Injectable anesthetics (Garcia) Flashcards
Anesthetics are
- very liposoluble
- highly protein bound
- reach the brain rapidly
- redistributed to other tissue
- muscle
- accumulation in fat
Hypoproteinemic dogs
- need less drugs
- more free drug in bloodstream
Propofol
- alkylphenol compound
- insoluble in water
- egg lecithin
- contamination
- 6 hours opened => throw away
- shelf life 3 yrs
Effects of propofol
- induction in 30 seconds
- bolus to avoid excitation
- apnea => not a big deal if intubated and no brain tumor
- duration => 10-15 min
- Cumulative
- splenic engorgement
Gaba
- main system of inhibitory neurons
- gabanergic drugs tent to inhibit inhibitory neurons first = excitation
- give fast bolus of 1/3 of dose to avoid excitation
- benzos also
Benzos have minimal
cardiovascular effect
metabolism
- when a patient has a CRI of propofol for several days, waking up depends on metabolism, not redistribution
Propofol blocks
- sypathetic nervous transmission
- alpha receptors
Drugs that cause splenic engorgement
- propofol
- acepromazine
Ketamine
- cyclohexamine
- dissociation between thalamus and limbic system
- hepatic metabolism in dogs and horses
- eliminated unchanged by cats
- large therpeutic index
- can be given IM
Remeber that with ketamine you will not stop
palpebral reflex
You have to be careful about using ketamine in cats with
renal failure
Ketamine and cardiovascular
- sympathetic stimulation
- inc HR and BP
-
careful in HCM and renal failure (Cats)
- increase oxygen demand in thick muscle. Leads to infarc.
- Direct myocardial depressant
- may inc IOP
- avoid with glaucoma and p w/ inc intracranial pressure
- arrhythmogenic
Ketmine and respiratory
- Apneustic breathing
- Apnea
- Maintained laryngeal reflexes and PaO2
- still swallows
- may be difficult to intubate
Ketamine and neurologic
- inc ICP and CBF
- Somatic analgesia
- Excitement at emergence
- motor activity
- Sensitivity to touch
- violent recovery
Ketamine Clinical effects
- inc salivation and mucus
- poor muscle relaxation
- reflexes are maintained
- rough recoveries
- often combined with benzos
Telazol
- same sites of action as ketamine/diazepam
- 1:1 combo
- tiletamine
- zolazepam
- lyophilized powder
- reconstituted with sterile water
Telazol cardiovascular
- similar to ketamine
- inc HR, BP and SVR
- due to sympathetic stimulation
Telazol neurologic
- maintained reflexes
- coughing
- swallowing
- corneal reflexes
Telazol respiratory
similar to ketamine
Etomidate
- Acts on GABA A receptors
- Propylene Glycol based
- Hemolysis
- propylene glycol-osmolality
- Imidazole derivative
- Expensive
Etomidate used primarily in …….. patients
cardiovascular
Etomidate and cardiorespiratory
- cardiovascular and respiratory stability
Etomidate and neurologic
- CNS friendly
- Myclonus
- poor muscle relaxation
- Usually combined with benzos or opioids
Etomidate other side effects
- adrenal suppression
- be careful of an addisonian crisis
Don’t use etomidate in a septic patient because of its
adrenal suppression
Alfaxalone
- similar to propofol
- very expensive
- Neurosteroid in ciclodextrin
- act on GABA
- relaxation is better than ketamine
Alfaxalone cardiorespiratory
- minimal cardiovascular effects
- inc HR and C.O.
- dec BP (vasodilation)
- Dose dependent respiratory depression
- apnea after bolus
Alfaxalone Neurologic
- CNS friendly
- potential protective effect in premature fetus when labor is induced by glucocorticoids (Betamethasone)
- Excitation in cats during recovery (IM route)
Opioids are a good alternative for a …..
sick patient
Opioids
- Narcosis not anesthesia
- cardiovascular friendly
- dec HR, respiratory depression
- can be treated with anticholinergics
- analgesia
- used in sick patients
- cardiovascular compromised
- reversible
- short actig (fentanyl)
Propofol summary
- Fast acting
- No problem if given perivascular
- short cardiovascular depression
- apnea, respiratory depression
- CNS friendly
- Contamination
Ketamine summary
- Inc sympathetic tone
- Poor muscle relaxant
- Combine with Benzodiazepines for induction
- Increase mycardium work load
- Increase ICP, CBF, IOP, dec seizures threshold
- Rough recoveries
- Apneustic breathing, apnea
- Maintained reflexes
Telazol summary
- similar effects of Ket/val
- Smaller volume
- Associated with rough recoveries w/o premeds
- Can be reconstituted with Ketamine and alpha2s
Etomidate summary
- minimal cardiovascular changes
- adrenal depression
- poor muscle relaxant
- combined with opioid or benzo for induction
- expensive
- good for cardiac patients
Opioids summary
- Fentanyl and hydromorphone bolus
- dec HR and ventilation
- no myocardial depression
- reversible
- analgesic
- short acting (fentanyl)