Anaesthesia for Dental, Ocular and Airway Surgery Flashcards
what range of procedures fall under dental surgery?
scale and polish to full resections and jaw repair
what is the main obstacle to anaesthetic monitoring with dental procedures?
access to mouth and face can be difficult
what is a significant risk associated with dental procedures?
aspiration and hypothermia
why are aspiration and hypothermia such a risk with dental surgery?
lots of water used
what types of patient are often having dental surgery?
geriatric
those with underlying conditions
what are the main anaesthetic considerations associated with dental surgery?
pain
haemorrhage
hypothermia
aspiration of water/fluids
procedure could be very long
concurrent disease
is dental scaling alongside other surgical procedures recommended?
no
what are the anaesthetic considerations for geriatric patients?
reduced functional residual capacity
reduced cardiovascular reserve
reduced muscle mass
increased fat tissue
prone to hypothermia
may have reduced liver and kidney function
what is the effect of reduced cardiovascular reserve in geriatric patients?
baroreceptor function reduced so more prone to hypotension
less tolerant of tachycardia as max HR is lower
what is the effect of reduced functional residual capacity in geriatric patients?
more prone to hypoxia
what is functional residual capacity?
volume remaining in the lungs after a normal, passive exhalation
what is the effect of reduced liver and kidney function in geriatric patients?
reduced drug metabolism
longer duration of action
exacerbated drug effects
what tests may be carried out on a patient pre-op?
blood and urine testing
US
ECG
X ray
full clinical exam
assessment of other disease processes
what is commonly seen in cats with dental disease?
anorexia
why may preoperative fluid be needed for geriatric patients?
support for kidneys to prevent reduction in GFR and further damage
why must hypotension be avoided in patients with underlying kidney disease?
reduced GFR can exacerbate kidney problems
what medication may dental patients be on already?
NSAIDs
antibiotics
what must be considered when picking a breathing system for dental surgery?
no mcgill (eww)
what are the intraoperative considerations for dental surgery?
analgesia
manage airway
hypothermia is significant risk
eye care (human and patient!)
what additional analgesia can be considered for dental procedures?
local block
why is MAC sparing important especially for geriatric patients?
VA have significant vasodilatory effect and so lead to hypotension - need to avoid in geriatric patients
what type of ET tube must be used in dental surgery and why?
cuffed due to high risk of aspiration
what must be placed in the mouth prior to dental surgery commencing?
mouth pack (may need to change if surgery is long)
what is involved in ET tube management during a dental?
ensure no kinking or twisting
care when turning the patient
what are the main concerns if a dental procedure is running long?
hypothermia
patient may be wet
require sedation top up
what type of mouth gaga must be avoided in cats?
spring loaded
why must spring loaded mouth gags be avoided in cats?
can cause damage to facial nerves and could lead to blindness
define MAC
minimum concentration of vapour in the alveoli that is needed to prevent motor response in 50% of subjects in response to surgical stimulus
is haemorrhage a concern in dental surgery?
yes - mouths can bleed a lot, also may be difficult to calculate with the volume of water in use
what are the main positioning concerns during dental surgery?
will be in the same position for a while
joints should be padded
sores avoided
watch for atelectasis
what is atelectasis?
complete or partial collapse of the entire lung or lobe of the lung
when can atelectasis occur?
if the lung becomes deflated (patient in one lateral for too long) or filled with alveolar fluid
what can be considered if the dental procedure is taking too long?
staging - ensure owner is aware on admit that this may happen
why are local blocks for dental so useful?
dentals are very painful
MAC sparing
improved post op pain management
improved speed of recovery and return to eating
how long may local blocks provide post op pain management?
up to 6 hours
what should owners be made aware of if local blocks are to be used?
may be clipped patches on patients face
can RVNs perform dental blocks?
yes
what are the main dental blocks used?
rostral maxillary (infraorbital)
caudal maxillary
caudal mandibular
mental
what is blocked by a rostral maxillary (infraorbital) nerve block?
soft tissues, incisors, canine and premolar teeth
where is the infraorbital foramen located in dogs?
on the maxilla, dorsal to third maxillary premolar
why should care be taken when performing a rostral maxillary (infraorbital) block in cats and brachycephalic dogs?
foramen is located at the level of the medial canthus of the eye so care must be taken when injecting
what is the preferred maxillary block?
caudal maxillary
what is blocked by a caudal maxillary nerve block?
