Taken from Clinical Anesthesia by Barash et al.

1. Peripheral Nerve
Blockade:
Axillary Block
Bien S. Tardo
Post-Graduate Intern

2. Provide longer & more localized pain relief than neuraxial
techniques
Avoid side effects of systemic medication
Premedication & Sedation
Although a mild dose of opioid (50 to 100 μg of fentanyl)
will help ease the discomfort of nerve localization, patient
responsiveness must be maintained
Small doses of propofol or midazolam may provide
excellent amnesia at levels of consciousness that still allow
cooperation

3. Upper Extremity
Innervation is derived from 5 closely approximated nerve
roots, extending from C5 to T1 (brachial plexus)
Produce the terminal nerves of the arm & hand

5. Major Motor Function of the Individual Nerves of the
Brachial Plexus
Nerve Major Motor Function
Axillary Abduction of the shoulder
Musculocutaneous Flexion of the elbow
Radial Extension of the elbow, wrist, & finger
Median Flexion of the wrist & finger
Ulnae Flexion of the wrist & finger

6. Brachial Plexus: Axillary Technique
• Carries the least chance of pneumothorax
• Nerves are anesthetized around the
axillary artery, where they have regrouped
into their terminal branches
• Because of the observation that the single
sheath may be broken up into separate
compartments by fascial septa
surrounding individual nerves in the axilla,
local anesthetic should be injected at
multiple sites in the axilla

7. Tourniquet Placement
Placement of a blood draw type tourniquet distal to the injection
site encourages proximal movement of the anesthetic within the
axillary sheath
The tourniquet is placed while the arm is at the patient’s side
If the tourniquet is placed as high as possible on the patient’s
arm before abduction of the arm, the tourniquet will generally
be very close to the ideal location of 3 cms from the axillary
crease upon abduction
The tourniquet is left in place for 10 mins following the injection

8. Approach
 The nerves that will be blocked lie w/in a
neurovascular sheath
 As the Medial, Posterior, & Lateral cords of
the Brachial Plexus enter the arm they divide
into the Median, Radial, Ulnar,
Musculocutaneous & Axillary Nerves
 The Axillary Artery (becoming Brachial
Artery) & Axillary Vein are within the
neurovascular sheath at this level as well
 Median & musculocutaneous nerves lie on
the superior aspect of the artery
 Ulnar & radial nerves lie below & behind the
vessel

9. 1. The patient lies supine with the arm extended 90 degrees from the
side & flexed at the elbow
Extension beyond 90 degrees potentially compresses the axillary
artery because of the pressure from the head of the humerus &
may make identification of the landmarks more difficult
2. Axillary artery is marked as high in its course in the axilla as is
practical
Usually felt in the intramuscular groove between the
coracobrachialis & triceps muscles
Also passes between the insertions of the pectoralis major &
latissimus dorsi muscles on the humerus

10. 3. After aseptic preparation, a skin wheal is raised over the proximal
portion of the artery
Index & middle fingers of the nondominant hand straddle the
artery just below this point, both localizing the pulsation &
compressing the neurovascular bundle below the intended site of
injection

11. Transarterial
Takes advantage of the fact that the axillary artery is w/in the
neurovascular sheath
By going through the artery, anesthetic is placed reliably within the
neurovascular sheath, & can then diffuse, over time, into the
nerves
Palpation of the artery should be done with several fingers to
better localize the vessel

12. Transarterial
By palpating immediately proximal to the tourniquet, & injecting
proximal to the palpating fingers, the physician is able to inject
very proximally on the arm
This will ensure the highest probability of success
Though relatively superficial, the axillary artery can be difficult to
palpate in some patients, & time should be spent to ensure
accurate localization

13.  2 fingers of equal length straddle the artery while the
needle is introduced along its long axis with a central
angulation
 The palpating fingers serve not only to identify the
vessel but also to compress the perivascular sheath &
encourage spread of anesthetic solution centrally

14. Injection
A 5/8 inch straight 25 gauge or ¾ inch 25 gauge butterfly needle
(with extension tubing) is preferred
The needle is inserted toward the palpated artery
When a flash is seen, insertion is continued until blood return
ceases
A <0.5ml volume is then injected to clear the hub/extension
tubing & aspiration is repeated to confirm position immediately
behind the artery

