Anaesthetics: Principles and Pharmacology Flashcards
what does anaesthesia mean?
without feeling/ perception
what is general anaesthesia?
produces insensibility in the whole body usually causing unconsciousness
caused by centrally acting drugs: hypnotics, analgesics
what is regional anaesthesia?
produces insensibility in an area or region of the body
local anaesthetics applied to nerves supplying the relevant area
what is local anaesthesia?
produces insensibility in only the relevant part of the body
local anaesthetic applied directly to the tissues
what types of drugs have been developed to be used in anaesthesia?
anaesthetics: inhalational, intravenous, local
muscle relaxants
analgesics
what advancements have been made in anaesthetic techniques and equipment?
- tracheal intubation
- ventilation
- fluid therapy
- regional anaesthesia
- monitoring
what is the triad of anaesthesia?
- analgesia
- hypnosis
- relaxation
what agents assist in relaxation during anaesthesia?
- muscle relaxants
- local anaesthetics
- general anaesthetic agents
what agents assist in analgesia during anaesthesia?
- local anaesthetics
- opiates
- (general anaesthetic agents)
what agents assist in hypnosis during anaesthesia?
- general anaesthetic agents
- (opiates)
what is meant by balanced anaesthesia?
using multiple agents to do different jobs
- doses titrated separately = more accurate to requirements
- prevents overdose, allows flexibility
what problems does polypharmacy present?
increased chance of drug reactions/ allergies
what problems does muscle relaxation present?
- artificial ventilation
- airway control
what problems does separation of relaxation and hypnosis present?
risk of awareness
how do general anaesthetic agents work?
hyperpolarise neurones making them less likely to fire
inhalational agents
- dissolve in membranes -> direct physical effect
IV agent
- allosteric binding to GABA receptors -> open chloride channels
what care is required when a patient is under general?
ABC - long drawn out resus
- airway management
- respiratory function (breathing)
- cardiovascular monitoring
- care of an unconscious patient
what are the features of IV anaesthesia?
rapid onset of unconciousness
rapid recovery
how does the concentration of IV agent differ in tissue over time?
- blood and vessel rich organs: decreases
- viscera: rapid increase then slower decrease
- muscle: slow increase and decrease in muscle
- fat: slow increase
what are inhalational agents composed of?
halogenated hydrocarbons
how are inhalational anaesthetics administered?
uptake and excretion via lungs
- partial pressure gradient: lungs > blood > brain
- cross the alveolar BM easily
- arterial partial pressure equates closely to alveolar partial pressure
what is MAC?
minimum alveolar concentration
- drug concentration required in alveoli to produce anaesthesia
- low number= high potency
what are the features of inhalational anaesthetics?
induction: slow
maintenance: prolong duration and therefore very flexible
awakening: stop inhalational administration
washout using gas agent minus the anaesthetic to reverse concentration gradient
what sequences of anaesthesia can be used?
IV induction and inhalational maintenance
what IV agents are used?
- propofol
- opiate (remifentanil)