all bones of maxilla, soft and hard palates, soft tissues of the nose, upper lip, dentition rostral to maxillary second molar
where is the foramen located for a caudal maxillary block?
needle is inserted caudal and centrally behind the last maxillary molar
what is blocked by a mandibular nerve block?
entire hemimandible teeth of the lower jaw
where is the foramen for the mandibular nerve block located?
needle inserted percutaneously at the ventral angle of the mandible
why may bilateral mandibular nerve blocks be discouraged?
loss of sensation to tongue can affect ability to swallow
risk of damage to self due to lack of sensation during recovery
is a mental nerve block commonly seen?
no
what is blocked by a mental nerve block?
lower incisors, skin and tissues rostral to foramen
how easy is the foramen for a mental nerve block to find?
tough in small animals
easy to palpate in large animal
what type of mandibular block may be preferred in smaller animals?
mandibular
what equipment is needed for local block placement?
sterile needle and syringe
local agent
scrub
alcohol wipe/liquid
sterile gloves
what must be calculated prior to local block placement?
maximum patient dose
what must be considered when calculating maximum LA dose?
intubeaze
how much lidocaine is contained in one spray of intubeaze?
2.27mg in 0.14ml
what are the considerations post dental GA?
pain score and provide analgesia
keep warm
dry and clean patient
remove mouth pack and gag
TTE
IVFT if needed
thorough discharge to owners
what are the reasons for occular surgery?
cataracts
enucleation
eyelid mass removal
entropion
cherry eye
trauma
what are the pre op considerations for occular surgery?
pain
risk of eye rupture
underlying disease presence
specific medications the patient may be on
procedure to be performed
what medications may an ocular patient be on that must be considered/recorded?
NSAIDs
steroids
what may be done before ocular surgery?
bloods
clinical exam
history
pre-operative screening
what should be used to prep the eye?
iodine NOT hibi
what must be prevented from occuring pre or during eye surgery?
further eye trauma
how can further trauma to the eye be prevented under GA?
eye lube
care with masks
care with bear hugger
careful prep
what additional drugs may be needed for certain ocular procedures?
NMBA for central eye
why may NMBAs be useful for ocular procedures?
maintain a central eye
what is normal intraocular pressure?
15-20 mmHg
what is intraocular pressure determined by?
balance of aqueous humour production and absorption along with other factors e.g. pupil size, corneoscleral ridgidity, extraocular muscle tone and vascularity of globe
how should intraocular pressure be managed under GA?
avoid acute IOP increases
maintain normocapnia
avoid coughing (adequate depth)
avoid vomiting
avoid straining
avoid emetic drugs
awareness of drugs which affect IOP
avoid neck restraint
no jugular samples
avoid head down position
why should acute IOP increases be avoided?
to prevent damage to the eye
what drug should be avoided in patients underging ocular surgery?
ketamine
why is ketamine not advised for use with ocular patients?
may raise IOP
why is normocapnia vital for IOP?
hypercapnia leads to vasodilation and so raised IOP
what is the oculo-cardiac reflex?
sudden reduction in HR associated with traction on the eye or surrounding structures
what is the oculo-cardiac reflex caused by?
stimulation of the trigeminal and vagal nerves
what should happen if the oculo-cardiac reflex occurs?
surgical manipulation should stop and be managed by administration of anticholinergics
do NMBAs provide analgesia?
no!
how is a central eye most often maintained in ocular surgery?
NMBA
what are the analgesic considerations for ocular surgery?
pre-emptive and multimodal
opioids
NSAIDs
topical local drops
local blocks
what must be prevented in all ocular patients?
self mutilation - cone at all times as can rub face on things
what local block may be used during ocular surgery?
retrobulbar
what needle is used for retrobulbar blocks?
curved to access behind the eye
what nerves are blocked by a retrobulbar block?
2, 3, 4, 5 (ophthalmic and maxillary branches) and 6
what must be in place following all ocular surgery?
sedation and analgesia plan
what are the main post-op considerations for ocular surgery?
buster collar
analgesia
IVFT if needed
patient warming (care with eyes)
continue meds as needed
feed
outside
prevent increases in IOP (anti tussives/anti emetics)
sedation if necessary
why may patients with airway conditions present for surgery?
underlying airway condition
for treatment of airway condition
what types of procedures may an airway patient undergo?
