Revised Regional Anesthesia Manual—upper extremity blocks
Introduction
Peripheral nerve blocks are gaining widespread popularity for perioperative pain management
because of their specific advantages over general anesthesia and central neuraxial anesthesia.
1. Pain relief with PNB avoids side effects such as somnolence, nausea and vomiting, hemodynamic
instability and voiding difficulty inherent to general and central neuraxial anesthesia.
2. Patients who undergo surgery under PNB can bypass phase I recovery room and frequently be
discharged expeditiously following ambulatory surgery.
3. Patients with unstable cardiovascular disease can undergo surgery under PNB without significant
hemodynamic changes.
4. Patients who have abnormalities in hemostasis or infection which contraindicate use of central
neuraxial block can be candidates for surgery under PNB.
5. A substantial savings in operating room turnover time can occur if PNB is done outside the operating
room. If the patient has a functioning block preoperatively there is no induction or emergence time.
Patients with a PNB can frequently position themselves.
6. When used as part of a combined general regional technique, PNB facilitates lighter planes of
anesthesia, avoiding the use of opioids and allowing a quick emergence and recovery.
In order to carry out a regional block safely and effectively, the anesthesiologist must be proficient in
the following:
Anatomy
Have knowledge of the neural elements to be blocked, their relationship to muscular, vascular and
other anatomic structures and their ultimate motor and sensory innervation. Knowledge of the innervation
will provide guidance to select the most suitable technique for a particular surgical procedure. The bony,
vascular, muscular and fascial relationships will serve as landmarks to guide the needle to the appropriate
site, thus improving the success of the block and minimizing side effects and complications.
Pharmacology
Knowledge of local anesthetic pharmacology will assist in the selection of the most appropriate
local anesthetic drug and dosage. The anesthesiologist must also be familiar with the clinical
pharmacokinetics i.e. pattern of onset of and recovery of the nerve block. This allows an assessment of the
clinical efficacy of the block with respect to operative anesthesia and approximate duration of postoperative
analgesia after a particular local anesthetic drug has been injected.
Complications and side effects
Knowledge of the possible complications and the errors in the technique will help in preventing
the complication and also in managing them effectively in case they do occur. Knowledge of the possible
side effect which could occur from blockade of the other neural elements in the vicinity such as phrenic
nerve, recurrent laryngeal nerve and the sympathetic nerves will help in patient education as well as in
assessing the contraindication to the technique.
Local anesthetics: Clinical pharmacology, drug selection and toxicity
To select an appropriate local anesthetic drug for a specific clinical situation, one should be
familiar with the clinical pharmacology of the local anesthetic drugs and adjuvants.
Local anesthetics exert their effect either by inhibiting the excitatory process in the nerve endings
or in the nerve fibers. The following sequence of events is generally accepted as the mechanism of action of
local anesthetic agents:
1.
2.
3.
4.
Binding of the local anesthetic moiety to the receptor sites in the nerve membrane.
Reduction in sodium permeability
Decrease in the rate of depolarization
Failure to achieve threshold potential
5.
6.
Lack of development of propagated action potential
Conduction blockade
The pharmacological activity of local anesthetic agents is influenced by their chemical structure, lipid
solubility, protein binding, pKa.
Chemical Structure
Based on their chemical structure local anesthetics can be grouped into:
1.
2.
Aminoesters – Procaine, cocaine, tetracaine, choroprocaine. Aminoesters have an ester linkage
between the benzene ring and the intermediate chain. These are hydrolyzed in the plasma by
pseudocholinesterase. One of the primary metabolites of ester compounds is paraminobenzoic acid.
Paba has known allergic potential.
Aminoamides – Lidocaine, mepivacaine, bupivacaine, ropivacaine. Aminoamides have an amide link
between the benzene ring and intermediate chain. These are degraded in the liver by microsomal
enzymes. The amide drugs are not metabolized to paraaminobenzoic acid and rarely produce allergic
reactions. Multidose vials of amide local anesthetic may contain methylparaben (MPF should always be
used for regional anesthesia) which is a paraaminobenzoic acid derivative with allergic potential.
