Regional Anesthesia

Question 1

Benefits of block?

Answer 1

• 1. Fast Pain relief
• 2. Decreased risk of intraoperative bleeding, stroke, and MI
• 3. Decreased intraoperative need for narcotics
     * less N/V, less constipation, faster wake up and discharge
• 4. Minimal Risk compared to Traditional Pain Management
     * no respiratory depression
• 5. May be able to avoid General Anesthesia for certain cases
     * good for patient with bad heart, kidney, brain

Question 2

Risks and contraindications of blocks?

Answer 2

1. In rare cases, nerve damage can cause persistent numbness, weakness, or pain.
   
   • • most cases resolve within 6 months and almost all by a year
   • 0.05% risk of nerve damage
   • typically position related and generally a strip of numbness that is gone in a couple of weeks
   • if persistent weakness- dx- EMG- tests signal from the nerve, have to wait a couple of weeks before pt can get it
   • always think of who you’re blocking. If pt relies on arm for professional reasons (ie football player), don’t block them. too risky
2. Risk of systemic toxicity if the anesthetic is absorbed through the bloodstream into the body.
   
   1. if patient is maxed out on LA for block placement. DON’T GIVE IV LIDOCAINE ON INDUCTION
3. Block depending risks such as hematoma, pneumothorax, phrenic n. paralysis, etc.
4. Contraindications are decided on a case by case basis. Each person should be evaluated for their lung and heart function, prexisting motor or sensory loss, diabetic neuropathy, history of block failure or block related nerve injury in the past, body habitus, and coagulation status
   
   1. if you can compress the PNB site (IE ISB/SCB, you can hold pressure. But ICB, hard to hold pressure. Bad to block someone at increase r/f bleeding if you can’t hold pressure at PNB site.

Question 3

Who is a block candidate?

Answer 3

1. hose who have capacity and understand that they will have a numb arm
2. Those who are are IN-capacitated but the risk of GA for urgent/ emergent cases is life threatening compared to the risk of a block
   
   1. while she would not block someone with only one finger left from diabetic neuropathy, she would block them if there was a high risk of the patient dying on the table during induction
3. Patients with a history of Chronic Pain who are on high doses of opioids at home or who are on drugs such as suboxone that render administered opioids ineffective

Question 4

Who is NOT a block candidate?

Answer 4

1. Patient’s you do not trust to take care of themselves
2. Patient’s who do not have reliable help or will not be able to get into their homes due to the block
3. Patients who say NO
   
   1. never push someone to get a block. you can explain why the block is helpful but never coerce someone to do a block
4. Infection over the site (local anesthetic rendered ineffective)
5. Anti-coagulated and case requires a “deep” block
6. ** granted based on local anesthetic chosen, if you feel someone would benefit from a block but it needs to wear off you can use a shorter acting local anesthetic

Question 5

Allergy to LA? System toxicity?

Answer 5

True allergy to LA extremely rare

• Mostly due to preservatives, additives and metabolites
• Amides may contain methylparaben (amide’s have 2 i’s)- according to apex a preservative that can rarely cause allergic reaction
  
  • ​Esters have PABA which is more susceptible to allergic reaction (esters = only one “i” in name)
• No cross-sensitivity between classes of LA
• Often Epinephrine side effects mistaken as allergy

Systemic toxicity: dose- and time-dependent

• Adverse reactions more likely with higher serum levels/faster onset
• Rate of systemic absorption proportional to vascularity of site of injection: IV > Tracheal > Intercostal > Caudal > Epidural > Brachial plexus > Sciatic > Subcutaneous
• Main targets of toxicity: CNS, heart
• Receive relatively large fractions of cardiac output

Question 6

DOA for commonly used LA?

Answer 6

Ropivacaine – 12 hrs

Bupivacaine- 15 hrs *** with adjuncts, ropi and bupi can last 24 hours

Lidocaine- 2 hrs

Mepivacaine – 6 hrs **can be used for pts that need strong block for sx but the block also needs to wear off before they go home

Adjuncts can push the block time 2-12 hours

Question 7

Clinical symptoms of LA toxicity?

Answer 7

Propagation of subcortical limbic excitation

• Clinical symptoms (with increasing doses):
  
  • 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 and manifest as a seizure

Question 8

Cardiotoxicity with LA?