BOAS
investigative bronchoscopy
tracheal stenting
laryngeal paralysis surgery
what body systems are impacted by BOAS?
airway
GI
skin
joints
eyes
what are the primary abnormalities seen with a dogs that has BOAS?
stenotic nares
aberrant nasal turbinates
elongated/thickened soft palate
tracheal hypoplasia
what are primary BOAS abnormailitys?
those that are identified early on and present before significant clinical signs
what are secondary BOAS signs?
those seen as a consequence of a long standing increase in inspiratory pressures
what causes secondary BOAS signs?
as a consequence of primary abnormalities patients have to pull harder on inspiration. This creates negative pressure in the throat, neck and chest leading to the secondary respiratory and digestive problems
what are the secondary BOAS abnormalities?
laryngeal collapse
eversion of laryngeal saccules
GI signs (reflux and regugitation)
what are the main BOAS pre-anaesthesia considerations?
IV access asap as long as low stress
prevent stress to prevent obstruction
consider IM sedation if IV not possible
if IM premed will require constant monitor
control temperature (ensure not too hot)
what must happen if a BOAS dog receives an IM premed?
constant monitoring
oxygen ready
intubation tray ready
suction if regurgitation
what is hypothermia on pre-op exam of BOAS dogs associated with?
poorer outcomes
what VA is best for BOAS patients?
sevo may lead to quicker recovery and increased pharyngeal tone so airway is safer
iso slower recovery which may be preferrable if animal is stressed
why is recovery time from sevo quicker?
lower blood solubility so less potent
why do patients with lower pre-op rectal temps lead have a poorer outcome in BOAS surgery?
rectal temperature is linked to perfusion
poor perfusion illustrates hypoxia
what can happen if IV premed is given to BOAS patients?
severe sedation and airway obstruction
what drugs are often used for BOAS premed?
ACP or alpha 2 agonist with an opioid
what sedation level is needed for BOAS patients?
depends - some may need sedation for longer to reduce stress, others may need to recover quickly to ensure airway patency
should BOAS patients be preoxygenated?
yes but only if its low stress
what can be used to aid BOAS intubation?
u cath or intubation stylet
what must happen to all BOAS ET tubes?
cuffed before head is lowered
what should be done to manage regurgitation and aspiration risk in BOAS dogs?
suction available
head up induction
head down if regurge occurs until airway is secured
what are the peri-operative considerations for BOAS patients?
airway management is vital
may need ventilation
monitor carefully
maintain heat but don’t cook!
eye care crucial
what parameter is often elevated in BOAS patients?
EtCO2
what are the post op considerations for BOAS patients?
observation is key
delayed extubation
midl sedation with ACP or butorphanol can help recovery
care with warming
O2 supplementation in recovery if needed
pulse ox if possible
home ASAP
when should BOAS patients be extubated?
once actively swallowing and maintianing airway
until they will no longer tolerate
what may be used to assist obstructing BOAS dogs?
nebuliser
what can be added to a nebuliser to support BOAS dogs if they are obstructing?
adrenaline
why can adrenaline via a nebuliser help obstructing patients?
causes vasoconstriction and so swelling reduced
why may NSAIDs not be given intraoperatively to BOAS patients?
may need steroids in recovery if obstructing and so cannot be on NSAIDs due to interaction with prostaglandins
in what animals is laryngeal paralysis often seen?
older
overweight
large breed dogs
how will an animal with laryngeal paralysis present?
stridor
exercise intolerance
panting
coughing
hoarse bark
what is stridor?
high pitched, harsh sound heard during inspiration or expiration resulting from airflow through an obstructed airway
what is stridor caused by?
partial or complete blockage of the nasal passages or larynx or collapse of the trachea
what environmental factors can worsen laryngeal paralysis?
heat
how can laryngeal paralysis be managed?
non -surgical
surgical
how is laryngeal paralysis managed non-surgically?
weight loss
exercise restriction
owner education
what surgery is used to manage laryngeal paralysis?
unilateral arytenoid lateralisation (tieback)
how should a patient presenting with acute laryngeal paralysis be treated?
in a quiet, stress free environment
no IVC initially to keep stess low
use a fan to cool and help O2 delivery
O2 if tolerated
start hosp sheet
butrophanol from vet if needed
leave alone but observed until calm
why do patients needing laryngeal paralysis surgery often present with dyspnoea?
due to closure of vocal cords
what can be used to support patients breathing before laryngeal tieback?
