Intro To Anaesthetics Flashcards
Types of anaesthesia
- General: inhalational/volatile or IV
- Local: regional
What is conscious sedation
Use of small amounts of anaesthetics or benzodiazepines to produce a sleepy like state
Routes of general anaesthesia
Inhalational/volatile
IV
Examples of IV general anaesthesia
Propofol
Barbiturates
Etomidate
Ketamine
What is anaesthesia a combination of?
- Analgesia
- Hypnosis (loss of consciousness)
- Depression of spinal reflexes
- Muscle relaxation
What drug is normally used as premedication anaesthesia?
Hypotonic-benzodiazepine
What class of drug is usually used as intra operative analgesia?
Opioid
Outline the polypharmacology of anaesthesia
- premedication: benzodiazepine
- induction: IV or inhalational
- intraoperative analgesia: opioid
- intubation: muscle relaxant
- maintenance: IV or inhalational
- reversal of muscle paralysis + recovery: opioid/NSAIDs/paracetaoml
- provision for post op N+V: antiemetic?
What is volatile anaesthetic potency described by?
Minimum alveolar concentration
Stage 1 Guedel’s signs
Analgesia
Consciousness
Stage 2 guedel signs
Unconscious
Breathing erratic but delirium could occur > excitement phase
Stage 3 guedel’s signs
Surgical anaesthesia
Stage 4 guedel’s signs
Respiratory paralysis + death
What is the anatomical substrate for minimum alveolar concentration?
Spinal cord
What factors affect induction + recovery + potency?
Partition coefficients (solubility)
- blood:gas partition determines induction + recovery
- oil:gas partition determines potency
What does the blood:gas partition determine?
Induction + recovery
What does the oil:gas partition determine?
Potency
What increases minimum alveolar concentration?
- hyperthermia
- pregnancy
- alcoholism
- central stimulants
What decreases minimum alveolar concentration?
- increasing age
- hypothermia
- Other anaesthetics + sedatives
- Opioids
Why is nitrous oxide often added to other volatile agents?
To reduce the dosing needed + reduce side effects
Relationship between lipid solubility + potency
High potency - high lipid solubility
Relationship between potency + GABAA interaction
High interaction -
Examples of volatile anaesthetics
Halothane
Isoflurane
Sevoflurane
Desflurane
Describe GABAA
- ligand gated ion channel
- major inhibitory transmitter
- potentiate GABA activity
- sedation, anaesthesia + anxiolysis
What receptors do anaesthetics work on?
GABAA
OR
NMDA glutamate receptor
What anaesthesia act on NMDA receptors?
Xenon
Nitric oxide
Ketamine
What affect do general anaesthetics have on parts of the CNS
- reduces connectivity between reticular system
- hippocampus depressed
- brainstem depressed
- spinal cord depress dorsal horn + motor neuronal activity
What are the uses of IV general anaesthetics?
IV for induction
Total IV anaesthesia alone
What is the mechanism of action of IV anaesthetics?
- propofol + barbiturates: potentiate GABAA
- ketamine: inhibits NMDA receptor
Uses of local + regional anaesthesia
- dentistry
- obstetrics
- regional surgery
- post op for wound pain
- chronic pain management
Basic local anaesthetic structure
Aromatic ring + amine
Linked by ester or amide link
Examples of local anaesthetics
Lidocaine
Bupivacaine
Ropivacaine
Procaine
Target site for local anaesthetics
Voltage gated sodium channel
What are the adverse drug reactions of general anaesthesia?
Post op N+V
Hypotension
Post operative cognitive dysfunction
Chest infection
Mechanism of action of local anaesthetics
Block VGNCs
This prevents AP from being produced
What are the adverse drug reactions of local anaesthetics?
- Depends on agent used + usually result from systemic spread
- Allergic reactions + anaphylaxis
- Cardiovascular toxicity due to blockage of VGNC
What is minimum alveolar concentration?
The concentration at which 50% of people fail to respond to surgical stimulus
Relationship between minimum alveolar concentration and potency
High MAC = lower potency
