Introduction:
Regional anesthesia in children has gained popularity in recent decades. To correctly manage perioperative pain, a wide range of peripheral and central nerve blocks have been evolved. Caudal anesthesia is a standard regional anesthetic method to deliver pre and postoperative analgesia. It can be used as the sole anesthetic or as an adjunct to general anesthesia. Caudal anesthesia is primarily used in pediatric surgery of the sub-umbilical region and in adults to treat chronic low back pain. In addition, with the emergence of fluoroscopy and ultrasound-guided caudal epidural placement, appropriate needle placement can be assessed to minimize the block failure rate further.
What Is the Anatomy and Physiology of Caudal Anesthesia?
Clinicians execute caudal epidural techniques by approaching the epidural space through the sacral hiatus. The spinal cord ends at the lumbar first to the second and the dural sac at the sacral first to the second region in adults. The spinal cord ends at the lumbar third to the fourth region and the dural sac at the sacral third to the fourth region in children, with cephalad development over the first year of life. It can penetrate the dural sac during a caudal epidural block in young infants. The landmark-based approach is the most commonly used method for performing a caudal epidural block. Due to the challenges of threading a catheter at this location, these are most commonly used as single-shot techniques in adults. However, since single-shot practices are more prevalent in children, placing a catheter in children is simple and more straightforward than in adults. Caudal catheters can be securely placed for less than three days without any possibility of systemic infection, such as meningitis, epidural abscess, systemic sepsis, or even local infection.
What Are the Indications for Caudal Anesthesia?
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In pediatric patients, caudal anesthesia can be adequate for sub-umbilical procedures such as repair of inguinal hernias, urological procedures, anal repair of atresia, and lower-limb techniques. For these surgeries, caudal anesthesia can be used alone or in conjunction with general anesthesia.
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Caudal epidural injections can also assist in treating chronic low back pain and discomfort that has not responded to conservative medical treatment. However, while caudal epidural steroid treatments can treat noncancerous low back pain, they are best suited for patients who do not have facet joint pain or both discogenic and facet joint pain.
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Traditionally, caudal epidural analgesia with catheter placement was used in the obstetric population for labor analgesia during the second stage of labor.
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However, issues about the block efficacy, excessive doses of local anesthetic resulting in limb paralysis, and significant maternal hypotension due to poor control of the sympathectomy resulted in the adoption of lumbar epidurals as the cornerstone of labor analgesia.
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Caudal blocks may be recommended over lumbar epidural blocks because they deliver sensory and motor blocks of the sacral roots with narrow sympathectomy (from first thoracic to second lumbar region preganglionic sympathetic neurons extend) and are associated with a reduced danger of dural puncture.
What Are the Contraindications for Caudal Anesthesia?
Absolute Contraindications: Patient or guardian unwillingness, localized infection over the site of injection, severe problems in coagulation, elevated intracranial pressure, and allergy to medicines used for the technique are all contraindications to caudal anesthesia. In addition, raised intracranial pressure can increase susceptibility to herniation after epidural injection.
Relative Contraindications: Spinal stenosis increases the risk of neurologic side effects following a neuraxial procedure. In addition, because of the vasodilatory effects of the neuraxial method, hypovolemic patients have a higher probability of having hypotensive responses. Whereas severe coagulation and bleeding disorders are an absolute contraindication to neuraxial approaches, less severe coagulopathies warrant further consideration. The American Society of Regional Anesthesia provides the most recent guidelines for neuraxial techniques in thromboprophylaxis or anticoagulation. Because of the significant risk of seeding the epidural space and the possibility of vasodilation responding to hemodynamic instability, systemic infection is a relative contraindication to any epidural approach. However, once a patient has shown a response to antibiotic treatment, neuraxial procedures are safe to use. Other contraindications to be considered in the pediatric population include a pilonidal cyst, sacral anomalies (such as a history of meningomyelocele), or spinal dysraphism (such as tethered cord syndrome).
What Are the Equipment Required for Caudal Anesthesia?
The following instruments are required to carry out a caudal epidural block:
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A syringe of the correct size.
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Intravenous access catheter or needle.
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Medications and drugs.
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Alcohol, chlorhexidine, or an iodine solution are standard skin-cleaning solutions.
