1/8 General Anaesthesia Flashcards
(42 cards)
Name two main general anaesthetic targets and describe how they work.
GABA receptor: chloride channel, when open it allows Ca2+ into the cell causing hyperpolarization –> has inhibitory action
NMDA receptor: excitatory amino acid receptor, allows sodium and Ca2+ into cell, ketamine and nitrous oxide will antagonize the receptor (blocking etc.)
Name some other potential targets of general anaesthetic.
Two-pore domain K+ channels
Glycine receptors
Na+ channels
What is the overal mechanism of general anaesthetics?
Decrease in neurotransmission in the CNS –> loss of consciousness
What is anaesthetsia?
Loss of feeling
What is affected by general anaesthesia?
The whole body
What is affected by local anaesthesia?
Affects part to which it is applied (blocks local sodium channels to prevent excitation)
What is general anaesthesia?
A state of reversible unconsciousness with reduced sensitivity and response to stimuli.
What are the three required components needed to achieve general anaesthesia?
Unconsciousness
Analgesia
Muscle relaxation
Why do we use anaesthesia in animals?
To preform painful surgical/diagnostic procedures
To minimise patient suffering
To reduce risk to the vet and other individuals
To facilitate the procedure by immobilising the patient
Anaesthesia is typically acheived using more than one drug, name the three different categories of drugs used.
Premedicant drugs
Induction drugs
Maintenance durgs
What are premedicant drugs?
Drugs given prior to a general anaesthetic
Typically a sedative-opioid combination
What are induction drugs?
Usually IV agents
Used to achieve the transition from consciousness to unconsciousness
What are maintenance drugs?
Usually inhalents
Drugs used to maintain the anaesthetic state
What are the stages of anesthesia?
Stage 1: voluntary movement
Stage 2: Involuntary movement/excitation
Stage 3: Surgical anesthesia
Stage 4: Medullary paralysis (death)
What stages of anesthesia do modern drugs aim to avoid?
Stage 1 and 2
Almost all general anesthetics have a narrow therapeutic index (careful- want to avoid stage 4 too)
What system do you want to target with anesthetics?
CNS
What are the routes of administration for anesthetics?
Need to get drug to site of action quickly- crossing cell barriers
- IV, inhalation (other routes too slow)
Lipid solubility a key characteristics in allow drug across cell membranes and around body.
What makes the lungs a good drug delivery route?
Vast surface area, well perfused with blood supply
Can be used in systemic administration or locally.
What characteristics are important in a drug to allow for transport throughout the body (lipid theory)?
Receptor/protein targets
Lipid solubility
What are the advantages and disadvantages when using IV anesthetic agents for induction of anesthesia?
Advantages:
- rapid smooth induction (minimal excitment)
- rapid protection of the airways
- no environmental pollution
Disadvantages:
- IV access required
What is it called and what is required when using IV anesthetics for maintenance?
Total intravenous anesthesia (TIVA)- meaning that the entire anesthesia process is achieved through IV
Suitable pharmacokinetics are required
What are inhalation anesthetic agents typically used for?
Maintenance and occasionally to induce anaesthesia
What are the advantages and disadvantages of using inhalation agents for maintenance?
Advantage:
- delivery/elimination depends on ventilation
- rapid adjustment of anesthetic depth (breath-by-breath)
Disadvantages:
- equipment required (endotracheal tube, carrier gas (O2), vaporiser, breathing system etc.)
- environmental pollution
What are the advantages and disadvantages to using inhalation anesthetics for induction?
Advantages:
- IV access can be secured after induction
Disadvantages:
- Environmental pollution
- Takes longer and delay in securing airway can be issue
