Inadequate Spinal Anesthesia in Lumbar Spine Surgery is Related to Volume of the Thecal Sac.

BACKGROUND: Spinal anesthesia (SA) is used in lumbar surgery but initial adequate analgesia fails in some patients. In these cases, spinal redosing or conversion to general endotracheal anesthesia is required, both of which are detrimental to the patient experience and surgical workflow. METHODS: We reviewed cases of lumbar surgery performed under spinal anesthesia from 2017 - 2021. We identified 12 cases of inadequate first dose, then selected 36 random patients as controls. We used a measurement tool to approximate the volume of the dural sac for each patient using T2-weighted sagittal MRI sequences. RESULTS: Patients who had an inadequate first dose of anesthesia had a significantly larger dural sac volume, 22.8 ± 7.9 cm3 in the inadequate dose group, and 17.4 ± 4.7 cm3 in controls (p=0.043). The inadequate dose group was significantly younger, 54.2 ± 8.8 years in failed first dose, and 66.4 ± 11.9 years in control (p=0.001). The groups did not differ by surgical procedure (p=0.238), level (p=0.353), ASA score (p=0.546), or co-morbidities. CONCLUSIONS: We found that age, larger height, and dural sac volume are risk factors for an inadequate first dose of SA. The availability of spinal MRI in patients undergoing spine surgery allows the preoperative measurement of their thecal sac size. In the future, this data may be used to personalize spinal anesthesia dosing based on individual anatomic variables and potentially reduce the incidence of failed spinal anesthesia in spine surgery.

Spinal Anesthesia Reduces Perioperative Polypharmacy and Opioid Burden in Patients Over 65 Who Undergo Transforaminal Lumbar Interbody Fusion.

BACKGROUND: Polypharmacy and opioid administration are thought to increase the risk of postoperative cognitive dysfunction and delirium in elderly patients. Spinal anesthesia (SA) holds potential to reduce perioperative polypharmacy in spine surgery. As more geriatric patients undergo spine surgery, understanding how SA can reduce polypharmacy and opioid administration is warranted. We aim to compare the perioperative polypharmacy and dose of administered opioids in patients ≥65 years who undergo transforaminal lumbar interbody fusion (TLIF) under SA versus general anesthesia (GA). METHODS: A retrospective analysis of 200 patients receiving a single-surgeon TLIF procedure at a single academic center (2014-2021) was performed. Patients underwent the procedure with SA (n = 120) or GA (n = 80). Demographic, procedural, and medication data were extracted from the medical record. Opioid consumption was quantified as morphine milligram equivalents (MME). Statistical analyses included χ2 or Student's t-test. RESULTS: Patients receiving SA were administered 7.45 medications on average versus 12.7 for GA patients (P < 0.001). Average perioperative opioid consumption was 5.17 MME and 20.2 MME in SA and GA patients, respectively (P < 0.001). The number of patients receiving antiemetics and opioids remained comparable postoperatively, with a mean of 32.2 MME in the GA group versus 27.5 MME in the SA group (P = 0.14). Antiemetics were administered less often as a prophylactic in the SA group (32%) versus 86% in the GA group (P < 0.001). CONCLUSIONS: SA reduces perioperative polypharmacy in patients ≥65 years undergoing TLIF procedures. Further research is necessary to determine if this reduction correlates to a decrease the incidence of postoperative cognitive dysfunction and delirium.

Erector Spinae Plane Block Placement Utilizing Fluoroscopic Guidance Improves Efficiency in Lumbar Surgery.

