Regional Lecture I Part I Flashcards
What was the first regional anesthetic?
Cocaine
(probably ice actually was first)
First documented application of a druge to produce localized anesthesia?
Karl Kollar, a college and friend of Freud demonstrated the use of local anesthesia allowing him to perform painless eye surgery in 1884.
Who started injecting cocaine into nerves?
William Halsted and Alfred Hall
What was the first percuntaneous block?
axillary by G. Hirschel in 1911
types of regional anesthesia?
topical
local infiltration
field block
intravenous regional - bier block
peripheral nerve block
neuraxial
advantages of topical anesthesia?
super easy
low skill
low risk
great for mucous membranes
disadvantages of topical anesthesia?
short DOA 1-4hrs
slow onset over skin (needs soak time)
doesn’t work well on inflamed or infected tissue
DOA of local infiltration?
short 1-6 hours
what is a field block?
infiltration of LA around an area you wish to anesthetize
Uses for field blocks?
carotid endarterectomy (superficial cervical plexus)
I&D of wounds
intercostobrachial and medial brachial cutaneous nerves
dentistry
plastic surgery
good option to supplement patchy peripheral or neuraxial blocks?
field block
good option to supplement patchy peripheral or neuraxial blocks?
field block
disadvantages of field blocks?
inconsistent coverage
only covers superficial structures
relatively short duration of action
what is the only medication that can be used for a bier block?
0.5% lidocaine
What is bier block best suited for?
short soft tissue upper extremity procedures
can be used for lower extremity procedures too, but doesn’t work as well and has more risk of systemic toxicity.
advantages of bier block?
relatively easy to perform
provides surgical anesthesia quickly
disadvantages of bier block?
tourniquet pain limits useful duration
tourniquet must be inflated for at least 20min
must be able to get IV access
pt habitus must be suitable for proper tourniquet fit
failed tourniquets risk large volume of LA immediately entering central circulation > actue LA toxicity
how soon does tourniquet pain start?
within 30min
by 1 hour will have significant tourniquet pain
Procedure steps for Bier Block
place IV
double lumen tourniquet to upper arm (pad arm with cotton)
arm exanguination with esmarch bandage
inflate distal cuff, inflate proximal cuff, deflate distal cuff (always inflated to 50-100mmHg above SBP)
inject LA
LA dosing for bier block?
30-50ml of 0.5% lidocaine.
3mg/kg MAX!
how quickly does bier block work?
less than 5 min
what do you do once tourniquet pain starts?
inflate distal cufff, then deflate proximal cuff
how do you end a bier block?
use two stage tourniquet deflation
(deflate for 10sec, inflate for 1 min) x3
results in more gradual LA washout
indications for peripheral nerve blocks?
surgical anesthesia
post-op pain control
vascular dilation
chronic pain
contraindications to RA?
contralateral paralyzed diaphragm
severe aortic stenosis
preexisting peripheral neuropathy
4 blocks we should all know?
interscalene
axillary
femoral
popliteal
these will cover 90% of cases
Example of when SAB can be sole anesthetic?
C- section
Example of when wrist block can be sole anesthetic?
carpal tunnel surgery
Example of when infraclavicular block can be sole anesthetic?
AV fistula
Example of when intra-articular block can be sole anesthetic?
knee arthroscopy
Example of when topical lidocaine can be sole anesthetic?
cataracts
Which LAs have fast onset, short duration, and dense block?
lidocaine
mepivicaine
LA that has slower onset, long duration, and provides a dense block?
bupivicaine
exparel (liposomal bupivicaine) with very long action and ver slow onset
LA with sloer onset, long duration, but not as profound of a block?
Ropivicaine
What does epi do when added to LAs?
work as intravascular marker
decrease uptake > longer DOA
what does phenylephrine do when added to LAs?
decrase uptake > longer DOA
what does dexamethasone do when added to LA?
prolong duration
what does clonidine do when added to LAs?
prolong duration
what does bicarb do when added to LAs?
speed onset
Complications/risks of peripheral nerve blocks?
infection (very rare, still keep sterile though)
hematoma
indidental blockade
pneumothorax
nerve injury
intravascular injection
LA toxicity
total spinal anesthesia
What to know about infection risk with PNBs?