Lipid Solubility
Lipid solubility is the primary determinant of intrinsic anesthetic potency. Potency increases as a
function of lipid solubility until a blood/lipid partition coefficient of 4 is reached. Further increases in lipid
solubility do not cause a further increase in the local anesthetic potency. Based on the lipid solubility and
potency, local anesthetic drugs can be divided into 3 groups:
1.
Low lipid solubility/potency: Lipid partition coefficient < 1. These drugs must be administered in
high concentrations (2 to 3 %) to achieve effective neural blockade. Local anesthetic drugs in this
category include procaine and chloroprocaine.
2.
Intermediate lipid solubility/potency: Lipid partition coefficient 1-3. These drugs may be in
concentrations of 1 to 2%. Local anesthetic drugs in this category include lidocaine, mepivacaine, and
prilocaine.
3.
High lipid solubility/potency: Lipid partition coefficient >4. These drugs are clinically effective at
low concentrations <1%. Local anesthetic drugs in this category include tetracaine, bupivacaine, and
ropivacaine.
Protein Binding
Addition of larger chemical radicals to the amine or aromatic end of a local anesthetic compound increases
its binding to protein, which is a determinant of local anesthetic duration. Protein binding of commonly
used local anesthetics is:
Bupivacaine-------------------------95%
Tetracaine---------------------------95%
Ropivacaine-------------------------94%
Mepivacaine------------------------74%
Lidocaine----------------------------65%
Procaine-------------------------------6%
PKa
Pka is the pH at which ionized and unionized fractions of a substance are present in an equal amount. The
onset of local anesthetic effect will be determined by the total amount of unionized fraction of the local
anesthetic agent because the unionized fraction primarily diffuses across the nerve membrane. The
percentage of local anesthetic, which is present in the unionized form (cation or base) when injected into
the tissue at (pH 7.4) is inversely proportional to the pKa of the agent. As the pH of the local anesthetic
solution goes down, the unionized fraction will decrease when the pH increases the unionized fraction
increases. There is a correlation between the onset of the block and the pKa of local anesthetic drug. The
drugs with pKa of 7.6-7.8 ( lidocaine, mepivacaine, prilocaine) have a more rapid onset of action than do
bupivacaine and tetracaine which have a pKa of 8.1 and 8.6 respectively. At the body pH (7.4), 35 % of
lidocaine exists in unionized base form and only 5 % of bupivacaine exists in unionized base form.
Adjuvant Drugs
These drugs can reduce the onset time, prolong the duration, increase the density and reduce dosages of the
commonly used local anesthetics.
EpinephrineProlongs duration by vasoconstriction and slowed absorption. Duration can be
increased by 30-50%. Peak plasma concentrations can also be reduced by 50%. Can also be a marker for
intravascular injection—tachycardia.
ClonidineProlongs duration of local anesthetics by synergistic alpha-2 effects. Lesser or
no prolongation with Bupivacaine and Ropicacaine but can prolong Mepivacaine-Lidocaine by 40-400%
with 100 micrograms. Larger doses are not additive and cause more side effects.
Upper Extremity Blocks
The plexus of nerves innervating the upper extremity is contained in a fascial sheath, which is surrounded
by reliable anatomic landmarks. This allows an injection of local anesthetic to reliably block the sensory
and motor innervation to the upper extremity with two exceptions—
1.
2.
Areas of the upper extremity with cervical plexus innervation. The sensation of the skin overlying
the shoulder is supplied by the nerve roots C3 and C4 of the cervical plexus. These nerve roots lie
superior to the most cephalad aspect of the brachial plexus. Interscalene blocks done with large
volume of local anesthetic (35-40ml) may block these nerve roots as well in the vast majority of
cases. The surgical procedures where C3 and C4 blocks are beneficial usually involve the clavicle.
