Anaesthesia Flashcards
pre-op assessment
- full history
- owner questioning
- previous reaction to drugs
- confirm pre-op fasting times
pre-op fasting advantages/disadvantages
- reduces GOR, regurgitation, aspiration
- prolonged starvation can increase risk of GOR
routes of admin for induction
injectable (IV / IM)
inhalant (face mask / induction)
options for airway management
mask
laryngeal (LMA)
supraglottic device (V-gel)
ETT
complications during induction
- lack of airway patency
- aspiration/regurgitation
- hypothermia
- post-induction apnoea
FGF calculation
(BW x TV) x RR x CF
Min vol x RR x CF
dosage calculation
weight x dose/strength
2nd gas effect
2 gases in alveoli, nitrous diffuses into blood first as it has a bigger conc gradient. this concentrates the second gas which can then also diffuse into blood
equine catheter placement
left jugular vein
equine anaesthetic technique
ensure 5 point stance
how to perform a pre-anaesthetic assessment
- full history
- owner questioning (temperament)
- previous reactions to drugs/anaesthetics
- full clinical examination
- confirm pre-op fasting times
- procedure
ASA classification
ASA I- normal, healthy patient
ASA II- mild systemic disease
ASA III- systemic disease, well compensated or controlled by treatment
ASA IV- severe uncompensated systemic disease
ASA V- unlikely to survive 24hrs
pre-op fasting goal
the reduce volume of the stomach contents to prevent GOR/regurgitation and aspiration
pre-op fasting recommendations
cats- 6-8hrs
dogs- 8-10hrs
rabbits/small furries- no starvation, withhold food 30 mins before
- prolonged starvation can increase GOR
informed consent facts
- legal document to be stored on patient record
- must ensure owner understands what has been signed
- give copy of consent form to owner
communication to owner
- give realistic time frames for communication
- keep communication open
oxygen cylinder storage
- molybdenum steel
- well ventilated fire-proof room
- store full and empty cylinders seperately
cylinder yolk
screw that attaches to cyclinder
- contains a bodok seal providing a gas-tight seal
- allows unidirectional flows
- pin index safety system- prevents the cylinder being attached to the wrong inlet
pin index safety system
yolk on the anaesthetic machine has 2 protuding pins
- aligned with holes on the corresponding gas cylinder
- prevents the wrong one being attached to the wrong inlet
anaesthetic pipelines
- pipelines connect the anaesthetic machine to schrader sockets which attach to main source
- schrader probes- unique diameter index
-non-interchangeable screw thread- unique profile of each nut and probe for each gas
pressure regulator
- cylinder pressure needs to be reduced to a safe level (400kPa)
- smooths any fluctuations of pressure from gas supply
pressure gauges
- indicates the pressure of gas in kPa
- cyliner pressure is proportional to vol of gas contained in it
- as cyclinder empties, pressure gauge drops
- shows when the cylinder needs to be changed
O2 failure alarm
- should sound when the supply drops below 200kPa
- should cut out nitrous oxide delivery
- not all machines will make audible noise (warning message instead)
hypoxic guard
- not present in all machines
- O2 and N2O control valves are mechanically linked
- maintains min ratio
- prevents hypoxic micture being delivered to patient
check valve/non-return pressure relief safety valve
- positioned downstream of vaporiser
- prevents backflow of gas back into machine
- protects machine not patient
check valve/non-return pressure relief safety valve
- positioned downstream of vaporiser
- prevents backflow of gas back into machine
- protects machine not patient
flowmeter/rotameter
- measures the flow of a specific gas passing through
3 parts:
1. flow control valve- allows adjustment of gas flow
2. tepered transparent tube- visual scale
3. bobbin- floats as gas passes around (higher flow= higher bobbin)
vaporizers
- found on back bar of machine
- downstream of flowmeter
- contains volatile agent/liquid anaesthetic
- as gas passes through, it picks up vapour to pass to patient
common gas outlet
- attachment of breathing system
- delivers gas/es and anaesthetic agent to patient
- if obstructed the pressure relief safety valve should open
calibrated vaporizers
- gas enters and splits into:
1. bypass channel (avoids liquid anaesthetic)
2. into chamber (above liquid anaesthetic)
TEC- temp compensation mechanism
- wicks- increase surface area for evaporation of anaesthetic
- baffles- direct incoming gas down closer to surface of liquid
O2 flush
- supplies oxygen at 400kPa and 35-75L/min
- bypasses flowmeters and vaporizer
- use can cause barotrauma
- dilution of anaesthetic gases
scavenging definition
- removal of environmental contaminants
- waste anaesthetic volatile agents
two types:
1. active
2. passive
active scavenging
- waste gases are drawn outside the building by a fan and vent system
- requires an air break to prevent negative pressure applied to patients breathing system (prevents air being sucked out of patient)
passive scavenging
- waste gas is pushed by patients expiratoru effort into tubing either:
1. tubing leading out of the building (increases difficulty to exhale due to increased resistance)
2. tubing leading to a canister containing active charcoal (doesnt absorb N2O)
advantages and disadvantages of passive scavenging
advantages:
- versatile
disadvantages:
- canister needs to be weighed regularly
oxygen concentrators
- takes in air and purifies it
- used for at home patients requiring oxygen
- uses a moleccular sieve containing zeolite which removes nitrogen leaving the air 87-95% O2
liquid O2 supply
- to be kept at -183 degrees
- passed through a vaporiser and turned into a gas before being piped inside the building
patient saftey features on anaesthetic machines
- pin index system
- ratio regulators
- nitrous oxide cut-out
- O2 failure alarm
- reserve oxygen cylinders
dead space
volume of gas that doesnt eliminate CO2
tidal volume
volume of gas entering the lung with each inspiration
minute volume
volume of gas entering the lungs within a minute
functions of a breathing system
- provide O2 +/- anaesthetic agent
- enable IPPV or spontaneous ventilation
- enable scavenging of expired gases
non-rebreathing system components
- attachment to ET tube
- inspiratory and expiratory tubes
- APL valve
- reservoir bag
rebreathing system components: circle
- soda lime canister
- tubing to ET tube, scavenging
- reservoir bag
- unidirectional valve