Answer 8

LA-induced dysrhythmias: sodium channel blocking effect of LA

• Prolongation of impulse conduction may lead to malignant arrhythmias
• Lidocaine: less potent and toxic: “fast-in, fast-out”
• Bupivacaine: more potent and toxic: “fast-in, slow-out”
• R(+) enantiomer has greater affinity for Na+ channel binding and thus toxicity

Treatment:

• Supportive (correct any hypoxemia or acidosis)
• ACLS protocol (except should not use lidocaine); previously used Bretylium
• INTRALIPID (not propofol)

Question 9

Intralipid treatment for LA toxicity?

Answer 9

• Equipment:
  
  • 20% lipid emulsion
• Treatment regimen (NB: no standard method)
  
  • 1.5 mL/kg as an initial bolus, followed by
  • 0.25 mL/kg/min for 30-60 minutes
  • Bolus could be repeated 1-2 times for persistent asystole

Question 10

Max doses for common local anesthetics?

Answer 10

• Bupivicaine 2.5 mg/kg,
  
  • with epi 3mg/kg
• Ropivacaine 2.5-3 mg/kg
  
  • with epi 3.5 mg/kg
• Lidocaine 4mg/kg
  
  • with epi 7 mg/kg
• Mepivicaine 4mg/kg
  
  • with epi 7 mg/kg
• Chloroprocaine 12mg/kg

Question 11

Lidocaine (drug card)

Answer 11

CLASS=amide LA (& Class IB antiarrhythmic – its active metabolite monoethyglycinexylidide blocks Na+ channels in cardiomyocytes,decrease AP duration & refractory period)

• LA MOA- bind to H-gate of Na channel and physically obstruct the channel
• keeps Na channel in closed/inactivated state and prevents further transmission AP (unionized portion diffuses across membrane, ionized portion blocks channel)

Pharmacokinetics=

• pKa- 7.9; non-ionized- 24%, PB- 70% (PB 50% for antiarrhythmic); low potency & low lipid solubility
• Fast onset & moderate DOA (1-2hr); E1/2- 1.5hr (antiarrhythmic- 1-8 hrs)
• Intrinsic vasodilator activity; uptake into the lungs
• CYP450 liver metabolism that depends on HBF & excreted in urine
• 2 active metabolites- xylidide & monoethylglycinexylidide

SE= TNS, high incidence of cauda equina syndrome (specfiically high concentraiton lidocaine); BLUNT SNS TO DVL

LA toxicity

5-10 mcg/ml: circumoral numbness, lightheadedness, tinnitus, skeletal muscle twitching, visual disturbances, systemic hypotension, myocardial depression, & tachycardia, decreased SVR & cardiac output.

10-15 mcg/ml: seizures, unconsciousness

15-25 mcg/ml: apnea, coma

>25 mcg/ml: cardiovascular depression/collapse

CI= methemoglobinemia

LA hypersensitivity to amide LA, coagulopathies, infection, hypovolemia, refusal, inability to cooperate inexperience of provider

Antiarrhythmic hypersensitivity; WPW syndrome, HB, hepatic disease; CYP450 inhibitors such as Cimetidine & Propranolol decrease metabolism

Dose=

MAX: 4mg/kg & with epi 7mg/kg;

Spinal MAX- 30-100mg (1-2mL) (1.5-5%)

Epidural: 15-30 ml of 1-2%

PNB- volume depends on location- 1-2%

Intubation to blunt DVL & antiarrhythmic- 1-2 mg/kg (max antiarrhythmic: 3mg/kg)

Question 12

Bupivicaine (drug card)

Answer 12

CLASS= amide LA

Pharmacokinetics=

- pKa- 8.1; non-ionized- 17%, PB- 95%; very potent & highly lipid soluble

• Moderate onset & long DOA (4-8hr); E1/2- 3.5hr
• CYP450 liver metabolism that depends on HBF

SE= differential blockade; TNS, “very low risk for neuro complications with spinal” (CB) ; highly CV toxic hypotension, myocardial depression, AV block, arrhythmias; local anesthestic toxicity (cirucmoral numbness, tinnitus, vision changes, dizziness, restlessness, muscle twitching in face/extremities–> seizures)–> CNS depression, apnea, hypotension).

