Anemia and Optimal Transfusion Thresholds in Brain-Injured Patients: A Narrative Review of the Literature.

Anemia is a highly prevalent condition that may compromise oxygen delivery to vital organs, especially among the critically ill. Although current evidence supports the adoption of a restrictive transfusion strategy and threshold among the nonbleeding critically ill patient, it remains unclear whether this practice should apply to the brain-injured patient, given the predisposition to cerebral ischemia in this patient population, in which even nonprofound anemia may exert a detrimental effect on clinical outcomes. The purpose of this review is to provide an overview of the pathophysiological changes related to impaired cerebral oxygenation in the brain-injured patient and to present the available evidence on the effect of anemia and varying transfusion thresholds on the clinical outcomes of patients with acute brain injury.

Repeated blood-brain barrier opening with an implantable ultrasound device for delivery of albumin-bound paclitaxel in patients with recurrent glioblastoma: a phase 1 trial.

BACKGROUND: Low-intensity pulsed ultrasound with concomitant administration of intravenous microbubbles (LIPU-MB) can be used to open the blood-brain barrier. We aimed to assess the safety and pharmacokinetics of LIPU-MB to enhance the delivery of albumin-bound paclitaxel to the peritumoural brain of patients with recurrent glioblastoma. METHODS: We conducted a dose-escalation phase 1 clinical trial in adults (aged ≥18 years) with recurrent glioblastoma, a tumour diameter of 70 mm or smaller, and a Karnofsky performance status of at least 70. A nine-emitter ultrasound device was implanted into a skull window after tumour resection. LIPU-MB with intravenous albumin-bound paclitaxel infusion was done every 3 weeks for up to six cycles. Six dose levels of albumin-bound paclitaxel (40 mg/m2, 80 mg/m2, 135 mg/m2, 175 mg/m2, 215 mg/m2, and 260 mg/m2) were evaluated. The primary endpoint was dose-limiting toxicity occurring during the first cycle of sonication and albumin-bound paclitaxel chemotherapy. Safety was assessed in all treated patients. Analyses were done in the per-protocol population. Blood-brain barrier opening was investigated by MRI before and after sonication. We also did pharmacokinetic analyses of LIPU-MB in a subgroup of patients from the current study and a subgroup of patients who received carboplatin as part of a similar trial (NCT03744026). This study is registered with ClinicalTrials.gov, NCT04528680, and a phase 2 trial is currently open for accrual. FINDINGS: 17 patients (nine men and eight women) were enrolled between Oct 29, 2020, and Feb 21, 2022. As of data cutoff on Sept 6, 2022, median follow-up was 11·89 months (IQR 11·12-12·78). One patient was treated per dose level of albumin-bound paclitaxel for levels 1 to 5 (40-215 mg/m2), and 12 patients were treated at dose level 6 (260 mg/m2). A total of 68 cycles of LIPU-MB-based blood-brain barrier opening were done (median 3 cycles per patient [range 2-6]). At a dose of 260 mg/m2, encephalopathy (grade 3) occurred in one (8%) of 12 patients during the first cycle (considered a dose-limiting toxicity), and in one other patient during the second cycle (grade 2). In both cases, the toxicity resolved and treatment continued at a lower dose of albumin-bound paclitaxel, with a dose of 175 mg/m2 in the case of the grade 3 encephalopathy, and to 215 mg/m2 in the case of the grade 2 encephalopathy. Grade 2 peripheral neuropathy was observed in one patient during the third cycle of 260 mg/m2 albumin-bound paclitaxel. No progressive neurological deficits attributed to LIPU-MB were observed. LIPU-MB-based blood-brain barrier opening was most commonly associated with immediate yet transient grade 1-2 headache (12 [71%] of 17 patients). The most common grade 3-4 treatment-emergent adverse events were neutropenia (eight [47%]), leukopenia (five [29%]), and hypertension (five [29%]). No treatment-related deaths occurred during the study. Imaging analysis showed blood-brain barrier opening in the brain regions targeted by LIPU-MB, which diminished over the first 1 h after sonication. Pharmacokinetic analyses showed that LIPU-MB led to increases in the mean brain parenchymal concentrations of albumin-bound paclitaxel (from 0·037 µM [95% CI 0·022-0·063] in non-sonicated brain to 0·139 µM [0·083-0·232] in sonicated brain [3·7-times increase], p<0·0001) and carboplatin (from 0·991 µM [0·562-1·747] in non-sonicated brain to 5·878 µM [3·462-9·980] µM in sonicated brain [5·9-times increase], p=0·0001). INTERPRETATION: LIPU-MB using a skull-implantable ultrasound device transiently opens the blood-brain barrier allowing for safe, repeated penetration of cytotoxic drugs into the brain. This study has prompted a subsequent phase 2 study combining LIPU-MB with albumin-bound paclitaxel plus carboplatin (NCT04528680), which is ongoing. FUNDING: National Institutes of Health and National Cancer Institute, Moceri Family Foundation, and the Panattoni family.

