An early comparative analysis between GA and SA in spine surgery explored perioperative effects of the technique on cost and satisfaction among patients, anesthesiologists, and surgeons. Patients who underwent surgery under SA had better outcomes, including hemodynamic stability, shorter hospitalization time, and shorter time to return to work. Postoperatively, SA was associated with lower numeric pain rating scale (NPRS) scores and earlier time to mobilization and first oral intake. Moreover, SA had lower costs and higher reported satisfaction among patients, surgeons, and anesthesiologists.
Subsequent studies have consistently concluded that SA is associated with shorter surgical duration and less blood loss in patients compared to GA for spine surgery. Additionally, hospital length of stay has been reported to be shorter after SA, perhaps due to lower incidence of complications found in several series.
Early postoperative pain control may also be superior after SA in patients undergoing microdiscectomy, attributed to residual sensory block after SA. In addition to higher peaks in pain scores and significantly greater analgesic requirements among the GA group, more episodes of nausea were described, and more antiemetic medications were given.
Intraoperative neurophysiological monitoring (IONM) during procedures such as one and two-level microdiscectomies and laminotomies, use somatosensory evoked potentials (SSEPs), motor evoked potentials (MEPs), and electromyograms (EMGs) as routine during surgery. Surgeons can monitor spinal cord and nerve root function in real-time, take measures to prevent/lessen irritation or potential damage and can detect intraoperative neurologic injuries. Microdiscectomies and laminotomies are one of the most common spinal procedures, which can be performed in both its "open" and "minimally invasive" variations, is a well-established, safe procedure. However, studies have shown that the use of IONM in smaller, less complicated procedures such as microdiscectomies or laminotomies, may add to the overall cost without providing many benefits. Decompressive surgeries under SA cover only the spine and nerve roots within a specific region. Subsequently, SA does not transmit sensory impulses to the brain, therefore, neuromonitoring such as somatosensory evoked potentials (SSEPs) are not required in cases such as these. Certain types of IOMN can be performed under GA, as transmissions of sensory impulses are sent to the brain to identify neural irritation or injury and define the nature of the injury, which will allow the surgeon to complete the procedure without risking further injury.
Despite broad patient acceptance of SA for lower extremity procedures, and abundant evidence to support superior outcomes after orthopedic surgery, SA has never gained wide acceptance in lumbar spine surgery. Arguments against SA for lumbar decompression surgeries include the potential for airway complications in sedated prone positioned patients, the possibility for neural injury if an awake patient moves during decompressive procedures, the potential for intraoperative conversion to GA due to insufficient duration or failed SA, and confounding of the early postoperative neurologic examination.
The Erector Spinae Plane Block (ESP) is a novel fascial plane block, originally described as an effective treatment for thoracic neuritis. Since its first description, the ESP block has been applied to a broad range of surgical procedures, with benefits for opioid-sparing analgesia, a good safety profile, and few complications. The ESP block is considered to be relatively easy to perform when compared to other thoracic or neuraxial blocks, such as epidural and paravertebral blocks. The clinical findings of early studies have been supported by anatomical studies in cadavers demonstrating the appropriate spread of local anesthetic to the dorsal and ventral rami of the nerve roots of the thoracic spine.
The value of ESP block for spine surgery has likewise been suggested in case reports case series, and retrospective cohort studies. Each concludes significant opioid-sparing capacity and improved NRS pain scores in patients who receive ESP blocks for a variety of spine surgery procedures.
More recently, results from 2 RCTs describing outcomes after ESP block for lumbar decompression have been reported. In the first, 60 patients were randomized to receive bilateral ESPB or no intervention. NRS scores and tramadol consumption were significantly lower in the first 24 hours after surgery, and the time to requesting opioid analgesia was significantly longer in patients were received ESPB. In the second RCT, postoperative morphine consumption was lower in patients who received ESPB compared to patients who did not receive ESPB. NRS scores were lower up to 6 hours after surgery in the ESPB group, and patient satisfaction scores were higher
HSS anesthesiologists have been offering ESP blocks for spine surgery via posterior approach since 2017. A recent retrospective analysis of over 800 patients at HSS supports ESP blocks as analgesic and opioid-sparing in our spine surgery population.
As the above literature review suggests, there is unmet clinical and research need to explore the optimal anesthetic-analgesic regimen in patients undergoing minimally invasive lumbar decompression. This study has the potential to address the risk, benefits advantages and disadvantages of SOC GA for patients undergoing spine surgery.
