Peripheral Nerve Blocks

Question 1

What are advantages of peripheral nerve blocks?

Answer 1

Decrease in: 
     Stress response
     Systemic analgesia requirement
     opioid related side effects
     general anesthesia requirement
     incidence/occurrence of chronic pain

Potent analgesia

Question 2

T/F; Peripheral nerve block will decrease phantom pain for chronic issues?

Answer 2

True

Question 3

What type of patient selection should be considered for a peripheral nerve block?

Answer 3

Hx: Chronic Pain
Opioid resistance
Comorbidities
Do not tolerate opioid use (N/V)

Question 4

What are the consideration before doing a peripheral nerve block?

Answer 4

• Tourniquet placement
• bone grafting
• projected duration of surgery
• single injection or continous peripheral nerve block

Question 5

What are the risk to performing a peripheral nerve block?

Answer 5

Nerve injury
Local anesthetic toxicity
Intravascular injection
Perivascular absorption

Question 6

What are contraindication of a peripheral nerve block?

Answer 6

-Patient cooperation and participation
     Children
     Mentally handicap  
Bleeding disorders
Site of infection

Question 7

What is to be considered when choosing a local anesthetic for peripheral nerve block?

Answer 7

• Onset
• Desired duration
• Desired sensory
• Motor block

Question 8

Patient preparation is doing what?

Answer 8

• Use of hemodynamic monitors
• Supplemental oxygen
• Resusitative medication and equipment ready
• Patient positioning
• Intravenous premedication
• Strict Sterile Technique

Question 9

List the various Block Techniques.

Answer 9

• Field block technique
• Paresthesia Technique
• Nerve stimulation Technique
• Ultrasound technique

Question 10

Describe a field block technique.

Answer 10

• Local anesthetic injection that targets terminal cutaneous nerves
• Commonly used by surgeons to minimize incisional pain
• Undesirable when block may obscure the operative anatomy or where local tissue acidosis (infection) prevents effective local anesthetic function.

Question 11

Describe a paresthesia technique.

Answer 11

Formerly the mainstay of regional anesthesia

Practitioner uses known anatomic relationships and surface landmarks as a guide

Block needle is inserted in proximity of the target nerve or nerve plexus

When needle makes direct contact with a sensory nerve, a paresthesia is elicited and the LA is injected

Question 12

Describe a nerve Stimulation technique.

Answer 12

When the insulated needle is placed in proximity to a motor nerve, muscle contractions are induced.

It is common to redirect the block needle until muscle contractions occur at a current less than 0.5 mA

Some thought that a muscle contraction elicited at less than 0.2 mA implies intraneural needle placement.

30-40 ml of local anesthetic is injected with gentle aspiration, and divided doses.

Question 13

Describe a ultra sound technique.

Answer 13

Ultrasound for peripheral nerve location and subsequent block is becoming increasingly popular.

Used alone or with other techniques; (nerve stimulation)

Ultrasound uses high-frequency sound waves emitted from piezoelectric crystals that travel at different rates through tissues of different densities, returning a signal to the transducer.
1-20 MHz

Based on the amplitude of signal received, the crystals deform to create an electronic voltage “picture” or a two-dimensional grayscale image.

Question 14

What is echogenicity?

Answer 14

The degree of efficiency with which sound passes through a substance.

Question 15

What is hypoechoic?

Answer 15

• structures and substances through which sound easily passes. Appear dark or black on the ultrasound screen. (solid organs, deep structures - attenuation limits beam transmission to reach structures, resulting in a weak returning echo.
  )

Question 16

What is hyperechoic?

Answer 16

structures reflecting more sound waves appear brighter, “white” on the ultrasound screen. (diaphragm, gallstones, bone, pericardium)

Question 17

What is anechoic?

Answer 17

No reflection (fluid and blood filled structures)

Question 18

What probe uses a high frequency transducer that offers a high resolution picture with less tissue penetration.

• Good for superficial nerves
• Provide undistorted image
• First choice among practitioners

Answer 18

Linear Probe

Question 19

What probe uses a low frequency transducer that offers better tissue penetration with lower resolution, or poorer image quality.
-Good for deeper structures

Answer 19

Curvilinear Probe

Question 20

The optimal ________ varies depending on the ______ of the target nerve and ________ angle of the needle relative to the transducer.

Answer 20

Transducer, depth, approach

Question 21

Nerves are best imaged in ______-______ (short axis).

Answer 21

cross-section

Question 22

What is the characteristics of a nerve?

Answer 22

Honeycomb (popcorn effect)

Question 23

__-_____ needle alignment refers to aligning the needle with the long-axis of the transducer (along the ultrasound beam) so that the entire shaft and tip of the needle are visible. One of the disadvantages of the __-________ needle view is that, it is easy to lose the image with a slight movement of the transducer as the ultrasound beam is thin. This technique requires excellent hand-eye coordination.

Answer 23

In-plane, in-plane (Longitudinal, long-axis)

Question 24

This type of needle insertion refers to when the transducer and the needle are perpendicular to each other. It is important to slide the transducer along the shaft of the needle to identify the needle tip. Both the needle tip and shaft in cross section appear as a hyperechoic white dot on the screen. Since only the needle tip is observed as a bright dot, it is sometimes difficult to accurately observe the needle during advancement. Despite this, it is an easier approach for peripheral nerve blocks and central venous cannulation

Answer 24

Out-of-plane alignment (Transverse or short axis)

Question 25

What is a single shot injection nerve block?

Answer 25

nerve(s) are identified and local anesthetic is infiltrated via a one time injection, to achieve desired effect.

Question 26

What is a continous peripheral nerve block?

