292017
Description
Mind Map by melian.yates, updated more than 1 year ago
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Created by melian.yates
about 11 years ago
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|
General Anaesthetic Agents
- General Anaesthesia
- Unconsciousness
- Analgesia
- Muscle relaxation
- Muscle relaxation
- Analgesia
- Anaesthetics
- Interaction w/ ligand gated channels
- GABAa
- Glycine receptor
- NMDA
- Nicotenic Acetylcholine receptor
- Nicotenic Acetylcholine receptor
- NMDA
- Glycine receptor
- GABAa
- Potency correlated
to Lipid solubility
- Interaction w/ ligand gated channels
- Unconsciousness
- Injectable
- More action on Brain
- Minimal Equipment required
- Some require ventilation
- Some require ventilation
- No pollution from Gases & Inhalation agents
- Recovery relies on Redistribution & Metabolism
- Not all drugs are suitable for maintenance
- Induction
- Short procedures
- Short procedures
- Maintenance
- TIVA
- Incremental doses
- Continuous rate infusion (CRI)
- Continuous rate infusion (CRI)
- Incremental doses
- TIVA
- Supplementation to
Inhalational Anaesthesia
- Long term sedation in ICU
- Tx of Status Epilepticus
- Absorption
- IV (Most)
- Cause loss of
consciousness in
1 injection site -
brain circulation
time
- Exception: Ketamine
- Exception: Ketamine
- Cause loss of
consciousness in
1 injection site -
brain circulation
time
- IM
- IP
- SC
- Intra- animal...
- Intra- animal...
- SC
- IP
- IV (Most)
- Ideal Properties
- No drugs have all Ideal
characteristics
- No drugs have all Ideal
characteristics
- Drugs
- Barbituates
- Derivatives of Barbituric Acid
- Thiopental
- Used most often in Clinical Practice
- Not licensed
- Absorption
- Na+ salt formulation
- Alkaline solution (pH: 10.5)
- Very irritant on
Perivascular injection
- Necrosis!
- If accidental
Extravascular
injection
- Dilute w/ sterile saline
- Dilute w/ sterile saline
- Necrosis!
- Very irritant on
Perivascular injection
- Hypoproteinaemia:
Reduced Dose
- Na+ salt formulation
- Distribution
- Ultra-short acting
- Rapid loss of Consciousness
- Crosses Placenta
- Ultra-short acting
- Side Effects
- Dose dep. Resp. depression
- Apnoea (possible) after induction
- CV depression
- Hypotension
- Reduction of
myocardial
contractility
- Reduces SVR
- Compensatory
Tachycardia
possible
- Ventricular
Arrhythmias
possible
- Sensitizes heart to
Catecholamines
- Sensitizes heart to
Catecholamines
- Hypotension
- CV depression
- Apnoea (possible) after induction
- Dose dep. Resp. depression
- CNS
- Poor muscle relaxation
- NO Analgesic properties
(Hyperalgesia)
- NO Analgesic properties
(Hyperalgesia)
- Anti-convulsant
- Decreases
Intracranial
pressure
- Poor muscle relaxation
- Cheap
- Uses
- IV induction (Dogs & Cats)
- IV Catheter
- Premeds decrease dose
- Not recommended for
Maintanence
- Not recommended for
Maintanence
- IV Catheter
- IV induction (Dogs & Cats)
- Used most often in Clinical Practice
- Pentobarbital
- Not used in clinical
practice much anymore -
Long recovery time
- Licensed for Euthanasia of
small animals and cattle
- Oxygen analogue of Thiopental
- Absorption
- Soluble in H20 - Unstable
- Presented in Propylene Glycol
- IV (IP)
- Soluble in H20 - Unstable
- Distribution
- Slow Onset (Max effects)
- Long duration
of action
- Slow Onset (Max effects)
- Metabolism
- Rapid (Sheep, Goats & Horses)