Area of the upper extremity with intercosto-brachial (T2) innervation. The sensory innervation of
the axilla and anterior shoulder is T2, which is also derived from outside the brachial plexus. A T2
block is required for shoulder surgery with anterior incisions (anterior stabilization for shoulder
dislocation) and surgery involving the elbow and upper arm.
Innervation of the upper extremity
For convenience the branches of the brachial plexus which innervate the upper extremity can be divided into
supraclavicular (branches from roots and trunks) and infraclavicular branches from the divisions, cords
and nerves.
All the supraclavicular branches are motor with the exception of the suprascapular nerve, which provides
sensation to the shoulder joint. Suprascapular branches supply the scalene muscles, serratus anterior via the long
thoracic nerve, muscles of the upper back and contribute to the phrenic nerve.
The infraclavicular branches comprise all of the sensory and motor innervations to the upper extremity and
are important to the anesthesiologist both from the point of view of technique (distribution of parasthesia, motor
response if nerve stimulator is being used to locate the plexus) and extent of the block and identification of missed
nerves.
Anatomic relations of the Brachial plexus
Knowledge of the anatomic structures, which surround the brachial plexus, will help in the location of the
plexus as well as in the prevention of complications.
Perivascular compartment
This concept has promoted the single injection technique of the brachial plexus block. Clinically, proximal
blocks behave as if there were a sheath surrounding the plexus. A single injection technique lends itself to a short
onset and high success rate. However with a more distally placed block like an axillary block, a single injection
technique is less reliable because of the individual peripheral nerves begin to diverge. To improve the success of an
axillary block several strategies are used to improve proximal spread of local anesthetic- such as injecting high in
the axilla, adduction of the arm and application of pressure distal to the injection.
Vascular relationship
There are no major vessels at the level of the roots except for vertebral vessels, which lie far medially and
anterior to the plexus. A long needle directed horizontally in the interscalene space may get into the vertebral artery
or vein. The needle can also get into the subarachnoid or epidural space via the intervetebral foramen. The trunks of
the plexus also lie in close proximity to the subclavian artery, which separates them from the anterior scalene
muscle. . This relationship must be born in mind when doing a subclavian perivascular approach is being used.
Another anatomic fact is the significance that the inferior aspect of the trunk of the plexus may be trapped behind
and under the artery. In this situation, there is probably a mechanical barrier to the spread of local anesthetic if it is
placed high in the interscalene groove. So the most common elements of the brachial plexus missed with an
interscalene approach are C8 and T1.
Blocks above the clavicle
Level of the roots – Interscalene brachial plexus block
Trunks – Subclavian perivascular brachial plexus block/ classical supraclavicular brachial plexus block
Blocks below the clavicle
Division/Cords – Infraclavicular brachial plexus block
Cords/Terminal nerves – Axillary brachial plexus block
Axillary Approach of the Brachial Plexus
The axillary block is the most commonly used approach to the brachial plexus since this approach is free of
the risk of pneumothorax.
Position: The patient is placed supine with the arm abducted 90 degrees and flexion of the forearm with external
rotation so that the forearm lies parallel to the long axis of the body. Hyperabduction will obliterate the axillary
artery pulse in 80% of individuals because the artery is compressed between the head of the humerus and the
pectoralis minor muscle.
Needle placement: The arterial pulse should be identified and followed as proximal as possible, ideally to the point
where the pulse disappears beneath the pectoralis major. The artery is located between the index and middle fingers
of the non-dominant hand. With light digital pressure the artery is fixed against the humeral head high in the axilla.
A #22 gauge 1.5 cm B bevel needle is introduced slightly superior to the finger tip and advanced at about a 30
degree angle to the skin, tangential and parallel to the neurovascular bundle until one of the following 3 endpoints
are met.