Answer 26

involves placement of a percutaneous catheter adjacent to a peripheral nerve, followed by local anesthetic administration to prolong the effect.

Question 27

What are the advantages of a CONTINUOUS PNB?

Answer 27

``` -Decrease: resting and dynamic pain Supplemental analgesia requirements opioid related side effects sleep disturbance Time to discharge ``` -Improved patient Satisfaction ambulation -Accelerated resumption of passive joint range-of-motion

Question 28

Complications of CONTINUOUS PNB?

Answer 28

``` Systemic local anesthetic toxicity Catheter retention Nerve injury Infection Retroperitoneal hematoma Increased risk of falling (femoral nerve catheter) ```

Question 29

What is an intravenous regional anesthesia block called?

Answer 29

Bier Block

Question 30

Name the upper extremity brachial plexus blocks of PNB?

Answer 30

Interscalene block Supraclavicular block Infraclavicular block Axillary block

Question 31

Upper extremity terminal nerve blocks that are PNB:

Answer 31

``` Median nerve block Ulnar nerve block Radial nerve block Musculocutaneous nerve block Digital nerve blocks Intercostobrachial nerve block ```

Question 32

What should be known about a interscalene block?

Answer 32

Indicated for surgical procedures involving the shoulder and the upper arm Roots C5-C7 are most densely blocked with this approach The ulnar nerve originating from C8-T1 may be spared NOT appropriate for surgery at or distal to the elbow For complete surgical anesthesia of the shoulder, the C3-C4 cutaneous branches may need to be supplemented with a superficial cervical plexus block or local infiltration

Question 33

What are the contraindication of interscalene block?

Answer 33

Local infection Severe coagulopathy Local anesthetic allergy Patient refusal

Question 34

A properly performed ____________ block will invariably block the ipsilateral phrenic nerve. Careful consideration should be given to patients with severe pulmonary disease or preexisting contralateral phrenic nerve palsy.

Answer 34

interscalene

Question 35

Other Consideration with interscalene block?

Answer 35

Horner’s syndrome - may result from proximal tracking of local anesthetic and blockade of sympathetic fibers to the cervicothoracic ganglion Recurrent laryngeal nerve involvement often induces hoarseness. In a patient that has pre-existing contralateral vocal cord paralysis, respiratory distress may ensue. Vertebral artery injection - suspect if immediate seizure activity is observed (1ml of LA in vertebral artery) Spinal or epidural injection - Pneumothorax - possible due to close proximity of pleura

Question 36

What is a supraclaviular block?

Answer 36

Dense anesthesia of the brachial plexus for surgical procedures at or distal to the elbow. Does not reliably anesthetize the axillary and suprascapular nerves and is not ideal for shoulder surgery. Historically, the block fell out of favor due to the high incidence of complications that occurred with paresthesia and nerve stimulator techniques. Ultrasound guidance has improved its safety and increased its current use. Pneumothorax Dense anesthesia of the brachial plexus for surgical procedures at or distal to the elbow. Does not reliably anesthetize the axillary and suprascapular nerves and is not ideal for shoulder surgery. Historically, the block fell out of favor due to the high incidence of complications that occurred with paresthesia and nerve stimulator techniques. Ultrasound guidance has improved its safety and increased its current use. Pneumothorax

Question 37

Contraindications of a supraclavicual block.

Answer 37

Local infection Severe coagulopathy Local anesthetic allergy Patient refusal

Question 38

Complication of a supraclavicular clock?

Answer 38

Ipsilateral phrenic nerve palsy in ~50% of patients Horner’s syndrome Recurrent laryngeal nerve palsy Pneumothorax Subclavian artery puncture

Question 39

What is a axillary block?

Answer 39

At the lateral border of the pectoralis minor muscle, the cords of the brachial plexus form large terminal branches. Multiple injections of 10ml each may be required to reliably produce anesthesia of the entire arm distal to the elbow. At the lateral border of the pectoralis minor muscle, the cords of the brachial plexus form large terminal branches. Multiple injections of 10ml each may be required to reliably produce anesthesia of the entire arm distal to the elbow.

Question 40

Complications to axillary block?

Answer 40

Local infection Neuropathy Bleeding risk

Question 41

What is a block of terminal nerves?

Answer 41

A single terminal nerve is ds often anesthetizes for minor surgical procedures with a limited field or as a supplement to an incomplete brachial plexus block. Terminal nerves may be anesthetized anywhere along their course, but the elbow and the wrist are the favored sites for injection. See resources for specific blocks.

Question 42

What is Bier block good for?

Answer 42

Surgical anesthesia for short duration procedures 45-60 minutes Carpal tunnel release

Question 43

What is important to do after bier's block.

Answer 43

The tourniquet MUST be left inflated for a total of at least 15-20 minutes to avoid a rapid IV systemic bolus of local anesthetic resulting in toxicity. Slow, incremental deflation of tourniquet provides an additional margin of safety.

Question 44

Name the Lower extremity PNB

Answer 44

``` Femoral Nerve Block Lateral Femoral Cutaneous Nerve Block Obturator Nerve Block Posterior Lumbar Plexus Block (Psoas Compartment) Saphenous Nerve Block Sciatic Nerve Block Ankle Block ```

Question 45

What are the peripheral nerve clocks of the trunk?

Answer 45

Superficial Cervical Plexus Block Intercostal Block Paravertebral Block Transverse Abdominis Plane Block

Question 46

From greatest to least toxicity after a regional block.

Answer 46

1. Intercostal block 2. Caudal-lumbar epidural 3. Brachial plexus block 4. Sciatic-femoral blocks 5. Subcutaneous block.