Anaesthetics Flashcards
What are the broad categories of anasthesia?
- General
- Local
What are the methods of administration of general anasthesia?
- Inhalation, or volatile
- Intravenous
What is the difference in onset of action between inhalational and intravenous general anaesthesia?
Intravenous is quicker
What is conscious sedation?
The use of small amounts of anaesthetics or benzodiazepines to produce a ‘sleepy-like’ state
What are the stages in general anaesthesia?
- Premedication
- Induction
- Intraoperative
- Muscle paralysis
- Maintenenance
- Reversal of muscle paralysis and recovery, which includes post-operative analgesia
- Provision for PONV
What is often used in the premedication stage of anaesthesia?
A hypnotic, typically benzodiazepine
How is anaesthesia induction normally performed?
Usually IV, but may be inhalational
Give an example of a drug used in anaesthesia induction
Barbituates
What class of drug is usually used for intraoperative analgesia?
Opioids
What is the purpose of muscle paralysis in surgery?
To facilitate intubation/ventilation/stillness
Why is intubation important in anaesthesia?
Analgesia can cause respiratory depression, so you need a relaxant to allow airway access
How is maintenance anaesthesia administered?
Intravenous and/or inhalation
What is used for postoperative analgesia?
- Opioids
- NSAID
- Paracetamol
How is volatile general anaesthesia administered?
You fill a reservoir with the liquid drug which then evaporates. Fresh gas flows across evaporated liquid and the patient inahles it
What molecules will act as anaesthetics?
Any molecule with a volitile compononet
Describe the use of xenon as an anaesthetic
It is a very good anaesthetic in very high concentrations, and is good in neonates to prevent cerebral ischaemia
Give four examples of intravenous anaesthetic agents
- Propofol
- Barbiturates
- Etomidate
- Ketamine
What are the stages in Guedel’s signs?
- Stage 1 - Analgesia and consciousness
- Stage 2 - Unconscious, breathing erratic. Delirium could occur, leading to an excitement phase
- Stage 3 - Surgical anaesthesia
- Stage 4 - Respiratory paralysis and death
Describe the muscle tone in Guedel’s stage 1
Normal
Describe the eye movements in Guedel’s stage 1
Slight
How long does Guedel’s stage one last?
Only the first few breaths
Describe the muscle tone in Guedel’s stage 2
Normal to markedly increased
Describe the eye movements in Guedel’s stage 2
Moderate
Describe the muscle tone in Guedel’s stage 3
Progresses from slightly relaxed to markedly relaxed
Describe the eye movements in Guedel’s stage 3
Progresses from slight to none
Describe breathing in Guedel’s stage 3
Decreases until significantly reduced respiratory effort
What are the options once a patient reaches Guedel’s stage 4?
- Wake patient
- Ventilate the patient
What is anasthesia a combination of?
- Analgesia
- Hyponosis
- Depression of spinal reflexes
- Muscle relaxation
What is the end point of anasthesia dependant on?
Concentration
In what order to functions go under anaesthesia?
- Memory
- Consciousness
- Movement
- Cardiovascular response
What measure is used to describe potency for volatile anaesthetics?
MAC - Minimum Alveolar Concentration
What is MAC?
The alveolar concentration of the anaesthetic at which 50% of subjects fail to move to surgical stimulus
What is the alveolar concentration of anaesthetic equal to at equilibrium?
The concentration of anaesthetic in the spinal cord
What is the anatomical substrate for MAC?
The spinal cord
What important factor affects induction and recovery?
The partition coefficients (solubility)