principles of clinical practice: anaesthesia and analgesia Flashcards
triple
medetomidine hydrochloride, ketamine, and torbugesic
what want from anaesthesia
- unconcioussness
- analgesia
- muscle relaxation
analgesia in anaesthesia is necessary to
- inhibit processing of pain in CNS
- antinociception
central eye position in anaesthesia indicates
light or deep anaesthesia
eye position in adequate anaesthesia
rotated
palpebral reflex and anaesthesia
if there is one than anaesthesia is too light
movement is absent in what anaesthesia
adequate and deep anaesthesia
the cornea is dry when in anaesthesia
in deep anaesthesia
likelyhood that healthy dog dies due to anaesthesia
1 in 1849
likelyhood that healthy cat dies due to anaesthesia
1 in 895
likelyhood that healthy rabbit dies due to anaesthesia
1 in 72
likelyhood that healthy guinea pig dies due to anaesthesia
1 in 26
stuff that can happen due to anaesthesia (6)
- muscle nerve damage
- cerebral hypoxia causing poor recovery
- peripheral nerve damage
- spinal cord damage
- blindness
- post anaesthetic cognitive dysfunction
low albumin and anaesthetic
- means more free drug so the dose will have a greater effect
- risk of oedema developing
kidney failure and anaesthetic
- will show as increased creatinine or urea
- causing acidaemia
- increased free drug conc
- also depresses myocardial contractility
- and shifts HbO2 curve to right so lower affinity to oxygen
3 dangers of waste anaesthetic gas
- cancer
- miscarriage
- liver/kidney disease
gas cylinder size usually attached to an anaesthetic machine
size E
gas cylinder size normally attached to pipelines
size J
oxygen cylinder colour
black cylinder with white on top
nitrous oxide cylinder colour
blue
air cylinder colour
grey cylinder with black/white quarters on top
oxygen is stored at (pressure)
13700kPa or 137 bar
nitrous oxide stored how
as liquid with gas on top at 4400kPa (4.4 bar)
how tell how much nitrous oxide in cylinder
- weigh it
- molecular weight 44 so 1 mole is 44 g
- 1 mole of gas is 22.4 litres
pipeline system for gas end in valves called
schrader valves
max O2 concentration you get out of an O2 concentrator
95%
how read a flowmeter
- top of bobbin
- middle of ball bearing
low resistance or draw-over vaporises define
are in the system and gas that flows through them is generated by the patient
emergency oxygen flush delivers O2 at a flow of
30-70 liters per minute
2 rebreathing systems
- circle
- to-and-fro
minute volume define
volume of air inspired or expired in a minute
tidal volume define
volume of air inspired or expired in one breath
estimate tidal volume to be
10-15 ml/kg
magill fresh gas flow
equal to minute volume
fresh gas flow for IPPV magill
3 x minute volume
magill weight animal
over 10kg
lack types 3
- parallel
- mini
- co-axial
lack fresh gas flow
equal to minute volume
estimate of minute volume
200 ml/kg/min
IPPV flow rate lack
3 x minute volume
standard lack animal weight
over 10kg
mini lack animal weight
under 10kg
ayers T-piece flow rate
2.5 - 3 x minute volume
ayers T-piece animal weight
under 10 kg
bain appearance
co-axial T piece with inspiratory tube surrounded by expiratory tube
fresh gas flow rate bain
2.5-3 x minute volume
bain animal weight
10kg
using a circle fresh gas flow rate
- first 10-15 minutes use a higher fresh gas flow (100ml/kg/min)
- then reduce to 50ml/kg/min
when change carbon dioxide absorbers
when half of it has changed colour
anticholinergics action
block acetylcholine receptors of parasympathetic system
3 anticholinergics
- atropine
- glycopyrollate
- hyoscine
anticholinergics 5 side effects
- increase heart rate
- reduce salivation
- reduce gut motility
- dilate pupil of eye
- relax bronchi
3 tranquillisers and sedative agents groups
- phenothiazine
- 2-adrenoceptor agonists
- benzodiazepines
define maximal effect
- increaseing dose does not increase action only length
3 phenothiazines
- acepromazine
- chlorpromazine
- propionylpromazine
phenothiazines are (tranquiliser or sedative)
tranquiliser
phenothiazine action
- dopamine antagonist
- alpha 1 adrenoceptor antagonist
- antihistamine
- anticholinergic effects
acepromazine is a (2)
- antiemetic
- vasodilator
butyrophenones sedative or tranquiliser
tranquiliser
butyrophenone action
- alpha 1 adrenoceptor blocker
