Anaesthesia (SA) Flashcards
What is an ASA grade I patient?
Normal and Healthy
What is an ASA grade II patient?
Mild systemic Disease
What is an ASA grade III patient?
Severe systemic Dz
What is an ASA grade IV patient?
Severe systemic Dz that is a constant threat to life
What is an ASA grade V patient?
Moribund - will not survive without surgery
What is an ASA grade E patient?
Emergency
What is the difference between pain an nociception?
Pain is recognised by the brain at a cortical level.
What are the four stages of nociception?
Transduction
Transmission
Modulation
Perception
What is “transduction”? (with regard to nociception)
Conversion of stimulus into AP by nerve end receptors
How is stimulus intensity conveyed during “transduction” of nociception?
frequency of AP generation
What is “transmission”? (with regard to nociception)
Conduction of impulses to/from CNS.
Where do sensory impulses enter the CNS?
Dorsal Root
Where do motor impulses exit the CNS?
Ventral Root
What is “modulation”? (with regard to nociception)
Amplification/suppression of nociceptive input at spinal cord level
How does modulation of nociception take place?
Aletered neuronal sensitivity/altered neurotransmitter release
What is “perception”? (with regard to nociception)
Processing, integration and recognition of stimulus in HIGHER centres. MUST BE CONSCIOUS.
What is acute pain often associated with?
Tissue Damage (or the threat of)
What is chronic pain?
Pain which persists beyond the expected course. NO purpose or clear end-point.
Define Neuropathic Pain
Pain caused by nervous system dysfunction
Define Allodynia
Perception of pain when a normally non-noxious stimulus is applied
Define Hyperalgesia
An excessive reaction to a noxious stimulus
Which sensory neurons are “low threshold sensory nerves”?
A Beta
Which sensory neurons are “medium threshold pain nerves”?
A Delta
Which sensory neurons are “high threshold pain nerves”?
C
Which are the principal neurotransmitters involved with central modulation?
Serotonin
Nor-adrenaline
How can we reduce pain sensitisation?
Avoid experience of pain
Treat Pain aggressively
Which Analgesics work at the nerve terminal level?
NSAIDs
Local Anaesthetics
Opiates
Which analgesics work in the dorsal horn of the spinal cord?
NSAIDs Opiates NMDA antagonists Ca Channel Blockers Tramadol
Which analgesics work in the brainstem/cerebrum?
NSAIDs Opiates NMDA antagonists Ca Channel Blockers Tramadol
What are the 7 classes of drugs for acute pain?
NO PLANT
NSAID Opiate Paracetamol Local Anaesthetics Alpha 2 Agonists NMDA antagonist Tramadol
Name 6 drugs that may be used to treat chronic pain. (not NO PLANT)
Gabapentin Amantidine Anti-depressants Green-lipped mussel Elk Velvet Antler Capsacin
What are the 4 goals of sedation?
Relive Anxiety
Ease Handling
Analgesia
Decrease Muscle Tone
What are the 3 formulations of ACP?
2mg/ml
5mg/ml
10mg/ml
What is an appropriate dose for ACP in the dog?
0.01-0.05mg/kg (lower if IV/large dog)
What is an appropriate dose for ACP in the cat/
0.03-0.07mg/kg
How is ACP administered?
IM/IV/SC in smallies
IM ONLY IN HORSES
What is the time to onset for ACP?
30min
How long is the duration of ACP?
3-8h
How does ACP work?
anti-dopaminergic
How does ACP interact with other sedatives?
Potentiates their CNS depression
How does ACP cause vasodilation?
Alpha 1 adrenergic blockade
How does ACP affect respiratory function?
Not much EXCEPT pharyngeal relaxation (bad for brachys)
Describe the hepatic/renal toxicity of ACP
Not Applicable - no direct effects
What are some potentially beneficial off-target effects of ACP?
Anti-emetic
Anti-histaminic
What CV SE would make ACP contraindicated in boxers and brahcycephalics?
Can cause syncope
What Haem/biochem abnormality may ACP cause?
Decreased PCV
What analgesic effect does ACP offer?
NONE!
Where is ACP metabolised?
Liver - no significant metabolites
At high doses, what symptoms may ACP trigger?
Extrapyramidal - rigidity/tremors
Which drug is CI’ed with ACP?
Epinephrine - Beta agonist so will cause even more vasodilation/hypotension
Which alpha two agonists may be used in cats and dogs?
Medetomidine
Dexmdetomidine
Which alpha 2 agonists may be used in horses?
Xylazine
Detomidine
Romifidine
(+medetomidine)
Via which route are a2 agonists administered?
IM/SC/IV
How to alpha 2 agonists initiate sedation?
agonists of alpha 2 in locus coeruleus in the brainstem
How do a2 agonists affect administration of other sedatives?
REDUCE DOSE!
Describe the CV effects following a2 agonist administration.
Initial vasoconstriction
Reflex Bradycardia
Vasodilation
How do a2 agonists affect the respiratory system?
Reduce RR
May alter R pattern
What analgesic effect does an a2 agonist have?