15. Injection
The injection is then performed in 5.0 ml increments, aspirating
between injections to ensure that the correct position has been
maintained
When 5.0 ml remains, the needle is slowly withdrawn through the
artery, until blood return ceases
A <0.5ml volume is then injected to clear the hub/tubing, &
aspiration repeated to confirm position immediately superficial
to the artery
The last 5.0 ml is then injected, & the needle withdrawn

16. Injection
Aspirate every 5 ml to ensure that the needle has not inadvertently
entered an artery or vein
Monitor for signs & symptoms of intra-arterial injection including:
increased heart rate,
“funny” metallic taste
faintness
seizures
Some clinicians will inject half of the total local anesthetic dose
posterior to the artery & the other half anterior to the artery

18. Perivascular
Rather than penetrating the artery, the artery is carefully
localized, & the anesthetic injected at the same depth as the
artery, both superior, & inferior
5 to 10 mL of local anesthetic is injected closely on each side of
the artery, using multiple passes with a moving needle not
seeking nerve responses, producing a “wall of solution” that
intercepts the paths of each of the branches
When properly localized, the neurovascular sheath will display
the same sausage-like swelling post injection as is seen with the
transarterial method

19. Perivascular
After initial infiltration, sensation or motor function is tested
in the peripheral nerve distribution w/in 5 mins
If anesthesia is not present, reinjection of the area is again
performed with multiple passes
Simpler & can be performed rapidly, but requires clear
identification of the pulse

20. Anesthetic mixtures
Duration Drug Dosing Volume Comments
Short
<40 minutes
Lidocaine 0.5% 5.0 mg/kg
1 ml per kg body weight
Dilute 1.0 % lido 1:1 with
normal saline to maximum of
50 ml
Use 40 ml for small adults <50kg
Medium
40-90 minute
Lidocaine 0.5% with
epinephrine
5 mg/kg
1 ml per kg body weight
Dilute 1% lido 1:1 with
normal saline to maximum of
50 ml
Use 40 ml for small adults <50kg
Long
>90 minutes
Lidocaine 1.0% with
epinephrine
Bupivicaine 0.25%
20 ml lidocaine with epi.
20 ml 0.25% Bupivicaine
Dilute with normal saline to
total of 50 ml
Use 15 ml Lidocaine/15 ml
Bupivicaine/10.0 ml saline for small
adults <50kg

21. Complications
Neuropathy is the foremost consideration
Hematoma can occur if the vessel is punctured, but this is
rarely a problem

22. Pitfalls of ANB
1. Infiltrating too deep
 As already noted, the neurovascular compartment is very superficial
 If the needle is advanced too far beyond the artery you will inject
deep to the neurovascular compartment, & a block will not be
achieved
 The correctly performed injection into the neurovascular
compartment produces a “sausage like”, confined, subcutaneous
swelling, that is easily seen in all but the most obese patients

23. Pitfalls of ANB
2. Using too small a volume of anesthetic
The ANB is a volume dependent technique
 At least 40 ml is needed to diffuse adequately in the adult patient
 When using the transarterial/perivascular techniques the objective is
to fill the neurovascular compartment with anesthetic that then
diffuses into the nerves
 An adequate volume is required to both surround the nerves, & to
move proximally far enough to reach the musculocutaneous/
proximal nerves

24. Pitfalls of ANB
3. Attempting procedure too soon
 Immediate rest pain control is generally achieved with a properly
placed injection
 If a gentle manipulation is attempted immediately after the block,
however, some pain will still be felt
 The person performing the reduction in this case should be
instructed to wait before performing the procedure
 A significant number of patients will be ready at 5 mins, but the
density of anesthesia will generally increase for 20-30 mins

25. Pitfalls of ANB
4. Not injecting proximally enough on the arm
 The more proximally on the arm the ANB is performed the more
likely it will be complete
 The musculocutaneous nerve has already left the neurovascular
bundle at the point where the injection is performed: consequently,
proximal placement of the anesthetic is required