- dopamine antagonist
example 1 butypophenone
azaperone
5 alpha 2 adrenoceptor agonists
- xylazine
- medetomidine
- dexmedetomidine
- detomidine
- romfidine
alpha 2 adrenoceptor agonist actions
centrally to inhibit norepinephrine release
- peripherally in post synaptic receptors
benzodiazepines actions
enhance affinity of GABAa receptor to GABA so enhancing inhibitory transmission
profofol metabolism
not all by the liver
alfaxalone anaesthesia is a (type)
steroid
alfaxalone given
i/v or i/m
ketamine is a
dissociative anaesthetic
ketamine given
i/v or i/m
ketamine pros
- some analgesic properties
- no CVS depression
thiopentone metabolism
slowly
it accumulates in body fat
thipentone given
i/v
if extravascular then get skin necrosis
etomidate pros
good in sick animals as minimal CVS/resp depression
etomidate cons
immunosuppresive
endotracheal tube and occlusion in lung overcome
murpheys eye in end of tube
3 methods maintenance with i/v
- intermittent boluses
- continuous rate infusion (CRI)
- partial i/v anaesthesia (PIVA) uses some gas as well
intermittent bolus mainenance anaesthesia cons
swinging plane of anaesthesia
solubility inhalational anaesthetics
more soluble in blood the less concentrated it is in brain
blood:gas partition coefficient define
- number of parts of gas in blood vs alveolus
- if high then means more soluble in blood
MAC define
- minimum alveolar concentration of gas required to prevent movment in response to pain in 50% of animals
isoflurane dog MAC
1.3
isoflurane MAC cat
1.6
isoflurane MAC horse
1.3
sevoflurane MAC dog
2.3
sevoflurane MAC cat
2.6
sevoflurane MAC horse
2.3
how much sevoflurane is metabolised
2%
% isoflurane metabolised
0.2%
sevoflurane metabolism theory
free fluoride ions released which are toxic to kidney
sevoflurane and older hot soda lime
react to make nephrotoxic compound
newer ones dont do this
nitrous oxide MAC
200%
nitrous oxide use
- used for mild analgesic properties
- speeds up second gas used
- has to be stopped 10 min before end to help reduce diffusion hypoxia as it reduces lungs O2 partial pressure
in horse during anaesthesia what needed for good recovery
good muscle perfusion
horse systolic blood pressure
110
horse diastolic blood pressure
70
horse mean blood pressure
90
ABP monitoring indirect method how to
- use cuff that has width of 40% of circumference
- find pulse using doppler thing
- inflate cuff till doppler stops
- deflate cuff and when noise starts thats the systolic blood pressure
oscillometric method arterial blood pressure monitoring pros
- gives systolic mean and diastolic pressures automatically
direct method ABP motioring how to
- put in arterial catheter
- measures everything with electronic transducer
pros of direct ABP measurment
- gives continuous blood pressure
- allows blood gas samples to be taken
pulse oximetry measures
- haemoglobin O2 saturation
- heart rate
pulse oximetry cons
- cant tell partial pressure O2
- misreads carboxyhemoglobin and methemoglobin
capnography measures
end tidal CO2
end tidal CO2 is normally
35-45mmHg
in hyperventilation and cardiac arrest ETCO2
decreases
in hypoventialtion ETCO2
increases
define hypoawemia
low O2 in blood
hypercapnia define
high CO2 in blood
3 causes of hypercapnia
- hypoventilation
- rebreathing exhaled gas
- increased basal metabolic rate
hypercapnia causes 6 things
- tachycardia
- arrhythmias
- hypertension
- increased intracranial pressure
- CV depression
- respiratory acidosis
intrapleural pressure is always
negative
IPPV causes intrapleural pressure to
go above 0 throughout resp cycle
increased intrapleural pressure causes
- decreased venous return and so decreased cardiac output
dobutanine effect on heart
- inotrope
- mild chronotroph
dobutamine actions
beta 1 receptors
increased intracranial pressure triggers what reflex
cushings reflex
rabbits prone to post op
post op ileus due to pain/stress
rabbit consider for anaesthetic
most rabbits have subclinical resp problem. assume that all rabbits have
indication of rabbit resp disease
nasal discharge
4 blood sample taking sites rabbit
- cephalic vein
- marginal ear vein
- lateral sephanous vein
- jugular
before inducing rabbit anaesthesia
- apply EMLA cream 1 hour before venepuncture
- place an i/v catheter
2 common premeds used on rabbit
- hypnorm