OBJECTIVE: The erector spinae plane block (ESPB) is a novel regional analgesic technique which improves postoperative outcomes in lumbar surgery patients including length of hospitalization, days to ambulation, and postoperative opioid use. Traditionally, the block is administered by anesthesiologists trained in the ultrasound guidance technique. The use of fluoroscopic guidance may improve the efficiency and accessibility of the ESPB for spine surgeons. We aim to measure the time to administer an ESPB using fluoroscopic guidance and localize the anesthetic using intraoperative three-dimensional (3D) imaging. METHODS: Two neurosurgeons administered an ESPB to patients undergoing lumbar surgery. Time from insertion of the spinal needle to localize the erector spinae plane using C-arm guidance to time of complete injection and removal of the needle from the skin was recorded. One patient underwent O-arm imaging following injection of an Isovue-Exparel solution at the L3 level to visualize spread of the anesthetic. RESULTS: A total of 21 patients were enrolled in this study. The average duration to perform an ESPB under fluoroscopic guidance was 1.2 minutes. The Isovue-Exparel solution was injected at the L3 level and was well distributed along the ESP on intraoperative O-arm imaging. The anesthetic dissected the erector spinae muscle from the transverse process at L2, L3, and L4. CONCLUSIONS: Fluoroscopic guidance allows efficient and appropriate delivery of the anesthetic to the erector spinae plane. Performing an ESPB with fluoroscopic guidance improves efficiency and accessibility of the analgesic technique for spine surgeons, reducing dependence on anesthesiology personnel trained in administering the block.

The Relationship of Spinal Anesthesia Dosing Based on Thecal Sac Area to Anesthetic Failure in Lumbar Surgery.

BACKGROUND AND OBJECTIVES: Greater thecal sac volumes are associated with an increased risk of spinal anesthesia (SA) failure. The thecal sac cross-sectional area accurately predicts thecal sac volume. The thecal sac area may be used to adjust the dose and prevent anesthetic failure. We aim to assess the rate of SA failure in a prospective cohort of lumbar surgery patients who receive an individualized dose of bupivacaine based on preoperative measurement of their thecal sac area. METHODS: A total of 80 patients prospectively received lumbar spine surgery under SA at a single academic center (2022-2023). Before surgery, the cross-sectional area of the thecal sac was measured at the planned level of SA injection using T2-weighted MRI. Patients with an area <175 mm2, equal to or between 175 and 225 mm2, and >225 mm2 received an SA injection of 15, 20, or 25 mg of 0.5% isobaric bupivacaine, respectively. Instances of anesthetic failure and adverse outcomes were noted. Incidence of SA failure was compared with a retrospectively obtained control cohort of 250 patients (2019-2022) who received the standard 15 mg of bupivacaine. RESULTS: No patients in the individualized dose cohort experienced failure of SA compared with 14 patients (5.6%) who experienced failure in the control cohort (P = .0259). The average thecal sac area was 187.49 mm2, and a total 28 patients received 15 mg of bupivacaine, 42 patients received 20 mg of bupivacaine, and 10 patients received 25 mg of bupivacaine. None of the patients experienced any adverse outcomes associated with SA. Patients in the individualized dose cohort and control cohort were comparable and had a similar distribution of lumbar procedures and comorbidities. CONCLUSION: Adjusting the dose of SA according to thecal sac area significantly reduces the rate of SA failure in patients undergoing lumbar spine surgery.

Correlation of thecal sac cross sectional area to total volume.

BACKGROUND: Spinal anesthesia (SA) has been increasingly utilized in lumbar surgery due to its various advantages over general anesthesia (GA), however failure of the first dose requiring intraoperative conversion to GA occurs in as many as 3.6% of SA patients. Some studies have reported that a larger thecal sac volume may dilute the anesthetic and play a role in first dose failure. Unfortunately, easy determination of thecal sac volume has not been reported in the literature. Thus, we sought to determine whether cross-sectional area obtained from MRI accurately predicts the volume of the thecal sac. METHODS: We conducted a retrospective review of 80 patients who underwent lumbar surgery with spinal anesthesia. T1 and T2-weighted MRI sequences were used to measure thecal sac area at each level between L1-S1. The volume of the thecal sac was calculated using HorosTM. A statistical model was derived relating the area at each level to the thecal sac volume. Of the 80 patients, 20% were reserved and utilized to test the accuracy of the statistical model. RESULTS: The area of the thecal sac positively correlated with volume at each lumbar level. The area of the thecal sac at the L4-L5 level most accurately represented total thecal sac volume (R2 = 0.588, RMSE = 2.76). CONCLUSION: Cross-sectional area of the L4-L5 spinal level obtained from MRI sequences may be utilized as a proxy for thecal sac volume.

Evaluating the potential impact of spinal anesthesia use in lumbar surgery on global healthcare cost and climate change.

