Regional anesthesia

Regional anesthesia involves the injection of local anesthetic agents around nerves in the peripheral nervous system or central nervous system to achieve reversible numbing of pain conduction in the corresponding innervated tissue. Regional anesthesia can be divided into peripheral nerve blocks, neuraxial anesthesia (i.e., spinal anesthesia, epidural anesthesia), and intravenous regional anesthesia.

See also “Local anesthesia” and “Local anesthetic agents.”

• Goal: used prior to certain medical procedures to reduce pain. ^[1]
• Types of anesthetic agents: See “Local anesthetic agents.”
• General contraindications to regional anesthesia
  • Absolute: allergy to a class of anesthetic
  • Relative
    • Active inflammation or infection at the injection site
    • Coagulopathy
    • Neurological deficits in the area of distribution
• Types
  • Peripheral nerve blocks
  • Neuraxial anesthesia (i.e., epidural anesthesia, spinal anesthesia)
  • Intravenous regional anesthesia (Bier block): a local anesthetic agent is injected intravenously into an extremity that has been separated from the central circulation with a tourniquet and exsanguinated by compression to provide an anesthetized, bloodless surgical field

Definition ^[1]

Injection of local anesthetic agents around nerves in the peripheral nervous system to achieve reversible numbing of pain conduction in the corresponding innervated tissue

Indications ^[1]

General

• Nonthoracoabdominal surgery or minor procedures (e.g., closed reductions)
• Wound repair in which infiltration anesthesia may distort the anatomy
• Large area of anesthesia required
• Postoperative pain control

Head, neck, and thorax

Upper extremity

Lower extremity

Contraindications

See “General contraindications to regional anesthesia.”

Procedure ^[1]

• Injection site: varies based on the target nerve
• Approach
  • Single injection
  • Continuous administration via a catheter
• Technique: varies based on the target nerve
  • Place the patient in a position that allows easy access to the target nerves.
  • Perform skin preparation and maintain a sterile field.
  • Identify the targeted nerve using anatomical landmarks and/or:
    • Ultrasound
    • Nerve stimulation test
  • Inject the local anesthetic agent around the target nerve.

Complications

See “Complications of regional anesthesia.”

Peripheral nerve blocks do not carry the risks associated with general anesthesia (e.g., respiratory depression, aspiration) and neuraxial anesthesia (e.g., CSF leak syndrome, urinary retention). ^[1]

Avoid discharging patients after major nerve blocks until sensation and function have returned to baseline levels to reduce the risk of secondary injury. ^[1]

Monitor for delayed-onset LAST, especially if high doses of local anesthetic agents were used.

Definition ^[2]

• Local anesthetics with or without opioids and alpha-adrenergic agonists are injected into the epidural space and act on the spinal nerve roots.
• Epidural anesthesia blocks several nerve roots around the site of injection and barely affects the function of the nerve roots above and below (segmental anesthesia).

Indications ^[2]

• Used for a variety of surgeries of the lower body (e.g., cesarean delivery, hernia repair, appendectomy, prostate and bladder surgeries, knee surgery)
• During labor
• Perioperatively
• Chronic pain management (e.g., spinal stenosis, disk herniation)

Contraindications ^[2]

See also “General contraindications to regional anesthesia.”

• Absolute
  • Uncorrected hypovolemia
  • Increased intracranial pressure
  • Infection at the puncture site
• Relative
  • Coagulopathy
  • Spinal deformities
  • Sepsis, systemic bacteremia, amniotic infection syndrome
  • Neurological deficits caused by, e.g., disk prolapse, paraplegic syndrome, and multiple sclerosis

Procedure ^[2]

• Injection site
  • May be performed at any vertebral level (cervical, thoracic and lumbar spine)
  • Needle inserted into the epidural space between the ligamentum flavum and dura mater
• Approaches to inject the local anesthetic
  1. Catheter placement, which has the advantage of repeated/continuous administration of anesthetic drugs (most commonly performed)
  2. Single-shot technique

Complications

See “Complications of regional anesthesia” and “Complications of neuraxial anesthesia.”

Definition

• Local anesthetics with or without opioids and alpha-adrenergic agonists are injected into the cerebrospinal fluid (CSF) in the lumbar spine and act directly on the spinal cord
• Combined spinal and epidural anesthesia (CSE)
  • Combines the advantages of spinal anesthesia (rapid action, motoric block) with the advantages of epidural anesthesia (favorable post-operative pain management via an epidural catheter)
  • Plays a major role in obstetrics and orthopedics.

Indications

Used for a variety of lower extremity, lower abdominal, pelvic, and perineal procedures (e.g., cesarean delivery, hip and knee replacement), e.g:

• Cesarean delivery: T4–6 (mamillary line)
• Pelvic, urethral, and renal pelvic surgery: T6–8 (xiphoid)
• Transurethral surgery including stretching of the bladder, vaginal birth, hip surgery: T10 (navel)
• Transurethral surgery without stretching of the bladder: L1 (inguinal ligament)
• Knee and foot surgery: L2/3
• Perineal surgery: S2–5

Contraindications

See “Contraindications” in “Epidural anesthesia.”

Procedure

• Injection site
  • Injection usually performed below L2 to avoid damage to the spinal cord
  • Needle inserted into subarachnoid space between the arachnoid and pia mater
• Approach: almost always single-shot technique

Complications

See “Complications of regional anesthesia” and “Complications of neuraxial anesthesia.”

See also “Adverse effects of local anesthetic agents.”

Complications of regional anesthesia ^[1]

• Nerve injury
• Local anesthetic systemic toxicity
• Hematoma
• Infection
• Secondary injury

Complications of neuraxial anesthesia ^[3][4][5]

• CSF leak syndrome
• Spinal epidural hematoma; and spinal epidural abscess
• Meningitis
• Hypotension
  • Pathophysiology: sympathetic blockade causes vasodilation and decreases venous return → reduced cardiac output
  • Clinical features: hypotension, dizziness, lightheadedness, and nausea shortly after administering anesthetic
  • Diagnostics: clinical diagnosis
  • Treatment: IV fluid resuscitation + small doses of epinephrine
• Sympathetic block → peripheral vasodilation, bradycardia, and hypotension (Bezold-Jarisch reflex) → relative hypovolemia
• Postoperative urinary retention
• Back pain
• Anterior spinal artery syndrome
• Conus medullaris syndrome

Total spinal anesthesia ^[6]

• Definition: complete spinal space affected by local anesthetic drug
• Pathophysiology: drug overdose during spinal block or accidental spinal anesthesia during epidural block (intrathecal injection) → excessive cranial spread of the local anesthetic drug → inhibition of the intercostal respiratory muscles and sympathetic block → bradycardia and hypotension → reduced perfusion of the brainstem → total spinal anesthesia → circulatory and respiratory arrest
• Clinical features
  • Hypotension and cardiac decompensation
  • Apnea
  • Loss of consciousness
  • Mydriasis (dilated pupils), fixed pupils
• Prophylaxis: correct catheter placement
  • Negative aspiration test: Aspiration of blood indicates a perforated blood vessel or intravascular placement of the catheter. Aspiration of CSF may be caused by catheter insertion into the intrathecal space.
  • Intrathecal test dose injection : Numb legs point to a misplaced catheter.
• Therapy
  • Immediate intubation unless already performed
  • Stabilization of BP via fluid resuscitation and catecholamines

We list the most important complications. The selection is not exhaustive.