Electroencephalographic Burst-Suppression, Perioperative Neuroprotection, Postoperative Cognitive Function, and Mortality: A Focused Narrative Review of the Literature.

Burst-suppression is an electroencephalographic pattern that results from a diverse array of pathophysiological causes and/or metabolic neuronal suppression secondary to the administration of anesthetic medications. The purpose of this review is to provide an overview of the physiological mechanisms that underlie the burst-suppression pattern and to present in a comprehensive way the available evidence both supporting and in opposition to the clinical use of this electroencephalographic pattern as a therapeutic measure in various perioperative settings.

Cautionary findings for motor evoked potential monitoring in intracranial aneurysm surgery after a single administration of rocuronium to facilitate tracheal intubation.

Administration of rocuronium to facilitate intubation has traditionally been regarded as acceptable for intraoperative motor evoked potential (MEP) monitoring because of sufficiently rapid spontaneous neuromuscular blockade recovery. We hypothesized that residual neuromuscular blockade, in an amount that could hinder optimal neuromonitoring in patients undergoing intracranial aneurysm clipping, was still present at dural opening. We sought to identify how often this was occurring and to identify factors which may contribute to prolonged blockade. Records of 97 patients were retrospectively analyzed. Rocuronium was administered to facilitate intubation with no additional neuromuscular blockade given. Prolonged spontaneous recovery time to a train-of-four (TOF) ratio of 0.75 after rocuronium administration was defined as 120 min, which was approximately when dural opening and the setting of baseline MEPs were occurring. Logistic regression analysis was used to identify factors related to prolonged spontaneous recovery time. Prolonged spontaneous recovery time to a TOF ratio of 0.75 was observed in 44.3% of patients. Multivariable analysis showed that only the dosage of rocuronium based on ideal body weight had a positive correlation with prolonged spontaneous recovery time (P = 0.01). There was no significant association between dosage of rocuronium based on total body weight, age, sex, or body temperature and prolonged recovery time. This study demonstrates that the duration of relaxation for MEP monitoring purposes is well-beyond the routinely recognized clinical duration of rocuronium. Residual neuromuscular blockade could result in lower amplitude MEP signals and/or lead to higher required MEP stimulus intensities which can both compromise monitoring sensitivity.

Sevoflurane versus PRopofol combined with Remifentanil anesthesia Impact on postoperative Neurologic function in supratentorial Gliomas (SPRING): protocol for a randomized controlled trial.

BACKGROUND: Patients with intracranial tumors are more sensitive to anesthetics than the general population and are therefore more susceptible to postoperative neurologic and neurocognitive dysfunction. Sevoflurane or propofol combined with remifentanil are widely used general anesthetic regimens for craniotomy, with neither regimen shown to be superior to the other in terms of neuroprotective efficacy and anesthesia quality. There is no evidence regarding the variable effects on postoperative neurologic and neurocognitive functional outcome under these two general anesthetic regimens. This trial will compare inhalational sevoflurane or intravenous propofol combined with remifentanil anesthesia in patients with supratentorial gliomas and test the hypothesis that postoperative neurologic function is equally affected between the two regimens. METHODS: This is a prospective, single-center, randomized parallel arm equivalent clinical trial, which is approved by China Ethics Committee of Registering Clinical Trials (ChiECRCT-20,160,051). Patients with supratentorial gliomas diagnosed by magnetic resonance imaging will be eligible for the trial. Written informed consent will be obtained before randomly assigning each subject to either the sevoflurane-remifentanil or propofol-remifentanil group for anesthesia maintenance to achieve an equal-desired depth of anesthesia. Intraoperative intervention and monitoring will follow a standard anesthetic management protocol. All of the physiological parameters and other medications administered during the intervention will be recorded. The primary outcome will be neurologic function change assessed by National Institute of Health Stroke Scale (NIHSS) within 4 h after general anesthesia when observer's assessment of alertness/sedation (OAA/S) reaches 4. Secondary outcomes will include NIHSS and modified NIHSS change 1 and 2 days after general anesthesia, hemodynamic stability, intraoperative brain relaxation, quality of anesthesia emergence, quality of anesthesia recovery, postoperative cognitive function, postoperative pain, postoperative neurologic complications, as well as perioperative medical expense. DISCUSSION: This randomized equivalency trial will primarily compare the impacts of sevoflurane-remifentanil and propofol-remifentanil anesthesia on short-term postoperative neurologic function in patients with supratentorial gliomas undergoing craniotomy. The exclusion criteria are strict to ensure that the groups are comparable in all aspects. Repeated and routine neurologic evaluations after operation are always important to evaluate neurosurgical patients' recovery and any newly presenting complications. The results of this trial would help specifically to interpret anesthetic residual effects on postoperative outcomes, and perhaps would help the anesthesiologist to select the optimal anesthetic regimen to minimize its impact on neurologic function in this specific patient population. TRIAL REGISTRATION: The study was registered and approved by the Chinese Clinical Trial Registry (Chinese Clinical Trial Registry, ChiCTR-IOR-16009177). Principle investigator: Nan Lin (email address: linnan127@gmail.com) and Ruquan Han (email address: hanrq666@aliyun.com) Date of Registration: September 8th, 2016. Country of recruitment: China.