Good - but sedative lasts 2-3x longer.
How do alpha 2 agonists affect the kidneys?
Cause diuresis
How do alpha 2 agonists affect GI motility?
Decrease it
How do alpha 2 agonists affect blood sugar?
Cause hyperglycaemia - decrease insulin secretion
Where are a2 agonists metabolised?
Liver
Name the alpha 2 antagonist commonly used.
Atipamezole
In which animals are A2 agonists CI’ed?
DCM
MVD
Which benzodiazepines are commonly used in veterinary anaesthesia?
Midazolam
Diazepam
Which benzodiazepines are licenced for veterinary anaesthesia?
None
What dosage is used for benzodiazepines as part of an anaesthesia protocol?
0.2mg/kg
What dosage is used for benzodiazepines to control seizures?
0.5mg/kg
via which route can midazolam but NOT diazepam be given?
IM
via which route can diazepam but NOT midazolam be given?
Oral (not in cats)
How long does onset of benzodiazepines take following administration?
Minutes
Which benzodiazpine has the shorter DOA and faster onset?
Midazolam
How do benzodiazepines induce sedation?
Binding to specific sites on GABA receptor in brain and SC
What effect do benzodiazepines have on the heart (at a normal dose)?
minimal
What are the potential CVS side effects caused by the propylene glycol found in diazepam?
Haemolysis, CV arrhythmias and hypotension
What effect do benzodiazepines have on the resp system?
Minimal but will enhance effect of other drugs
What is an occasional liver SE of benzodiazepine use in cats?
Fulminant Hepatic Failure
Which haem/biochem abnormality would increase the free fraction of benzodiazepines, leading to a greater effect?
Hypoproteinaemia
In which animals are benzodiazepines CI’ed?
PSS
Severe Hepatic disease
Hepatic Encephalopathy
What may occur if benzodiazepines are given to young, excitable animals w/o sedation?
Excitement
Disinhibition
Why is diazepam less suitable than midazolam for infusion? (2)
Many active metabolites that may undergo enterohepatic recycling/accumulation
AND
May bind to some plastics
Name 2 drugs that may reverse the action of benzodiazepines?
Flumazenil
Surmazenil
Name two commonly used veterinary barbiturates.
Thiopental
Pentobarbital
What class of drug does alfaxalone come under?
Neurosteroid
Which class of drug does propofol fall under?
Phenol
Name the most common phencyclidine derivative used in veterinary medicine.
Ketamine
Which barbiturate is “ultra-short” acting and how long does it last?
Thiopental
5-15min
Which barbiturate is “short” acting and how long does it last?
Pentobarbital
45-90min
How long does reconstituted thiopental last?
6d
What is the pH of thiopental and why is this significant?
10.5 - very irritant so IV only and CARE with extrvasation
What is the site of action for thiopental?
GABAa
What is the onset for thiopental and why?
20-40s
V lipid soluble so crosses BBB easily
How does thiopental cause arrhythmias?
Causes myocardial sensitisation to catecholamines
What direct effect does thiopental have on the heart?
Myocardial depression - negative inotrope
What effect does thiopental have on BP?
Vasodilator so causes hypotension
How is thiopental cerebroprotective?
Decreased cerebral metabolic rate and blood flow
What are the two occasions thipental is used?
Top Up boluses (esp horses)
Induction if intracranial disease
In which species is alfaxalone licenced?
Dogs and Cats
What is the pH of alfaxalone?
6.5-7 (non irritant)
What is the site of action of alfaxalone?
GABAa receptor
What CVS effects does administration of alfaxalone have?
Vasodilation with REFLEX tachycardia.
What is a potential surgical benefit of using alfaxalone?
Good Muscle Relaxation
Describe the analgesic properties of alfaxalone
None
Via what route is alfaxalone administered?
IM or IV
What is the dose of alfaxalone for dogs?
2mg/kg
What is the dose of alfaxalone for cats?
2-3mg/kg
What is alfaxalone used for?
Induction/maintenance of smallies
OR
Sedation
In what species is propofol licenced?
Dogs and Cats
What is the site of action for propfol?
GABAa receptor?
What is the pH of Propofol?
7.8
What CVS effects does administration of propofol have?
Mildly negative inotrope
Vasodilation
Hypotension
How is propofol cerebroprotective?
Decreased cerebral metabolic rate and blood flow
Describe the analgesic properties of propofol.
none
What must be noted about propofol administration in cats?
CAN ACCUMULATE
How is propofol metabolised?
Rapidly in the liver.
ALSO lung, kidney and GI
What common side effect is seen with propofol administration in cats?
Heinz Body Anaemia
What is the reccomended dose for propofol?
2-6mg/kg
How should propofol be administered?
IV!!! ONLY!
Which species is ketamine licenced in?
Cats, Dogs and Horses
What is the pH of ketamine?
4
Which isomer of ketamine is more potent?
S(+) > R (-)
What is the site of action for ketamine?
NDMA receptor - antagonist
What is the onset of action for ketamine?
1-2min
What is the overall effect of ketamine on the CVS?
