Regional anaestesia Flashcards
What are the 2 parts of the anesthesia triage that are satisfied by regional anaesthesia
Analgesia and muscle relaxation
What are the 6 main benefits of regional anaesthesia
- Pre emptive analgesia
- Post op analgesia
- Hemodynamically stable
- Rapid recovery
- Reduces the surgical stress response
- Reduces the risk of general anaestesia
What is the mechanism of hypotension in neuraxial blocks
It causes sympathetic blockades that result in vasodialation
What are the 5 types of regional anaesthesia
- Topical
- Wound infiltration
- IV
- Peripheral nerve block
- Central nerve block
What are the 3 modes of delivery of topical anaesthesia
- Aerosolized
- Topical creams
- Direct application in drops
What are the 2 mechanisms of delivery of infiltration regional anaestesia
Sub cut
Intradermal
What are the 3 main types of peripheral nerve blocks
- Single nerve block
- Plexus block
- Deep infiltration e.g. Transversus abdominis plane block
What are the indications for a spinal and an epidural
A spinal provides complete anaesthetic while an epidural is used for analgesia in combination with a GA
What are the 7 absolute contraindications to a neuraxial block
- Patient refusal
- Logistical issues e.g. inability to convert to a GA
- Local infections
- Coagulopathies
- Severe hypovolemia
- Raise ICP
- Fixed cardiac output states
What are some of the relative contraindications of a neuraxial block 7
- Systemic sepsis
- Uncooperative patient
- Preexisting neurological deficits
- Regurge lesions
- Severe spinal deformaties
- Previous spinal surgery
- Complex surgery where the block may not last long enough
What are the 4 common presentations of a high spinal
- Severe hypotension
- Bradycardia
- Difficulty breathing
- LOC
What is the mechanism of a post dural headache
CSF leakage from the hole in the dura causing traction on the meninges
What are 2 possible prevention strategies for post dural puncture headaches
- Small guage needles
- Pencil tip needles
What is the SG of CSF
1.004
What 3 surgery types are epidurals used in
- Thoracic
- Abdominal
- Hip and leg surgery
What are epidurals used for in labour
For analgesia in NVD
Which nerves are the easiest to block
Thinner are easier
Are myelinated or non myelinated easier to block
The easiest are myelinated fibers because they only need to be blocked at the nodes
WHat is the chemical structure of a LA
It is a lipophilic aromatic ring and a hydrophilic tertiary group that is attached with an intermediate ring
What are the 2 main classes of LA
- Esters
- Amides
What are examples of ester LA
Cocaine
What are 3 examples of amide LA
- Lignocaine
- Bupivacaine
- Ropivacaine
Which form of the drugs can cross the neuronal membrane and how does that affect the drug
Only non ionised forms of the drug can cross, because the drug is a weak base at low pH it becomes dissociated and thus ionised
What are the factors that affect the activity of LA
- Lipid solubility
- Intermediate chain
- Protein binding
- pKa
- pH
Which LA can cause CVS toxicity
Bupivacaine
What is the MOA and reason for giving Intralipid
Acts as a circulating lipid sink that acts to bind free bupivicaine
What are 3 ways of preventing systemic toxicity
- Avoid exessive doses
- Use vasoconstriction in the area
- Avoid intravascular injections
What is the benefit of adding NaHCO3- to the LA
It increases the pH meaning that there is a higher proportion of unionised drug
What are the contraindications to vasoconstriction in LA
- Areas with no colateral supply
- IV regional anasetics
- Unstable angina or dysrrhythmia
- Placental uterine insuffiecenty
- Psychiaric drugs
What is the most widely used LA
Lignocaine
What can decrease the toxicity of lignocaine
Adrenaline
What is an antidysrhythmic LA
Lignocaine
Which LA are contraindicated in biers blocks
Bupivacaine
What is the benifit of bupivacaine
It has a long duration of action
What is the toxic dose of lignocaine with and without adrenaline
With 7mg /kg
Without 3mg/kg