CI= refusal, inability to cooperate, coagulopathies, hypovolemia, infection @ site; inexperience of clinician; extreme caution in poor CV function & HB

Dose=

• MAX- 2.5mg/kg
• Spinal MAX - spinal-15-20mg (0.5, 0.75%, 3-4 mL)
• Epidural- 15-30 ml of 0.125-0.5%
• PNB- amount depends on location- 0.25-0.5%

Question 13

Where do each of the UE PNB work on the brachial plexus?

Answer 13

• Interscalene- Roots/trunks
• Supraclavicular- division
  
  • easiest block to have in arsenal
  • all the nerves are packaged in one location
• infraclavicular- cords
• axillary- branches
  
  • fails the most because you have to get them individually

Question 14

Targets for ISB?

Answer 14

• Start at clavicle, look at divisions (SCB) then follow it up until you see the “stoplight” of C5, C6, C7
  
  • in theory the stoplight is C5-C7. There are sometimes anatomical variation in C5,C6 C7 and C5 will have to 2 branches. Never put needle between the 2 because you can cause nerve damage.
• only used for shoulder surgery. you don’t get coverage of C8 (ulnar nerve)

Link for VIDEO

• Brachial plexus sandwiched b/w anterior and middle scalene muscles
• recognize the brachial plexus is lateral/superficial to Carotid artery and internal jugular vein
  
  • ​many vasculature in brachial plexus
    
    • ​vertebral artery is very close to target- risk for intravascular injection
• Pre-vertebral fascia has to be breached by needle to place LA in interscalene groove

Question 15

Technique for ISB?

Answer 15

• Sterilize skin
• Some providers admin LA
• don’t place needle too deep. placement of small gauge needle can result in intraneural injection
• needle placed lateral to medial
  
  • enters prevertebral fascia and transveres the middle scalene muscle
  • if using nerve stim- elicit nerve response, then decrease to <0.3 mA to ensure motor stim is lost and decreases r/f intraneural injection.
• maintain injection pressure <15 psi
• typically uses 15- 25 mL to ensure fast, reliable onset of anesthesia

Question 16

Complications of interscalene block?

Answer 16

• Pneumothorax
  
  • in theory could cause a pneumothorax, but you’d have to be “way off”
• Epidural/intrathecal injection
  
  • spine is also right by block site. can accidentally due epidural/intrathecal injection and then patient will go unconscious.
• Vertebral/carotid artery injection
  
  • nterscalene block done at C6 cricoid cartilage area. very close to vertebral artery
• Hematoma
• Ulnar sparing

Question 17

S/E of ISB?

Answer 17

• 100% ipsilateral phrenic nerve paralysis
• Ipsilateral Horner’s syndrome common
• Frequent blockade of recurrent laryngeal nerve
• Not a benign block. Less LA= less S/E
  
  • ​let patient know they’ll have droopy eyelid, numb face etc

Question 18

US Landmarks for supraclavicular block

Answer 18

• US probe right on top of clavicle
• Aim to get US view with brachial plexus on top of first rib, less risk for pneumothorax (5%)
• “bunch of grapes” is the brachial plexus
  
  • ​ulnar nerve right by subclavian artery

VIDEO SCB

• Easier to perform PNB with shoulder elevated
• place probe slightly cranial to clavicle and ID subclavian artery. scan upwards then trace nerves back to supraclavicular position to identify all the branches.
• ID pleura and first rib in US. Avoid pleura
• May have to retract and reposition needle to get shallower branches of brachial plexus

Question 19

Indication for SCB? Anatomy for SCB?

Answer 19

• Useful for procedures at elbow or more distal
• With neurostimulation has a substantially higher rate of pneumothorax compared to other upper extremity blocks
• Small studies suggest that there may be a lower pneumothorax rate with ultrasound guided technique in experienced hands

Anatomy

• Rapid onset as nerves are bundled tightly at this level (trunks/division)
• Anterior scalene inserts onto first rib
• Anterior scalene is in contact with pleural dome on medial side
• COPD is a relative contraindication for this block as pleural apex may be higher

Question 20

Indication for infraclavicular and approach for ICB?

