Modulation of Cerebral Function by Muscle Afferent Activity, with Reference to Intravenous Succinylcholine.

Cerebral Function and Muscle Afferent Activity Following Intravenous Succinylcholine in Dogs Anesthetized with Halothane: The Effects of Pretreatment with a Defasciculating Dose of Pancuronium. By WL Lanier, PA Iaizzo, and JH Milde. Anesthesiology 1989; 71:87-95. Reprinted with permission. By the mid-1980s, it was widely assumed that if the depolarizing muscle relaxant, succinylcholine, given IV, produced increases in intracranial pressure, it did so because fasciculations produced increases in intrathoracic and central venous pressures that were transferred to the brain; however, there was no direct evidence that this was true. In contrast, we explored the possibility that the succinylcholine effect on the brain was explained by the afferentation theory of cerebral arousal, which predicts that agents or maneuvers that stimulate muscle stretch receptors will tend to stimulate the brain. Our research in tracheally intubated, lightly anesthetized dogs discovered that IV succinylcholine (which does not cross the blood-brain barrier) produced a doubling of cerebral blood flow that lasted for 30 min and corresponded to activation of the electroencephalogram and increases in intracranial pressure. Later, in our Classic Paper, we were able to assess simultaneously cerebral physiology and afferent nerve traffic emanating from muscle stretch receptors (primarily muscle spindles). We affirmed that the cerebral arousal response to succinylcholine was indeed driven by muscle afferent traffic and was independent of fasciculations or increases in intrathoracic or central venous pressures. Later research in complementary models demonstrated that endogenous movement (e.g., coughing, hiccups) produced a cerebral response very similar to IV succinylcholine, apparently as a result of the same muscle afferent mechanisms, independent of intrathoracic and central venous pressures. Thus, the importance of afferentation theory as a driver of the cerebral state of arousal and cerebral physiology during anesthesia was affirmed.

Hydraulic stimulation of carotid artery baroreceptors as a likely cause of transient asystolic cardiac arrest during diagnostic angiography or surgical endarterectomy.

We describe two patients-both who underwent general anesthesia-in whom we theorize that hydraulic pressure on carotid artery baroreceptors resulted in transient asystolic cardiac arrest (TACA) during diagnostic or therapeutic procedures. Patient #1 was a 58-year-old female who experienced TACA in response to rapid injection of radiocontrast material into the carotid artery during diagnostic cerebral angiography. Her history was remarkable for aneurysmal subarachnoid hemorrhage at least 13 hr prior to angiography, radiographic evidence of intracranial hypertension, and baseline bradycardia, collectively suggestive of increases in baseline vagal tone. Potentially contributing to TACA, the patient had a 90° curve in the internal carotid artery, just distal to the carotid bifurcation and tip of the angiography catheter, that likely diminished runoff of injected contrast solution and, in turn, would have exacerbated any intracarotid pressure increases in response to injection. There was no evidence of increased baseline vagal tone in Patient #2, a 79-year-old female having carotid endarterectomy surgery. She experienced TACA immediately after full release of an occlusive clamp on the common carotid artery proximal to the now closed carotid arteriotomy, but while the internal carotid was still occluded. Of note, the carotid artery baroreceptors were not treated with local anesthetic in these patients, thus they should have retained much of their normal function. We describe the possible pathomechanisms involved in TACA in these patients, measures to diminish the likelihood of the phenomenon occurring in future patients, and methods for treating the asystole.

Clinical and Imaging Outcomes of Surgically Repaired Cerebrospinal Fluid-Venous Fistulas Identified by Lateral Decubitus Digital Subtraction Myelography.