Introduction: Despite recent evidence demonstrating its safety and efficacy, spinal anesthesia remains a seldom-utilized anesthetic modality in lumbar surgical procedures. In addition, numerous clinical advantages, such as reduced cost, blood loss, operative time, and inpatient length of stay have been consistently demonstrated with spinal anesthesia over general anesthesia. Research question: In this report we aim to examine the differences between spinal anesthesia and general anesthesia with regard to accessibility and climate impact and determine whether wider adoption of spinal anesthesia would have a meaningful impact on the global population. Materials and Methods: The climate impact of spinal fusions performed under spinal and general anesthesia were obtained from recent studies published in the literature. Cost of spinal fusions was obtained from an unpublished study performed at our institution. Volume of spinal fusions performed in several countries were ascertained from published reports. Data on cost and carbon emissions were extrapolated based on volume of spinal fusions in each of the nations. Results: In the U.S., use of spinal anesthesia for lumbar fusions would have resulted in savings of 343 million dollars in 2015. A similar reduction in cost was seen with each country studied. Additionally, spinal anesthesia was associated with 12,352 â€‹kg carbon dioxide equivalents (CO2e) while general anesthesia produced 942,872 â€‹kg CO2e. Similar reduction in carbon emissions was seen with each country studied. Discussion and conclusion: Spinal anesthesia is safe and effective for both simple and complex spine surgeries, it reduces carbon emissions, permits lower operative times, and decreases cost.

The Emerging Significance of Amyloid Deposits in the Ligamentum Flavum of Spinal Stenosis Patients: A Review.

Spinal stenosis is one of the most common neurosurgical diseases and a leading cause of pain and disability. Wild-type transthyretin amyloid (ATTRwt) has been found in the ligamentum flavum (LF) of a significant subset of patients with spinal stenosis who undergo decompression surgery. Histologic and biochemical analyses of LF specimens from spinal stenosis patients, normally discarded as waste, have the potential to help elucidate the underlying pathophysiology of spinal stenosis and possibly allow for medical treatment of stenosis and screening for other systemic diseases. In the present review, we discuss the utility of analyzing LF specimens after spinal stenosis surgery for ATTRwt deposits. Screening for ATTRwt amyloidosis cardiomyopathy through LF specimens has led to the early diagnosis and treatment of cardiac amyloidosis in several patients, with more expected to benefit from this process. Emerging evidence in the literature also point to ATTRwt as a contributor to a previously unrecognized subtype of spinal stenosis in patients who might, in the future, benefit from medical therapy. In the present report, we review the current literature regarding the early detection of ATTRwt cardiomyopathy via LF screening and the possible contribution of ATTRwt deposits in the LF to spinal stenosis development.

Assessing the Safety and Efficacy of Spinal Anesthesia in Patients with Significant Comorbidities.

BACKGROUND: Spinal anesthesia is an effective modality for lumbar surgery. Patient eligibility with respect to medical comorbidities remains a topic of debate. Obesity (body mass index ≥30 kg/m2), anxiety, obstructive sleep apnea, reoperation at the same level, and multilevel operations have variously been reported as relative contraindications. We hypothesize that patients undergoing common lumbar surgeries with these comorbidities do not experience greater rates of complications compared with controls. METHODS: We analyzed a prospectively collected database of patients undergoing thoracolumbar surgery under spinal anesthesia and identified 422 cases. Surgeries were less than 3 hours (the duration of action of intrathecal bupivacaine) and include microdiscectomies, laminectomies, and both single-level and multilevel fusions. Procedures were performed by a single surgeon at a single academic center. In overlapping groups, 149 patients had a body mass index ≥30 kg/m2, 95 had diagnosed anxiety, 79 underwent multilevel surgery, 98 had obstructive sleep apnea, and 65 had a previous operation at the same level. The control group included 132 patients who did not have these risk factors. Differences in important perioperative outcomes were assessed. RESULTS: There were no statistically significant differences in intraoperative and postoperative complications except 2 cases of pneumonia in the anxiety group and 1 case in the reoperative group. There were also no significant differences for patients with multiple risk factors. Rates of spinal fusion were similar among groups, although mean length of stay and operative time were different. CONCLUSIONS: Spinal anesthesia is a safe option for patients with significant comorbidities and can be considered for most patients undergoing routine lumbar surgeries.