- Rapid (Sheep, Goats & Horses)
- Elimination
- Low Clearance:
Dogs, Cats &
Pigs
- Low Clearance:
Dogs, Cats &
Pigs
- NOT recommended for
Anaesthesia
- Not used in clinical
practice much anymore -
Long recovery time
- Phenobarbital
- Methohexital
- Not used much in
clinical practice yet
- Not used much in
clinical practice yet
- Low doses: Sedatives & Hypnotics
- Higher doses: Anaesthetic agents
- Slow onset & prolonged action
- Slow onset & prolonged action
- Higher doses: Anaesthetic agents
- Increased Lipid Solubility
- Increases Potency
- Rapid onset of action
- Shortens duration of action
- Shortens duration of action
- Rapid onset of action
- C5: Increasing carbon chain
- Branched chains e.g. thio, metho
- Double/triple bonds
- C2: Replacing O with S
- e.g. thio
- e.g. thio
- C2: Replacing O with S
- Double/triple bonds
- Added phenyl group
confers
Anti-convulsant
properties
- Ex. Phenobarbital
- Ex. Phenobarbital
- Branched chains e.g. thio, metho
- Methohexital > Thiopental > Pentobarbital
- Increases Potency
- pKa & Protein binding
- Ex. Thiopental
- pKa = 7.6 (61% unionized @ pH 7.4)
- PPB: 85%
- pKa = 7.6 (61% unionized @ pH 7.4)
- Only unionized unbound
drug is free to cross
membranes
- Lipid soluble
drugs cross faster
- Lipid soluble
drugs cross faster
- Ex. Thiopental
- Distribution
- Vd: Large (> 1L/kg)
- Rapid distribution to tissues
- Accumulation in Fatty tissues
- Redistribution important for Recovery
- Redistribution important for Recovery
- Accumulation in Fatty tissues
- Rapid distribution to tissues
- Drug injected into circulation
- Distribution to
highly
vascularized
tissues (secs)
- [Thiopental] in brain
reaches high level
quickly after injection
- Above yellow line: Unconsciousness
- Below yellow line: Consciousness
- Below yellow line: Consciousness
- Above yellow line: Unconsciousness
- Takes
longer to
equilibriate
with tissues
- Fat poorly perfused
(vs. muscle, etc.)
takes longest to
equilibriate w/ blood
- Fat poorly perfused
(vs. muscle, etc.)
takes longest to
equilibriate w/ blood
- [Thiopental] in brain
reaches high level
quickly after injection
- Distribution to
highly
vascularized
tissues (secs)
- Vd: Large (> 1L/kg)
- Metabolism
- Liver
- Slow: Cats, Dogs, Horses
- Fast: Ruminants
- Oxidation & Desulfation
- Slow: Cats, Dogs, Horses
- Prolonged Recovery
- Large Doses
- Repeated Doses
- Accumulation:
Repeated
administration of
Thiopental
- Accumulation:
Repeated
administration of
Thiopental
- Note: Greyhounds
- Large Doses
- Liver
- Derivatives of Barbituric Acid
- Phenols
- Propofol
- Absorption
- White aqueous/oil
emulsion - soybean oil,
egg lecithin & glycerol
- Lipid formulation - Very
good culture medium
- Lipid formulation - Very
good culture medium
- Lipid free
micro-emulsion,
antimicrobial
preservative
- IV
- Non-irritant
Extravascularly
- Pain on injection
- Pain on injection
- Crosses Placenta
- Dose given to Effect
- White aqueous/oil
emulsion - soybean oil,
egg lecithin & glycerol
- Distribution
- Very lipid soluble
- Almost entirely unionized at pH: 7.4
- PPB: 98%
- Rapid induction
- Vd: Large (>4L/kg)
- Very lipid soluble
- Metabolism
- Much higher
metabolism than
Thiopental
- Better
Pharmakinetics
for Repeated
Doses
- Can infuse for many
Hrs (Dog)
- I.e. Rapid recovery
- Better
Pharmakinetics
for Repeated
Doses
- Liver
- Quinol sulfate &
Glucuronide conjugates
- Note: Cats
- Note: Cats