Risk is < 1%
cPNB ^ risk compared to single shot
femoral and axillary sites have ^ risk
localized infection more frequent than full sepsis
how to lower risk of infection with PNBs?
avoid puncture of infected tissue
ensure goo aseptic technique
skin prep, sterile technique, catheter
dressed well (biopatch etc)
judicous pt selection
reduce trauma with block placement
What about PNBs in pt that are already septic or infected?
no clear data
some say no ^ risk for SS
Eddie would not place continuous catheter
what factors increase risk of infection with PNB?
recent trauma
recent ICU admission
compromised immunity (including DM)
catheter in place for > 48hrs
absence of ABX use
What increase risk of hematoma with PNBs?
prolonged needling
larger size needle
trans-arterial technique
pt with coagulopathy
what are the coagulopathy guidelines for PNBs?
same as neuraxial
Caveat - common and well accepted to judiciously practice outside of these guidelines
different blocks have different risks
how to decrease risk of hematoma with PNBs?
consciously avoid vascular structures (both deep and superficial, veins collapse easily with minimal pressure from needle or US, so you may pierce vein and not see it, or get bloody aspiration)
hold pressure after inadvertent vascular puncture (5min for arterial)
what is the risk of hematoma from PNB?
can put pressure on the nerve > nerve injury
risk of incidental blockade of what nerve with ISB/supraclavicular/superficial cervical blocks?
phrenic nerve
recurrent laryngeal nerve
sympathetic cervical ganglion
what happens with incidental blockade of phrenic nerve?
diaphragm paralysis > decreased ventilation
this is VERY common, approaching 100%
usually not clinically significant in healthy patients.
what happens with incidental blockade of recurrent laryngeal nerve?
Ipsilatetal vocal cord paralysis > hoarseness
what happens with incidental blockade of sympathetic cervical ganglion?
horner’s syndrome
what incidental blockade can occur with a paravertebral block?
costal or epidural spread
why could intrarterial injection of LA be less dangerous than venous?
because most flow to periphery and allow time for LA to be absorbed by other tissues.
most veins flow directly to the heart
which arteries flow directly to the brain?
vertebral and carotid
What LA volume can cause almost immediate seizure and neurological LA toxicity?
even 1-3ml
What is LAST?
local anesthetic systemic toxicity
are neurological s/s always visible in LAST?
no, maybe be delayed or absent
what might be the first sign of LAST?
CV instability
why is it easy to not notice intravenous injection?
compression of vessels during US/needling can hide it with no aspiration of blood.
Methods to prevent LAST?
monitors: ECG, BP, Sat
communication with pt
frequent gentle aspiration every 3-5 ml
slow injection of LA
avoid traumatic needling
judicious dosing of LA
epi marker in blocks with ^ volume
be prepared to treat
how long is continuous monitoring required after high dose blocks?
30min of ECG, BP, and Sat
what symptoms of LAST should pt be aware of and be told to communicate
metallic taste, ears ringing, circumoral numbness, anxiety, double vision, dizziness, etc.
when to decrease LA dose in PNBs?
advanced age
poor cardiac function
preexisting conduction abnormalities
decreased plasma proteins
How should you be prepared to treat LAST?
have 20% lipid emulsion in area where blocks are performed
have a plan: ASRA/NYSORA checklists
What epi dose is used in PNBs?
1:200,000
when do you not add epi to blocks?
fingers, nose, PP, and toes. (also ears)
Epi ammount in normal (emergency) epi syringe?
1mg/10ml or 100mcg/ml or 1:10,000
CNS symptoms of LAST?
first: excitation: agitation, confusion, twitching, seizure
later: depression: drowsy, obtunded, coma, apnea
neuro symptoms may be subtle/absent
also, benzos can hide the seizures
CV signs of LAST
excitation followed by depression
^BP ^HR, ventricular ectopy, multiform VT, VF > decrease in BP, bradycardia > asystole
hallmark sign of cardiac toxicity of LA?
