Anaesthetics Flashcards
What are the 2 main categories of anaesthesia?
General- Unconscious, requires support of ventilator
Regional- Block feeling to isolated area (eg: Limb)
What is the purpose of fasting before a general anaesthetic?
Empties stomach
Reduces risk of reflux stomach contents into oropharynx and being aspirated
What are the risks of aspiration in administering a general anaesthetic?
Can lead to aspiration pneumonitis and pneumonia
What are the fasting guidelines related to general anaesthetic?
6h no food/feeds before operation
2h no clear fluids (nil by mouth)
Outline preoxygenation in general anaesthetic
Several minutes before general anaesthetic breathing 100% oxygen
Gives reserve of oxygen between losing consciousness and successful intubation and ventilation
Outline premedication before general anaesthetic
Given to relax patient, reduce anxiety, reduce pain and make intubation easier
Benzo (midazolam)- Relax muscle, reduce anxiety (also causes amnesia)
Opiate (fentanyl)- Reduce pain and hypertensive response to laryngoscope
Alpha-2-adrenergic agonist (clonidine)- Sedation and pain
What is the purpose of cricoid pressure in an RSI?
Compresses oesophagus and prevents stomach contents refluxing into pharynx
What is the triad of general anaesthesia?
Hypnosis
Muscle relaxation
Analgesia
List IV options for hypnotic agents in general anaesthesia
Propofol (most common)
Ketamine
Thiopental sodium (less common)
Etomidate (rarely used)
List inhaled options for hypnotic agents in general anaesthesia
Sevoflurane (most common)
Desflurane (bad for environment)
Isoflurane (rarely used)
NO- Combined with others- May be used for children
What is a common way to administer hypnotic agents for general anaesthesia?
IV meds for induction agent, inhaled meds for maintenance
What is Total IV anaesthesia?
Uses IV meds for induction and maintenance of GA
Propofol most common
Give nicer recovery than inhaled options
Outline use of muscle relaxants in GA
Block NMJ
ACh released by axon but is blocked from stimulating response from muscle
Relax and paralyse muscles
What are the 2 categories of muscle relaxants used in GA?
Depolarising (eg: Suxamethonium)
Non-depolarising (eg: Rocuronium and atracurium)
What reverses the effects of NMJ blocking meds in GA?
Cholinesterase inhibitors- Neostigmine
Which med is used specifically to reverse effects of non-depolarising muscle relaxants following GA?
Sugammadex
What are the options for analgesia in GA?
Opiates most common:
Fentanyl
Alfentanil
Remifentanil
Morphine
What is given for symptoms control at the end of a procedure requiring GA?
Antiemetics:
Ondansetron
Dexamethasone
Cyclizine
What is the MoA of ondansetron and its CIs?
5HT3 receptor antagonist
Avoid in risk of prolonged QT interval
What is the MoA of cyclizine and which patients is caution given?
H1 receptor antagonist
Caution- HF and elderly
Outline emergence from GA
Before waking:
Muscle relaxant needs to wear off- Use nerve stimulator on ulnar nerve and watch for thumb movement
After waking:
Stop inhaled anaesthetic
Extubate when breathing for themselves
What are the risks of GA?
Sore throat
Post-operative N+V
Accidental awareness
Aspiration
Dental injury
Anaphylaxis
CV events- MI, stroke, arrhythmias
Malignant hyperthermia
Death
What is malignant hyperthermia?
Rare potentially fatal hypermetabolic response to anaesthesia
Certain medications and genetic mutations (autosomal dominant) increase risk
Which medications increase risk of malignant hyperthermia?
Volatile anaesthetics- Isoflurane, sevoflurane, desflurane
Suxamethonium
How does malignant hyperthermia present?
Hyperthermia
Increased CO2 production
Tachycardia
Muscle rigidity
Acidosis
Hyperkalaemia
How is malignant hyperthermia managed?
Dantrolene- Interrupts muscle rigidity and hypermetabolism- Interferes with movement of calcium ions in skeletal muscle
Outline peripheral nerve blocks
Regional anaesthesia
Patient remains awake
Local anaesthesia injected around specific nerves- Area distal anaesthetised
Injection under US guidance with nerve stimulator
When is central neuroaxial anaesthesia used?
C section
Transurethral resection of prostate (TURP)
Hip fracture repair
What is central neuraxial anaesthesia?
Spinal anaesthetic/spinal block
Type of regional anaesthesia
Local anaesthetic injected into CSF within subarachnoid space
Only used in lumbar spine (L3/4 or L4/5)
Takes 1-3h to wear off