Answer 20

• Surgery on the arm, forearm, and hand (mid-humerus down)
• May be the best choice for elbow surgery

Approach- VIDEO LINK

• Brachial plexus block at level of cords as arranged around the axillary artery
  
  • cords hang out below pec major/pec minor
  • block can be pretty deep (as deep as 6 cm)
  • posterior cord below axillary artery, medial cord on side near axillary vein, lateral cord on opposite side axillary artery
• Almost no risk of pneumothorax
  
  • lung very far away
  • very limited block of phrenic nerve (only 10% as compared to 100% ISB, 50% SCB)
• Similar drug dosing as ISB or supraclavicular

Question 21

Anatomy for axillary block?

Technique?

Answer 21

• Uses the axillary artery as a landmark
  
  • very superficial block that’s very compressible- good for anti-coag pts. no risk for pneumothorax
• The radial nerve runs behind the artery
• The ulnar nerve runs inferiorly
• The medial nerve lies superior to the artery

VIDEO LINK

• transducer position- perpendicular to humerus in the axillary fossa
• Goal- local anesthetic spread around the axillary artery and nerves
• volume 15-20 mL
• lots of variation in anatomy for this block
  
  • ​in order to get musculocutaneous, 3-5 injections of 5-7 mL are necessary to cover median, radial, ulnar and musculocutaneous

Question 22

Complications of infraclavicular block?

Answer 22

• Pneumothorax- lung is actually very far away and very protected. minimial risk
• Hematoma- much more frequent because the block is so deep.
• Nerve damage
• Technically Challenging- one of the hardest block because its very difficult to see needle with such a steep angle

Question 23

Technique for ICB?

Answer 23

VIDEO

• Patient positioned in supine position with arm abducted
• palpate clavicle, position probe caudal to clavicle slightly lateral to MCL
• locate axillary artery since brachial plexus will be located around axillary artery
• position probe so axillary artery is in far side of picture
• slowly insert needly as parallel as possible and inject local anesthetic while approaching the artery
• inject LA around axillary artery to sufficiently numb all the cords.
• 30-40 mL injectate usually sufficient
  
  • ​from video- for sx with nerve block only–> 1% mepivicaine (4 hours block); 0.5% levobupivacaine (12 hours)
    
    • ​GA and nerve block for postop analgesia
      
      • ​0.25% bupivacaine

Question 24

Axillary block complications/side effects?

Answer 24

• High failure rate for single injection
  
  • high rate of failure d/t missing musculocutaneous nerve. (this nerve breaks off early and sits in brachioradialis muscle)
• Can miss musculocutaneous
• Requires abduction of arm
  
  • ​cannot do this block if they can’t position their arms correctly
• Absent risk of pneumothorax
  
  • no risk of phrenic N involvement either.

Question 25

How do you perform isolated nerve blocks?

Answer 25

* Less common bl: individual nerves (ulnar/ radial/ median) * Block Ulnar at elbow * Block Median at antecubital fossa (travels with brachial artery) * Block Radial at lateral elbow within brachioradialis muscle

Question 26

Anatomy of the lumbar plexus?

Answer 26

* Derived from L2 to L4 * Divides into femoral, lateral femoral cutaneous (LFCN) and obturator nerves * Provides motor and sensory to most of thigh, anterior knee and sensory to medial leg

Question 27

Femoral nerve anatomy?

Answer 27

* *can perform block without ultrasound. palpate femoral artery and go lateral* * *2 major fascias* * *​fascia lata- on top (think latte)* * *fascia iliaca- on bottom* * *fem artery between fascia and nerve below both* * *​if you can get through 2 fascia, and inject on fascia iliaca, it will get nerve* * *Very superficial block, US depth only needs to be at 2 cm* [VIDEO](https://www.youtube.com/watch?v=1mkHrVxdGNg) * *US transducer placed over anterior thigh at inguinal crease* * *Fem nerve will be immediately lateral to femoral artery.* * *Fascial sheaths will be easily visible* * *​Fascia iliac envelope femoral nerve* * *​fascia iliaca on top of iliopsoas muscle* * *Ensure absence of motor response \<0.3 mA to decrease risk of intrafascicular injection* * *several large vessels in vicinity of femoral nerve, always carefully aspirate to avoid inadvertent vascular injection*

Question 28

Landmarks for adductor canal block?