Somatosensory evoked potential loss due to intraoperative pulse lavage during spine surgery: case report and review of signal change management.

Intraoperative neurophysiologic monitoring (IONM) includes various neurophysiologic tests which assess the functional integrity of the central and peripheral nervous systems during surgical procedures which place these structures at risk for iatrogenic injury. The rational for using IONM is to provide timely feedback of changes in neural function to enable the reversal of such insult before the development of irreversible neural injury. There are various causes of intraoperative loss of neuromonitoring signals and it is important to systematically rule out all possible causes quickly and thoroughly in order to target the cause of signal loss, correct it and take measures to prevent the same in the future. One such rare cause, is targeted and pressurized cold (room temperature) irrigation of the surgical site, which may induce irritation and vasospasm leading to ischemia of the affected portion of the spinal cord, hence leading to signal changes. We present this case to stress the importance of having knowledgeable members of the team who are well acquainted with all aspects of monitoring in close proximity to the operating room, so as to minimize troubleshooting time. Furthermore, we suggest the use of warm (body temperature) saline during irrigation to the surgical site, especially when using pressurized irrigation systems.

A comparison of hemoglobin measured by co-oximetry and central laboratory during major spine fusion surgery.

BACKGROUND: Many factors affect the accuracy of hemoglobin concentration values. In this study, we evaluated whether the hemoglobin concentration obtained by means of arterial blood gas (ABG) co-oximetry and complete blood count (CBC) central laboratory techniques clinically correlate when using simultaneous measurements of hemoglobin concentration obtained during complex spine fusion surgery. METHODS: Three hundred forty-eight patients who underwent spinal fusion of >3 bony levels between September 2006 and September 2010, with concurrent ABG and CBC samples, were identified. The mean difference between pairs of measured hemoglobin values was determined using limits of agreement analysis. Error grid analysis was used to delineate correlation of samples in relation to hemoglobin values within the range considered for transfusion. RESULTS: The median difference (ABG-CBC) between the measured hemoglobin values was 0.4 g/dL (95% confidence interval [CI], 0.35-0.40 g/dL; P < 0.0001). Limits of agreement analysis correcting for repeated observations in multiple patients demonstrated that the mean difference between measured hemoglobin values (i.e., bias) was 0.4 g/dL (95% CI, 0.36-0.41 g/dL), and the 95% limits of agreement of the difference between paired measurements were -0.70 to 1.47 g/dL. The magnitude of the difference between the measured hemoglobin values was >0.5 g/dL in 44.5% of patients (95% CI, 42.2%-46.8%); however, 6.8% (95% CI, 5.8%-8.1%) of paired measurements had a difference of >1.0 g/dL. There was only fair-to-moderate agreement between the CBC and ABG values within the clinically significant range of hemoglobin values of 7 to 10 g/dL (Cohen κ = 0.39; 95% CI, 0.33-0.45). CONCLUSIONS: The hemoglobin values obtained from ABG and CBC cannot be used interchangeably when verifying accuracy of novel point-of-care hemoglobin measurement modalities or when managing a patient with critical blood loss.

