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Lothar Schilling, Andrew A. Parsons and Michael Wahl

✓ The smooth-muscle relaxant action of adenosine 5′-triphosphate (ATP)-sensitive potassium (KATP) channels in cerebral arteries of large diameter has been confirmed in a number of in vitro studies, but there is still debate about the presence of KATP channels in small cerebral arteries. In the present study, the authors compare the effects of cromakalim and bimakalim, two putative KATP channel activators, in different parts of the feline isolated middle cerebral artery (MCA) designated proximal, intermediate, and distal. The latter corresponds to those small pial arteries that are usually studied in vivo. In ring segments precontracted with 10−5 M of uridine-5-triphosphate (UTP), both cromakalim and bimakalim induced concentration-related relaxation, with bimakalim being more potent than cromakalim, and no significant differences noted among segments obtained from the different regions of the MCA. In vessels precontracted by adding 30 mM KCl the potency of cromakalim and bimakalim was reduced compared with that obtained after UTP precontraction. In the presence of 10−6 M glibenclamide, an antagonist of KATP channel activators, the concentration—effect curve to bimakalim was shifted to the right in the proximal and distal MCA, indicating a similar route of action for bimakalim and cromakalim in these arteries. The present study therefore indicates the presence of KATP channels in isolated small cerebral arteries according to results obtained in vivo. Activators of KATP channels may prove helpful in the treatment of vasospasm, which may occur in large and small cerebral arteries after subarachnoid hemorrhage.

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Jeff Ehresman, Andrew Schilling, Zach Pennington, Chengcheng Gui, Xuguang Chen, Daniel Lubelski, A. Karim Ahmed, Ethan Cottrill, Majid Khan, Kristin J. Redmond and Daniel M. Sciubba

OBJECTIVE

Vertebral compression fractures (VCFs) in patients with spinal metastasis can lead to destabilization and often carry a high risk profile. It is therefore important to have tools that enable providers to predict the occurrence of new VCFs. The most widely used tool for bone quality assessment, dual-energy x-ray absorptiometry (DXA), is not often available at a patient’s initial presentation and has limited sensitivity. While the Spinal Instability Neoplastic Score (SINS) has been associated with VCFs, it does not take patients’ baseline bone quality into consideration. To address this, the authors sought to develop an MRI-based scoring system to estimate trabecular vertebral bone quality (VBQ) and to assess this system’s ability to predict the occurrence of new VCFs in patients with spinal metastasis.

METHODS

Cases of adult patients with a diagnosis of spinal metastasis, who had undergone stereotactic body radiation therapy (SBRT) to the spine or neurosurgical intervention at a single institution between 2012 and 2019, were retrospectively reviewed. The novel VBQ score was calculated for each patient by dividing the median signal intensity of the L1–4 vertebral bodies by the signal intensity of cerebrospinal fluid (CSF). Multivariable logistic regression analysis was used to identify associations of demographic, clinical, and radiological data with new VCFs.

RESULTS

Among the 105 patients included in this study, 56 patients received a diagnosis of a new VCF and 49 did not. On univariable analysis, the factors associated with new VCFs were smoking status, steroid use longer than 3 months, the SINS, and the novel scoring system—the VBQ score. On multivariable analysis, only the SINS and VBQ score were significant predictors of new VCFs and, when combined, had a predictive accuracy of 89%.

CONCLUSIONS

As a measure of bone quality, the novel VBQ score significantly predicted the occurrence of new VCFs in patients with spinal metastases independent of the SINS. This suggests that baseline bone quality is a crucial factor that requires assessment when evaluating these patients’ conditions and that the VBQ score is a novel and simple MRI-based measure to accomplish this.

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Jeff Ehresman, Zach Pennington, Andrew Schilling, Ravi Medikonda, Sakibul Huq, Kevin R. Merkel, A. Karim Ahmed, Ethan Cottrill, Daniel Lubelski, Erick M. Westbroek, Salia Farrokh, Steven M. Frank and Daniel M. Sciubba

OBJECTIVE

Blood transfusions are given to approximately one-fifth of patients undergoing elective lumbar spine surgery, and previous studies have shown that transfusions are accompanied by increased complications and additional costs. One method for decreasing transfusions is administration of tranexamic acid (TXA). The authors sought to evaluate whether the cost of TXA is offset by the decrease in blood utilization in lumbar spine surgery patients.

