Regional Flashcards
What’s the initial dose of 20% intralipid (mL/kg) for LAST?
1.5mL/kg over 1 minute
What’s the initial infusion rate of intralipid for LAST? At which rate can it be increased to if CV instability hasn’t been restored?
15mL/kg/hr, can double to 30mL/kg/hr
How many further boluses of intralipid can be given for LAST? How many mins between boluses?
2, 5 mins between
What’s the maximum cumulative dose of intralipid?
12mL/kg
Which nerve supplies sensory to radial side of forearm?
Lateral antebrachial cutaneous nerve, from musculocutaneous
From which roots does the musculocutaneous nerve originate?
C5-7
Do the lateral or medial pectoral nerve have a cutaneous branch?
No
What are some advantages of axillary brachial plexus block over supraclavicular
- no risk of pneumothorax
- no risk of Horner’s
- no risk of phrenic nerve block
- excellent for forearm and hand surgery (supraclav block possible to spare ulnar)
- superficial + easier landmark (i.e. AxA)
-multiple needle redirections; good for training
Describe the PECS 1 block
Patient supine, arm by side or abducted 90 degrees. with US (transducer at mid-clavicular level angled inferolaterally), identify the pecs minor, major & pectoral branch of thoracoacromial artery. Local anaesthetic hydrodissects the fascial plane between pecs major & minor, aiming to block the medial & lateral pectoral nerves (depth 1-3cm depending on body habitus), providing anaesthesia to pecs muscles
Describe the PECS 2 block
hydrodissection with LA of the plane between pecs minor & serratus anterior, aiming to block the upper intercostal nerves (so blocking supply to the axilla & chest); blocks ant rami of intercostal nerves 3-6, intercostobrachial & long thoracic. the injection is directed lateral to the PECS 1 block, at approx anterior axillary line, level of 4th rib, depth approx 3-6cm depending on body habitus
Where’s the serratus anterior plane block directed?
interfacial plane between serratus anterior & lat dorsi
What dose ranges are recommended for PECS blocks? So, what’s a good volume/concentration for the PECS II blocks for a smaller adult
Dose-finding studies haven’t been performed
NYSORA suggests volume of 0.2mL/kg of a long-acting anaesthetic
30mL 0.3% (90mg), dilute 150mg to 50mL, discard 20mL
For which blocks is dexmed useful?
Only those for which prolonged block is not detrimental to recovery & only for those not involving motor block (eg. ok for adductor canal).. for others, insertion of catheter/infusion more useful & less problematic
What innervates the pecs major & minor?
lateral (from the lateral cord of the brachial plexus, C5-7) & medial (from the medial cord of the brachial plexus, C8,T1) pectoral nerves
What innervates serratus anterior?
long thoracic nerve, C5-7, aka “nerve to serratus anterior”
What innervates subclavius?
upper trunk of the brachial plexus (C5,6)
From where do the intercostal nerves originate & what do they supply?
Anterior rami of thoracic spinal nerves, provide segmental somatic sensory innervation to skin, lateral cutaneous branches of T2-6 (accessible at mid-axillary line) innervate the breast
From where does the thoracodorsal nerve originate & what does it supply?
Posterior cord (C6-8), supplies lat dorsi muscle, is a prominent nerve from the posterior cord, coursing in the posterior axillary wall. It’s adjacent to the thoracodorsal artery.
What nerves & artery lie on the serratus anterior muscle?
intercostobrachial, long thoracic & thoracodorsal nerves; thoracodorsal artery.
What nerve supplies teres major & subscapularis?
subscapular, C5-6
Where does the subclavian artery become the axillary? which branches does it give off?
after it passes the lateral border of the first rib.
Superior thoracic- supplies pecs
thoracoacromial- deep to pecs minor, pierces clavipectoral fascia in infraclavicular fossa
lateral thoracic- supplies b both pecs muscles
Thoracodorsal- initially known as sub scapular artery when it’s located in the posterior axillary wall, becomes thoracodorsal & courses with the thoracodorsal nerve
Of which intercostal nerves is the intercostobrachial nerve the cutaneous nerve for?
2nd in 67% & 3rd in 33% of cases
What are the nerves of the axilla?
intercostal T3-9, intercostobrachial, thoracodorsal & long thoracic
What do the intercostal nerves supply?
Motor to intercostal muscles, sensory info from skin & pleura, have anterior accessory branch innervating sternum. Lateral branches innervate pectoral & axillary regions, posterior hemithorax to scapula.
in which position is the thoracodorsal nerve (C6-8, nerve to lat dorsi) vulnerable?
when humerus abducted & laterally rotated, in danger during reconstructive surgery or operations involving lower axilla
What are big advantages of the PECSII blocks over paravertebrals?
coverage of axilla
What are indications for US-guided sciatic block?
Foot & ankle surgery, below knee amputation, analgesia following surgery involving posterior compartment of the knee
How is the transducer placed for anterior, trans gluteal or subgluteal & approaches to sciatic block? What are complications & issues with each?
anterior= curved transducer placed transverse on proximal medial thigh @ level of lesser trochanter, pt has thigh slightly abducted/ER, not good for catheter insertion due to multiple muscles being traversed (generally about 6-8cm to the nerve), awkward location & catheter perpendicular to the nerve is difficult but useful for pts who can’t be lateral- use US guidance to limit risk of femoral artery puncture
transgluteal= transverse on posterior buttock, btwn ischial tuberosity & greater trochanter
subgluteal= transverse on gluteal crease
What supplies the skin of posterior thigh?
posterior femoro cutaneous nerve, deviates from the sciatic nerve proximal to the level of the anterior approach to sciatic block. This isn’t an issue unless surgical incision involves the posterior thigh.
