Anaesthesia Flashcards
What is tidal volume
Volume of gas exhaled in one breath
10-15ml/kg x BW
What is minute volume
Volume of gas expired in one minute
TV x RR
Anatomical and equipment dead space
Volume of gas that is not involved in gas exchange
Anatomical- doesn’t reach alveoli
Equipment- in breathing circuit
What is neuroleptanalgesia
Combo of opioid and sedative to produce calm and pain reduced state
Anaesthesia sparing effect
Use of other agents or drugs to reduce amount of volatile agent needed
Second gas effect
Giving nitrous oxide to speed uptake of volatile agent
What is critical tension
Rise in anaesthetic agents in the blood that affects the brain
What is BG solubility coefficient
How likely agent is to dissolve in the blood (low does not dissolve easy and reaches brain quicker)
Sevo- low
ISO- high
What is the MAC
Minimum alveolar concentration- % concentration of agent in the alveoli for patient to the anaesthetised
Low MAC = more potent, high solubility
How are anaesthetic agents removed from the body
Exhalation
Metabolised by kidneys and liver
Excreted in bile and urine
4 responses to pain
Spinal- limb withdrawal
Medullary - increases HR, RR, BP
Hypothalamic- hormone release
Cortical- physical acts
What is balanced anaesthesia
Use of multiple drugs in combo to provide anaesthesia triad
Individual doses reduced and reduced drug effects
Triad of anaesthesia
- Narcosis
- Analgesia
- Muscle relaxation
Aims of pre med
Smoother induction and recovery
Sedation
Analgesia
Reduces anaesthetic doses
Counter effects of other drugs
4 methods to maintain anaesthesia
- Injectables alone
- Inhalation alone
- TIVA
- PIVA
Inhalation agents
Liquid at room temp (not N2O)- vaporised into gas
Mixed with carrier gas - N2O, O2, medical air
Iso, sevo, des
Injectables
Use of injectables
IV or IM
Alpha 2s, ketamine, opioids, benzos
TIVA
Total IV agents
CRI or incremental
Need to combine with analgesia
Propofol, alfaxalone, ketamine
PIVA
Partial IV
Mix of inhalation and injectable
CRI or incremental
Lidocaine (not for cats), opioids, ketamine
Neuromuscular blockage
Agents cause muscle relaxation
Need IPPV , analgesia, unconsciousness
Blocks action potential at NJM
Depolarising or non depolarising
Monitor with peripheral nerve stimulator
FGF formula
FGF rate= minute volume x circuit factor
Non rebreathing circuits
T piece
Bain
Lack
Magill
Humphrey ADE
Re breathing circuits
Circle
To and fro
Humphrey ADE circle
T piece circuit factor
2.5-3
Bain circuit factor
2.5-3
Lack circuit factor
1-1.5
Magill circuit factor
1-1.5
FGF calculation
- TV = 10-15mg/kg x BW
- MV= TV x RR
- FGF= MV x CF
