects.
6
1) resp. depression, 2 min. apnea (30-40%) → slow administration to counteract (20 sec)
Doxapram: only resp. stimulant drug
2) negative inotropic → hypotension
3) post-narcotic excitation (acepromazine + diazepam as premed to prevent)
4) septicaemia (bact. in bottle)
5) pancreatitis
6) appetite stimulating (small dosage to treat anorexia)
Propofol pharmacokinetics.
adme
Administration: IV
Distribution: crosses placenta (not sign. if done within 20 min, freq. used in caesarians)
Metabolism: slower in cats (bc. no glucuronidation)
Total recovery dog: 20 min; cat: 30 min
Excretion: kidney, but also extrahepatic (lung, GI)
Propofol indication/use.
4
1) Simple surgical intercentions
2) Induction
3) Anti-epileptic
4) TIVA (propofol + fentanyl)
Name two imidazoles.
Etomidate
Metomidate
Imidazole pharmacological effects.
7
1) Unconsciousness
2) Muscle relaxation
3) Ø analgesia
4) Short duration 5-10 min
5) Recovery (quick, but less smooth)
6) Decreased ICP
7) Decreased intraocular pressure
Imidazole side effects.
5
1) Tissue necrosis, only IV administration
2) Negligible cardiovascular effects! (unless high dose)
3) Respiratory depression (give slowly)
4) Pre- and post-narcotic tremors, seizures (prevent by benzodiazepine premed)
5) Adrenocortical suppression! Less cortisol prod. → can’t adapt to stress → serious problem if readministered