Answer 28

* *blocks saphenous* (terminal branch of femoral nerve) * *saphenous nerve is on top of FA like a hat. sometimes can be to the s*ide * *adductor canal named because it looks like a canal* * *​sartorius on top* * *vastus medialis lateral* * *adductor longus medial* * *technically saphenous is sensory, but if you didn't block low enough, one branch can go into the knee and provide motor for vastus medialis, and cause weakness* [VIDEO](https://www.youtube.com/watch?v=_lp1rKuqzsk) * *Pt supine with thigh adducted and externally rotated* * *probe placed transverse between middle and distal 1/3 of ant medial thigh* * *ID femoral artery- move probe distally until femoral artery is immediate under sartorius (boat shaped muscle)* * *​nerve to vastus medialis also located in adductor canal* * *numb skin with lidocaine prior to insertion of block needle* * *in plane insertion of block needle lateral to medial* * *visualize needle puncturing fascia of sartorius, negative aspiration and then inject local* * *only 10 cc or so of LA because you don't want motor blockade!*

Question 29

Sciatic nerve anatomy

Answer 29

* The largest nerve in the body (1.5-2 cm wide) * Derives from L4-S3 nerve roots * Supplies sensory to posterior thigh and all but medial aspect of leg and foot * Supplies motor to hamstring and all muscles in leg and foot

Question 30

Indications for femoral nerve block?

Answer 30

* Surgery on the anterior thigh, knee and hip * *with amputation above knee, femoral blockade much more effective* * *amp below knee- sciatic nerve more important* * Management of tourniquet pain * Hip Fractures

Question 31

Pathway of sciatic nerve?

Answer 31

* Leaves the pelvis through greater sciatic foramen * Innervates posterior thigh through posterior femoral cutaneous n. * Divides above popliteal fossa into tibial and common peroneal n. * _**\*therefore two places to block this nerve\***_ * subgluteal/infragluteal/sciatic approach (same name) * popliteal approach * *the nerve "flies apart" and comes back to heart shape. higher in leg, flattens into disc. doesn't look like nerve until you look at it a lot* * *typically need to use curvilinear probe on infragluteal approach.* * *good for procedures with thigh tourniquets. provide coverage to posterior leg.*

Question 33

Landmark for popliteal block?

Answer 33

* *want to hit sciatic nerve before it divides back into common peroneal and tibial.* * *​if you go too low, you'll only get tibial N and then have a failed block* [VIDEO](https://www.youtube.com/watch?v=v-Wb_N98h1Q) * *Scan up and down leg to find location where common peroneal and tibial comes together* * *small amt LA to numb skin* * *when block needle placed, inject LA* * *​inject 30 mL LA. don't use epi! because vascularity if tenuous* Picture: * Right: * BF: biceps femoris * ST: semitendinosus * T: tibial * CP: common peroneal * Spares motor weakness of the thigh

Question 34

Where is the IPACK block?

Answer 34

Between vessel and femur so that only sensory is affected

Question 35

Mneumonic to remember expected motor response from nerve stim in popliteal block?

Answer 35

* TIP * Tibial= inversion and plantar flexion * PEED * Peroneal= eversion dorsiflexion

Question 36

Indication for sciatic block?

Answer 36

* For procedures where a thigh tourniquet will be used * Procedures involving posterior thigh * Procedures below the knee * Amputations *

Question 40

Troubleshoot block failure?

Answer 40

1. Time 2. Ice or sharp (temperature/ sensation) NOT pressure NOT muscle strength * *temperature/sensation goes first* * *just because they can move their fingers doesn't mean block doesn't work. temp sensation goes first then motor. might just need more time* 3. Take picture of block in real time and review anatomy 4. Issue with Medication * *issue with wrong concentration actually being put in vial* 5. Paresthesias during block?

Question 41

Peripheral nerve catheters?

Answer 41

Prolonging your block 1. Inpatient pump 2. OnQ pump 3. Lower dose local anesthetic 4. If well maintained can keep for \> 7 days 5. New drug (not FDA approved for all blocks): Exparel