Overview of Regional Anesthesia

Patients are more likely to accept a peripheral if they are assured that sedation can be administered. Considerations/relative contraindications include skin infection, coagulopathy, or preexisting neuropathy

Preparation for Peripheral Blocks

Should be evaluated medically exactly the same way as a patient undergoing general anesthesia. IV catheter must be in place, and the OR must be equipped with general anesthetic equipment.

Agent Onset Duration Lidocaine (1%) 10-20 mins 2-3 hours Mepivacaine (1.5%) 10-20 mins 2-3 hours Ropivacaine (0.5%) longer 6-8 hours Bupivacaine (0.375%) longer 6-8 hours

Epinephrine (5 ucg/mL ie 1:200,000) serves as a marker for intravascular injection in addition to prolonging the block

Block Techniques


Not intentionally elicited because of the risk of nerve injury [Selander et. al. Acta Anaesth Scand 23: 27, 1979]. Never inject anesthetics in the presence of a paresthesia

Nerve Stimulation

Cathodal (+) stimulation is more effective than anodal (-). Surface anode can be located anywhere. If a motor response can be elicited via 0.5 mA, the needle is probably close enough to expect a successful block. Some authors have suggested changing the threshold – a study of 20 pig sciatic nerves showed that response to nerve stimulation with currents <0.2 mA occur only when the needle tip is positioned intraneurally, however, motor response can be absent with intraneural needle placement at a current intensity of up to 1.7 mA. Thus, if you can get a response at anything < 0.2 mA you are definitely intraneural, however an intraneural needle may still require as much as 1.7 mA of current to elicit a response [Hadzic Reg Anesth Pain Med 29: 185, 2004]. Additionally, a case report of four patients who experienced paresthesias despite the use of a nerve stimulator set at 1.2 mA casts further doubt on the reliability of nerve stimulators [Mulroy MF et al. Anesth Analg 95: 762, 2002; FREE Full-text at Anesthesia & Analgesia]. Lastly, when trying to anesthetize a plexus, nerve-based stimulation may fail if the individual nerves are not in close enough proximity (increasing pulse width frmo 0.1 ms to 0.3 ms may help with pure sensory nerves). Do not use nerve stimulators used for NMJ blockade as they can deliver large currents (> 50 mA) and may be inaccurate at low currents


High resolution ultrasound can improve block success and minimize the volume of local anesthetic employed. Frequencies of 10 MHz or higher are required to distinguish tendons from nerves

Peripheral Nerve Catheters

Can be placed adjacent to peripheral nerves to ensure postoperative analgesia. Some practitioners will first inject local anesthetic in order to generate more space prior to placing the catheter

Anatomic Blocks

Cervical Plexus (C1-4)

Inject LA along the posterior lateral border of the SCM, just under the platysma, with the patient’s head turned opposite. This block by itself is sufficient for a carotid endarterectomy (Pandit et. al. Anesth Analg 91: 781, 2000).

Brachial Plexus

Interscalene Block

(Brachial and cervical plexus, sparing C8-T1 fibers ie hand, medial forearm) Inject 25 – 40 cc LA into the interscalene groove adjacent to the C6 transverse process – to help locate this, note that a line extending laterally from the cricoid cartilage will intersect the interscalene groove at C6. Perform this on the patient’s side for comfort. The brachial plexus is only 1-2 cm deep to the skin surface, thus 40 cc of LA will anesthetize the brachial plexus (and cervical plexus), permitting surgery on the acromioclavicular joint, although the C8-T1 fibers may be spared (thus the medial forearm and hand may not receive adequate anesthesia).