- Quinol sulfate &
Glucuronide conjugates
- Extrahepatic Clearance
- Lungs, Kidneys, Blood
- Lungs, Kidneys, Blood
- Much higher
metabolism than
Thiopental
- Elimination
- Rapid Clearance (10-20x faster
than Thiopental)
- Rapid Clearance (10-20x faster
than Thiopental)
- Licensed in Dogs & Cats
- Side Effects
- Dose dependent Resp. depression
- Post- induction Anpnoea > Thiopental
- Post- induction cyanosis
- Due to opening of
shunts in the
lungs
- Concern if
existing
respiratory
compromise
- Transient -
improves w/
intubation & O2
- Due to opening of
shunts in the
lungs
- Post- induction cyanosis
- Post- induction Anpnoea > Thiopental
- Administer SLOWLY
- Dose dependent cardiovascular depression
- Reduced SVR
- No Compensatory Tachycardia
- No Compensatory Tachycardia
- Reduced SVR
- Dose Dependent
- High Doses: More
pronounced
- High Doses: More
pronounced
- Dose dependent Resp. depression
- Effects
- Not Arrhytmogenic & does not
sensitize heart to
Catecholamines
- Occasional Muscle
twitching or Opistotonus
- Can cause Overdose
- Usually good muscle relaxation
- Can cause Overdose
- Decreases Intracranial pressure
- Bronchodilation
- Anti-convulsant
- Low Doses: Sedation in ICU
- Low Doses: Sedation in ICU
- Anti-convulsant
- Bronchodilation
- Not Arrhytmogenic & does not
sensitize heart to
Catecholamines
- Uses
- Same day, Short Procedures
- TIVA (Dogs)
- Rabbits, birds, reptiles
- Dose decreased by pre-med
- Same day, Short Procedures
- Absorption
- Propofol
- Cyclohexanones
- Derivatives of Phencyclidine
- LSD, Ectasy
- LSD, Ectasy
- Ketamine
- Racemic mixture
- S(+) more potent
- R(-) More cardiac
depression & delirium
- S(+) more potent
- Licensed Dogs, Cats,
Horses, non-human
Primates
- Absorption
- Pain on IM Injection
- IV
- SC
- IP
- MM
- Mucous membranes
- Health & Safety concerns
- Health & Safety concerns
- Mucous membranes
- MM
- IP
- SC
- Pain on IM Injection
- Distribution
- Rapid after IV
- PPB: 25-30%
- Accumulation possible - Not
as quickly as Thiopental
- Accumulation possible - Not
as quickly as Thiopental
- Longer than other
Injectables, changes
conformation
post-injection before
crossing BBB
- PPB: 25-30%
- Placental transfer
- Rapid after IV
- Metabolism
- Liver
- Enzymatic induction
- Enzymatic induction
- Liver
- Elimination
- Kidneys (Urine)
- Active Metabolite ( Norketamine)
- Active Metabolite ( Norketamine)
- Kidneys (Urine)
- CNS
- NMDA receptor antagonist
- Nicotinic, muscarinic, opiod,
monoaminergic receptors
- Anti-hyperalgesic properties
- Reduces MAC
- Reduces MAC
- Nicotinic, muscarinic, opiod,
monoaminergic receptors
- Unconsciousness
- Dissociative Anaesthesia
- Should NEVER be
given on it's own (+
Sedative)
- Should NEVER be
given on it's own (+
Sedative)
- Dissociative Anaesthesia
- Cranial nerve reflexes maintained
- NMDA receptor antagonist
- Uses
- Chronic pain
- Horses: (after alpha 2 agonist)
- Induction
- Top-up/ Maintenance
- Top-up/ Maintenance
- Induction
- Cats & Dogs: Combined
with ACP, alpha 2 agonists,
opiods, benziadiazepines
- Cattle, sheep, pigs
- Small mammals, birds & exotics
- Small mammals, birds & exotics
- Cattle, sheep, pigs
- Chronic pain
- CVS
- Increased sympathetic tone
- Increased HR & Contractility
- Increased CO & ABP
- Increased mVO2
- Increased mVO2
- Increased CO & ABP
- Increased HR & Contractility
- Direct -ve Inotropic Effect
- Increased sympathetic tone
- Resp.
