Epidural anesthesia
Applied anatomy of the epidural space
The epidural space, a potential space surrounding the spinal meninges, contains fat, nerve roots, and vascular plexuses. The anatomy of the spine, ligaments, meninges, and blood flow throughout the spinal cord are described in detail in Chapter 57. Knowledge of surface anatomy (Figure 123-1) and key anatomic features of the cervical, thoracic, and lumbar spinal regions (Box 123-1) are critical to the performance of safe and reliable epidural needle placement.
All segments of the spinal canal from the base of the skull to the sacral hiatus are accessible to epidural injection. Epidural anesthesia, provided either alone or in combination with general anesthesia, may be adapted to almost any surgical procedure that takes place below the level of the patient’s chin. Ideally, needle and catheter placement should occur at the level of the surgical incision (e.g., lumbar placement for lower extremity operations and thoracic placement for thoracic/abdominal operations) to allow for block of only the parts of the body that fall within the surgical field. However, a lumbar technique may be used for even upper abdominal procedures, although it would result in a complete sympathectomy, including potentially blocking the cardiac accelerator fibers. Assessment of the dermatomal sensory level enables the anesthesiologist to determine approximate level of sympathectomy and anticipate the resulting hemodynamic effects (Table 123-1).
Table 123-1
Sensory Level of Epidural Blockade Required for Surgical Procedures
| Cutaneous Landmark | Segmental Level | Type of Operation | Significance |
| Fifth finger | C8 | All cardioaccelerator fibers (T1-T4) blocked | |
| Nipple line | T4-T5 | Upper abdominal | Possibility of cardioaccelerator blockade |
| Tip of xiphoid | T6 | Lower abdominal | Splanchnics (T5-L1) blocked |
| Umbilicus | T10 | Hip |