Risk of pneumothorax is remote but real. An ipsilateral phrenic nerve block occurs in almost 100% (Urmey WF et al. Anesth Analg 72: 498, 1991). This procedure is therefore contraindicated in anyone with respiratory insufficiency or a contralateral nerve palsy. Recurrent laryngeal nerve is occasionally blocked as well, and this can lead to complete airway obstruction in patients with an existing vocal cord palsy (thus ask about hoarseness or previous neck surgery). Slight caudad direction of the needle reduces the risk of accidental epidural, subarachnoid, or vertebral artery injection. Meticulous aspiration is a requirement

Supraclavicular Block

25 – 40 cc LA, inserted at the point at which the lateral edge of the SCM inserts into the clavicle. Advantages include rapid onset and ability to block regardless of arm position. Phrenic nerve is blocked in ~ 50% of cases but since it is unilateral is rarely of clinical significance – consider avoiding in patients with COPD. Pneumothorax has a 1% incidence (signs = cough, dyspnea, pleuritic chest pain) – many advocate the use of ultrasound for this particular block

Infraclavicular Block

30 – 40 cc of LA injected – with the arm abducted to 90 degrees, draw a line between the C6 transverse process and the axillary artery, make a mark 2.5 cm distal to the point where this line crosses the clavicle, and aim your needle towards the axillary artery pulsation. Advantages include lower incidence of pneumothorax and neurologic complications (needle is remote from the lung and neuraxis). Disadvantages include the risk of patient comfort as well as the pain associated with penetration of the pectoralis major/minor muscle

Axillary (and Musculocutaneous) Block

(blocks the hand, forearm, and elbow)

40 cc of LA. Patient is positioned supine w/ arm abducted to 90 degrees and externally rotated. Palpate the axillary artery, then advance a 2.5-3.75 cm needle through it (until aspiration no longer produces blood) – inject 15 cc of LA, then withdraw needle through axillary artery until blood flow stops, and inject other 15 cc of LA. Inject an additional 5 cc lf LA in a fanning pattern into the coracobrachialis to block the musculocutaneous nerve, and another 5 cc subcutaneously which will block the intercostobrachial, medial brachial cutaneous, and medial antebrachial cutaneous nerves. Will block the hand, forearm, and elbow (Schroeder LE et. al. Anesth Analg 83: 747, 1996). Risks include intravascular injection (and subsequent toxicity) and hematoma

Distal Wrist

Anesthesia of the hand can be used in and of itself, or also used to supplement a brachial plexus block with incomplete sensory distribution. Note that elbow blocks do not provide more coverage than wrist blocks

Median Nerve Block

3-5 cc of LA between the palmaris longus and flexor carpi radialis tendons

Ulnar Nerve Block

Inject just medial to the ulnar artery, inbetween the flexor carpi ulnaris and the ulna. Add additional anesthetic in a ring around the wrist to anesthetize the dorsal cutaneous branch, which often arises proximal to the wrist

Radial Nerve Block

Subcutaneous infiltration within the anatomic snuffbox


Insufficient for surgical anesthesia but very helpful for post-operative analgesia. To perform the block, draw vertical lines on the back 5-7 cm from the midline, and mark the intersection with the inferior aspect of the ribs. Advance a needle at ~ 80 degrees until the rib is contacted, then march caudally until off of the rib edge, at which point one can advance 3-5 mm and inject (with frequent aspiration). Note that above the 5th rib, palpation is difficult and a paravertebral approach is more ideal

Complications include pneumothorax and intravascular injection. Also, note that systemic absorption is VERY high after intercostal blocks

Ilioinguinal and Iliohypogastric

Can provide anesthesia in the inguinal and genital regions. To perform this block, insert a needle 3 cm medial and 3 cm inferior to the ASIS. Use a 22 gauge needle to contact the iliac bone on its inner surface, then inject local anesthesia while slowly withdrawing the needle, repeating the process 1-2 more times and directing more medially each time (to anesthetize a fan-shaped area). Occasionally this block will need to be supplemented with a genitofemoral nerve block

Femoral Nerve

20 cc LA. Abduct the thigh slightly and rotate externally, then draw a line from the ASIS to the pubic tubercle (represents the inguinal ligament). Mark the femoral artery 1-2 cm caudal to this line, then inject 1 cm lateral with a 22 gauge, 40 mm needle (2-3 cm depth) – with intermittent aspireation, inject 20 cc LA


Infiltrate local anesthetic around the saphenous vain at the level of the tibial tuberosity. Ultrasound may be used to guide this block, as the saphenous vein can be difficult to palpate [Gray Reg Anesth Pain Med 28: 148, 2003]

