Trans-Auricular Stimulation for Postoperative Inflammation in Spine Surgery

Long-segment spinal fusions are effective interventions to relieve pain, neurological compromise, or disability related to a variety of causes of advanced spinal degeneration or spinal deformity. Despite advancements in minimally invasive spine surgery, revision of prior instrumentation, correction of coronal or sagittal imbalance, bony decompression, and multilevel arthrodesis often must be performed via open surgery. While these procedures can produce excellent results with regards to postoperative alignment, neural decompression, and functional improvement, they are long and invasive cases requiring large incisions and extensive soft tissue dissection and osseous manipulation. As such, postoperative adverse events or complications are common (e.g., DVT/PE, wound healing problems, infection, nerve stretch injury, etc.). These patients almost universally experience significant postoperative pain, require postoperative rehabilitation, and are at high-risk for hospital readmissions. Moreover, the sterile trauma from long-segment spinal surgeries is a tremendous systemic inflammatory stimulus that yields downstream sequelae such as hyperglycemia, elevated inflammatory markers (e.g. cytokines), signs of microvascular ischemia, and other stress-related outcomes. Attempts to control this inflammation and reduce the adverse effects of these surgeries are lacking, particularly with respect to non-pharmacologic options.

Vagal nerve stimulation (VNS) is a promising emerging modality by which the body's systemic inflammatory response may be attenuated. Importantly, VNS may be successfully applied via noninvasive auricular stimulation. This technique has been trialed as non-pharmacologic pain control adjunct after multiple types of surgeries or painful medical events, but none as traumatic as long-segment spinal fusion. It also has been shown to yield substantial anti-inflammatory effects in numerous animal models. Furthermore, auricular VNS has been extensively studied at Washington University School of Medicine in multiple neurological conditions, including aneurysmal subarachnoid hemorrhage, acute ischemic stroke, and intraparenchymal hemorrhage. The use of noninvasive VNS devices has been shown to be an intervention that is safely administered and does not cause undue distress to patients. Given these promising aspects of VNS, Washington University's particular interest in this treatment modality, and the unmet postoperative care needs for long-segment spinal fusion patients, the investigators propose prospectively studying the effects of auricular VNS in a population of patients at Barnes-Jewish Hospital who have undergone long-segment fusion surgeries. The investigators hypothesize that perioperative VNS will mitigate the systemic inflammatory reaction in these patients as demonstrated by reduced inflammatory markers (both direct and indirect) and improved inflammatory-mediated clinical outcomes.

This study will be a randomized controlled trial assessing differences between accepted perioperative care plus auricular VNS (the intervention) as compared to accepted perioperative care plus a sham stimulus. The VNS device will be a noninvasive stimulator applied to the left ear to stimulate the auricular branch of the vagus nerve. All patients will be fitted with the device, and the sham stimulus will not receive the required therapeutic stimulation through the device. Patients will receive stimulation twice on the day of surgery followed by twice daily during the duration of their postoperative hospital admission. Relevant inflammatory cytokines, laboratory tests, pain scores, clinical outcomes, and imaging studies will be obtained for each patient. Post-hospital disposition, delayed adverse outcomes, and hospital readmissions will also be tracked after discharge.

Inclusion criteria

• Long-segment spinal fusions (defined as constructs spanning at least L2-pelvis for thoracolumbar fusions or C2-T2 for cervical fusions)
• Ability to undergo a reliable neurologic examination and pain assessments

Exclusion criteria

• Patients <18 years of age
• Shorter-segment spinal fusions than those described above
• Undergoing current active cancer therapy
• Undergoing treatment with immunosuppressive drugs
• Additional spinal surgery within past 6 months
• Sustained bradycardia or presence of pacemaker
• History of substance abuse