Epidural anesthesia is a form of neuraxial anesthesia that involves injecting a local anesthetic into the epidural space of the spine to numb the spinal nerve roots within it. This type of anesthesia is commonly used for surgeries involving the abdomen, pelvis, and lower extremities, and is occasionally used alongside general anesthesia for procedures involving the thorax. It can also be used for postoperative pain relief after these surgeries. An uncommon technique for epidural placement is the caudal approach, which is used largely for young pediatric patients.
The procedure for administering epidural anesthesia involves inserting a needle between the coccygeal, lumbar, thoracic, or cervical vertebrae and injecting the anesthetic medication into the epidural space. The epidural space is the area between the dural sac and the inside of the bony spinal canal, extending from the foramen magnum to the sacral hiatus. Epidural anesthesia can be administered using either the epidural needle alone or a catheter inserted through the needle into the epidural space. It is commonly performed at the lumbar or thoracic vertebral levels and occasionally at the cervical level; the specific level is determined by surgical needs. Epidural anesthesia is commonly used for lower abdominal and lower extremity surgery, although the sensory level needed often differs based on the dermatome level of the skin incision. For instance, in cesarean deliveries, a T4 spinal level is required for a low abdominal incision despite the incision being made at the T11 to T12.
A caudal approach for epidural placement is primarily used in pediatrics for surgeries up to the umbilicus and in adults for chronic low back pain management. While caudal blocks were historically used in obstetrics for labor analgesia during the second stage of labor, concerns regarding efficacy, limb paralysis from large local anesthetic amounts, and maternal hypotension led to the adoption of lumbar epidurals as the mainstay. In children, common neuraxial anesthesia techniques include continuous epidural and single injection or continuous caudal epidural techniques. Single injection epidural anesthesia with a caudal approach is frequently used for postoperative analgesia in infants and toddlers, providing four to six hours of pain relief for abdominal procedures. To extend block duration and depth, nonopioid adjunctive medications, such as preservative-free clonidine, can be added to the caudal block. However, infants and young children undergoing regional anesthesia techniques may be at increased risk of local anesthetic systemic toxicity. Caudal epidural injections can also manage chronic low back pain, especially for patients with facet joint pain or those with both discogenic and facet joint pain.
The caudal approach to epidural anesthesia can be performed using the blind technique, ultrasound guidance, or fluoroscopic guidance. The blind technique involves identifying the sacral hiatus and inserting a needle at a 45-degree angle. In ultrasound-guided caudal blocks, a transducer is used to visualize the sacral hiatus and guide needle insertion. Fluoroscopy allows for visualization of the sacral hiatus and confirmation of needle tip placement. Guidance helps improve the accuracy and safety of caudal blocks.
While caudal blocks have a high success rate and are relatively safe, they can be associated with complications. A significant complication of a caudal block is the occurrence of total spinal anesthesia, which can result from an inadvertent dural puncture followed by the intrathecal injection of a local anesthetic. This complication is more prevalent in infants than adults due to the caudal displacement of the dural sac in infants, which terminates at the S3-4 level, compared to adults, whose dural sac ends at the S1-2 level. Other potential complications include subdural, intravascular, or intraosseous injections, infections, hypotension, nerve root injuries, antesacral injections with rectal perforation, hematoma formation, local anesthetic toxicity, delayed respiratory depression, urinary retention, and sacral osteomyelitis.
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