Ventricular ectopy, multiform VT, VF
hallmark of severe LA toxicity?
progressive decrease in BP, bradycardia>asystole
how does LAST progress?
maybe slow or fast, and some S/S may be subtle or absent
when should you be vigilant in monitoring RA?
always during and after RA!!!
LAST treatment
- call for help/lipid emulsion therapy
- ASRA/NYSORA checklists
- alert cardiopulmonary bypass team/nearest facility that has it
- Airway mgmt (100% FIO2 mask or vent)
- abolish seizure, versed or propofol but avoid propofol if CV is unstable
- manage cardiac arrhythmias ACLS
what meds to avoid during LAST?
Ca++ chanel blockers
beta blockers
lidocaine
phenytoin
vasopressin (contraversial)
Lipid emulsion dosing for LAST?
Bolus 1.5ml/kg about 100ml (based on lean body weight)
infusion of 0.25ml/kg about 18ml
repeat bolus Q 5 min if persistent CV collapse
infusion doubled to 0.5ml/kg if hypotension continues
continue infusion for at least 10min after CV is stable
this is with all other ACLS meds as well
what is upper limit for lipid emulsion therapy?
10ml/kg over first 30min.
what is a rare but profound complication of PNB?
pneumothorax
which PNBs have the higest risk of pneumothorax?
Brachial plexus blocks
supraclavicular highest
ISB, ICB, and suprascapular lower
Thoracic blocks
paravertebral
PEC blocks
intercostal blocks
Do you get JVD with pneumothorax?
yes
late sign of pneumothorax?
tracheal shift away from pneumothorax
gold standard for diagnosing a pnemothorax?
CT scan
are chest X-rays sensitive to finding pneumos?
no
What is likely best way to diagnose pneumo and also has 100% negative predictive value?
ultra sound
what kind of probe should you use for lung ultrasound?
linear trasnducer - best image
phased array - gets deeper for obese pts or large breasts, but image quality goes down
where to start with probe during lung ultrasound?
midclavicular line and 2nd-4th interspace,
probe oriented parasagittally
move from midclavicular line to ant axillary line
what are you looking for with lung ultrasound?
pleural sliding during respiration
acoustic artifacts seen with pleural layers are touching
lung edge - where lung stops touching chest wall d/t air pocket
What does it mean if you don’t see pleural sliding?
air is present = pneumothorax
sliding looks like shimmering line
in what mode do you see pleural sliding?
2D
what is M-mode?
shows motion over time
what does normal lung look like in m-mode?
sea shore pattern
what does pneumothorax look like in M bode?
bar code pattern
no motion seen, so same appearance above/below pleural line
When are B-lines and comet tails present?
normal lung tissue
What are B-lines?
acoustic differences of air/water in lung tissue
what are comet tails?
US waves bouncing off interface of the pleural layers. they move synchronously with respiration
What does it mean if B-lines and comet tails are not present?
pneumothorax
regarding B-lines and comet tails, even if you only have 1 what does that mean?
no pneumo
what are A lines?
horizontal lines equally spaced emanating from the pleural lines. Just an echo of the sound waves back to prove because there is nothing for them to bounce off of.
a lines equal pneumothorax
what is the most specific sign for a pneumothorax?
lung point assessment. it is also the most difficult to find, even for experienced operators.
what is lung point assessment?
shows location on chest where lung stops touching the chest wall.
by finding edges of air pockets allows for calculation to estimate size of the pnemo
can pneumos resolve spontaneously over time?
yes, sometimes
how often do transient nerve injuries occur with PNBs?
Up to 10%
usually resolve in days to weeks, rarely weeks to months for resolution
are nerve injuries from PNB common?
no, they are an infrequent complication
how often to permanent nerve injuries occur from PNB?
1.5/10,000
what are the effects of a permanent nerve injury from PNB?
range from localized numbness to paralysis
how does risk of nerve injury varry throughout the body?
risk decreases distally
pre-existing diseases the increase risk of nerve injury?
DM, PVD, atherosclerosis