- medetomidine
EMLA cream is
mix of lidocaine and prilocaine
hypnorm is
mix of fentanyl and fluanisome
hypnorm cons
- resp depression
- poor muscle relaxant
- can induce ileus
alpha 2 agonist can be reversed with
atipamezole
intubating rabbit
spray larynx with anaesthetic
cons rabbit laryngeal mask
when cuff blown up can cut of circulation to tongue and make it go blue
3 commonly used unlicensed rabbit analgesic
opiods - bupenorphine - butorphanol NSAIDs - meloxicam
rats, mice, gerbil i/v access
lateral tail vein
guinea pig i/v access
medial metatarsal vein
healthy horse probability of anaesthetic death
1 in 110 horses
starvation time for horse pre op
8 hourse
starvation time pre laproscopy horse
48 hours
horses need what drug pre op
anti-tetnus
acepromazine is
long acting injectable premed
acepromazine actions
stabilizes cardiac membrane so reducing chances of adrenaline induced arrhythmia
alpha 2 adrenoceptor agonists action
sedation
analgesia in horse
- opiods
- NSAIDs
ketamine in horses usually used with what as induction
alpha 2 agonists
guaiphensin action
muscle relaxant
guaiphensin in horse anaesthesia
- given before induction or with induction
horse and intubation
will always damage the horse trachea
isoflurane horse recovery
can be too fast need a sedative to improve quality
isoflurane halothane compare
iso is more respiratory depressant so may need IPPV
lateral recumbency horse position anaesthesia
- front bottom leg should be a bit in front
- back bottom leg should be a bit behind
- head should be raised slightly
hypotension and horse anaesthetic
minimum blood pressure usually 30-45 minutes post induction, it improves normally due to an increase in systemic vascular resistance and so causes poor perfusion to extremities
tx hypotension (4)
- decreases anesthetic
- give large volume crystalloids
- inotropic agents
- hypercarbia (increase CO2)
hypercarbia define
increase of CO2 in blood
hypercarbia anaesthetic horse
- increases as horse is recumbent
- causes increased cardiac output and blood flow and muscle tremours
tx horse hypercarbia
IPPV
hypoxaemia anaesthetic horse
occurs in large horses in dorsal recumbency
how to external cardiac massage a horse
jump on it landing on its chest with your knees
major cause equine death post anaesthesia
equine post-anaesthetic myopathy
equine post-anaesthetic myopathy due to
poor perfusion through weight and hypotension
how to position a horse post anaesthetic
- left lateral recumbency if has been in dorsal
- if been in lateral you can leave to reduce chances of hypoxia or swap sides to improve muscle perfusion
3 consideration ruminant anaesthesia
- bloat
- salivation
- regurgitation
bloat and the heart
reduces venous return
IV sites cows
- tail vein
- jugular
- milk vein if desperate
sedation in ruminants done with
alpha2 agonists
alpha 2 agonists and ruminants 4 side effects
- pulmonary oedema
- reduces eructation and swallowing
- urine production
- urethral flow issues
- uterine contraction
3 local anesthetic licensed large animals
- procaine
- benzocaine
- tetracaine
2 types paravertebral block
- proximal
- distal
proximal paravertebral block where
- T13
- L1
- L2
distal paravertebral block where
at lateral processes of
- L1
- L2
- L4
caudal epidurals where
where dip made when tail lifted up and down
what caudal epidural block of
rectum and more depending on dose
2 induction agents cow
- xylazine
- ketamine
best combo anaesthetic for LA
ketamine and diazepam
when extubate ET tube LA
when animal can support its own head
halothane and small ruminants
can be hepatotoxic
camelids develop what with stress
third compartment stomach ulcers
pigs i/v injections
can use ear veins
pigs and intubation
hard as have small cricothyroid junction and marked laryngeal reflexes
how to intubate a pig
put in going down, rotate 180 and push round then rotate 180 again
define malignant hyperthermia
muscles contract producing a lot of heat
tx malignant hyperthermia
switch to dantrolene though it is expensive
prevention malignant hyperthermia
can do a test
pigs and anaesthetic risk (3)
- malignant hyperthermia
- hypothermia
- obstruction
1ml of blood weighs
1.2 g
dog has how much blood
80ml/kg
how long does mrphine last
4 hours
an overinflated ET tube can cause
tracheal rupture and generalised emphysema
