Lumbar disc disease encompasses several pathological processes including disc space collapse, annular tearing, desiccation of the nucleus pulposus, and disc bulging, causing symptoms of neurologic compromise, radiculopathy, and back pain. While the first laminectomy and discectomy was described in the literature almost 100 years ago, the advent of the surgical microscope in the 1970s brought about the modern microdiscectomy, making the wide exposure required with laminectomy unnecessary.^1-2

Most disc disease may be treated by nonsurgical means, but when pain is unremitting or a neurologic deficit exists, surgery may be necessary. Commonly accepted indications for surgery include a six-week failure of conservative management, new neurologic deficits during conservative treatment, and patients who know that surgery is likely and do not wish to invest time in conservative treatment. Emergent indications include the acute development of a motor deficit and cauda equina syndrome.³

Lumbar spine surgery can be performed under general anesthesia, neuraxial anesthesia, or local anesthetic infiltration with monitored anesthesia care. General anesthesia is the most common technique for lumbar spine surgery, reasons for which are multifactorial. Anesthesiologists may be more comfortable with general anesthesia as the airway is secured in the prone position, surgeries of greater duration can be performed, and there is the perception of greater patient acceptance.⁴ Despite its greater use, there are disadvantages to general anesthesia, including less stable hemodynamics, more nausea and vomiting, greater intraoperative blood loss, and more need for rescue analgesics postoperatively.⁵

In addition to general and spinal anesthesia, discectomy procedures can be performed safely and effectively under local anesthesia if done endoscopically. This technique offers several advantages over microdiscectomy including shorter post anesthesia care unit (PACU) stays and decreased postoperative pain, bleeding, length of stay, and overall recovery time.⁶

NEURAXIAL ANESTHESIA CAUTIONS

Patient, procedure, and surgeon selection are extremely important when performing spine surgery under spinal anesthesia. Like all regional anesthetics, the patient must be consentable and cooperative. The patient should not be hypovolemic or have a fixed cardiac outflow obstruction. The patient cannot be coagulopathic nor be allergic to local anesthetics. There cannot be infection at the spinal injection site. Finally, this technique should be avoided in patients with intracranial hypertension.⁷ Due to the duration of spinal anesthesia, this technique should probably be avoided in procedures lasting more than 3 hours and therefore may preclude its use in complex surgery, in teaching environments, or with less experienced surgeons. Anesthesiologists should take the same precautions as for any patient in the prone position, with special consideration for the unsecured airway. Special care should be taken in patients with obstructive sleep apnea, issues with neck mobility, obesity, or a known difficult airway. The possibility of losing the airway in the prone position with limited choices in useful airway devices and an inability to perform normal airway rescue maneuvers must be taken into account when considering this technique.⁸ One must also consider the profound decrease in preload that can occur with neuraxial anesthesia and the use of the kneeling position that is oftentimes utilized for minimally invasive spine surgery.

NEURAXIAL ANESTHESIA BENEFITS AND TECHNIQUE

Studies support the use of neuraxial anesthesia over general anesthesia in certain lumbar spine surgery patients. The potential advantages of regional anesthesia include the lack of airway instrumentation, stable hemodynamics, a shorter hospital stay, and reduced health care costs. According to a meta-analysis published this year, the use of spinal anesthesia for lumbar spine surgery is associated with a lower incidence of intra-operative hypertension and tachycardia, reduced opioid and other analgesic requirements in the PACU, less postoperative nausea and vomiting (PONV) at 24 hours, and a shorter hospital length of stay compared with general anesthesia.⁹ This study also suggests that there are no differences between the anesthetic techniques in terms of intraoperative hypotension, blood loss, surgical time, and PONV in the PACU.⁹ Notably, no studies to date report any increased neurologic complications with spinal anesthesia versus general anesthesia administration for spine surgery.

Decreased blood loss with the use of neuraxial anesthesia is a hypothetical advantage due to reduced episodes of intraoperative hypertension, reduced venous congestion, and lower intrathoracic pressure in a spontaneously ventilating patient. However, the current literature does not conclusively suggest a decrease in blood loss in neuraxial techniques for lumbar surgery.⁹

A recent retrospective study of 400 patients performed at Massachusetts General Hospital suggested a cost reduction with the use of spinal anesthesia. The median operating room (OR) times of the general anesthesia cases in this study were longer than the neuraxial anesthetic cases (175 ± 39 and 158 ± 33 minutes, respectively) by approximately 20 minutes. Spinal anesthesia was also associated with a 10.3% lower direct OR cost compared with general anesthesia.¹⁰ While variability exists among institutions, the results of this review encourage the use of regional anesthesia in these short (<2 hour) elective lumbar spine surgeries. According to the Healthcare Cost and Utilization Project (HCUP) Statistical Briefs, laminectomy was listed as the third most common operating room procedure in 2012, with 468,200 cases performed that year.¹¹ Clearly, a cost savings for this common surgical procedure could be substantial if more procedures were performed under a neuraxial anesthetic.><2 hour) elective lumbar spine surgeries. According to the Healthcare Cost and Utilization Project (HCUP) Statistical Briefs, laminectomy was listed as the third most common operating room procedure in 2012, with 468,200 cases performed that year.¹¹ Clearly, a cost savings for this common surgical procedure could be substantial if more procedures were performed under a neuraxial anesthetic.

