Peripheral Nerve Blocks Flashcards
What determines our choice of anesthetic? (5)
time to onset
duration of action
degree of sensory block to motor block
risk of cardiac toxicity
how many areas need to be blocked
What is the dose and duration of bupivacaine?
3mg/kg
1.5 - 8 hours
What is the dose and duration of lidocaine?
- 5 mg/kg, 7 with epi
- 75 - 2 hours
What is the dose and duration of mepivicaine?
4.5 mg/kg, 7 with epi
1-2 hours
What is the dose and duration of ropivacaine?
3 mg/kg
1.5-8 hours
Name the amides: (5)
bupivacaine
lidocaine
mepivacaine
prilocaine (used for dental, PNB)
ropivacaine
Name the esters: (5)
benzocaine
chloroprocaine
cocaine
procaine
tetracaine
What are the concentrations of bupivicaine?
- 25%
- 5%
- 75%
What are the concentrations of lidocaine?
0.5-5%
What are the concentrations of mepivacaine?
1-3.5% in 0.5% increments
What are the concentrations of ropivacaine?
0.2, 0.5, 0.75, 1%
What is the max dose and duration of chloroprocaine?
12 mg/kg
All esters are 0.5 - 1 hr except tetracaine.
What is the max dose and duration of cocaine?
3mg/kg
All esters are 0.5 - 1 hr except tetracaine.
What is the max dose and duration of tetracaine?
3mg/kg
1.5-6 hours
What is the max dose and duration of procaine?
12 mg/kg
0.5-1 hr
Why do we use epinephrine? (4)
Intravascular marker: increase HR by 20%
Improves quality of block: increased neuronal uptake, and alpha2- adrenergic receptors
Decreases absorption: prolong action
Vasoconstriction on surgical field
What amount of epinephrine do we add to LA?
5 mcg/ml (1:200,000)
2.5 mcg/ml (1:400,000)
What are the major risks of nerve blocks?
Systemic toxicity, rare but fatal
Infection
Peripheral nerve damage
Note: Use B bevel needles (short bevel) to reduce risk of nerve damage.
What vascular areas are most to least prone to systemic toxicity? (8)
Tracheal
Intercostal
Caudal
Paracervical
Epidural
Brachial plexus
Sciatic
subcutaneous
What are the signs and symptoms of CNS excitation toxicity? (6)
Dizziness
Tinnitis
Circumoral numbness
Muscle twitches
Slurred speech
Seizures
What are the cardiovascular signs of toxicity? (5)
Depress myocardial conduction and contractility
Produce arterial vasodilatation, except cocaine
Hypotension
Bradycardia, PVCs, PACs
VT or VF
How do you prevent systemic toxicity?
Incremental injection
Frequent aspiration
Adding a marker
Limiting LA dose and concentration
Continual communication with patient
In a nerve block, proceed with caution in what patients?
Patients with cardiac conduction abnormalities
Kidney or liver disease
Acidosis
How do you treat seizures from systemic toxicity?
midazolam, propofol, thiopental
How do you treat cardiac toxicity/respiratory depression during systemic toxicity?
Airway management
ACLS/BLS: avoid calcium channel blockes, B-blockers and lidocaine
IV lipid infusion
Cardiopulmonary bypass
How do you provide LAST lipid treatment?
20% Intralipid
- 5 mL/kg as an initial bolus, followed by
- 25 mL/kg/min for 30-60 minutes
Bolus could be repeated 1-2 times for persistent cardiac collapse
Infusion rate could be increased if the BP declines.
What are the methods to place nerve blocks?
Ultrasound technique: direct visualization
Peripheral nerve stimulator: motor response
Paresthesia technique: sensory response
What nerves are included within the brachial plexus?
C5-C8, T1
What nerves can accidentally be blocked when blocking the brachial plexus?
Superficial cervical plexus: C3-C4
Phrenic nerve: C3, C4, C5
Intercostobrachial nerve: T2
Name the brachial plexus blocks: (4)
Interscalene
Supraclavicular
Infraclavicular
Axillary
Name the block performed with the ultrasound positions indicated in the image:
- Interscalene (roots/trunks)
- Supraclavicular(divisions)
- Infraclavicular(cords)
- Axillary(branches)
- Mid-humeral(branches)
What are the most commonly performed blocks for regional anesthesia?
Interscalene
What block provides anesthesia and analgesia for shoulder, humerus, and clavicle?
Interscalene
What block is performed at the level of the roots/trunks of BP, between the anterior & middle scalene muscle?
Interscalene
What block is traditionally unsuccessful for forearm and hand surgery because the ulnar nerve is often missed?
Interscalene
What are the adverse effects and possible complications of brachial plexus blocks?
- phrenic nerve palsy
- Horner’s syndrome (stellate ganglion block)
- Cervical plexus block (small pupil, drooped eyelid)
- Recurrently laryngeal nerve palsy
- Possible vertebral artery injection
- Pneumothorax (PTX)
- Epidural, subarachnoid injection
What anesthetic is often used for humeral fractures or shoulder surgery?