OBJECTIVE: To describe clinical and radiographic outcomes of surgical repair of cerebrospinal fluid-venous fistula (CVF), an increasingly recognized cause of spontaneous intracranial hypotension that is poorly responsive to epidural blood patch (EBP). METHODS: Retrospective review identified adult patients who had lateral decubitus digital subtraction myelography indicative of cerebrospinal fluid leak at Mayo Clinic between November 2018 and February 2020, with clearly localized CVF, followed by surgical treatment. Patients without available imaging before or after surgery were excluded. History of EBP and clinical response to EBP were evaluated along with surgical outcomes. RESULTS: Of 25 patients with CVF who met protocol criteria and were included in the data analysis, 22 (88%) received EBP, but clinical benefit lasting ≥4 weeks occurred in only 2 of 22 (9%). Headache was the most prominent preoperative feature among patients (24/25; 96%). Following surgery, 18 of 24 (75%) patients had complete headache improvement, 4 (17%) had partial improvement, and 2 (8%) had no improvement. Ten of 25 (40%) patients reported cognitive disturbance at baseline; at follow-up, 5 of 10 (50%) had complete improvement, 3 (30%) had partial improvement, and 2 (20%) had no improvement. On postoperative brain magnetic resonance imaging, 6 of 25 (24%) patients had complete resolution of findings by Bern score criteria, 18 (72%) showed partial improvement, and 1 (4%) patient showed no improvement. Adverse events were minor and included surgical site pain and paresthesias. CONCLUSIONS: Surgical repair of CVF resulted in improvements in headache and other symptoms, with few side effects.

Dealing with inappropriate-, low-quality-, and other forms of challenging peer review, including hostile referees and inflammatory or confusing critiques: Prevention and treatment.

Within the context of journal peer review, when high-quality referee input is coupled with appropriate editorial oversight from a journal's leadership, the result can be the selection and publication of high-quality manuscripts that are ideally targeted to the journal's readership's interests. However, in its worse forms, flawed referee input and indifferent- or misdirected journal leadership can result in damage to the quality of materials published and the relationships among, and careers of, the involved parties. This article identifies methods that journals can employ to select journal leaders and educate authors, referees, and editors in an attempt to prophylax against problematic peer review. The article then identifies 17 categories of inappropriate or flawed critiques. Next it outlines a plan of action: 1) to prevent potentially harmful reviews from reaching authors, and 2) for instructing authors on how to respond to perceived challenging or problematic reviews, or perceived erroneous journal decisions. Elsewhere, the article introduces an approach to diffuse hostilities that may follow the publication of controversial articles. The synthesis within this article approaches peer review as a continuous quality improvement exercise in which referees, authors, and journal leadership will gain a broader understanding of the standards of biomedical publication and professionalism.

Pituitary Tumor Surgery: Comparison of Endoscopic and Microscopic Techniques at a Single Center.

OBJECTIVE: To understand the transition from microscopic surgery (MS) to endoscopic surgery (ES) on the pituitary across the United States, we assessed a single institution practicing both procedures to discern advantages and disadvantages for each. PATIENTS AND METHODS: Retrospective institutional chart review of 534 patients in a large practice over a 6-year period (January 1, 2014, to December 31, 2019) comparing a single MS neurosurgeon with a single ES neurosurgeon operating on the same days. RESULTS: In this series, 14% (n=75) of patients had a prior operation, there were no carotid artery injuries, the overall risk for a postoperative infection was 0.4% (n=2), and risk for a postoperative cerebrospinal fluid leak requiring treatment was 2.0% (n=11). Mean ± SD hospital stay was 1.3±0.04 days; readmission for any reason within 30 days occurred in 3.4% (n=18) of patients. The mean volumetric resection for MS was 86.9%±1.7% and for ES was 91.7%±1.3% (P=.03). There was a higher rate of notable events (P=.015) with MS, but MS had 16% lower cost and operative times were 48 minutes shorter than for ES (83±7 vs 131±6 minutes). The ES required substantially fewer postoperative secondary treatments such as radiation therapy (P=.003). CONCLUSION: Pituitary surgery is a very safe and effective procedure regardless of technique. The MS has shorter operative times and overall lower cost. The ES results in increased volumetric resection and fewer secondary treatments. Both techniques can be valuable to a large practice, and understanding these niches is important when selecting optimal approaches to pituitary surgery for a given patient.

Airway management in patients who develop neck hematomas after carotid endarterectomy.

