Drugs Flashcards
What IV induction agents are used in anaesthetics?
-Propofol
-Thiopentine
-Etomidate
-Ketamine
What are the main and positive features of propofol?
-Most commonly used inducted agent
-Lipid-based, white
-Excellent at SUPPRESSING AIRWAY REFLEXES
-Decreases incidence of PONV
What are the negative effects of propofol?
-Causes a marked drop in BP and HR
-Can cause involuntary movements
What are the main features of thiopentine?
-A barbiturate
-Has a faster onset of action than propofol
-Used mainly in RAPID SEQUENCE INDUCTION
-Has anti-epileptic properties and PROTECTS THE BRAIN
What are some negative effects of thiopentine?
-Drops BP but increases HR
-Can cause a rash / bronchospasm
-Contraindicated in prophyria
What are the main features of etomidate?
-Rapid onset
-LOWEST INCIDENCE OF HYPERSENSITIVITY REACTION
What are some negative effects of etomidate?
-Spontaneous movements
-High incidence of PONV
What are the main features of ketamine?
-Causes DISSOCIATIVE ANAESTHESIA (anterograde amnesia + profound analgesia)
-Slow onset (90 seconds)
What are the negative effects of ketamine?
-Rise in HR and BP
-N+V
-Vivid dreams, hallucinations
What are the dose ranges for IV induction agents?
-Etomidate = 0.2-0.3mg/kg
-Ketamine = 1-1.5mg/kg
-Propofol = 1.5-2.5mg/kg
-Thiopentine = 4-5mg/kg
What inhalational anaesthetics are there?
-Sevoflurane
-Desflurane
-Isoflurane
What are the main features of each inhalational agent?
-Sevoflurane = sweet smelling
-Desflurane = low lipid solubility, rapid onset and offset, good for long operations
-Isoflurane = least effect on organ blood flow
What is the difference between depolarising and non-depolarising neuromuscular blockers?
DEPOLARISING = act on nicotinic receptors and are very slowly hydrolysed by acetylcholinesterase, causing muscle to contract, then fatigue and relax
NON-DEPOLARISING = block the nicotinic receptors, causing the muscle to relax
What are examples of procedures where neuromuscular blockers would be used?
-Mid-line laparotomy (paralysis of abdominal muscles)
-ENT operations (relaxation of vocal cords)
What are the features of depolarising NMBs?
-SUXAMETHONIUM is main one
-Has a rapid onset and offset
-Used in rapid sequence induction
-Adverse features = muscle pains, fasciculations, malignant hyperthermia, suxamethonium apnoea
What are the features of non-depolarising NMBs?
-Slow onset and variable duration
-Less SEs
-Compete with ACh for receptors
-Reversal by geostimine and glycopyrrolate
What are examples of non-depolarising NBMs and how are they categorised?
-Short-acting = atracurium, mivacurium
-Intermediate-acting = vecuronium, rocuronium
-Long-acting = pancuronium
What is neostigmine and how does it work?
-Reversal agent
-An anti-cholinesterase, prevents breakdown of ACh
-Combined with anti-muscarinic agent glycopyrrolate
What anti-emetics are commonly used in anaesthesia?
-Ondansetron (most commonly used) = 5HT3 blocker
-Cyclizine = antihistamine
-Dexamethasone = steroid
-Metaclopramide, haloperidol = anti-dopaminergic
What analgesics are used in anaesthetics?
-Opioids
-Morphine
-Paracetamol
What is the process of general anaesthesia?
- Arrival
- Monitoring
- IV access
- Induction of anaesthesia –> analgesia, muscle relaxation
- Maintenance of amnesia, analgesia, muscle relaxation and replacement of fluid / blood
- Reverse muscle relaxation but maintain post-op analgesia
- Transfer to recovery
What are ephedrine, phenylephrine and metaraminol and how do they work?
-Vaso-active drugs causing rise in BP
-EPHEDRINE = rise in HR and heart contractility causing a rise in BP
-Phenylephrine = vasoconstriction causes rise in BP and drop in HR
-Metaraminol = vasoconstriction causes rise in BP
Where can you do a spinal block?
-Aiming for subarachnoid space but avoiding spinal cord
-Between L2 and S2
(spinal cord ends in lower border of L1, subarachnoid space ends at S1)
Where can you do an epidural injection?
-Aiming for epidural space but want to minimise risk of damage to spinal cord
-Below L1 reduces risk
-For labour analgesia = done at same level as spinal
-For laparotomy = done at thoracic level
Why are neuraxial blocks preferred over opioids?
-Better for those with respiratory disease - painful wounds may cause reduced lung expansion and increased risk of post-op respiratory depression
-IV analgesics are less desirable for those with obstructive sleep apnoea and PONV
What safe doses of local anaesthetic are used?
-Lignocaine (0.5 and 1%) without adrenaline = 3mg/kg
-Lignocaine with adrenaline = 7mg/kg
-Bupivicaine (0.25 and 0.5%) = 2mg/kg
How do you calculate a maximum dose in ml for a patient?
-Recommended dose x weight / concx10
-Eg lignocaine without adrenaline 0.5% for a 65kg man = 3x65 / 0.5x10
What are the signs and symptoms of local anaesthetic toxicity?
-Numbness around the mouth, tongue paraesthesia
-Dizziness
-Restlessness and agitation –> CNS depression
-Muscle twitching
-Respiratory arrest
-Cardiac arrhythmias