Ropivacaine 0.75%
What is also known as the spinal of the arm?
Supraclavicular block
What block is performed at the DIVISIONS of the brachial plexus and is used to perform surgery for the entire arm, below the shoulder?
Supraclavicular block
What are the risks of supraclavicular blocks?
pneumothorax
50% chance of phrenic nerve block
recurrent laryngeal nerve block
vascular puncture
What block is indicated for elbow, forearm, and hand surgery?
infraclavicular, aka axillary block
least preferred
What block is performed at the level of the terminal branches: median, ulnar, radial, and musculocutaneous nerves?
axillary
Axillary block has a low complication rate and low rate of infection/hematoma. True or false?
false
low complication
high infection rate/hematoma
What position must the arm be in for an axillary block?
abducted
What nerve often gets overlooked in brachial plexus blocks?
musculocutaneous nerve
What block provides surgical anesthesia for short procedures (<45-60 minutes) in the forearm, hand, or leg?
Bier block
What items do you need to perform a bier block?
IV inserted on the hand
double pneumatic tourniquet
eschmark elastic bandage
0.5% lidocaine (50ml)
What are the benefits of continuous peripheral nerve blocks?
Decreased sleep disturbances
Increased patient satisfaction
Possible improved early rehabilitation
Decreased narcotic side effects:
- Nausea/vomiting
- Pruritis
- Sedation
The lumbar plexus is comprised of the ventral rami of what nerves?
Name them:
T12, L1-L4
Iliohypogastric/ilioinguinal
Femoral
Obturator
Lateral femoral cutaneous
The sacral plexus is comprised of the ventral rami of what nerves?
Name them:
L4-S4
Sciatic nerve
Tibial
Common peroneal
What are the most commonly blocked nerves in the lumbar plexus?
femoral
sciatic
obdurator
What type of block is good for providing analgesia for the hip, anterior thigh, and knee?
lumbar plexus block
What nerves does the lumbar plexus block cover?
LFCN
femoral
obturator
What is a lumbar plexus deep block’s distance from skin to lumbar plexus?
5-10 cm
What are the complications of a lumbar plexus block?
renal puncture
spinal or epidural injection
hematoma
LAST
What is the largest branch block of the lumbar plexus that arises from L2, L3, and L4?
femoral nerve block
What nerve emerges from the psoas muscle and gives off articulating branches to the hip?
femoral nerve
What nerve enters the leg under the inguinal ligament and then quickly divides?
femoral nerve
Is the femoral nerve located more medially or laterally?
laterally
What muscle is on the anterior division of the femoral nerve?
sartorius
What muscle is located on the posterior division of the femoral nerve?
Saphenous nerve (most medial)
Muscular (quadriceps muscle)
Articular branches ( knee)
Femur
Where do we place the transducer for a femoral nerve block?
Over the femoral artery at the level of inguinal ligament
What is the needle approach to a femoral nerve block?
lateral to medial
What type of block do we use for:
knee surgery: TKA, ACL reconstruction, patellar surgery
femoral ORIF, skin grafting, muscle biopsy?
femoral
What block do we use for surgery involving the medial aspect of the leg?
femoral nerve block
What nerve tends to be overlooked in a femoral nerve block and may need to be blocked also?
saphenous nerve
What is the onset time for a femoral block using ultrasound with 20ml of buivacaine 0.5%?
about 15 minutes vs. about 30 minutes for an unguided block
For any surgery involving the medial aspect of the foot/ankle or a popliteal/sciatic nerve block. you must also have what nerve blocked?
saphenous nerve
What is the largest sensory branch of the femoral nerve?
saphenous nerve
What are the 4 main locations we can block the saphenous nerve?
femoral nerve
adductor canal
below the knee
medial malleolus
What is the largest nerve in the human body?
sacral plexus, sciatic nerve
L4-S3
What are the imaging areas for the sciatic nerve?
popliteal
mid-thigh
subgluteal
transgluteal
What is the sensory nerve to the posterior hip and knee?
sciatic nerve
The sciatic nerve innervates what muscles? (motor function)
hamstrings and lower leg below the knee
When do we use a sciatic nerve block?
Knee surgery(TKA), foot and ankle surgery
What are the complications of a sciatic nerve block?
partial block, nerve injury
What are complications of popliteal fossa sciatic nerve blocks?
incomplete blocks due to anatomical variations
sciatic nerve divides into the tibial nerve and common peroneal nerve at varying locations above the popliteal fossa
What is the main obstacle of subgluteal sciatic nerve blocks?
depth of nerve, especially in large pts
Sciatic nerve blockade in the subgluteal region is convenient and easily accessible. True or false?
true
Where do you insert for sciatic nerve block?
groove just lateral to the upper portion of the biceps femoris muscle
What are the indications for an ankle block?
foot and toe surgery
good if no tourniquet is used above the calf
What nerves are blocked in an ankle block?
Deep peroneal
Superficial peroneal
Posterior tibial
Sural
saphenous
What is the concentration of benzocaine?
20% topical only
For lumbar plexus block, what type of probe do you need?
low frequency
