Anaesthetics: Principles and Pharmacology Flashcards
(39 cards)
What does anaesthesia mean?
Without feeling/ perception
What is general anaesthesia?
- An anaesthesia which produces insensibility in the whole body, usually causing unconsciousness
- Caused be centrally acting drugs
What is regional anaesthesia?
- An anaesthesia which produces insensibility in an area or region of the body
- Caused by local anaesthetics applied to nerves supplying the relevant area
What is local anaesthesia?
- An anaesthesia which produces insensibility in only the relevant part of the body
- Caused by local anaesthetic applied directly to the tissues
What types of drugs have been developed to be used in anaesthesia?
- Inhalational anaesthetics
- Intravenous anaesthetics
- Muscle relaxants
- Local anaesthetics
- 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 are titrated separately and are therefore more accurate to requirements
- Helps to prevent overdose
- Allows flexibility
What problems does polypharmacy present?
Increased chance of drug reactions/ allergies
What problems does muscle relaxation present?
- Requirement for artificial ventilation
- Means of airway control
What problems does separation of relaxation and hypnosis present?
Risk of awareness
How do general anaesthetic agents work?
- Interfere with the neuronal ion channels
- Hyperpolarise the neurones making them less likely to fire
- Inhalational agents dissolve in the membranes to have a direct physical effect
- IV agents work by allosteric binding to GABA receptors to open chloride channels
- Leads to loss of cerebral function from most complex to most primitive
What care is required when a patient is under general?
- Airway management
- They have an impairment of respiratory function and control of their breathing
- Cardiovascular monitoring
- General care of an unconscious patient
- Long drawn out resus
What are the features of IV anaesthesia?
Rapid onset of LOC
-1 arm to brain circulation
Rapid recovery
- Due to the disappearance of the drug from circulation
- Redistribution vs metabolism
How does the concentration of IV agent differ in tissue over time?
- Decreases in blood and vessel rich organs
- Rapid increase then slower decrease in viscera
- Slow increase and decrease in muscle
- Slow increase in fat
What are inhalational agents composed of?
Halogenated hydrocarbons
How are inhalational anaesthetics administered?
- At induction given at high levels to create concentration gradients (lungs>blood>brain)
- They therefore cross the alveolar BM easily
- The arterial concentration equates closely to alveolar partial pressure
What is MAC?
- Minimum alveolar concentration
- The concentration of drug required in the alveoli to produce anaesthesia
- Low number= high potency
What are the features of inhalational anaesthetics?
Induction
-Slow
Maintenance
-Can be used to 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?
- Inhalational induction and maintenance
- IV induction and maintenance
Most common
-IV induction and inhalational maintenance
What IV agents are used?
- Propofol
- Opiate (remifentanil)
