Local Anesthesia Techniques: A Guide PDF

Regional Anesthetic Techniques BY Dr. Yasser Osman Types of regional anaesthetic techniques: Surface (topical) anaesthesia. Local infiltration. Nerve block (e.g. median nerve block). Ganglion block (e.g. trigeminal ganglion block). Plexus block (e.g. brachial plexus block). Cent...

Regional Anesthetic Techniques BY Dr. Yasser Osman Types of regional anaesthetic techniques: Surface (topical) anaesthesia. Local infiltration. Nerve block (e.g. median nerve block). Ganglion block (e.g. trigeminal ganglion block). Plexus block (e.g. brachial plexus block). Central neuronal block (spinal and epidural). Local intravenous anaesthesia. Local infiltration anaesthesia: Local infiltration is performed by injecting the LA drug around the lesion (e.g. lipoma), thus blocking the nerve endings. Xylocaine (0.5-1%) and bupivacaine (0.25%) are usually used.  Nerve or plexus blocks Nerve or plexus blocks can be done by injecting the local anesthetic drug around the nerve trunks at a distance from the area to be operated on. The procedure is named according to the area injected e.g. brachial plexus block, median nerve block…etc. The drugs in current use are xylocaine (1-2%, lasting 1-1.5 hour, with a maximum dose of 400-500 mg) and bupivacaine (0.5%, lasting 5-7 h, with a maximum dose 200 mg). Nerve localization techniques for regional block include; anatomical landmarks, peripheral nerve stimulation, and ultrasound (US).  Spinal anaesthesia (Intrathecal or subarachnoid block) Spinal anaesthesia is carried out by injecting the LA agent into the subarachnoid space below the level of the spinal cord. to provide anaesthesia for operations on the lower half of the body. Anatomical considerations: The vertebral column consists of 33 vertebrae: 7 cervical, 12 thoracic, 5 lumber, 5 sacral and 4 coccygeal. The spinal cord extends down to the second lumber vertebra (L2) and the dural sac to the second sacral vertebra (S2). The subarachnoid space between L2 and S2 contains only CSF and nerve roots (cauda equina). Puncture for spinal anaesthesia can be done only below L2. An important landmark is the highest point of the iliac crest, which is usually at the level of L4 spinous process or L4-5 interspace. Preparations for spinal anaesthesia: Preoperative assessment including explanation of the technique. Reassure the patient that adequate sedation will be given. Insert IV line & give preloading fluids. All vital functions should be monitored before and during the operation. Prepare for general anaesthesia at any time during the procedure. Technique of spinal anaesthesia: Equipment: Swabs to apply antiseptic (betadine) to the skin. A sterile gauze to remove excess antiseptic. A small gauge needle to give local anesthesia before spinal puncture. Spinal needle syringes, LA drug. All equipment should be placed in a sterile towel on a trolley before starting lumber puncture.  Patient’s position Sitting position: Lateral position: The most common position for lumbar It is used when it is difficult for puncture (LP). the patient to sit for LP. Easier to perform LP in this position. If the patient is sedated, sitting Easy identification of landmarks (obese position may be hazardous. patients). Puncture: Position the patient with spine flexed to separate the spinous processes and open the spaces for easy passage of the needle to the subarachnoid space. The procedure is performed under aseptic technique Identify the injection site (intervertebral space) using the anatomical landmarks. LA is injected.  Advance the spinal needle with its stylet in place in a direction perpendicular to the skin but pointed slightly cephaled. A click can be felt as the dura is pierced. Remove the stylet confirms that the tip of the needle in the subarachnoid space. free flow of clear CSF The LA agent should be injected when CSF can be aspirated before injection. After injection of LA agent, the needle and syringe are withdrawn, and the patient is turned to the supine position. A-Midline approach. Skin Subcutaneous tissue Supraspinous ligament Interspinous ligament Ligamentum flavum Epidural space Dura mater Arachnoid mater Is difficult in old patient with densely calcified ligaments , a lateral approach may be tried  B-Paramedian or Lateral Approach In this approach (lateral), the needle is introduced 1 cm lateral to the midline. The needle is directed at an angle, which allow the tip to penetrate the dura in the midline. Same as midline excluding supraspinous & interspinous ligaments (para vertebral muscles ) Skin Subcutaneous tissue para vertebral muscles Ligamentum flavum Epidural space Dura mater Arachnoid mater  Directions of the spinal needle bevel: It is better that the bevel is parallel to the fibers of the ligamentum flavum and dura so as to split these fibers (i.e. less leak of CSF) rather than cut them (more leak of CSF) as the needle is advancing. This will reduce the chances of postdural puncture headache. Epidural anesthesia Epidural anesthesia is Central neuronal block obtained by injecting LA solution into epidural space (extradural) where Spinal nerve roots pass. What is the epidural space ? Techniques of epidural anaesthesia: The most popular method to locate the epidural space is the loss of resistance technique. An epidural needle is inserted through skin and advanced in the middle line until the spinal ligaments are entered. Then, the stylet is removed and an air or saline filled syringe with freely movable plunger is attached. If the needle tip is in spinal ligament, it is difficult to inject the syringe. The needle is advanced very slowly and the plunger is pressed. As soon as the needle Pierce the ligamentum flavum and enters the epidural space, there is no further resistance to the plunger.  For short procedure, a single dose of LA solution is sufficient. For longer operation and if postoperative analgesia is required, catheter is inserted via the needle into the epidural space and used for continuous epidural analgesia. Epidural needle: The standard needle used for epidural anesthesia is the Tuohy’s needle It is a large needle (18 G) It allows a catheter to pass through it easily. It has a curved blunt tip that helps to avoid dural puncture and allows for the direction of the catheter. Some have wings at the hub for greater user control. It has 1 cm graduations in it’s shaft. Epidural kit