- Laryngeal & Pharangeal
reflexes maintained
- Transient resp. depression
- Apneustic pattern
- Bronchodilation
- Bronchodilation
- Apneustic pattern
- Laryngeal & Pharangeal
reflexes maintained
- Side Effects
- Increased ICP,
CMRO2, IOP &
Mydriasis
- Seizures possible
- Increased Salivation
- Muscle rigidity & spontaneous
muscle movements common
- Increased ICP,
CMRO2, IOP &
Mydriasis
- Racemic mixture
- Dissociative Anaesthesia
- Maintains reflexes
- Analgesia
- Maintains reflexes
- Derivatives of Phencyclidine
- Steroids
- Alphaxalone
- + Alphadalone (Saffan)
- Weak anaesthetic
- Increases solubility of Alphaxalone
- Increases solubility of Alphaxalone
- Small mammals & birds
- GABAa receptor binding
- Absorption
- Viscous solution
- Cremophor EL
- Causes Histamine release
- Do NOT use in Dogs
- Potentially fatal
Anaphylactoid Rxn
- Oedema & flushing of paws
- Tx w/ antihistamines, corticosteroids
- Tx w/ antihistamines, corticosteroids
- Oedema & flushing of paws
- Potentially fatal
Anaphylactoid Rxn
- Do NOT use in Dogs
- Causes Histamine release
- Cremophor EL
- IV & IM
- Non-irritant
- Can be topped-up
- TIVA
- TIVA
- Non-irritant
- No bacteriostatic agent
- Preceiptates
(refridgerated)
- Preceiptates
(refridgerated)
- Viscous solution
- Distribution
- Rapid Onset (IV): 5-20 min
- Lower doses: Sedation (IM)
- PPB: < 50%
- Top-up (IV): Induction
- PPB: < 50%
- Lower doses: Sedation (IM)
- Rapid Onset (IV): 5-20 min
- Metabolism
- Liver
- Liver
- High therapeutic index
- CVS
- Transient Hypotension
- Transient Hypotension
- Resp.
- Resp.
depression
(Dose
dependent)
- Resp.
depression
(Dose
dependent)
- CNS
- Muscle relaxation
- Twitching (Recovery)
- Twitching (Recovery)
- Muscle relaxation
- Weak anaesthetic
- Potent anaesthetic
- No cremaphor
- No Histamine
release
- No Histamine
release
- Not irritant if extravascular
- IM, CRI
- Licensed for Dog & Cat
- Premeds Imp.
- Very expensive
- + Alphadalone (Saffan)
- Progesterone derivatives
- Etomidine
- GABAa receptors
- Absorption
- Propylene glycol
+ H2O mixture
- Soybean oil,
glycerol egg
- Soybean oil,
glycerol egg
- Propylene glycol
+ H2O mixture
- Distribution
- PPB: 75%
- Rapid Onset
- Rapid Onset
- PPB: 75%
- Metabloism
- No accumulation
- Hepatic & Plasmatic esterases
- Inactive metabolites
- Inactive metabolites
- Hepatic & Plasmatic esterases
- No accumulation
- GABAa receptors
- Etomidate
- Not licensed in animals
- Expensive
- Minimal
cardiovascular
effects
- Suitable for
animals w/ CV
problems
- Minimal effect on
ICP, CPP, CBF
- Minimal Resp. depression
- Minimal Resp. depression
- Suitable for
animals w/ CV
problems
- Inhibition of
Cortisol synthesis
- Not licensed in animals
- Alphaxalone
- Barbituates
- More action on Brain
- Inhalation
- More action on spinal cord
- Rapid recovery after hrs of maintenance
- No (or little) metabolism of drugs
- More equipment needed
- Need to scavenge
- More action on spinal cord
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