Chapter 47. Neuraxial Anesthesia

1. A systematic and rational approach based on a thorough 3-dimensional understanding of anatomy should be used when accessing the subarachnoid or epidural space.

2. Anesthetic doses, agents, and combinations of agents should be individualized to optimize neuraxial blockade for a given clinical setting.

3. Hypotension and bradycardia associated with neuraxial anesthesia should be identified early and treated aggressively to minimize development of cardiovascular collapse and poor outcome.

4. Our understanding of potential neurotoxicity and the nature of transient neurologic symptoms (TNS) are continuing to evolve. However, there is growing consensus that TNS may not represent direct neural toxicity.

5. Evaluating the appropriateness of neuraxial procedures in patients receiving anticoagulant and antiplatelet medications is a challenge. Clinicians should be familiar with the recommendations presented by the American Society of Regional Anesthesia and Pain Medicine in the consensus statement addressing these issues.

6. When suspicion of spinal hematoma or abscess is credible, definitive diagnosis with appropriate imaging and prompt surgical decompression within 4 to 8 hours of onset of neurologic symptoms is crucial to improve chances of recovery of function.

7. Developing an understanding of the nature of combined spinal–epidural anesthesia and facility with its techniques can expand a clinician's armamentarium to provide neuraxial anesthesia and optimize patient care.

With more than 100 years of use, neuraxial anesthesia has enjoyed much success and endured controversy. With the stage set by the developments of the hollow needle and syringe, the discovery of neuraxial anesthesia began in 1885 when Corning was experimenting with effects of cocaine on the spinal nerves of dogs. Bier brought spinal anesthesia into clinical use for surgery in 1898, but only after self-experimentation and a personal experience with a well-described postmenigeal puncture headache. Epidural anesthesia gained widespread attention in the setting of labor analgesia, maintaining the medical community's interest in neuraxial blockade despite rapid advancements in techniques for general anesthesia in the 1940s and 1950s. More recently, the introduction of continuous catheter techniques, combined spinal–epidural anesthesia, and various neuraxial anesthetic adjuvants has presented further opportunities to provide our patients the many benefits of neuraxial blockade.

Neural Structures

A thorough appreciation for the anatomy of spinal structures is necessary for appropriate technique, patient selection, and management of neuraxial anesthesia. The spinal structures are identified by cervical, thoracic, lumbar, sacral, and caudal regions (Fig. 47-1). The spinal cord begins at the base of the brainstem and continues caudad terminating as the conus medullaris, typically at the L1-L2 level in the adult, although the terminus rarely may be as high as T12 or as low as L4. The spinal cord has cervical and lumbar enlargements to accommodate the increased neuronal supply to the limbs. Rootlets emerge from the dorsal and ventral surface of the spinal cord and converge to form the respective ventral and dorsal roots of the spinal nerves at each spinal level (Fig. 47-2).