Nicardipine is superior to esmolol for the management of postcraniotomy emergence hypertension: a randomized open-label study.

BACKGROUND: Emergence hypertension after craniotomy is a well-documented phenomenon for which natural history is poorly understood. Most clinicians attribute this phenomenon to an acute and transient increase in catecholamine release, but other mechanisms such as neurogenic hypertension or activation of the renin-angiotensin-aldosterone system have also been proposed. In this open-label study, we compared the monotherapeutic antihypertensive efficacy of the 2 most titratable drugs used to treat postcraniotomy emergence hypertension: nicardipine and esmolol. We also investigated the effect of preoperative hypertension on postcraniotomy hypertension and the natural history of postcraniotomy hypertension in the early postoperative period. METHODS: Fifty-two subjects were prospectively randomized to receive either nicardipine or esmolol as the sole drug for treatment of emergence hypertension at the conclusion of brain tumor resection (40 subjects finally analyzed). After a uniform anesthetic, standardized protocols of these antihypertensive medications were administered for the treatment of systolic blood pressure (SBP) >130, with the goal of maintaining SBP <140 throughout the first postoperative day. In the event of study medication "failure," a "rescue" antihypertensive (labetalol or hydralazine) was used. The O'Brien-Fleming Spending Function was used to calculate the appropriate α value for each interim analysis of the primary outcome; univariate analysis was performed otherwise, with a 2-sided P<0.05 considered statistically significant. RESULTS: The incidence of nicardipine failure (5%, 95% confidence interval [CI] 0.1%-24.9%) was significantly less than that of esmolol (55%, 95% CI 31.5%-76.9%) as a sole drug in controlling SBP after brain tumor resection (difference 99% CI 13.8%-75.7%, P = 0.0012). The presence of preoperative hypertension or the approach to surgery (open craniotomy versus endonasal transsphenoidal) had no significant effect on the incidence of failure of the antihypertensive regimen used. We did not observe a difference in the need for opioid therapy for postcraniotomy pain between drug groups (99% CI difference -39.2%-30.2%). Failure of the study drug predicted the need for rescue drug therapy in the initial 12 hours after discharge from the recovery room (difference success versus failure = -41.7%, 99% CI difference -72.3% to -1.8%, P = 0.0336) but not during the period 12 to 24 hours after discharge from the recovery room (difference success versus failure = -27.4%, 99% CI difference -63.8%-9.2%, P = 0.143). However, in those patients carrying a preoperative diagnosis of hypertension, the need for rescue medication was only different during the period 12 to 24 hours after discharge from the recovery room (difference normotensive versus hypertensive = -35.4%, 99% CI difference -66.9% to -0.3%, P = 0.0254). CONCLUSIONS: Nicardipine is superior to esmolol for the treatment of postcraniotomy emergence hypertension. This type of hypertension is thought to be a transient phenomenon not solely related to sympathetic activation and catecholamine surge but also possibly encompassing other physiologic factors. For treating postcraniotomy emergence hypertension, nicardipine is a relatively effective sole drug, whereas if esmolol is used, rescue antihypertensive medications should be readily available.

Abdominal circumference but not the degree of lumbar flexion affects the accuracy of lumbar interspace identification by Tuffier's line palpation method: an observational study.

BACKGROUND: Lumbar puncture for spinal or epidural anesthesia is commonly performed by palpating bony landmarks, but identification of the desired intervertebral level is often inaccurate. It is unclear whether such inaccuracy is related to patient factors, such as body mass index and degree of lumbar flexion. We hypothesized that overweight patients and patients with less of an ability to hyperflex their lumbar spines are prone to inaccurate lumbar spinous intervertebral level identification. METHODS: 52 adult volunteers were included in this study. 7 anesthesiologists with different years of experience identified and marked subjects' levels of the iliac crests, then marked the presumed interspaces. Lumbar X-ray was then performed with metal markers, and actual radiographic findings were identified and compared to the initial markings. RESULTS: Patients with larger abdominal circumferences (mean (SD), 94.0(12.1) cm), higher body mass indices (25.9(3.9) kg/m(2)), and aged between 50 and 70 years old had lumbar interspaces that were higher than the presumed level; patients with smaller abdominal circumferences (82.8(13.5) cm) and lower body mass indices (21.6(4.1) kg/m(2)) had intervertebral levels that were lower than the presumed level. Cobb's angle, indicating the degree of lumbar flexion, did not affect the accuracy obtained. CONCLUSIONS: Patients' abdominal circumference, body mass index, and age are factors that may impact the accuracy of lumbar level identification. Tuffier's line, as identified by palpation, does not seem to be a reliable landmark for proper lumbar interspace identification in all cases.

