Kristopher T. Kimmell

Clinical factors associated with venous thromboembolism risk in patients undergoing craniotomy

OBJECT Patients undergoing craniotomy are at risk for developing venous thromboembolism (VTE). The safety of anticoagulation in these patients is not clear. The authors sought to identify risk factors predictive of VTE in patients undergoing craniotomy. METHODS The authors reviewed a national surgical quality database, the American College of Surgeons National Surgical Quality Improvement Program. Craniotomy patients were identified by current procedural terminology code. Clinical factors were analyzed to identify associations with VTE. RESULTS Four thousand eight hundred forty-four adult patients who underwent craniotomy were identified. The rate of VTE in the cohort was 3.5%, including pulmonary embolism in 1.4% and deep venous thrombosis in 2.6%. A number of factors were found to be statistically significant in multivariate binary logistic regression analysis, including craniotomy for tumor, transfer from acute care hospital, age ≥ 60 years, dependent functional status, tumor involving the CNS, sepsis, emergency surgery, surgery time ≥ 4 hours, postoperative urinary tract infection, postoperative pneumonia, on ventilator ≥ 48 hours postoperatively, and return to the operating room. Patients were assigned a score based on how many of these factors they had (minimum score 0, maximum score 12). Increasing score was predictive of increased VTE incidence, as well as risk of mortality, and time from surgery to discharge. CONCLUSIONS Patients undergoing craniotomy are at low risk of developing VTE, but this risk is increased by preoperative medical comorbidities and postoperative complications. The presence of more of these clinical factors is associated with progressively increased VTE risk; patients possessing a VTE Risk Score of ≥ 5 had a greater than 20-fold increased risk of VTE compared with patients with a VTE score of 0.

Risk factors associated with venous thromboembolism in patients undergoing spine surgery

OBJECTIVE Patients undergoing spinal surgery are at risk for developing venous thromboembolism (VTE). The authors sought to identify risk factors for VTE in these patients. METHODS The American College of Surgeons National Surgical Quality Improvement Project database for the years 2006-2010 was reviewed for patients who had undergone spinal surgery according to their primary Current Procedural Terminology code(s). Clinical factors were analyzed to identify associations with VTE. RESULTS Patients who underwent spinal surgery (n = 22,434) were identified. The rate of VTE in the cohort was 1.1% (pulmonary embolism 0.4%; deep vein thrombosis 0.8%). Multivariate binary logistic regression analysis revealed 13 factors associated with VTE. Preoperative factors included dependent functional status, paraplegia, quadriplegia, disseminated cancer, inpatient status, hypertension, history of transient ischemic attack, sepsis, and African American race. Operative factors included surgery duration > 4 hours, emergency presentation, and American Society of Anesthesiologists Class III-V, whereas postoperative sepsis was the only significant postoperative factor. A risk score was developed based on the number of factors present in each patient. Patients with a score of ≥ 7 had a 100-fold increased risk of developing VTE over patients with a score of 0. The receiver-operating-characteristic curve of the risk score generated an area under the curve of 0.756 (95% CI 0.726-0.787). CONCLUSIONS A risk score based on race, preoperative comorbidities, and operative characteristics of patients undergoing spinal surgery predicts the postoperative VTE rate. Many of these risks can be identified before surgery. Future protocols should focus on VTE prevention in patients who are predisposed to it.

Risk of Reoperation for Hemorrhage in Patients After Craniotomy

OBJECTIVE To identify clinical factors predictive of patients returning to the operating room (OR) for hemorrhage after craniotomy. METHODS A national surgical quality database (American College of Surgeons National Surgical Quality Improvement Project) was reviewed for patients undergoing craniotomy based on Current Procedural Terminology (CPT) code. CPT codes were also used to identify patients returning to the OR for hemorrhage. RESULTS Of 5520 patients who underwent craniotomy in 2012, 81 (1.5%) had a reoperation for hematoma evacuation. Preoperative and intraoperative factors associated with reoperation for hemorrhage included preexisting hypertension, bleeding disorder, and primary craniotomy for hematoma evacuation. Postoperative factors included ventilator dependence >48 hours, unplanned reintubation, and blood transfusion during or after the index operation. A risk score based on these factors was predictive of reoperation for hemorrhage with a receiver operating characteristic area under the curve of 0.767. Restricting the score to preoperative factors was still predictive of reoperation (area under the curve = 0.683). CONCLUSIONS Reoperation for evacuation of hematoma is influenced by several clinical factors. A risk score based on these factors is predictive of return to the OR and may be used to identify patients at risk.