Periprocedural Polypharmacy in Lumbar Fusions Performed Under Spinal Anesthesia Compared With General Anesthesia.

BACKGROUND: Spinal anesthesia (SA) is a safe and effective alternative to general endotracheal anesthesia (GEA) for lumbar surgery. Foremost among the reasons to avoid GEA is the desire to minimize postoperative cognitive dysfunction (POCD). Although POCD is a complex and multifactorial entity, the risk of its development has been associated with anesthetic modality and perioperative polypharmacy, among others. OBJECTIVE: To determine whether SA reduced polypharmacy compared with GEA in patients undergoing transforaminal lumbar interbody fusion (TLIF). METHODS: Demographic and procedural data of 424 consecutive TLIF patients were extracted retrospectively. Patients undergoing single-level TLIF through GEA (n = 186) or SA (n = 238) were enrolled into our database. Perioperative medications, excluding antibiotic prophylaxis and local anesthetics, were classified into various categories. RESULTS: Patients in the SA cohort received a mean of 4.5 medications vs a mean of 10.5 medications in the GEA cohort ( P < .0001). This reduction in perioperative medications remained significant after a multivariate analysis to control for confounders ( P < .001 for all variables). The use of vasopressors was significantly reduced in the SA cohort ( P < .001), which coincided with a significant reduction in hypotensive episodes ( P < .001). Patients undergoing TLIF through GEA had 3.6 times greater odds of experiencing a hypotensive episode intraoperatively (odds ratio = 3.62, 95% CI [2.38-5.49]). CONCLUSION: Spinal anesthesia is associated with a significant decrease in perioperative medications and may confer superior intraoperative hemodynamic stability, which lowers pressor requirements. The decrease of perioperative medications may be an important contribution in reducing the incidence of POCD in patients undergoing TLIFs, although this requires further study.

Clinical Outcomes of Liposomal Bupivacaine Erector Spinae Block in Minimally Invasive Transforaminal Lumbar Interbody Fusion Surgery.

BACKGROUND: Postoperative pain is a barrier to early mobility and discharge after lumbar surgery. Liposomal bupivacaine (LB) has been shown to decrease postoperative pain and narcotic consumption after transforaminal lumbar interbody fusions (TLIFs) when injected into the marginal suprafascial/subfascial plane-liposomal bupivacaine (MSSP-LB). Erector spinae plane (ESP) infiltration is a relatively new analgesic technique that may offer additional benefits when performed in addition to MSSP-LB. OBJECTIVE: To evaluate postoperative outcomes of combining ESP-LB with MSSP-LB compared with MSSP-LB alone after single-level TLIF. METHODS: A retrospective analysis was performed for patients undergoing single-level TLIFs under spinal anesthesia, 25 receiving combined ESP-LB and MSSP-LB and 25 receiving MSSP-LB alone. The primary outcome was length of hospitalization. Secondary outcomes included postoperative pain score, time to ambulation, and narcotics usage. RESULTS: Baseline demographics and length of surgery were similar between groups. Hospitalization was significantly decreased in the ESP-LB + MSSP-LB cohort (2.56 days vs 3.36 days, P = .007), as were days to ambulation (0.96 days vs 1.29 days, P = .026). Postoperative pain area under the curve was significantly decreased for ESP-LB + MSSP-LB at 12 to 24 hours (39.37 ± 21.02 vs 53.38 ± 22.11, P = .03) and total (44.46 ± 19.89 vs 50.51 ± 22.15, P = .025). Postoperative narcotic use was significantly less in the ESP-LB + MSSP-LB group at 12 to 24 hours (13.18 ± 4.65 vs 14.78 ± 4.44, P = .03) and for total hospitalization (137.3 ± 96.3 vs 194.7 ± 110.2, P = .04). CONCLUSION: Combining ESP-LB with MSSP-LB is superior to MSSP-LB alone for single-level TLIFs in decreasing length of hospital stay, time to ambulation, postoperative pain, and narcotic use.

Assessing the impact of spinal versus general anesthesia on postoperative urinary retention in elective spinal surgery patients.