BACKGROUND: Progressive airway compromise from neck hematoma and edema is a feared complication of carotid endarterectomy (CEA). Despite this, the relationship of airway management technique to patient outcome has not been systematically studied in this population. We report the rate of successful airway management using various techniques in post-CEA patients. METHODS: A 10-year retrospective analysis was conducted to identify patients requiring airway management for neck exploration within 72 hours after CEA at Mayo Clinic, Rochester, MN. RESULTS: Three thousand two hundred twenty-five patients underwent CEA over a 10-year period at our institution. Forty-four (1.4%) required neck exploration for hematoma, and 42 of these required airway management immediately before neck exploration surgery. (The tracheal tube had not been removed after CEA in the remaining 2 patients.) The average interval between the completion of CEA and return to the operating room for hematoma evacuation was 6.0 +/- 6.0 hours (mean +/- SD; range, <1-32 hours). Fiberoptic airway management, performed before the induction of anesthesia, was successful in 15 of 20 patients (75%) and, in patients in whom fiberoptic tracheal intubation failed, direct laryngoscopy (DL) was successful in all 5 (3 before and 2 after the induction of general anesthesia). In the remaining 22 patients, DL was used as the initial management technique without a trial of fiberoptic intubation. DL was successful in 5 of 7 patients (71%) when performed before induction of general anesthesia and was successful in 13 of 15 patients (87%) when performed after induction of general anesthesia. Hematoma decompression facilitated DL in 3 of 4 failures of DL; tracheostomy was performed in the remaining patient. An arterial site of bleeding was subsequently identified in 36% of patients in whom no difficulty was encountered during laryngoscopy for hematoma evacuation versus 6% in whom difficulty was noted (P = 0.03). In 36 of 44 patients (82%), the tracheal tube was removed within 24 hours of surgery for neck exploration. No adverse events related to airway management were noted. There were no deaths at 2 weeks after hematoma evacuation. CONCLUSIONS: Multiple techniques resulted in successful airway control both before and after the induction of general anesthesia. Tracheal intubation was accomplished with both fiberoptic visualization and DL. In instances of poor direct visualization of the glottis, decompression of the airway by opening of the surgical incision may facilitate intubation of the trachea.

General anaesthesia for MRI in children with hypotonia: a case series.

BACKGROUND AND OBJECTIVE: To characterize the safety of general anaesthesia, used to facilitate MRI in children with clinical hypotonia, and to determine whether this technique could be performed safely as an outpatient procedure. METHODS: All children (age

Is nitrous oxide use appropriate in neurosurgical and neurologically at-risk patients?

PURPOSE OF REVIEW: To address controversial issues surrounding the use of nitrous oxide as a component of anesthesia in neurosurgical and neurologically at-risk patients. RECENT FINDINGS: Nitrous oxide has been used as a component of general anesthesia for over 160 years and has contributed to countless apparently uneventful anesthetics in neurologically at-risk patients. Avoidance of nitrous oxide in specific circumstances, such as pre-existing pneumocephalus, during acute venous air embolism, and in patients with disorders of folate metabolism, is warranted. However, various controversies exist regarding the use of this drug in the general neurosurgical population. Specifically, some suggest a possible association between nitrous oxide and the postoperative development of tension pneumocephalus despite lack of data to support this notion. Additionally, data describing alterations of cerebral hemodynamics and metabolism and exacerbation of ischemic neurologic injury by nitrous oxide are inconsistent. Recent data derived from humans having cerebral aneurysm clipping failed to show any long-term adverse effect from the use of nitrous oxide on gross neurologic or cognitive function. SUMMARY: Except in a few specific circumstances, there exists no conclusive evidence to support the dogmatic avoidance of nitrous oxide in neurosurgical patients.

Evidence versus advocacy, as related to radiofrequency denervation in the treatment of chronic low back pain and the MINT trials.

