Peripheral Nerve Blocks Flashcards
What are advantages of peripheral nerve blocks?
Decrease in:
Stress response
Systemic analgesia requirement
opioid related side effects
general anesthesia requirement
incidence/occurrence of chronic pain
Potent analgesia
T/F; Peripheral nerve block will decrease phantom pain for chronic issues?
True
What type of patient selection should be considered for a peripheral nerve block?
Hx: Chronic Pain
Opioid resistance
Comorbidities
Do not tolerate opioid use (N/V)
What are the consideration before doing a peripheral nerve block?
- Tourniquet placement
- bone grafting
- projected duration of surgery
- single injection or continous peripheral nerve block
What are the risk to performing a peripheral nerve block?
Nerve injury
Local anesthetic toxicity
Intravascular injection
Perivascular absorption
What are contraindication of a peripheral nerve block?
-Patient cooperation and participation
Children
Mentally handicap
Bleeding disorders
Site of infectionWhat is to be considered when choosing a local anesthetic for peripheral nerve block?
- Onset
- Desired duration
- Desired sensory
- Motor block
Patient preparation is doing what?
- Use of hemodynamic monitors
- Supplemental oxygen
- Resusitative medication and equipment ready
- Patient positioning
- Intravenous premedication
- Strict Sterile Technique
List the various Block Techniques.
- Field block technique
- Paresthesia Technique
- Nerve stimulation Technique
- Ultrasound technique
Describe a field block technique.
- 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.
Describe a paresthesia technique.
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
Describe a nerve Stimulation technique.
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.
Describe a ultra sound technique.
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.
What is echogenicity?
The degree of efficiency with which sound passes through a substance.
What is hypoechoic?
- 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.
)
What is hyperechoic?
structures reflecting more sound waves appear brighter, “white” on the ultrasound screen. (diaphragm, gallstones, bone, pericardium)
What is anechoic?
No reflection (fluid and blood filled structures)
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
Linear Probe
What probe uses a low frequency transducer that offers better tissue penetration with lower resolution, or poorer image quality.
-Good for deeper structures
Curvilinear Probe
The optimal ________ varies depending on the ______ of the target nerve and ________ angle of the needle relative to the transducer.
Transducer, depth, approach
Nerves are best imaged in ______-______ (short axis).
cross-section
What is the characteristics of a nerve?
Honeycomb (popcorn effect)
__-_____ 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.
In-plane, in-plane (Longitudinal, long-axis)
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
Out-of-plane alignment (Transverse or short axis)
What is a single shot injection nerve block?
nerve(s) are identified and local anesthetic is infiltrated via a one time injection, to achieve desired effect.
What is a continous peripheral nerve block?
involves placement of a percutaneous catheter adjacent to a peripheral nerve, followed by local anesthetic administration to prolong the effect.
What are the advantages of a CONTINUOUS PNB?
-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
Complications of CONTINUOUS PNB?
Systemic local anesthetic toxicity Catheter retention Nerve injury Infection Retroperitoneal hematoma Increased risk of falling (femoral nerve catheter)
What is an intravenous regional anesthesia block called?
Bier Block
Name the upper extremity brachial plexus blocks of PNB?
Interscalene block
Supraclavicular block
Infraclavicular block
Axillary block
Upper extremity terminal nerve blocks that are PNB:
Median nerve block Ulnar nerve block Radial nerve block Musculocutaneous nerve block Digital nerve blocks Intercostobrachial nerve block
What should be known about a interscalene block?
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
What are the contraindication of interscalene block?
Local infection
Severe coagulopathy
Local anesthetic allergy
Patient refusal
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.
interscalene
Other Consideration with interscalene block?
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
What is a supraclaviular block?
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
Contraindications of a supraclavicual block.
Local infection
Severe coagulopathy
Local anesthetic allergy
Patient refusal
Complication of a supraclavicular clock?
Ipsilateral phrenic nerve palsy in ~50% of patients
Horner’s syndrome
Recurrent laryngeal nerve palsy
Pneumothorax
Subclavian artery puncture
What is a axillary block?
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.
Complications to axillary block?
Local infection
Neuropathy
Bleeding risk
What is a block of terminal nerves?
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.
What is Bier block good for?
Surgical anesthesia for short duration procedures
45-60 minutes
Carpal tunnel release
What is important to do after bier’s block.
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.
Name the Lower extremity PNB
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
What are the peripheral nerve clocks of the trunk?
Superficial Cervical Plexus Block
Intercostal Block
Paravertebral Block
Transverse Abdominis Plane Block
From greatest to least toxicity after a regional block.
- Intercostal block
- Caudal-lumbar epidural
- Brachial plexus block
- Sciatic-femoral blocks
- Subcutaneous block.
