Chapter 16

• Spinal, epidural, and caudal blocks are also known as neuraxial anesthesia. Each of these blocks can be performed as a single injection or with a catheter to allow intermittent boluses or continuous infusions.
• Performing a lumbar (subarachnoid) puncture below L1 in an adult (L3 in a child) avoids potential needle trauma to the cord.
• The principal site of action for neuraxial blockade is the nerve root.
• Differential blockade typically results in sympathetic blockade (judged by temperature sensitivity) that may be two segments higher than the sensory block (pain, light touch), which in turn is usually two segments higher than the motor blockade.
• Interruption of efferent autonomic transmission at the spinal nerve roots can produce sympathetic and some parasympathetic blockade.
• Neuraxial blocks typically produce variable decreases in blood pressure that may be accompanied by a decrease in heart rate and cardiac contractility.
• Deleterious cardiovascular effects should be anticipated and steps undertaken to minimize the degree of hypotension. Volume loading with 10–20 mL/kg of intravenous fluid for a healthy patient will partially compensate for the venous pooling.
• Excessive or symptomatic bradycardia should be treated with atropine, and hypotension should be treated with vasopressors.
• Major contraindications to neuraxial anesthesia are patient refusal, bleeding diathesis, severe hypovolemia, elevated intracranial pressure, infection at the site of injection, and severe stenotic valvular heart disease or ventricular outflow obstruction.
• For epidural anesthesia, a sudden loss of resistance is encountered as the needle penetrates the ligamentum flavum and enters the epidural space. For spinal anesthesia, the needle is advanced further through the epidural space and penetrates the dura–subarachnoid membranes as signaled by free flowing cerebrospinal fluid.
• Epidural anesthesia is a neuraxial technique offering a range of applications wider than the typical all-or-nothing spinal anesthetic. An epidural block can be performed at the lumbar, thoracic, or cervical level.
• Epidural techniques are widely used for operative anesthesia, obstetric analgesia, postoperative pain control, and chronic pain management.
• Epidural anesthesia is slower in onset (10–20 min) and may not be as dense as spinal anesthesia.
• The quantity (volume and concentration) of local anesthetic needed for epidural anesthesia is very large compared with spinal anesthesia. Significant toxicity can occur if this amount is injected intrathecally or intravascularly. Safeguards against this include the epidural test dose and incremental dosing.
• Caudal epidural anesthesia is one of the most commonly used regional techniques in pediatric patients.

Wayne Kleinman is the Director of Obstetric Anesthesia, Encino-Tarzana Regional Medical Center, Los Angeles, California.

Spinal, caudal, and epidural blocks were first used for surgical procedures at the turn of the twentieth century (see Chapter 1). These central blocks were widely used prior to the 1940s until increasing reports of permanent neurological injury appeared. However, a large-scale epidemiological study conducted in the 1950s indicated that complications were rare when these blocks were performed skillfully with attention to asepsis and when newer, safer local anesthetics were used. A resurgence in the use of central blocks ensued, and today they are once ...

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