In 2017, JAMA: Journal of the American Medical Association published the results of the MINT trials, prospective research involving 681 patients, all of whom received exercise therapy for low back pain. Half of the patients were randomized to additionally receive radiofrequency denervation (RFD) treatment. 88% of patients completed the 3-month follow-up, and 77% completed the 12-month follow-up. In this context, RFD provided no added benefit over the baseline of exercise therapy. In 2018, five authors, all experts in pain medicine, published a 'Daring Discourse' article in the journal Regional Anesthesia and Pain Medicine (RAPM), criticizing the findings of the MINT trials. Although 3 of the 5 authors of the RAPM 'Daring Discourse' article reported in conflict of interest statements-as is appropriate-that they were consultants to corporations that produce RFD equipment, the authors failed to disclose that 4 of 5 are on the editorial board of RAPM and all 5 are current officers in the medical organization that owns RAPM: that is, the American Society of Regional Anesthesia and Pain Medicine. Noteworthy, there was no published response from the MINT trial investigators to the Daring Discourse criticisms, either in the aforementioned example or in downstream venues where some of the same Daring Discourse authors continued their widely disseminated criticisms of the JAMA/MINT trials report. We believe that these actions taken by the Daring Discourse authors and RAPM have unfairly tipped the scales in the evaluation and application of RFD treatment of low back pain. In our commentary, we discuss: (1) the challenges associated with using clinical trials to predict clinical efficacy, (2) appropriate and inappropriate uses of postpublication commentary on original research findings, (3) the use of inappropriate commentary (and related means) to alter clinical practice in the presence of contradictory research findings, and (4) potential conflicts of interest related to the authors' and Journal's publication of the unopposed MINT trials criticism.

Effect of nitrous oxide use on long-term neurologic and neuropsychological outcome in patients who received temporary proximal artery occlusion during cerebral aneurysm clipping surgery.

BACKGROUND: The authors explored the relationship between nitrous oxide use and neurologic and neuropsychological outcome in a population of patients likely to experience intraoperative cerebral ischemia: those who had temporary cerebral arterial occlusion during aneurysm clipping surgery. METHODS: A post hoc analysis of a subset of the data from the Intraoperative Hypothermia for Aneurysm Surgery Trial was conducted. Only subjects who had temporary arterial occlusion during surgery were included in the analysis. Metrics of short-term and long-term (i.e., 3 months after surgery) outcome were evaluated via both univariate and multivariate logistic regression analysis. An odds ratio (OR) greater than 1.0 denotes a worse outcome in patients receiving nitrous oxide. RESULTS: The authors evaluated 441 patients, of which 199 received nitrous oxide. Patients receiving nitrous oxide had a greater risk of delayed ischemic neurologic deficits (i.e., the clinical manifestation of vasospasm) (OR, 1.78, 95% confidence interval [CI], 1.08-2.95; P = 0.025). However, at 3 months after surgery, there was no difference in any metric of gross neurologic outcome: Glasgow Outcome Score (OR, 0.67; CI, 0.44-1.03; P = 0.065), Rankin Score (OR, 0.74; CI, 0.47-1.16; P = 0.192), National Institutes of Health Stroke Scale (OR, 1.02; CI, 0.66-1.56; P = 0.937), or Barthel Index (OR, 0.69; CI, 0.38-1.25; P = 0.22). The risk of impairment on at least one test of neuropsychological function was reduced in those who received nitrous oxide (OR, 0.56; CI, 0.36-0.89; P = 0.013). CONCLUSION: In this patient population, use of nitrous oxide was associated with an increased risk for the development of delayed ischemic neurologic deficits; however, there was no evidence of detriment to long-term gross neurologic or neuropsychological outcome.

Effect of Promotion via Social Media on Access of Articles in an Academic Medical Journal: A Randomized Controlled Trial.

PURPOSE: To study the effect of a planned social media promotion strategy on access of online articles in an established academic medical journal. METHOD: This was a single-masked, randomized controlled trial using articles published in Mayo Clinic Proceedings, a large-circulation general/internal medicine journal. Articles published during the months of October, November, and December 2015 (n = 68) were randomized to social media promotion (SoMe) using Twitter, Facebook, and LinkedIn or to no social media promotion (NoSoMe), for 30 days (beginning with the date of online article publication). Journal website visits and full-text article downloads were compared for 0-30 and 31-60 days following online publication between SoMe versus NoSoMe using a Wilcoxon rank-sum test. RESULTS: Website access of articles from 0 to 30 days was significantly higher in the SoMe group (n = 34) compared with the NoSoMe group (n = 34): 1,070 median downloads versus 265, P < .001. Similarly, full-text article downloads from 0-30 days were significantly higher in the SoMe group: 1,042 median downloads versus 142, P < .001. Compared with the NoSoMe articles, articles randomized to SoMe received a greater number of website visits via Twitter (90 vs 1), Facebook (526 vs 2.5), and LinkedIn (31.5 vs 0)-all P < .001. CONCLUSIONS: Articles randomized to SoMe were more widely accessed compared with those without social media promotion. These findings show a possible role, benefit, and need for further study of a carefully planned social media promotion strategy in an academic medical journal.