1.
Slow needle placement until a parasthesia is obtained (Success rate 85-90%).
2.
The transarterial approach: The needle is slowly advanced until bright red blood is obtained during continuous
advancement. Once blood return is obtained, the needle should be advanced through the wall of the axillary
artery until no additional blood can be aspirated. Once it has been verified by the aspiration that the needle tip
lies posterior to the arterial wall (just 1-mm), the total anesthetic volume (40-50 ml) is injected in 5-ml
increments posterior to the artery. Splitting the local anesthetic volume to deposit posterior and anterior reduces
rather than increases the success rate of the block. The success of the block is related to the close proximity of
the needle tip to the posterior wall of the artery (clinical sign to ensure this is aspiration of slight blood stained
fluid during intermittent aspiration and injection). After approximately 20 ml of local anesthetic injection the
needle can be withdrawn back though the artery and advances again through the posterior wall. This reconfirms
that the needle tip is in close proximity to the posterior wall of the artery. Appropriately performed, the
transarterial approach has nearly 100% success rate. A sharp needle (not a blunt tipped nerve stimulator needle)
should be used for the transarterial technique.
3.
Axillary block using a nerve stimulator – Using an insulated needle, connect the negative lead to the needle.
Use low output current (.3-.5ma) at l sec twitch rate. Look for an appropriate motor response in the hand in the
distribution of the ulnar, radial, or median nerves. Please note that motor response at the elbow (biceps twitch)
indicates that stimulation of the musculocutaneous nerve, which is outside the sheath. The injection at the
endpoint will result in the block of the musculocutaneous only.
Epinephrine 1:200,000 (5 mcg/ml) should be used in all perivascular blocks. Direct close attention to the ECG
or pulse oximeter pulse tone to effectively identify intravascular injection. After injecting 40-45cc, a small
volume of local anesthetic should be injected subcutaneously over the axillary artery to block the branches of
the intercostobrachial and medial brachial cutaneous nerve.
Assessing the Success of the Axillary Block
If the onset of proximal motor block (loss of forearm extension; i.e. inability to point to the ceiling – radial
nerve block) occurs within minutes of the injection, you can expect good surgical anesthesia in 20 minutes.
Check the sensory distribution of the individual nerves to identify the unblocked nerves.
(Push, Pull, Pinch, Pinch)
Interscalene approach to the brachial plexus
This technique for brachial plexus anesthesia is used for surgical procedures of the upper arm and shoulder.
This approach is specifically suited for shoulder surgery since it blocks the suprascapular nerve which supplies
sensation to the shoulder joint.
Technique: The key to success is correct identification of the interscalene groove. The patient should be supine
and asked to elevate the head, bringing the sternocleidomastoid muscle into prominence. The index and middle
fingers are places behind the clavicular head of the sternocleidomastoid muscle and the patient is asked to relax
and turn the head and onto the opposite side with the chin in the midclavicular line. Turning the neck too far
laterally will make the scalene muscles difficult to palpate. The palpating fingers are moved medially behind the
sternocleidomastoid to lie on the anterior scalene muscle. The palpating fingers are then rolled laterally until the
groove between the anterior and middle scalene muscles is identified. Please note that the groove is wider
distally, so keep the distal palpating finger in the groove just above the clavicle. Keep the middle finger firmly
in the distal part of the groove and the palpating index finger at the level of C6 anterior to the external jugular
vein. If there is difficulty in identifying the anterior scalene muscle, ask the patient to maximally inhale. This
makes the anterior scalene muscle more prominent and its palpation easier. The needle is inserted in the into the
interscalene groove at the level of C6 which can be identified by drawing a line from the crycoid cartilage to the
interscalene groove. An additional landmark is the external jugular vein when visible crosses the interscalene
groove at the level of C6. With both the index and middle fingers in the groove, a #22 gauge B-bevel needle is
inserted at the level of C6 perpendicular to all planes mostly mesiad, but slightly caudad and posterior. . The
appropriate needle placement should be 60 degrees from the sagittal plane. The needle is advanced until a
parasthesia is elicited in the shoulder or there is a motor evoked response in the forearm at <0.5 mA or the
transverse process is contacted. If bone is contacted then the needle tip should be withdrawn and redirected
caudad until the appropriate motor response or parasthesia is obtained.