OBJECTIVE: Postoperative urinary retention (POUR) is a common and vexing complication in elective spine surgery. Efficacious prevention strategies are still lacking, and existing studies focus primarily on identifying risk factors. Spinal anesthesia has become an attractive alternative to general anesthesia in elective lumbar surgery, with the potential of having a differential impact on POUR. METHODS: 422 spinal anesthesia procedures were prospectively collected between 2017 and 2021 and compared to 416 general anesthesia procedures retrospectively collected between 2014 and 2017, at a single academic center by the same senior neurosurgeon. The main outcome was POUR, defined as the need for straight bladder catheterization or indwelling bladder catheter placement after surgery due to failure to void. A power calculation was performed prior to data collection. RESULTS: The general anesthesia group had a higher rate of POUR (9.1 %) compared with the spinal anesthesia group (4.3 %), p = 0.005. At baseline, the spinal anesthesia cohort had an older average age and fewer patients with a history of previous spine surgery. Other comorbid conditions were comparable between the groups. For perioperative characteristics, spinal anesthesia patients had higher ASA scores, shorter operative times, shorter lengths of hospital stay, less operative levels, and zero use of intraoperative bladder catheterization. Acute pain service consult was similar between the groups. A multivariable logistic regression revealed that spinal anesthesia was associated with a significantly lower rate of urinary retention in the spinal anesthesia group (p = 0.0130), after adjusting for potentially confounding factors. Other statistically significant risk factors for POUR included diabetes, (p = 0.003), BPH (p = 0.014), operative time (p = 4.94e-06), and ASA score (p = 0.005). CONCLUSIONS: We collect and analyze one of the largest available cohorts of patients undergoing simple and complex surgeries under spinal and general anesthesia, finding that spinal anesthesia is independently associated with a lower incidence of POUR compared to general anesthesia, even when adjusted for potentially confounding risk factors. Further prospective trials are needed to explore this finding.

Lumbar stenosis due to wild-type transthyretin amyloid-induced thickening of the ligamentum flavum: a separate etiology from degeneration of intervertebral discs?

OBJECTIVE: Wild-type transthyretin amyloid (ATTRwt) is deposited in the ligamentum flavum (LF) of a subset of patients with spinal stenosis who undergo decompressive surgery, although its role in the pathophysiology of spinal stenosis is unknown. It has been theorized that degeneration of intervertebral discs causes increased mechanical stress and inflammatory/degenerative cascades and ultimately leads to LF fibrosis. If ATTRwt deposits contribute to LF thickening and spinal stenosis through a different pathway, then patients with ATTRwt may have less severe disc degeneration than those without it. In this study, the authors compared the severity of disc degeneration between patients with lumbar stenosis with and without amyloid in their LF to test whether ATTRwt is a unique contributor to LF thickening and spinal stenosis. METHODS: Of 324 consecutive patients between 2018 and 2019 who underwent decompression surgery for spinal stenosis and had LF samples sent for pathological analysis, 31 harboring ATTRwt were compared with 88 controls. Patient medical records were retrospectively reviewed for demographic and surgical information. Disc degeneration was assessed on preoperative T2-weighted MR images with the modified Pfirrmann grading system at every lumbar disc level. RESULTS: Baseline characteristics were similar between the groups, except for a statistically significant increase in age in the ATTRwt group. The crude unadjusted comparisons between the groups trended toward a less severe disc degeneration in the ATTRwt group, although this difference was not statistically significant. A multivariable linear mixed-effects model was created to adjust for the effects of age and to isolate the influence of ATTRwt, the presence of an operation at the level, and the specific disc level (between L1 and S1). This model revealed that ATTRwt, the presence of an operation, and the specific level each had significant effects on modified Pfirrmann scores. CONCLUSIONS: Less severe disc degeneration was noted in patients with degenerative spinal stenosis harboring ATTRwt compared with those without amyloid. This finding suggests that ATTRwt deposition may play a separate role in LF thickening from that played by disc degeneration. Future studies should aim to elucidate this potentially novel pathophysiological pathway, which may uncover an exciting potential for the development of amyloid-targeted therapies that may help slow the development of spinal stenosis.