Hyperglycemia in patients undergoing cerebral aneurysm surgery: its association with long-term gross neurologic and neuropsychological function.

OBJECTIVE: To evaluate whether elevated intraoperative blood glucose concentrations are associated with an increased risk of long-term neurologic dysfunction in patients at risk for ischemic brain injury. PATIENTS AND METHODS: Data from 1000 patients were retrieved from the Intraoperative Hypothermia for Aneurysm Surgery Trial database. All patients were recruited between February 2000 and April 2003, and underwent surgery for aneurysm clipping within 14 days of subarachnoid hemorrhage. Gross neurologic and neuropsychological function was evaluated at 3 months after surgery using certified observers and standardized assessment instruments. Intraoperative blood glucose concentrations, measured once when the aneurysm clip was placed, were correlated with neurologic outcome using both univariable and multivariable logistic regression analyses. RESULTS: Blood glucose concentrations at the time of aneurysm clipping ranged from 59 to 331 mg/dL. At 3 months after surgery, those with blood glucose concentrations of 129 mg/dL or more (upper 2 quartiles) were more likely to have impaired cognition (P=.03). Those with glucose concentrations of 152 mg/dL or more (upper quartile) were more likely to experience deficits in gross neurologic function assessed by the National Institutes of Health Stroke Scale (P<.05), but not other scoring scales. Length of stay in intensive care units was longer in those with glucose concentrations of 129 mg/dL or more, but there was no difference among glucose groups in the duration of overall hospital stay or the fraction of patients discharged to home. CONCLUSION: In patients at high risk for ischemic brain injury, intraoperative hyperglycemia, of a magnitude commonly encountered clinically, was associated with long-term changes in cognition and gross neurologic function.

Effect of nitrous oxide on neurologic and neuropsychological function after intracranial aneurysm surgery.

BACKGROUND: Laboratory studies suggest that nitrous oxide augments brain injury after ischemia or hypoxia. The authors examined the relation between nitrous oxide use and outcomes using data from the Intraoperative Hypothermia for Aneurysm Surgery Trial. METHODS: The Intraoperative Hypothermia for Aneurysm Surgery Trial was a prospective randomized study of the impact of intraoperative hypothermia (temperature = 33 degrees C) versus normothermia (temperature = 36.5 degrees C) in patients with aneurysmal subarachnoid hemorrhage undergoing surgical clipping. Anesthesia was dictated by a limited-options protocol with the use of nitrous oxide determined by individual anesthesiologists. All patients were assessed daily for 14 days after surgery or until hospital discharge. Neurologic and neuropsychological testing were conducted at 3 months after surgery. Outcome data were analyzed via both univariate tests and multivariate logistic regression analysis correcting for factors thought to influence outcome. An odds ratio (OR) greater than 1.0 denotes a worse outcome in patients receiving nitrous oxide. RESULTS: Outcome data were available for 1,000 patients, of which 373 received nitrous oxide. There was no difference between groups in the development of delayed ischemic neurologic deficit. At 3 months after surgery, there were no significant differences between groups in any outcome variable: Glasgow Outcome Score (OR, 0.84; 95% confidence interval [CI], 0.63-1.14; P = 0.268), National Institutes of Health Stroke Scale (OR, 1.29; 95% CI, 0.96-1.73; P = 0.087), Rankin Disability Score (OR, 0.84; 95% CI, 0.61-1.15; P = 0.284), Barthel Activities of Daily Living Index (OR, 1.01; 95% CI, 0.68-1.51; P = 0.961), or neuropsychological testing (OR, 1.26; 95% CI, 0.85-1.87; P = 0.252). CONCLUSIONS: In a population of patients at risk for ischemic brain injury, nitrous oxide use had no overall beneficial or detrimental impact on neurologic or neuropsychological outcomes.