Regional Anesthesia Techniques in Modern Neuroanesthesia Practice: A Narrative Review of the Clinical Evidence.

Neurosurgical procedures are often associated with significant postoperative pain that is both underrecognized and undertreated. Given the potentially undesirable side effects associated with general anesthesia and with various pharmacological analgesic regimens, regional anesthetic techniques have gained in popularity as alternatives for providing both anesthesia and analgesia for the neurosurgical patient. The aim of this narrative review is to present an overview of the regional techniques that have been incorporated and continue to be incorporated into modern neuroanesthesia practice, presenting in a comprehensive way the evidence, where available, in support of such practice for the neurosurgical patient.

Perioperative Methadone for Spine Surgery: A Scoping Review.

Complex spine surgery is associated with significant acute postoperative pain. Methadone possesses pharmacological properties that make it an attractive analgesic modality for major surgeries. This scoping review aimed to summarize the evidence for the perioperative use of methadone in adults undergoing complex spine surgery. The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). A search was performed using MEDLINE, CINAHL, Cochrane Library, Scopus, Embase, and Joanna Briggs between January 1946 and April 2023. The initial search identified 317 citations, of which 12 met the criteria for inclusion in the review. There was significant heterogeneity in the doses, routes of administration, and timing of perioperative methadone administration in the included studies. On the basis of the available literature, methadone has been associated with reduced postoperative pain scores and reduced postoperative opioid consumption. Though safety concerns have been raised by observational studies, these have not been confirmed by prospective randomized studies. Further research is required to explore optimal methadone dosing regimens, the potential synergistic relationships between methadone and other pharmacological adjuncts, as well as the potential long-term antinociceptive benefits of perioperative methadone administration.

Adenosine-induced flow arrest to facilitate intracranial aneurysm clip ligation does not worsen neurologic outcome.

BACKGROUND: When temporary arterial occlusion of the parent artery is difficult for anatomical reasons, or when inadvertent aneurysmal rupture occurs during surgical dissection, adenosine administration can be used to produce flow arrest and brief, profound systemic hypotension that can facilitate intracranial aneurysm clip ligation. There is a concern, however, that the flow arrest and profound hypotension produced by adenosine, although brief, may cause cerebral ischemia and therefore worsen neurologic outcome compared with other techniques to facilitate aneurysm clip ligation. Therefore, we performed a retrospective, case-control study to determine whether adenosine-induced flow arrest had negative effects on the neurologic outcome of our patients. METHODS: We reviewed the perioperative records of all patients in our intracranial aneurysm surgery outcomes database between August 1, 2006, and June 15, 2012. The primary outcome was the presence or absence of a poor neurologic outcome 48 hours after surgery, with a modified Rankin scale score >2 being defined as a poor neurologic outcome. The neurologic outcome at the time of hospital discharge was a secondary outcome. Secondary outcomes related to cardiac morbidity included atrial or ventricular arrhythmia requiring treatment and elevated cardiac biomarkers consistent with ischemia (i.e., Troponin-I). RESULTS: During the study period, adenosine-induced flow arrest was used in 72 of the 413 patients (17.4%) who underwent intracranial aneurysm clip ligation. The difference in the incidence of poor neurological outcome, with or without the use of adenosine, was no larger than 15.7% at 48 hours after surgery (P =0.524) or -12.7% at discharge (P = 0.741). In addition, the difference in the incidence of cardiac morbidity was no larger than -16.0% for persistent arrhythmia (P = 0.155) or -9.4% for biomarkers of myocardial ischemia (P = 0.898) in the initial 48 hours after surgery. CONCLUSION: When used to facilitate intracranial aneurysm clip ligation, adenosine-induced flow arrest was associated with no more than a 15.7% increase or a 12.7% decrease in the incidence of a poor neurologic outcome at either 48 hours or at the time of hospital discharge. In addition, adenosine use was not associated with cardiac morbidity in the perioperative period (i.e., persistent arrhythmia or biomarkers of cardiac ischemia).

Multimodal Analgesia and Intraoperative Neuromonitoring.