Sympathetic activation (inc HR, CO, BP)
Why is the overall CVS effect of ketamine counter-intuitive?
Directly depresses myocardium - would not expect inc CO
What is the effect of Ketamine of the resp system?
minimal resp depression but strange breathing pattern
How does ketamine increase ICP?
promotes cerebral blood flow
How does ketamine increase IOP?
increases extraocular muscle tone
Why should ketamine be administered alongside a benzodiazepine?
Poor muscle relaxant
How is ketamine metabolised?
In the liver - to norketamine
EXCEPT IN CATS! urinary excretion unchanged.
how is ketamine administered? which route is preferable and why?
IV or IM
IM can be painful so IV preferable
What is the dose for induction using ketamine in:
a) dogs
b) cats
C) horses?
Dog: 2.5mg/kg
Cat: 3-5mg/kg
Horse: 2.2mg/kg
What is the dose for analgesia using ketamine?
0.1-0.5mg/kg
What is the difference between ketamine and tiletamine?
Tiletamine has a longer DOA
What is the pH of tiletamine and why is this significant?
2-3.5 PAINFUL
What receptor does Tiletamine act on?
NDMA
When do we use Tiletamine?
Zoo/Wild animal darting
What is the dosage for tiletamine induciton?
5-7mg/kg
What route is tiletamine administered by?
IM or IV
What are the two extracellular compartments?
Interstitial
Intravascular
What % of body weight is Intracellular fluid?
40%
What % of body weight is extracellular fluid?
20%
What % of body weight is Interstitial fluid?
15%
What % of canine/equine body weight is plasma?
8-9%
What % of feline/rabbit/ruminant body weight is plasma?
6-7%
What are the 4 types of fluid loss?
Pure Water
Water and electrolytes
Water, electrolytes & protein
Blood
What fluids should be used to replace water?
Crystalloid - Low Na+
5% glucose or 4% glucose + NaCl
What fluids should be used to replace ECF?
Balanced Crystalloid (Hartmanns or 0.9% NaCl)
What fluids should be used to replace ECF with protein?
Colloids
What fluids should be used to replace blood?
Colloid + Crystalloid
Blood
What are the signs of <5% dehydration?
None
What are the signs of 5-7% dehydration?
Tacky/dry oral MMs, Normal/Dec skin turgor
What are the signs of 8-10% dehydration?
V. dry oral MM
Dull/sunken eyes
Loss of skin turgor
What are the signs of 10-12% dehydration?
Dry MM,
Sunk eyes
Loss of turgor
Altered mentation
What are the signs of 12-15% dehydration?
All signs of lower level dehydration
+ dying
What does CRT give us an indication of?
Blood volume
Capillary tone
What does a CRT <1s indicate?
Poor Perfusion or Hypovolaemia
What does a CRT >2s indicate?
Septic Shock
What is the equation for calculating BP?
BP = SV x HR
What should normal systolic BP range be?
90-160
What should normal MAP range be?
60-140
What is the normal RR for a dog/cat?
10-30bpm
Which drug(s) may cause tachypnoea?
Methadone
Which drug(s) may cause bradypnoea?
Isoflurane, propofol, fentanyl
What is the consequence of increased dead space?
Hypoventilation leading to hypercapnia and tachypnoea
What is the normal range of expiratory CO2?
35-45mmHg
What value should PaO2 be above?
96%
What is the normal temperature range for a dog?
37.5-39 Degrees celsius
Which drug should be avoided if there is a worry of hypothermia and why?
ACP - vasodilation and reset of hypothermic threshold
What should the cuff size be for oscillometric BP?
40% of circumf of limb
What are 4 potential complications of invasive BP monitoring?
Infection
Thrombosis
Embolism
Haemorrhage
Which negative inotrope may be given as a CRI to manage BP?
Dobutamine ( B1 adrenergic agonist - CARDIOSELECTIVE)
Which + inotrope can be used in a dose-dependent fashion to control BP?
Dopamine
Which 2 drugs can be used to induce vasoconstriction?
Phenylephrine
Nor-adrenaline
What % of blood volume does the venous system hold?
60%
Where does oedema usually build up in venous overload?
Limbs
Under Jaw
Why does GA tend to cause hypercapnia?
Reduced medulla sensitivity
What type of acid/base abnormality is caused by uncorrected hypercapnia?
Respiratory Acidosis
What capnographic sign demonstrates rebreathing?
Progressive increase in respiratory baseline
What are 3 possible causes of rebreathing Co2?
Exhausted soda lime
Low FGF in non-rebreathing system
Leaking expiratory valve
What capnographic sign demonstrates hypoventilation?
Progressive increase in Alveolar Plateau.
What can we do to correct hypoventilation under GA?
Reduce Depth
IPPV
Check intubation
Oscillations in the inspiratory downstroke are caused by what?
Cardiac oscillation
What capnographic sign may indicate increased expiratory resistance?
Slow transition to plateau from expiratory upstroke
What are 4 possible causes of pulse oximetry error?
Hair/ambient light reduces accuracy
Non-pigmented skin required
Motion = error
Clip exsanguinates thin tissue
