Peripheral Nerve Blocks Part 1 Flashcards
What is the difference between a pain block and an anesthetic block?
pain block decreases pain but does not eliminate sensation, whereas an anesthetic block does
What are absolute contraindications to peripheral nerve blocks?
patient refusal, coagulopathy, infection at the site of block, severe hypovolemia, severe aortic or mitral valve stenosis, increased ICP
What are frequently used anesthetics for peripheral nerve blocks?
0.5% ropivacaine, 0.75% ropivacaine, 0.5% bupivacaine
What does the addition of vasoconstrictors to blocks do?
delays absorption and prolongs block
What does the addition of Decadron do to PNBs?
increase DOA
What does the addition of bicarb do to PNBs?
decreases onset and increases density of the block
What type of needle is usually used for PNBs?
20-22 G short bevel needle
Describe how to use nerve stimulators to localize a nerve
start with a stimulus around 1.5 mA and dial down to around 0.5 to ensure motor response is still stimulated (only works on motor nerves, not sensory) - caution: if response still seen at 0.2-0.3 it may be intraneural
What is attenuation?
as US waves travel through tissue, it loses energy and amplitude decreases (absorption, reflection, scattering)
What is gain?
degree of receiver amplification
What are some indications for a Bier block?
short operative procedures for the extremities, pain therapy
What kind and how much LA do you use for a Bier block?
12-15 mL of 2% lidocaine OR 30-40 mL of 0.5% lidocaine
Describe how a Bier block is performed
1) double pneumatic tourniquet placed over soft cloth on upper arm 2) distal PIV placed 3) arm elevated for 1-2 minutes for passive exsanguination 4) rubber Esmarch bandage wrapped from hand to distal cuff of tourniquet 5) inflate distal cuff, then proximal cuff, then deflate distal cuff 6) remove Esmarch bandage and inject LA 7) arm lowered, IV cannula removed
What is the max dose of LA that can be used in a Bier Block?
no more than 3 mg/kg
What can you do if a patient starts c/o tourniquet pain during a Bier block?
inflate distal cuff, then deflate proximal duff (NEVER release proximal cuff before inflation of distal cuff- results in rapid loss of anesthesia and risk of LAST)
How do you deflate the tourniquet at the end of a Bier block?
should be inflated for at least 20 minutes after LA injection- once ready for release, deflate tourniquet for 10 seconds, and reinflate for 1 minute (results in more gradual washout of LA)
What is a stellate ganglion block and why is it performed?
injection of LA in sympathetic nerve tissue of neck located on either side of voice box; blocks sympathetic nerves that go to the arms and face- may reduce pain, swelling, color and sweathing changes in UE and improve mobility
What are some conditions a stellate ganglion block is used for?
Reflex Sympathetic Dystrophy (RSD), Sympathetic Maintained Pain, Complex Regional Pain Syndrome, Herpes Zoster (shingles)
What is a common side effect of a stellate ganglion block?
Horner’s syndrome (decreased pupil size, eye drooping, decreased facial sweating)
What nerves are blocked with a wrist block? How much LA is used?
radial, ulnar, median (5 mL for median and ulnar nerve, 10 mL for radial)
Describe how to block the ulnar nerve for a wrist block
1) insert needle under tendon of flexor carpi ulnaris muscle close to distal attachment above styolid process of ulna 2) advance needle 5-10 mm to just past the tendon of flexor carpis ulnaris 3) after negative aspiration, 3-5 mL LA injected 4) subQ injection of 2-3 mL of LA just above tendon of flexor carpi ulnaris to block cutaneous branches of ulnar n.
Describe how to block the median nerve for a wrist block
1) insert needle between tendons of flexor palmaris longus and flexor carpi radialis
2) needle inserted until it pierces deep fascia and 3-5 mL of LA injected
* insert needle until it hits bone, then withdraw 2-3 mm to inject LA
Describe how to block the radial nerve for a wrist block
inject 5 mL of LA subQ just proximal to radial styloid, aiming medially, then extend infiltration laterally using another 5 mL
How long is the onset time for a wrist block?
10-15 minutes (sensory develops faster than motor)
What is the indication for a cutaneous nerve block of the upper extremity? How much LA is used?
mostly used as supplement to major blocks of the upper extremity; 5-10 mL
Describe the anatomy of the intercostobrachial nerve and how it is anesthetized
lateral cutaneous branch of ventral primary ramus of T2 that communicates with medial cutaneous nerve of arm- provides innervation to skin of axilla and medial aspect of proximal arm; both nerves are anesthetized by subQ infiltration of skin on medial aspect of arm
Why is an intercostobrachial nerve block performed?
to supplement brachial plexus block to achieve more complete anesthesia of upper arm
Describe how to perform an intercostobrachial nerve block
1.5 inch 25G needle inserted at level of axillary fossa- entire width of medial aspect of arm is infiltrated with LA to raise subQ wheal
What are indications for a medial cutaneous nerve block of the forearm?
blockade of lateral antebrachial cutaneous nerve, insertion of AV graft, superficial procedures on volar surface of forearm
Describe how to perform a medial cutaneous nerve block of the forearm
1.5 inch 25 G needle used to infiltrate LA subQ over entire medial aspect of arm just below elbow crease
What are some indications for a lateral cutaneous nerve block of the forearm?
insertion of AV grafts, superficial procedures on volar aspect of forearm, supplement axillary brachial plexus block in which musculocutaneous block not performed/failed
How is a lateral cutaneous nerve block performed?
1.5 inch 25 G needle used to infiltrate LA subQ over entire lateral aspect of arm just below elbow crease