Please note that when a large volume of local anesthetic (35-40 ml) is injected especially in a thin patient, a
visible swelling will appear above the clavicle defining the inferior portion of the supraclavicular brachial
plexus. Due to the distance of the C8 and T1 nerve roots from the sight of injection, the ulnar nerve is
frequently missed with the interscalene approach. Also, the intercostobrachial and brachial cutaneous nerves,
which supply the axilla and medial aspect of the upper arm, will be missed.
Assessing the success of the Interscalene Block
Motor block precedes sensory block. Innervation to the shoulder flexors are the first blocked. If the patient
cannot lift the shoulder of the table within 2-3 minutes of local anesthesia (even with 0.5% Bupivacaine) expect
good surgical anesthesia for shoulder surgery within 20 minutes.
.
Infraclavicular brachial plexus block
Anatomy: The boundaries of the infraclavicular fossa are pectoralis major and minor muscles anteriorly, ribs
medially, clavicle and coracoid process superiorly and humerus laterally. The plexus is approached in close
proximity to the coracoid process.
Technique: the patient is supine, the ipsilateral arm is abducted to a 90-degree angle and the patient’s head
is turned to the opposite side.
The following landmarks are identified and marked –
1.
2.
3.
4.
Medial head of the clavicle
Acromion process – The most prominent structure on the superior aspect of the shoulder. Axillary
artery – at the highest point in the axilla place a mark on the pectoralis major, Doppler can be used to
mark the axillary artery along the infraclavicular area
Mark the midpoint of the clavicle between the Acromion and the sternal head of the clavicle.
Needle entry site is – 2.5 cm below the midpoint of the clavicle along the axillary artery.
The anesthesiologist stands at the patient’s side opposite to the one being blocked. The needle entry
site is infiltrated with local anesthesia. A 10 cm insulated block needle is inserted at a 60 degree angle
to the sagittal plane directed away from the rib cage towards the axilla. Pectoralis major contractions
are observed at a depth of 1 – 3 cm. The plexus lies 3 – 7 cm deep. Since musculocutaneous and
axillary nerves are outside the sheath, motor response of those two nerves (i.e. deltoid and biceps
contractions) should not be accepted. If these two motor responses are obtained redirect the needle
injection toward the apex of the axilla. The ideal motor evoked response is hand movement at (.3.4)mA. Once ideal motor evoked response is obtained inject 40 – 50 ml of local anesthesia
incrementally. If no motor response is encountered, progressive needle redirection to 80 degrees will
yield an appropriate response.
Suprascapular Nerve Block
The suprascapular nerve provides sensory innervation to 70% of the shoulder joint. The suprascapular
nerve supplies Superior and posteriosuperior regions of the shoulder joint capsule and variable portions of the
overlying skin. Anteriorly and inferiorly the skin and joint capsule are supplied by the axillary nerve, upper and
lower subscapular nerves. Suprascapular nerve blocks can be used for postop analgesia but not for operative
anesthesia.
Technique: The patient should sit up and lean forward with the arms hanging loosely at the side. Draw a line along
the length of the spine of the scapula. Palpate the acromion process at the edge of the spine of the scapula. At the
point where the thicker acromion process fuses with the thinner spine of the scapula is marked. The skin is prepped.
