Anaesthetics Flashcards
What are the two types of anaesthetic that can be given?
General and local
What is meant by the term MAC
Minimum alveolar concentration - the concentration at which 50% patients fail to move to surgical stimulus.
At equilibrium alveolar concentration is equal to spinal cord.
It is a measure of potency for volatile anaesthetics.
Typically, what medication is given at the pre-op stage
Benzodiazepines- hypnotic
Most anaesthetics have which element group attached to their structures?
Fluorine or chlorine
Which chemically inert element is commonly used in children as an anaesthetic?
Xenon
What three things do anaesthetics affect?
Muscle tone
Eye movement
Breathing
What is the first thing to be affected by anaesthetic?
Memory closely followed by consciousness
Why is volatile anaesthetic often given as a mixture with NO?
Reduces the MAC, therefore less dose is required for therapeutic effect
Why is analgesia also given to patients?
To aid recovery
Why are muscle relaxants given before intubation?
Anaesthetic whilst causing relaxation, doesn’t allow complete access to the airways and therefore relaxants aid intubation.
Why is intubation essential in the anaesthetised patient?
Because the muscles of inspiration become paralysed due to the systemic effect of muscle relaxation; without intubation, the patient will die.
In which ways can general anaesthesia be administered?
Inhaled or IV
What is meant by the term conscious sedation?
Small amount of anaesthetic or benzodiazepine to induce a ‘sleep-like state’ where maintain verbal contact but feel comfortable.
Which drug is given to patients before they are in recovery?
An anti-vomiting and nausea agent.
What is unusual about Guedel’s signs in stage 2?
Unconscious, erratic breathing and delirium can occur, leading to an excitement phase.
Anaesthesia is a combination of what 4 things?
Analgesic
Hypnotic
Depression of spinal reflexes
Muscle relaxant
What factors impact on MAC?
Age Hyperthermia/hypothermia Pregnancy Alcoholism Central stimulants Other anaesthetics Opioids
What partition coefficients affect induction and recovery of anaesthesia?
Blood:gas partition
Oil:gas partition
What are the main receptors which are targeted by anaesthetics?
GABAa receptors - with the exception of Xe,N2O and ketamine.
NMDA is the other potential target
What specific brain systems are targeted by anaesthetics?
Reticular formation
Hippocampus
Brainstem
Spinal cord dorsal horn and motor neurones
Name the main intravenous anaesthetics
Propofol- rapid
Barbiturates -rapid
Ketamine - slower
Target sites are GABAa except ketamine which is NMDA.
Potency in IV anaesthetics
Plasma concentration to achieve specific end point:
Induction in mixed anaesthesia - bolus to end point and then switch to volatile
TIVA (TOTAL IV ANAESTHESIA) use a defined PK based algorithm to infuse at a rate to maintain set point. Proceeded by a bolus.
Give examples when a local or regional anaesthetic may be used?
Dentist Obstetrics Regional/minor surgery Post op Chronic pain management
Name local anaesthetics
Lidocaine
Bupivacaine
Ropivacaine
Procaine
