![]() ![]() ![]() Meanwhile, patients taking warfarin must be reversed or withheld from taking the medication for five days and have a documented international normalized ratio (INR) of less than or equal to 1.4. For example, for patients receiving unfractionated heparin doses of 7,500 to 10,000 units twice daily, neuraxial anesthesia should be delayed four to twelve hours. Given a variety of anticoagulation medications, clinicians should stay up to date with the recommended parameters before administering any form of neuraxial anesthesia. Vitals and laboratory values should be reviewed, with an emphasis on coagulopathy indicators. A thorough physical exam should be performed focusing on the patients’ airway, neurologic functioning, and the structure and function of the back and spine. Patients should be asked about their medical conditions, prior anesthesia exposures, current medications, other drug and supplement use, family medical history, including reactions to anesthesia, and allergies. Preparation for epidural anesthesia should initially include obtaining a medical history and physical exam. The nipple line approximates T4, the inferior border of the scapula approximates T7, and the superior aspect of the iliac crests approximates L4. Surface landmarks can be used to approximate spinal levels. Alteration to respiratory function is generally spared, given the cervical innervation of the diaphragm. Interruption of this transmission from epidural anesthesia thus produces a sympathetic blockade or “sympathectomy,” possibly resulting in variable decreases of blood pressure and heart rate. Sympathetic outflow derives from nerve roots of the thoracolumbar region (T1-L2) levels. Blockade of the posterior nerve root interrupts somatic and visceral sensation, while blockade of the anterior nerve root interrupts motor and autonomic function. This is believed to be the principal site of action of epidural anesthesia. Local anesthetic (LA) and adjuvants are injected into the epidural space to anesthetize the spinal nerve roots. When approaching from a paramedian approach, only the ligamentum flavum is traversed. The ligamentum flavum is identified by its tough, gritty feeling as compared to the other layers. The ligamentum flavum anchors the laminae of each vertebra and serves as the posterior aspect of the epidural space. The supraspinous ligament anchors the tips of each spinous process, while the interspinous ligament anchors the body of each spinous process. When approaching the epidural space from a posterior midline approach, three ligaments are traversed from superficial to deep the supraspinous ligament, the interspinous ligament, and the ligamentum flavum. Within the epidural space lies epidural veins, fat, lymphatics, and nerve roots.Įpidural catheter placement can be performed in a sitting or lying position at the cervical, thoracic, lumbar, or sacral levels. The epidural space exists circumferentially between the dura mater and the ligamentum flavum, extending from the foramen magnum to the sacral hiatus. Nerve roots emerge bilaterally at each vertebral level to innervate their respective dermatomes.Įpidural catheters are placed within the epidural space. It is surrounded by three meningeal layers: the pia, arachnoid, and dura. The spinal cord runs through the vertebral canal, extending from the foramen magnum to roughly the L1 level in most adults. This includes 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal.
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