While intrathecal anesthesia is most commonly reported in the literature, a technique commonly utilized by author S.B.B. for short duration procedures utilizes epidural anesthesia. This technique involves gentle intravenous fluid loading (300–500 ml) and epidural catheter insertion two levels above the planned surgical site. The epidural is then dosed with fentanyl 100 mcg and lidocaine 2% in 5 mL incremental boluses until an adequate surgical level is obtained. The patient is kept alert until positioning is complete, monitored closely for hemodynamic changes, and the epidural catheter is then removed prior to the surgical incision. Sedation is titrated to patient comfort and generally consists of propofol, ketamine, midazolam, and fentanyl.

POTENTIAL RISKS/COMPLICATIONS

With every intervention, there are inherent risks. In the case of neuraxial anesthesia, surgeons are often apprehensive about patient movement. Intraoperatively, there is a risk of high spinal level resulting in apnea in the prone position, failed spinal attempt, surgical delay, and the possible need to convert to general anesthesia. Surgeon unfamiliarity with neuraxial anesthesia and anesthesiologist discomfort with a patient in the prone position without a secure airway can also preclude a team from offering a spinal or epidural to a patient having lumbar surgery.⁴ Most studies to date are supportive of neuraxial anesthesia for these cases and cite reduced postoperative analgesic requirements, shorter hospital length of stay, reduced urinary retention, and reduced hemodynamic fluctuation.

One prospective study of 100 patients reports that PONV is more common in patients receiving spinal anesthesia instead of general anesthesia. In this study, general anesthesia with total intravenous anesthesia (propofol and alfentanil for maintenance of anesthesia) was used instead of inhalation agents. As a result, the antiemetic effect of propofol in the neuraxial anesthetic arms of other studies was neutralized. This very interesting study reveals that the spinal anesthetic may not be the cause of reduced nausea and vomiting but that spinal anesthesia may actually result in more PONV than general anesthesia.¹²

CONCLUSIONS

While the majority of elective lumbar spine procedures—such as discectomy, decompression of spinal stenosis, and fusion for degenerative instability—are performed under general anesthesia, the evidence is largely supportive of using spinal or epidural anesthesia. The benefits are compelling: a spontaneously ventilating, awake patient with a decreased incidence of intraoperative hypertension and tachycardia, reduced analgesic requirement in the postanesthesia care unit, less PONV, and a shorter length of hospital stay. Under the appropriate circumstances, neuraxial anesthesia should be considered as a reasonable alternative anesthetic plan for lumbar surgery.

REFERENCES

1. Mixter WJ, Barr JS. Rupture of the intervertebral disk with involvement of the spinal canal. N Engl J Med. 1934;211:210–215.
2. Caspar W. A new surgical procedure for lumbar disk herniation causing less tissue damage through a microsurgical approach. Adv Neurosurg. 1977;4:74– 80.
3. Kroll D. Lumbar microdiscectomy. Tech Reg Anesth Pain Manag. 2013;17:36–38.
4. McLain RF, Bell GR, Kalfas I, Tetzlaff JE, Yoon HJ. Complications associated with lumbar laminectomy: a comparison of spinal versus general anesthesia. Spine. 2004:29:2542–2547.
5. Sanusi T, Davis J, Nicassio N, Malik I. Endoscopic lumbar discectomy under local anesthesia may be an alternative to microdiscectomy: a single centre’s experience using the far lateral approach. Clin Neurol Neurosurg. 2015;139:324–327.
6. Nicassio N, Malik I. Spinal anaesthesia in Spinal Surgery, Topics in Spinal Anaesthesia. Whizar-Lugo V (ed.). Rijeka, Croatia: In Tech;2014. Available at: https://www.intechopen.com/books/3819. Accessed June 2017.
7. Chui J, Craen RA. An update on the prone position: continuing professional development. Can J Anaesth. 2016;63:737–767.
8. Meng T, Zhong Z, Meng L. Impact of spinal anesthesia vs. general anesthesia on perioperative outcome in lumbar spine surgery: A systematic review and metaanalysis of randomized, controlled trials. Anaesthesia. 2017;72:391–401.
9. Walcott BP, Khanna A, Yanamadala V, Coumans JV, Peterfreund RA. Cost analysis of spinal and general anesthesia for the surgical treatment of lumbar spondylosis. J Clin Neurosci. 2015;22:539–543.
10. Fingar KR, Stocks C, Weiss AJ, Steiner CA. Most frequent operating room procedures performed in U.S. hospitals, 2003–2012: statistical brief #186. In: Healthcare Cost and Utilization Project (HCUP) Statistical Briefs [Internet]. Rockville, MD:Agency for Healthcare Research and Quality;2006. Available at: https://www.ncbi.nlm.nih.gov/books/NBK274246/ Accessed June 2017.
11. Sadrolsadat SH, Mahdavi AR, Moharari RS, et al. A prospective randomized trial comparing the technique of spinal and general anesthesia for lumbar disk surgery: a study of 100 cases. Surg Neurol. 2009;71:60–65.