sedation
what is a significant risk with laryngeal paralysis patients?
aspiration
regurgitation
what drugs are often used following laryngeal tieback surgery?
antitussive
what may the VS wish to do before intubation in airway patients?
assess larynx
what is involved in the post op care of laryngeal paralysis patients?
close observation
monitor for regurge
pain score
avoid collars/neck leads
feed wet food from height
water from height
avoid excitement
consider sedation
what is a huge risk in the laryngeal tieback surgery recovery period?
aspiration pneumonia
what should laryngeal tieback patients be fed following surgery?
wet food in balls
from height
why may patients need bronchoscopy?
chronic cough
suspected lung infection
feline asthma
airway parasites
chronic AP
neoplasia
what parameter may be altered in patients in for bronchoscopy?
low saturation on room air
what may be given to patients before bronchoscopy?
terbutaline (especially in cats)
what is the benefit of terbutaline?
bronchodilation
what are the CVS effects of terbutaline?
tachycardia
what is usually performed alongside bronchoscopy?
BAL - bronchoalveolar lavage
what must be doe before any BAL is done?
sample taken of the scope itself to check for any artefact
what are the pre-op considerations for bronchoscopy?
history and clinical exam
assess degree of respiratory compromise
rule out cardiac disease
screening tests - (blood gas and xrays)
how may a patient be stabilised before bronchoscopy?
O2 and sedation if needed
inhaled bronchodilators
systemic steroids
antitussives
what is a key concern with airway management and bronchoscopy?
ET tube may have to be removed to fit scope in trachea
how could oxygen be delivered to a patient if the ET tube is removed for bronchoscopy?
flow by oxygen through a urinary catheter down beside the scope
what must happen to bronchoscopy patients before induction?
preoxygenation
why is temperature important in bronchoscopy patients?
coupage needed so may be uncovered and become cold
what drugs may be used for induction of anaesthesia for bronchoscopy patients?
propofol
ketamine
why may propofol and ketamine be used for anaesthesia for bronchoscopy patients?
bronchodillatory effects
how can the airway be managed during bronchoscopy?
large diameter ET tube - pass scope through
small diameter ET tube - extubate and use TIVA
could also use SGAd or LMA
what monitoring is especially useful while actively performing bronchoscopy?
pulse ox
doppler
why is TIVA of benefit for bronchoscopy?
anaesthetic maintained even when extubated
no risk of leakage of inhaled agent into room if ET tube is being moved
what are the potential intra-operative risks for bronchoscopy?
hypoxia
bronchoconstriction
desaturation
reduced lung compliance
laryngeal oedema in cats
airway or lung rupture
what may cause bronchoconstriction during bronchoscopy?
following BAL due to irritation caused by fluid
what will be seen on capnography if bronchoconstriction is present?
shark fin
when is airway or lung rupture likely during bronchoscopy?
following FB removal or biopsy
what equipment should be prepared for bronchoscopy?
scope
scope pre-sample
sterile saline
collection pots
mouth gag (not spring loaded in cats)
u cath
syringes
crash box
induction agent
why may a Ucath be used in bronchoscopy?
blind BAL
what is required during BAL?
coupage
what are the main bronchoscopy recovery considerations?
risky period
coughing likely
may obstruct
constant monitoring needed until standing
pulse ox if tolerated
O2 by mask/flow by if tolerated
head should be elevated
what serious complication may be seen following bronchoscopy?
pneumothorax (possibly tension)
what are the post bronchoscopy complications?
haemorrhage in the airways
desaturation
pneumothorax due to damaged bronchi
what is the difference between tension pneumothorax and simple pneumothorax?
tension has a one way valve which increases the compression of the lung by air in the pleural space with every breath
simple pneumothorax is non-compressive and air can still move in and out of the pleural space
what can be used if the ET tube is at risk of kinking during bronchoscopy?
armored ET tube
what is pharyngostomy intubation?
intubation of the pharynx - bypassing the oral cavity
when may pharyngostomy intubation be used?
where orotracheal intubation is not possible (e.g. fractured jaw)
what are the main monitoring challenges associated with dental, ocular and airway surgery?
access is limited
monitoring equipment may need to be placed elsewhere (e.g. SpO2 or temperature probe)
difficult to assess depth
eye lubrication key and may be difficult
what monitoring equipment is vital in managing tube patency?
capnography
when is nutrition a consideration?
all head / facial surgery especially if animal is previously anorexic
