Regional Anesthetic Techniques Overview

Regional Anesthetic Techniques

• Regional anesthetic techniques involve injecting anesthetic drugs near nerves, ganglia, or plexuses to block pain signals.
• Types of regional anesthetic techniques include surface (topical), local infiltration, nerve block, ganglion block, plexus block, central neuronal block (spinal and epidural), and local intravenous anesthesia.

Local Infiltration Anesthesia

• Local infiltration involves injecting the local anesthetic (LA) drug around the affected area (like a lipoma), blocking nerve endings.
• Commonly used LA drugs are xylocaine (0.5-1%) and bupivacaine (0.25%).

Nerve or Plexus Blocks

• Nerve or plexus blocks involve injecting LA around nerve trunks, to numb the area served by those nerves.
• The procedure's name relates to the specific area injected (e.g., brachial plexus block, median nerve block).
• Xylocaine (1-2%, lasting 1-1.5 hours, max dose 400-500 mg) and bupivacaine (0.5%, lasting 5-7 hrs, max dose 200 mg) are commonly used.
• Techniques for nerve localization include anatomical landmarks, peripheral nerve stimulation, and ultrasound (US).

Spinal Anesthesia (Intrathecal or Subarachnoid Block)

• Spinal anesthesia involves injecting the LA into the subarachnoid space below the spinal cord, to numb the lower half of the body.
• The spinal cord extends to the second lumbar vertebra (L2), and the dura sac extends to the second sacral vertebra (S2).

Anatomical Considerations

• The vertebral column consists of 33 vertebrae (7 cervical, 12 thoracic, 5 lumbar, 5 sacral, 4 coccygeal).
• The subarachnoid space between L2 and S2 contains CSF and nerve roots (cauda equina).
• Spinal anesthesia can be performed only below the L2 vertebra.
• The highest point of the iliac crest is typically at the level of the L4 spinous process (L4-L5 interspace).

Preparations for Spinal Anesthesia

• Preoperative assessment, including explaining the technique.
• Providing adequate sedation.
• Inserting an IV line and giving preloading fluids.
• Monitoring vital signs during the procedure.
• Preparing for general anesthesia if needed.

Technique of Spinal Anesthesia

• Apply antiseptic (betadine) to the skin.
• Remove excess antiseptic with sterile gauze.
• Use a small gauge needle to give local anesthesia before the spinal puncture.
• Use sterile spinal needles, syringes, and LA drugs.
• Arrange all equipment on a sterile trolley before the puncture.

Patient's Position

• Sitting position: The most common for lumbar puncture (LP), easier to perform LP and identify landmarks (helpful for obese patients).
• Lateral position: Useful when the patient can't sit, or when sedation makes sitting risky.

Puncture

• Position the patient with a flexed spine to separate the spinous processes, creating space for the needle.
• Perform the procedure under aseptic conditions.
• Identify the injection site (intervertebral space) using anatomical landmarks.
• Inject the LA.

Spinal Needle Advancement

• Advance the spinal needle with its stylet in place, perpendicular to the skin, aiming slightly cephalad.
• Remove the stylet to ensure the needle is in the subarachnoid space (check for CSF flow).
• Inject the LA after confirming the subarachnoid space.
• After injecting, withdraw the needle and syringe.
• Move the patient to the supine position.

A-Midline Approach

• Anatomical approach involving skin, subcutaneous tissue, supraspinous, interspinous ligaments, ligamentum flavum, epidural space, dura mater, and arachnoid mater on the midline.

B-Paramedian or Lateral Approach

• A slight lateral approach, 1cm lateral to the midline, allowing the needle to penetrate the dura on the midline.
• Includes similar anatomy as the midline approach, but focuses on the paravertebral muscles.

Directions of the Spinal Needle Bevel

• The needle bevel should be parallel to the ligamentum flavum and dura fibers to split the fibers, reducing the chance of CSF leak and post-dural puncture headache.

Epidural Anesthesia

• Epidural anesthesia is a central neuronal block where LA solution is injected into the epidural space outside the dura mater, where the spinal nerve roots pass.

What is the Epidural Space?

• The epidural space is between the dura mater and the ligamentum flavum, outside the spinal cord.

Techniques of Epidural Anesthesia

• The loss of resistance technique is used to locate the epidural space.
• An epidural needle is advanced through the skin and advanced until the spinal ligaments are detected.
• The stylet is removed and an air or saline-filled syringe is attached.
• Slowly advance the needle, when the needle pierces the ligamentum flavum, and there is no resistance, the epidural space is found.

Epidural Procedures: Single Dose vs. Catheter

• A short procedure requires a single dose of LA.
• Longer procedures or when postoperative analgesia is needed, a catheter is inserted for continuous epidural analgesia.

Epidural Needle: Tuohy's Needle

• The standard epidural needle is the Tuohy's needle.
• It is a large gauge needle (typically 18 G).
• It has a curved blunt tip to help avoid dura puncture.
• Some needles have wings for user control.
• Graduations (1 cm) help users track the needle's depth.

Epidural Kit

• Various instruments needed for epidural procedures like syringes, needles, catheters, and sterile coverings are part of this kit.