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Personal safety equipment (sterile gloves, mask, head cap).
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In pediatric or adult patients, ultrasound can help with caudal epidural placement. For example, Shin et al. reported that using ultrasound to identify the sacral hiatus aided in completing the caudal epidural installation.
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Fluoroscopy-guided caudal epidural blocks are the gold standard for an effective caudal epidural block. However, this is rarely executed in an operating room setting due to technical difficulties and exposure to radiation to both the patient and providers.
What Is the Technique of Caudal Anesthesia?
Caudal blocks can be performed using the blind technique, ultrasound guidance, or fluoroscopic guidance.
1. Blind Caudal Epidural Block :
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The sacral hiatus is recognized by sacral cornua landmarks on each side superior to the gluteal cleft and at the apex of a triangle created by the posterior superior iliac crests. After aseptic techniques, the beveled needle or angiocatheter is introduced at a 45-degree angle.
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A "pop" sensation may be experienced, suggesting passage through the sacrococcygeal ligament and into the epidural space. Unfortunately, this loss of resistance method has an error rate of 26 percent.
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As a result, many people recommend performing the "whoosh test," which has a considerably higher specificity, and involves auscultation of the thoracolumbar area while administering air into the region.
2. Ultrasound-Guided Caudal Epidural Block:
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The patient lies flat with the chest down, and in the backup or lateral decubitus position. A linear transducer of about 7 to 13 MHz (if the patient is an obese, curved transducer of about two to five MHz) transversely in the middle of the sacrum can be installed.
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The transverse view reveals the following hyperechoic components, the sacrococcygeal ligament, which is superficial between two sacral cornua and the deeper sacral bone. The focus is the hypoechoic structure between the sacrococcygeal ligament and the sacral bone.
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After that, the probe is rotated 90 degrees for the longitudinal view, allowing the needle to be inserted "in-plane" into the sacral hiatus. Because the needle is not visible after the tip of the apex, it should not be advanced further than five millimeters after the tip to prevent a dural puncture.
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Using color doppler to detect unidirectional flow can assist in determining the success of a caudal block.
3. Fluoroscopy-Guided Caudal Epidural Block:
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The sacral hiatus is accessible in the prone position as an abrupt drop-off at the end of the fourth sacral lamina. Therefore, the needle can be advanced into the sacral canal, and can check the placement of the needle tip by injecting a contrast medium, ruling out the intravascular or intrathecal injection.
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The caudal block's effectiveness in children already under general anesthesia is evaluated by analyzing the anal sphincter's laxity. Dave et al. reported that the anal sphincter tone test, rather than the swoosh test or the heart rate response to the injection, was the strongest indicator of a successful caudal block.
What Are the Complications of Caudal Anesthesia?
The following are some of the most prevalent potential complications with caudal anesthesia.
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Injections can be subdural, intravascular, or intraosseous.
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Any infection at the site of injection.
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Decreased blood pressure.
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Injury to the roots of the nerves.
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Anti-sacral injection with rectum perforation.
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Formation of a hematoma.
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Toxicity from local anesthetics.
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Respiratory depression is delayed.
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Retention of urine.
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Osteomyelitis of the sacrum.
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Total spinal anesthesia, which can result from an accidental dural puncture following intrathecal injection of local anesthetic, is a detrimental side effect of a caudal block. Because of the caudal dislocation of the dural sac, which ends at the sacral third to the fourth level, this difficulty is much more prevalent in infants (compared to the sacral first to the second in adults).
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Brown et al. found a 0.69 percent rate of seizure development with caudal anesthesia versus 0.01 percent with lumbar or thoracic epidurals. Therefore, an epinephrine test dose must be administered to diagnose an intravascular injection.
Conclusion:
Caudal anesthesia is one of the oldest neuraxial anesthetic techniques still in use today. While its initial use in obstetric analgesia has declined, it is still widely used in pediatrics for sub-umbilical operations and managing patients suffering from chronic low back pain and radiculopathy. In addition, it is frequently used as the sole anesthetic technique in pediatric surgeries, reducing the risks associated with general anesthesia. Caudal blocks have an excellent success rate, are generally safe, and have a limited chance of complications.
