Drugs Used for the Induction of Anaesthesia Flashcards
What are the aims of anaesthetics?
Amnesia
Analgesia
+/- muscle relaxation
What are the phases of general anaesthesia?
Induction
Maintenance
Emergence
What apparatus is used in spontaneous ventilation?
Laryngeal mask airway (LMA)
In which patients is spontaneous ventilation used?
Those with minimal aspiration risk
What apparatus is used in intermittent positive pressure ventilation (IPPV)?
Endotracheal tube (ETT)
In which patients is IPPV used?
Those with minimal aspiration risk, and
- Muscle relaxant needed for surgery
- Intra-abdominal pathology
- Obesity
- Shared airway
- Prone position
- Long procedure
For whom is rapid sequence induction used?
Those at high risk of gastric aspiration; eg:
- Pregnancy
- Unfasted patients (SBO)
What is the most common agent used to induce general anaesthesia?
Propofol
What is the onset and offset of propofol?
Short
What is the post-anaesthesia effect of propofol?
Smooth wake-up
No hangover effect
What is the mechanism of action of propofol?
Potentiates action of GABA receptors > inhibits neurotransmission
What is the metabolism of propofol?
Mostly hepatic metabolism
- Liver dysfunction doesn’t change dose
What are the central nervous system effects of propofol?
Sedation
Induces general anaesthesia
No analgesia
What are the cardiovascular effects of propofol?
Decreases MAP
What are the respiratory effects of propofol?
Dose dependent ventilation depression
Apnoea in 25-30%
Decreased response to hypoxia
Decreased laryngeal and pharyngeal reflexes
What are the other effects of propofol?
Anticonvulsant (potential)
Anti-emetic
Antipruritic
Pain on injection
What is the mechanism of action of ketamine?
NMDA receptor antagonists
What is the metabolism of ketamine?
Hepatic
What is the excretion of ketamine?
Renal
What are the central nervous system effects of ketamine?
Dissociative amnesia Disconnects cortical and limbic system Intense analgesia Emergence delirium Cerebral vasodilator - Don't use in head injury because increases ICP
What are the cardiovascular effects of ketamine?
Increases
- MAP
- HR
- CO
What are the respiratory effects of ketamine?
No airway depression
Airway irritant > increased secretions and salivation
What are the analgesic uses of ketamine?
Chronic pain management
In which patients is ketamine useful for in the induction of anaesthesia?
Haemodynamically unstable patients
What is the drug class of fentanyl?
Synthetic opioid
What is the metabolism of fentanyl?
Hepatic
What are the central nervous system effects of fentanyl?
Analgesia
Euphoria/dysphoria
Sedation
What are the respiratory effects of fentanyl?
Respiratory depression
Depressed airway reflexes
Reduces response to hypercapnia/hypoxia
What are the cardiovascular effects of fentanyl?
Decreased HR
What are the other effects of fentanyl?
Itch
Constipation
What are the five actions of benzodiazepines?
Anxiolysis Sedation Retrograde amnesia Anticonvulsant activity Muscle relaxant
What is the drug class of midazolam?
Benzodiazepine
When is midazolam used?
Anxiolysis prior to induction of anaesthesia
Can be used as adjunct to opioids and propanol for sedation
