How is a lumbar paramedian epidural block administered for pain management?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Answer

Answer

Approximately 1 mL of local anesthetic is used to infiltrate the skin and subcutaneous tissues, as well as the supraspinous and interspinous ligaments. A 25-gauge, 2-inch to 2.5-inch needle or an 18-gauge or 20-gauge, 3.5-inch needle is inserted exactly in the midline through the previously anesthetized area. The needle stylet is removed and a loss-of-resistance glass syringe filled with air or preservative-free normal saline is attached.

Alternatively, the physician can use a 12-cc plastic syringe filled with the intended injectate for also following loss the of resistance maneuver. By exerting constant pressure on the plunger of the syringe with the right hand, the right-handed physician advances the needle slowly with the left hand until lack of resistance is discerned. The operator uses the right hand to monitor resistance through a syringe containing air or preservative-free normal saline. With constant light pressure applied to the plunger of the syringe by the right thumb, the needle and syringe are advanced in a slow and deliberate manner. As the bevel passes through the ligament flavum and enters the epidural space, a sudden loss of resistance is noted.

If the operator appreciates it, the plunger can be depressed effortlessly under minimal, if any, pressure detected through the right thumb. Needle position within the epidural space can also be checked using fluoroscopic verification and by repeating the “loss of resistance” maneuver. The lumbar epidural space should accept 0.5-1 mL of air or sterile preservative-free saline without significant resistance. The force required to depress the plunger should not exceed that which is necessary to overcome the resistance of the needle.

Any significant pain or sudden increase in resistance during the injection suggests incorrect needle placement. The physician should immediately stop the injection and assess the position of the needle using fluoroscopy. If the needle remains satisfactorily placed and loss of resistance within the epidural space is confirmed without additional patient report of pain, gentle aspiration is checked to assure that the needle is not positioned in the subarachnoid space or that it is not intravascular. If CSF is aspirated, the operator can repeat the block attempt at a different interspace. If aspiration of blood occurs, the needle should be rotated tightly and the aspiration test repeated. If the aspiration of blood continues, the procedure should be aborted due to the danger of developing an epidural hematoma, and possibly neurological compromise. [19]

If the operator is confident that his needle is correctly placed in the midline of the intended epidural space, then injection of up to 5 to 7 mL of solution can be performed. For diagnostic and prognostic blocks, 1% preservative-free lidocaine provides adequate information. For therapeutic blocks, 0.25% preservative-free bupivacaine combined with 40-80 mg of methylprednisolone is commonly injected. In some cases. this procedure is repeated on a daily basis or every other day for the treatment of acute painful disorders that require pain reduction, even if only temporary. [19]


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