A 25 or 27 gauge needle is used to anesthetize the needle entry site at the marked point. An insulated block needle –
(Stimuplex) 22g 2 inch (<70 kg) or 4 inch (>70 kg) is introduced through the marked point. The needle should
contact bone at a depth of one inch. The needle is walked superiorly and medially until it slides off into the
suprascapular notch. The needle should be advanced no more than 1 cm from the suprascapular notch because of the
risk of pneumothorax. Stimulation of the suprascapular nerve causes contraction of the supraspinous and
infraspinous muscles with abduction and external rotation of the arm. With the appropriate motor evoked response,
inject 10 – 15 ml of local anesthesia.
Intravenous Regional Anesthesia (IVRA, Bier Block)
IVRA can be used for short surgical procedures on the extremities. IVRA involves an IV injection of local
anesthetic mixture into an exsanguinated extremity that is vascularly isolated by a tourniquet. It is technically
simple. High reliability (97-100%), ease of administration and safety are major advantages of this technique. IVRA
is suitable for surgical procedures below the elbow in the upper extremity and below the knee in the lower extremity
of less than 1-hour duration. The only drug specifically approved by the FDA for IVRA is Lidocaine 0.5%
preservative-free. For upper extremity blocks, a volume of 40-50 ml is used and for the lower extremity blocks, a
concentration of 0.25% with a volume of 100-125 ml is used. The purpose of using a high volume is to assure an
adequate distribution of local anesthetic in the entire venous system of the exsanguinated extremity.
Technique of IVRA
1.
2.
Start an IV infusion in the uninvolved extremity for drug administration and hydration.
Apply the appropriate monitors; give supplemental oxygen and adequate sedation to make the patient
comfortable. Check baseline SBP so that the appropriate tourniquet inflation pressure can be used
(100 mm Hg higher than SBP).
3. Place a 20 or 22 G angiocath near the surgical site preferably in the dorsum of the hand. Do not place
the angiocath near the site of the surgical incision.
4. Apply Webril gauze to the upper arm from armpit to elbow. This protects the skin and the ulnar nerve
in the cubital tunnel.
5. Apply two separate tourniquets of the Webril. Place a 24-cm tourniquet proximally and 18-cm
tourniquet distally on the upper arm. In obese patients with conical shaped upper arm, use a single
large 30-cm tourniquet.
6. Elevate the extremity and exsanguinate with an Esmarch bandage from hand to distal tourniquet.
While wrapping the arm be careful not to wrap the area over the angiocath. Compression of the
angiocath hub beneath the Esmarch bandage can cause ulceration of the underlying skin.
7. Inflate the distal tourniquet to 250-mm Hg and then inflate the proximal tourniquet. Once the proximal
tourniquet is inflated, deflate the distal tourniquet. Ensure that the inflation pressure is at least 100 mm
Hg above the systolic pressure. In a hypertensive patient > 250 mm Hg may be needed. This is very
important for maintaining a bloodless surgical field.
8. Remove the Esmarch bandage and check for presence of a radial pulse.
9. Place a tourniquet proximal to the angiocath on the forearm and inject the local anesthetic solution into
the angiocath slowly.
10. Remove the angiocath and compress site for 2 – 3 minutes.
Tourniquet Pain
Tourniquet pain manifests itself in many forms: e.g. patient getting restless, vague complaints of aches and
pains and pressure in the arm, tourniquet site, or in the shoulder. This may occur 20-30 minutes after the inflation of
the proximal tourniquet. If you suspect that the patient is having tourniquet pain, inflate the distal cuff then deflate
the proximal cuff. Always inform the surgeons before switching the tourniquets as they may be in the middle of a
crucial maneuver and any tourniquet mishap may complicate their procedure. Supplemental analgesics and sedatives
are also used to prevent and manage tourniquet pain.
Suggested text books for reference
1.
2.
3.
4.
Neural Blockade in Clinical Anesthesia and Pain Management. Cousins and Bridenbaugh editors. Lippincott
Raven, 1999.
Atlas of Regional Anesthesia. David L. Brown. WB Saunders, 1998.
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