Intro to Blocks/Segna Flashcards
full onset of nerve blocks may not occur for
30 minutes
benefits of blocks
- fast pain relief
- decreased risk of intraoperative bleeding, stroke, MI
- decreased intraoperative need for narcotics = less N/V, less constipation, faster wake up, discharge
- minimal risk - (dont get resp. depression) compared to tradiational pain managemnet
- may be able to avoid general anesthesia for certain cases (do entire cases under block)
rate of absorption in LAs
rate of absoprtion in LAs
- depends on vascularity
- increased vascularity will lead to faster systemic absorption, higher blood levels, shorter time to obtain peak levels,
- also greater risk for toxicity
Intravenous > Tracheal > intercostal > caudal > epidural > brachial plexus > sciatic > subq
Patients with hypoalbuminemia
are at a higher risk of LAST because LAs have a high degree of protein binding and the increased free fraction of the drug will predispose them to LAST
Clearance of LA is affected by
- shorter half life
- lower protein binding - more free drug
elimination rate dependent on concentration of free fraction
systemic toxicity
time and dose dependent
- more likely with higher serum levels/faster onset
- main. targets = CNS/ heart
true allergy to LA
is extremely rare
- esters -> PABA, cross rxn within group
- amides -> may contain methylparaben.
- no cross sensitivity between esters and amides
- epinephrine often MISTAKE as allergy
- patient should be fully monitored during entire block and at least 15 min after
Clinical Symptoms of LAST (Neuro)
- Early:
Circumoral numbness, dizziness, tinnitus, blurred vision
- restlessness, agitation, nervousness, seizures
- CNS depression: slurred speech, drowsiness, unconsciousness
- may bypass earlier symptoms with arterial (esp. vertebral) injections -> seizures
Clinical Symptoms of LAST (cards)
- LA-induced dysrhythmias: sodium channel blocking effect of LA
- prolongatoin of impulse conduction may lead to malignant arrhythmias
- lidocaine: less toxic bc fast in/fast out
- bupivacaine: more potent and toxic, fast in/slow out
treatment for LAST
- supportive (correct hypoxemia/acisosis)
- ACLS protocol - avoid lidocaine
- Intralipid:
- 20% emulsion
- 1.5mL/kg as initial bolus
- 0.25 mL/kg/min for 30-60 min
- bolus can be repeated 1-2 times for persistent asystole.
Commonly used block anesthetics and DOA
- ropivacaine: 12 hrs (pushed to 24 with adjuncts)
- bupiviaine: 15 hrs ~ 24 hrs
- lidocaine: 2 hrs
- mepivacine: 6 hours
supraclavicular block WITH neurostimulation has
a much higher rate of pneumothorax (5%) compared to other UE blocks
COPD is relatively contraindicaiton for
supraclavicular block because pleural apex may be higher
axillary nerve block has a high rate of failure for
single nerve injections
single injection ulnar block
block at elbow
single injection of median nerve
travels in antecubital fossa with brachial artery
single injection of radial nerve
travels at lateral elbow within brachioradialis
ischemia is an important component of
the bier block.
Blocks nerve conduction, may obtain anlagesia with normal saline in 20-25 minutes of ischemia.
bier block: mechanisms of action
- direct action by LA + retrograde flow into endonerium, capillary plexus, eventuallly into nerve trunks
- compression of nerve trunks (slow component)
Most common drugs for bier block
- 0.5% lidocaine or prilocaine
- NO epi added
Dosage ->
- UE = 50 mL
- LE = 100 mL
in bier block, tourniquet should be kept inflated for a minimum of
20 minutes
lumbar plexus is
- derieved from
- divdes into
lumbar plexus is
- derieved from L2,L3,L4
- divdes into:
- femoral
- lateral femoral cutaneous
- obturator
lateral femoral cutaneous
arises from L2-L3, part of lumbar plexus
Motor: NONE
sensory: lateral aspect of thigh
femoral nerve
- arises from
- motor
- sensory
femoral nerve
- arises from: L2, L3, L4
- motor:
- anterior branch - sartorius
- posterior branch: quads
- sensory: anterior thigh
obturator nerve
- arises from:
- motor:
- sensory:
obturator nerve
- arises from: L2, L3, L4
- motor: hip adductors
- sensory: distal inner thigh and part of hip
larger branch of the sciatic nerve
tibial (L4-S3)
peroneal: L4-S2
intercostobrachial nerve
arises from T2
Not anesthetized with any approah to the brachial plexus. Requires a field block.
the stellate ganglion is located at
C7
also called “cerivothoracic ganglion”
injection of LA into vertebral artery
as little as 1 mL of LA injected into vertebral artery can lead to seizure
Vertebral artery injection is most likely with
interscalene block
most common complication of supraclavicular block
pneumothorax
for an intraclavicular block the needle must pass through
pectoral major and minor
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