METHODS

The authors retrospectively reviewed patients who underwent elective lumbar or thoracolumbar surgery for degenerative conditions at a tertiary care center between 2016 and 2018. Patients who received intraoperative TXA (TXA patients) were matched with patients who did not receive TXA (non-TXA patients) by age, sex, BMI, ASA (American Society of Anesthesiologists) physical status class, and surgical invasiveness score. Primary endpoints were intraoperative blood loss, number of packed red blood cell (PRBC) units transfused, and total hemostasis costs, defined as the sum of TXA costs and blood transfusion costs throughout the hospital stay. A subanalysis was then performed by substratifying both cohorts into short-length (1–4 levels) and long-length (5–8 levels) spinal constructs.

RESULTS

Of the 1353 patients who met inclusion criteria, 68 TXA patients were matched to 68 non-TXA patients. Patients in the TXA group had significantly decreased mean intraoperative blood loss (1039 vs 1437 mL, p = 0.01). There were no differences between the patient groups in the total costs of blood transfusion and TXA (p = 0.5). When the 2 patient groups were substratified by length of construct, the long-length construct group showed a significant net cost savings of $328.69 per patient in the TXA group (p = 0.027). This result was attributable to the finding that patients undergoing long-length construct surgeries who were given TXA received a lower amount of PRBC units throughout their hospital stay (2.4 vs 4.0, p = 0.007).

CONCLUSIONS

TXA use was associated with decreased intraoperative blood loss and significant reductions in total hemostasis costs for patients undergoing surgery on more than 4 levels. Furthermore, the use of TXA in patients who received short constructs led to no additional net costs. With the increasing emphasis put on value-based care interventions, use of TXA may represent one mechanism for decreasing total care costs, particularly in the cases of larger spine constructs.

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Jeff Ehresman, Andrew Schilling, Zach Pennington, Chengcheng Gui, Xuguang Chen, Daniel Lubelski, A. Karim Ahmed, Ethan Cottrill, Majid Khan, Kristin J. Redmond and Daniel M. Sciubba

OBJECTIVE

Vertebral compression fractures (VCFs) in patients with spinal metastasis can lead to destabilization and often carry a high risk profile. It is therefore important to have tools that enable providers to predict the occurrence of new VCFs. The most widely used tool for bone quality assessment, dual-energy x-ray absorptiometry (DXA), is not often available at a patient’s initial presentation and has limited sensitivity. While the Spinal Instability Neoplastic Score (SINS) has been associated with VCFs, it does not take patients’ baseline bone quality into consideration. To address this, the authors sought to develop an MRI-based scoring system to estimate trabecular vertebral bone quality (VBQ) and to assess this system’s ability to predict the occurrence of new VCFs in patients with spinal metastasis.

METHODS

Cases of adult patients with a diagnosis of spinal metastasis, who had undergone stereotactic body radiation therapy (SBRT) to the spine or neurosurgical intervention at a single institution between 2012 and 2019, were retrospectively reviewed. The novel VBQ score was calculated for each patient by dividing the median signal intensity of the L1–4 vertebral bodies by the signal intensity of cerebrospinal fluid (CSF). Multivariable logistic regression analysis was used to identify associations of demographic, clinical, and radiological data with new VCFs.

RESULTS

Among the 105 patients included in this study, 56 patients received a diagnosis of a new VCF and 49 did not. On univariable analysis, the factors associated with new VCFs were smoking status, steroid use longer than 3 months, the SINS, and the novel scoring system—the VBQ score. On multivariable analysis, only the SINS and VBQ score were significant predictors of new VCFs and, when combined, had a predictive accuracy of 89%.

CONCLUSIONS

As a measure of bone quality, the novel VBQ score significantly predicted the occurrence of new VCFs in patients with spinal metastases independent of the SINS. This suggests that baseline bone quality is a crucial factor that requires assessment when evaluating these patients’ conditions and that the VBQ score is a novel and simple MRI-based measure to accomplish this.