Lateral Femoral Cutaneous

HIGHLY variable course, but can be blocked by injecting 5-10 cc 2m medial and 2 cm distal to the ASIS. This block can be used to supplement other LE blocks for surgery on or above the knee


Absent in 57%, highly variable, can also provide medial (20%) or posterior (23%) cutaneous innervation [Bouaziz H et al. Anesth Analg 94: 445, 2002; FREE Full-text at Anesthesia & Analgesia]. Insert a needle 1-2 cm distal and lateral to the pubic tubercle until the butic bone is reached, then redirect cephalad to reach the obturator canal, where 10-15 cc of LA are deposited. This can be a valuable supplement to sciatic, femoral, and LFCN blocks [Macalou D et al. Anesth Analg 99: 251, 2004; FREE Full-text at Anesthesia & Analgesia]


Draw a line from the PSIS and the greater trochanter, inserting a needle 5 cm caudad to the line. Inject 25-30 cc when near the nerve. Note that this block is generally combined with a femoral block

==Popliteal== (actually “proximal popliteal,” gets both tibial and common peroneal nerves) Posterior and lateral approaches, both of which are injected 5 to 10 cm proximal to the knee crease to ensure both tibial and common peroneal nerves are blocked (the sciatic divides into the common peroneal and tibial nerves somehwere in the popliteal fossa). For the posterior approach, needle is inserted just lateral to the midline. For the lateral approach, it is inserted just anterior to the biceps femoris (hamstring) tendon. 20 – 30 cc are injected. Ultrasound is useful as there is significant biologic variability in the point of division of the sciatic nerve


There are five peripheral nerves that supply the foot, all of which can be blocked at approximately the level of the malleoli. Tibial nerve (sole) is blocked with 3-5 cc of LA in a fanning pattern around the posterior tibial artery. Sural nerve (lateral foot) is blocked with 5 cc of LA in the groove between the lateral malleolus and the calcaneus (near the small saphenous vein). Saphenous nerve (medial foot) with 5 cc of LA anterior to the medial malleolus near the great saphenous vein. Deep peroneal nerve (webbing between toes 1 and 2) with 5 cc of LA adjacent to anterior tibial artery (or deep to the extensor hallucis longus tendon and extensor retinaculum if you can’t feel the pulse). Superficial peroneal nerve (dorsum of foot) with a subcutaneous ridge of LA between the medial and lateral malleoli over the anterior surface of the foot. Systemic toxicity after ankle block is rare, as the foot does not have generous blood supply

IV Regional Neural Anesthesia (aka “Bier block”)

Bier blocks can only be used for procedures lasting two hours or less. To perform a Bier block, an IV catheter is placed distally in the limb of interest, and the extremity is exsanguinated by compression with an Esmarch bandage and a tourniquet is then inflated to ~ 250 mm Hg. Local anesthetic (most commonly lidocaine is used to reduce cardiac toxicity) is injected, and the IV catheter is removed. If the procedure will last longer than 45 minutes, a second cuff is used, as the double-tourniquet technique can be used to reduce tourniquet pain

The main risk of an IVRNA is systemic toxicity following deflation of the cuff. Local anesthetic leves peak 2-5 minutes after deflation. Some recommend making sure that the cuff is inflated at least 20 minutes regardless of the procedure duration, then deflating twice if 20-40 minutes, and once if 40 or more minutes



W F Urmey, K H Talts, N E Sharrock
One hundred percent incidence of hemidiaphragmatic paresis associated with interscalene brachial plexus anesthesia as diagnosed by ultrasonography.
Anesth. Analg.: 1991, 72(4);498-503
[PubMed:2006740] [WorldCat.org] (P p)

L E Schroeder, T T Horlocker, D R Schroeder
The efficacy of axillary block for surgical procedures about the elbow.
Anesth. Analg.: 1996, 83(4);747-51
[PubMed:8831314] [WorldCat.org] (P p)

J J Pandit, S Bree, P Dillon, D Elcock, I D McLaren, B Crider
A comparison of superficial versus combined (superficial and deep) cervical plexus block for carotid endarterectomy: a prospective, randomized study.
Anesth. Analg.: 2000, 91(4);781-6
[PubMed:11004026] [WorldCat.org] (P p)