What vessel lies deep & medial to the femoral artery on US view for anterior approach sciatic block?
deep artery of the thigh
What vessel lies deep & medial to the femoral artery on US view for anterior approach sciatic block?
deep artery of the thigh
Where should the needle tip go for anterior approach sciatic nerve block?
Immediately adjacent to sciatic nerve, between adductor magnus & biceps femoris
A motor response at what stimulus intensity may suggest intramural injection? and opening pressure?
<0.5mA
>15psi
Key considerations in the approach to adjuvants for UL vs LL peripheral nerve block?
UL it may be total anaesthesia so onset more important, LL more often analgesia so prolonged DOA more important
concern re: distress/functional/dense block/LoS issues with UL
What’s the evidence generally about mixing LAs of longer & shorter duration?
only modestly faster onset but shorter duration- this could be considered inconsequential & detrimental, respectively, if the block is for analgesia vs anaesthesia
What’s an appropriate LA selection when rapid block onset & resolution are required?
2-chloroprocaine 3% (eg. for LL ambulatory surgery)- max dose sans epi 11mg/kg
which LA could be useful for surgical anaesthesia of 1-3hrs duration or as the primary block when a continuous postoperative technique used?
1-1.5% lignocaine
What % doses are appropriate for longer-duration surgical anaesthesia or analgesia?
anaesthesia: equipotent 0.5% bupivacaine or 0.75% ropivacaine
analgesia: bupivacaine 0.25% or ropivacaine 0.5%- bupivacaine 0.25% & ropivacaine 0.2% resulted in 24hr pain scores after ACL repair no different to 0.75% ropicacaine.
To what extent does epinephrine prolong LA? what’s another advantage of it?
prolongs intermediate-acting LA (50%) to a greater extent than long-acting (<20%)
the unique advantage of being a marker of intravascular injection
What are some characteristics of using clonidine as an adjuvant of peripheral nerve block?
also prolongs inter-mediate acting LAs (50%) to a greater extent than long-acting (20-30%). it doesn’t improve continuous infusion techniques.
may undesirably enhance motor block for UE surgeries
How does buprenorphine stack up as a block adjuvant?
mild to modest block prolongation but increases N&V
What dexamethasone doses are recommended for perineurial use?
4mg (9n fact, toxicity studies suggest limiting perineurial dose to 1-2mg); 8mg or higher prolong analgesia modestly but are no different to equivalent IV doses
What’s a plus of dexmedetomidine as an adjuvant for nerve blocks?
It is the most effective adjuvant for prolonging long-acting LA blocks
Which LA adjuvants is NOT considered off label for perineurial use?
epinephrine
buprenorphine, clonidine, dexmedetomidine & dexamethasone are all off-label
what’s the concentration of 1:200,000 dilution of epinephrine? and 1:400,000? what’s the advantage of the less concentrated?
5cmg/mL
2.5mcg/mL
1:400,000 same utility as an intravascular marker but has less detrimental impact on tachycardia or peripheral nerve blood flow
dosing of dexmedetomidine when added to nerve block?
1mcg/kg- increases sensory block of ropivacaine 0.5% by approx 25%
What are pt risk factors for LAST?
extremes of age
low m mass
female
cardiac, metabolic or liver disorders
Utility of PNS for limiting risk periop neurologic symptoms? and paraesthesia? injection pressure? US?
May be a specific but non-sensitive test to detect intraneural position of the needle tip
paraesthesia is an unreliablee marker as some pts can get PONS sans the sentinel paraesthesia- nonetheless paraesthesia or pain more likely associated
pressures <15psi usually recorded when needle 1mm from nerve, >=15psi suggests possible intraneural
No difference in prevalence of PONS btwn US & other localisation techniques however it is an exceedingly rare complication (long-term PONS (6-12/12) is 2-4 per 10,000 nerve blocks
Is it considered safe to do regional techniques on a pt under GA?
ASRA guidance suggests regional should not ROUTINELY be performed on adults under GA & LL blocks should only be done with extreme caution in a pt with concomitant neuraxial block
However, performance of nerve blocks under GA has been shown in multiple prospective studies to be safe.
What’s the prevalence of bacterial colonisation with LL perineurial catheters? risk factors?
29-57% (but it rarely causes infection requiring ABx or surgery)
catheter >24hrs, DM, ABx in the month before surgery
Indications for TAP block
postop analgesia for laparotomy, appendectomy, laparoscopy, caesarean- alternative to epidural analgesia for abdomen
Transducer position for TAP block
transverse on abdomen, @ anterior axillary line, between costal margin & iliac crest
Plane for TAP block? Volume?
Between TA & IO
20-30mL 0.2% ropivacaine/side
Nerves blocked with TAP block?
Anterior rami of lower 6 thoracic nerves, T7-T12 & L1
Unilat analgesia to skin, muscles & parietal peritoneum of anterior abdominal wall from T7 to L1 but in reality the spread is variable
Nerves blocked with TAP block?
Anterior rami of lower 6 thoracic nerves, T7-T12 & L1
Unilat analgesia to skin, muscles & parietal peritoneum of anterior abdominal wall from T7 to L1 but in reality the spread is variable; reliably blocks T10-L1 dermatomes
Which appears “thicker”; IO or EO?
IO
What volume of LA is used (0.25% ropivacaine) for paeds tap block?
0.4mL/kg per side
what are 2 branches of L1?
ilioinguinal & iliohypogastric
How do the analgesic efficacy of TAP block & epidural analgesia compare? other benefits?
no significant difference in day 1 post-op pain between groups, hypotension rate significantly lower & LOS shorter in TAP block group
reduces opioid consumption & LoS for RALP, decreases 24h mean pain score after minimally invasive nephrectomy
ERAS with TAP block improves bowel movement & decreases opioid consumption