Analysis of Venous Thromboembolism Risk in Patients Undergoing Craniotomy

OBJECTIVES Craniotomy poses a risk for postoperative venous thromboembolism (VTE), but the utility of anticoagulation in this patient population is unclear. We sought to identify risk factors predictive of VTE in patients undergoing craniotomy. METHODS The American College of Surgeons National Surgical Quality Improvement Project (ACS-NSQIP) database was reviewed for patients undergoing craniotomy. Clinical factors provided by the database were analyzed for association with VTE. RESULTS A total of 10,477 adult patients who underwent craniotomy from 2011-2012 were identified. The rate of VTE was 3.2% (pulmonary embolism [PE] was 1.3%; deep vein thrombosis [DVT] was 2.4%). Several factors were significant in univariate analysis, and a subset persisted after multivariate analysis. Patients were assigned a risk score on the basis of the presence of those variables. Higher risk scores were predictive of VTE risk, as well as increasing time from surgery to discharge and mortality. A receiver operating characteristics curve revealed a significant area under the curve (0.719) for scores being predictive of VTE risk. The model was validated against our similar analysis of 2006-2010 NSQIP data and demonstrated comparable findings. CONCLUSIONS The risk of postoperative VTE after craniotomy can be quantified by a simple risk score, with increasing risk factors conferring increased risk of VTE. On the basis of risk scoring, a subset of patients who would benefit from anticoagulation post craniotomy may be identified.

Risk Modeling Predicts Complication Rates for Spinal Surgery.

Study Design. Retrospective review of clinical data registry. Objective. In the current era of quality reporting and pay for performance, neurosurgeons must develop models to identify patients at high risk of complications. We sought to identify risk factors for complications in spine surgery and to develop a score predictive of complications. Summary of Background Data. We examined spinal surgeries from the American College of Surgeons National Surgical Quality Improvement Project (ACS-NSQIP) database. 22,430 cases were identified based on common procedural terminology. Methods. Univariate analysis followed by multivariate regression was used to identify significant factors. Results. The overall complication rate for the cohort was 9.9%. The most common complications were postoperative bleeding requiring transfusion (4.1%), nonwound infections (3.1%), and wound-related infections (2.2%). Multivariate regression analysis identified 20 factors associated with complications. Assigning 1 point for the presence of each factor a risk model was developed. The range of scores for the cohort was 0 to 13 with a median score of 4. Complication rates for a risk score of 0 to 4 was 3.7% and for scores 5 to 13 was 18.5%. The risk model robustly predicted complication rates, with complication rate of 1.2% for score of 0 (n = 412, 1.8% of total) and 63.6% and 100% for scores of 12 and 13 (n = 22 patients, 0.1% of total cohort) respectively (P < 0.001). The risk score also correlated strongly with total length of stay, mortality, and total work relative value units for the case. Conclusion. Patient-specific risk factors including comorbidities are strongly associated with surgical complications, length of stay, cost of care, and mortality in spine surgery and can be used to develop risk models that are highly predictive of complications. Level of Evidence: 3

Spinal dural attachments to the vertebral column: An anatomic report and review of the literature.

Background: The spinal dura is anchored within the vertebral canal by connective tissue in the epidural space as well as the spinal roots. Inadvertent disruption of these dural attachments may lead to durotomy and cerebrospinal fluid (CSF) leaks. We observed well-developed connective tissue ligaments connecting the lumbar dura to the spinal column and examined these tissues microscopically. Methods: Intraoperative images were obtained during lumbar laminectomy procedures. They demonstrated connective tissue attachments, linking the lumbar dura to the spinal column in the dorsal midline and dorsolaterally. Tissue samples were obtained and examined microscopically. We then conducted a search of the literature to find references to dural attachments to the spinal column. Results: Histological examination of the samples showed minimal cellular fibrous tissue. To date no references to these attachments have been made in neurosurgical literature. Previous studies, including live, cadaveric, and radiographic examinations, have demonstrated a dorsomedian fold of dura attached to the junction of the ligamentum flavum, and dorsolateral ligaments that divide the dorsal epidural space into an anterior and posterior compartment. Conclusions: Epidural fibrous connections or ligaments between the dura and the lumbar spinal column may be of clinical importance to the neurosurgeon. Care should be taken during lumbar procedures not to disrupt or tear these ligaments as this may cause dural tears and CSF leaks. Identifying these ligaments and cutting them sharply may prevent inadvertent durotomies.

