Thomas Drye, MDMadison Anesthesiology Consultants, LLP

Definition:Local anesthetic induced blockade of peripheral or spinal nerve impulses from a targeted body part with preserved level of consciousness

Categories:◦Intravenous (Bier block)◦Neuraxial (spinal, epidural)◦Peripheral nerve blocks (PNB)

Truncal (e.g. paravertebral, TAP blocks) Plexus (e.g. brachial plexus, lumbar plexus) Distal (e.g. femoral, sciatic)

More hemodynamic stability c/w neuraxial Anticoagulation less of an issue Increasing popularity due to advances in

ultrasound technology Introduction of perineural catheters

prolongs post-operative pain control benefits

Avoidance of general anesthesia◦Primary regional anesthetic vs. combination

with “light” general anesthetic◦Most patients request intra-operative

sedation◦Decreased PONV, sore throat, delirium,

airway obstruction and respiratory depression

◦Decreased time to discharge from PACU◦Increased patient satisfaction

Post-operative pain control◦Decreased narcotic requirements and

associated adverse side effects (e.g. nausea, pruritis, sedation, confusion, respiratory depression)

◦Earlier recovery of bowel function◦Improved tolerance of physical therapy◦Improved pain scores, but not always in

PACU◦Increased patient satisfaction

Infrastructure requirements and potential for surgeon delays

Failed Blocks Intraoperative awareness and non-operative

discomfort (e.g. positioning) Motor block Variable duration (approx. 4-40 hours) Rare serious complications (e.g. local

anesthetic toxicity, nerve injury)

Needle phobia or otherwise uncooperative Excessive sedation (adults) Infection (local and untreated systemic) Anticoagulation? Pre-existing nerve injury? Surgery specific (e.g. motor block and post-

op neurological examination) Block specific (e.g. pulmonary disease and

interscalene block)

Anatomy Loss of resistance and tactile feedback Evoked paresthesia Nerve stimulator (goal 0.3-0.5 mA) Ultrasound guided

Monitoring Availability of resuscitation equipment

(suction, airway management) Availability of resuscitation drugs (induction

agents, ACLS drugs, lipid emulsion) Pre-procedure confirmation (“timeout”) Aspiration before injection Incremental injection Do not inject when paresthesia present

Block voltage gated sodium channels on nerve cells preventing impulse conduction

Two classes: amide and ester local anesthetics

Rare allergic reactions Variable onset and duration

◦ Quick onset, short acting (lidocaine, mepivacaine)e.g. 1-2 hours following subcutaneous infiltration

◦ Slow onset, long duration (bupivacaine, ropivacaine) e.g. 2-8 hours following subcutaneous infiltration

Intravascular injection (immediate onset)

Systemic absorption (delayed onset) Central nervous system signs

◦1st excitation: perioral tingling, tinnitus, agitation

◦2nd depression: blurred vision, slurred speech, loss of consciousness

◦Seizure Cardiovascular toxicity

◦Cardiac arrhythmia and/or circulatory collapse◦Requires ~ 3x blood concentration that causes

seizures

For use in the treatment of life threatening local anesthetic toxicity

Novel therapeutic indication for an old medication (component of TPN)

First case reported in 2006, now with over a dozen reported cases

Mechanism of action unknown (“lipid sink?”)

Local anesthetic toxicity Bleeding/hematoma Infection Nerve injury

◦Transient paresthesias 1-3%◦Permanent nerve injury ~1/10,000

Failed block

Brachial plexus◦ Interscalene block◦ Supraclavicular block◦ Infraclavicular block◦ Axillary block

Lower extremity◦ Lumbar plexus block◦ Femoral nerve block and saphenous nerve block◦ Sciatic nerve blocks: anterior, gluteal, and

popliteal Truncal

◦ Paravertebral block◦ Transversus abdominis plane (TAP) block

Interscalene

Infraclavicular

Supraclavicular

Axillary

“Between the scalenes”

Anterior scalene muscle

Middle scalene muscle

IJ

CA

Primarily for shoulder or proximal humerus surgery - distal arm and hand are often sparred

Multitude of unique complications because of location in neck:◦ Vertebral artery injection- seizure with only very

small local anesthetic volume◦ Accidental epidural or spinal injection◦ Pneumothorax- pleural puncture, dome of lung

• Hemidiaphram paralysis (phrenic nerve blockade)

◦ 100% of interscalene blocks◦ May cause dyspnea, even respiratory failure,

depending on severity of underlying lung disease• Hoarseness (recurrent laryngeal nerve

blockade)• Horner’s syndrome (stellate ganglion blockade)

Myosis- constriction of the pupil Ptosis- drooping eyelid Anhidrosis- lack of sweating

“Spinal of the arm”- blocks shoulder, upper arm, forearm, and hand

50% incidence of phrenic nerve block with traditional technique, 0-20% with low volume US-guided technique

Risk of pneumothorax Risk of bleeding: non-compressible site

AV

Effective for procedures of the elbow, forearm, and hand

Safe alternative in patients with lung disease since phrenic nerve is sparred and no PTX risk

Safe alternative in anticoagulated patients due to easy compressibility and no at risk adjacent structures

Disadvantages: higher failure rate and tourniquet discomfort

Femoral nerve

Post-operative pain control for surgery of the thigh or knee, most commonly used for ACL repair and total knee arthroplasties (TKA)

“Only numbs the front”- incomplete analgesia after knee surgery because sciatic nerve innervates posterior knee compartment

Tibial nerve

Peroneal nerve

“Popliteal approach to the sciatic nerve” Effective for procedures of the leg distal to

the knee, particularly foot and ankle surgery

Longer duration than ankle block or subcutaneous infiltration

The terminal branch of the femoral nerve, the saphenous nerve (sensory only), innervates the medial ankle and requires separate block

Used increasing for breast surgery, either primary anesthetic or post-operative analgesic

Surgical block requires injections at multiple levels

Pneumothorax is most common serious complication

Paravertebral space

Tranversus Abdominis Plane

Used for post-operative analgesia for lower abdominal surgery (e.g. inguinal hernia, abdominal hysterectomy, Caesarean section)

Midline incisions require bilateral injections

Serious complications are extremely rare, and this block can be safely performed in an anesthetized patient

Peripheral nerve blocks are increasing in frequency due to recent advances in ultrasound technology

PNB’s have many advantages including decreased narcotic requirements and increased patient satisfaction

Serious complications are rare but do occur Choosing to perform PNB requires

consideration of each patient and surgical procedure, as well as individual surgeon preferences