The relationship between the zygomatic arch and the floor of the middle cranial fossa: a radiographic study.

OBJECTIVE Access to the floor of the middle cranial fossa (MCF) is often required for approaches to cranial base lesions. This study measures the craniocaudal distance between the zygomatic arch (ZA) and the floor of the MCF from a random sample of high-resolution computed tomography scans of the cranial base. Methods Forty computed tomography scans were imported into an OsiriX station and reconstructed in multiple planes. The most caudal point of the MCF was determined in each computed tomography scan. The distances between that point and the root of the zygoma and the middle point of the ZA were calculated. The thickness of the temporalis muscle and the vertical height of the zygoma were also calculated. A 2-tailed, paired Student t test was used to compare right and left measurements with a 95% confidence interval and P value <.05 as statistically significant. RESULTS The foramen ovale was consistently the lowest point of the MCF. The average root-to-floor measurement was 5.05 ± 0.42 mm above the floor of the MCF and distance of the mid-zygoma to the floor was 1.94 ± 0.61 mm above the floor of MCF. The average temporalis muscle thickness and vertical height of the ZA were 22.22 ± 0.36 mm and 8.10 ± 0.13 mm, respectively. The muscle-to-floor measurement (muscle thickness + mid-zygoma-to-floor measurement) was 24.16 ± 0.74 mm. Conclusion The routine use of a zygomatic osteotomy in approaches to the MCF does not provide very much increased exposure. However, in patients with exceptionally thick temporalis muscles or a high ZA, a zygomatic osteotomy may be helpful in providing exposure of the floor of the MCF.

Systematic Review of Safety and Cost-Effectiveness of Venous Thromboembolism Prophylaxis Strategies in Patients Undergoing Craniotomy for Brain Tumor

BACKGROUND Studies have evaluated various strategies to prevent venous thromboembolism (VTE) in neuro‐oncology patients, without consensus. OBJECTIVE To perform a systematic review with cost‐effectiveness analysis (CEA) of various prophylaxis strategies in tumor patients undergoing craniotomy to determine the safest and most cost‐effective prophylaxis regimen. METHODS A literature search was conducted for VTE prophylaxis in brain tumor patients. Articles reporting the type of surgery, choice of VTE prophylaxis, and outcomes were included. Safety of prophylaxis strategies was determined by measuring rates of VTE and intracranial hemorrhage. Cost estimates were collected based on institutional data and existing literature. CEA was performed at 30 d after craniotomy, comparing the following strategies: mechanical prophylaxis (MP), low molecular weight heparin with MP (MP+LMWH), and unfractionated heparin with MP (MP+UFH) to prevent symptomatic VTE. All costs were reported in 2016 US dollars. RESULTS A total of 34 studies were reviewed (8 studies evaluated LMWH, 12 for MP, and 7 for UFH individually or in combination; 4 studies used LMWH and UFH preoperatively). Overall probability of VTE was 1.49% (95% confidence interval (CI) 0.42‐3.72) for MP+UFH, 2.72% [95% CI 1.23‐5.15] for MP+LMWH, and 2.59% (95% CI 1.31‐4.58) for MP, which were not statistically significant. Compared to a control of MP alone, the number needed to treat for MP+UFH is 91 and 769 for MP+LMWH. The risk of intracranial hemorrhage was 0.26% (95% CI 0.01‐1.34) for MP, 0.74% (95% CI 0.09‐2.61) for MP+UFH, and 2.72% (95% CI 1.23‐5.15) for MP+LMWH, which were also not statistically significant. Compared to MP, the number needed to harm for MP+UFH was 208 and for MP+LMWH was 41. Fifteen studies were included in the final CEA. The estimated cost of treatment was

349 Safety of the Sitting Cervical Position for Elective Spine Surgery.

127.47 for MP,

Comparative Effectiveness Analysis of Treatment Options for Single Brain Metastasis.

142.20 for MP+UFH, and