Intraoperative neuromonitoring has been a valuable tool for ensuring the functional integrity of vital neural structures by providing real-time feedback to the operative team during procedures where neurological structures are at risk. Commonly used intravenous and inhaled anesthetic drugs are known to affect waveform parameters measured with various intraoperative neuromonitoring modalities. While the concept of opioid-sparing multimodal analgesia has gained popularity in recent years, the impact of such a strategy on intraoperative neuromonitoring remains poorly characterized, in contrast to the more well-established concepts and literature regarding the effects of other hypnotic agents on neuromonitoring quality. The purpose of this focused review is to provide an overview of the clinical evidence pertaining to the pharmacological interaction of certain multimodal analgesics with routine intraoperative neuromonitoring modalities.

Optimal Hemodynamic Parameters for Brain-injured Patients in the Clinical Setting: A Narrative Review of the Evidence.

Defining optimal hemodynamic targets for brain-injured patients is a challenging undertaking. The physiological interference observed in various intracranial pathologies can have varying effects on cerebral physiology at different time points. This narrative review provides an overview of cerebral autoregulatory physiology and common misconceptions, and examines the physiological considerations and clinical evidence for determining optimal hemodynamic parameters in acutely brain-injured patients with relevance to modern neuroanesthesia and neurocritical care practice.

Albumin Use in Brain-injured and Neurosurgical Patients: Concepts, Indications, and Controversies.

Human albumin has been used extensively for decades as a nonwhole blood plasma replacement fluid in the perioperative and critical care setting. Its potential advantages as a highly effective volume expander must be weighed, however, against its potential harm for patients in the context of various neurological states and for various neurosurgical interventions. This narrative review explores the physiological considerations of intravenous human albumin as a replacement fluid and examines the extant clinical evidence for and against its use within the various facets of modern neuroanesthesia and neurocritical care practice.

Adenosine-induced flow arrest to facilitate intracranial aneurysm clip ligation: dose-response data and safety profile.

BACKGROUND: Adenosine-induced transient flow arrest has been used to facilitate clip ligation of intracranial aneurysms. However, the starting dose that is most likely to produce an adequate duration of profound hypotension remains unclear. We reviewed our experience to determine the dose-response relationship and apparent perioperative safety profile of adenosine in intracranial aneurysm patients. METHODS: This case series describes 24 aneurysm clip ligation procedures performed under an anesthetic consisting of remifentanil, low-dose volatile anesthetic, and propofol in which adenosine was used. The report focuses on the doses administered; duration of systolic blood pressure <60 mm Hg (SBP(<60 mm Hg)); and any cardiovascular, neurologic, or pulmonary complications observed in the perioperative period. RESULTS: A median dose of 0.34 mg/kg ideal body weight (range: 0.29-0.44 mg/kg) resulted in a SBP(<60 mm Hg) for a median of 57 seconds (range: 26-105 seconds). There was a linear relationship between the log-transformed dose of adenosine and the duration of a SBP(<60 mm Hg) (R(2) = 0.38). Two patients developed transient, hemodynamically stable atrial fibrillation, 2 had postoperative troponin levels >0.03 ng/mL without any evidence of cardiac dysfunction, and 3 had postoperative neurologic changes. CONCLUSIONS: For intracranial aneurysms in which temporary occlusion is impractical or difficult, adenosine is capable of providing brief periods of profound systemic hypotension with low perioperative morbidity. On the basis of these data, a dose of 0.3 to 0.4 mg/kg ideal body weight may be the recommended starting dose to achieve approximately 45 seconds of profound systemic hypotension during a remifentanil/low-dose volatile anesthetic with propofol induced burst suppression.

Alternative anterior reference sites for measuring posterior tibial nerve somatosensory evoked potentials.

OBJECTIVE: The purpose of this study was to examine the utility and feasibility of using alternative anterior reference leads when measuring left posterior tibial nerve somatosensory evoked potentials (SEPs). METHODS: With IRB approval, 12 patients were monitored using both traditional (FPz and C4') and alternative anterior (F3 and F4) reference leads during routine spine surgery with SEP monitoring. Recordings from the routine and novel electrode pairs were collected and analyzed. RESULTS: All of the SEP amplitudes measured were of similar magnitude except for that of F3-F4, which was significantly lower (P < 0.001) than all of the other five lead combinations which were assessed (Cz'-FPz, C3'-C4', C3'-F4, Cz'-F3, and Cz'-F4). The latencies of the novel lead combinations (C3'-F4, Cz'-F3, Cz'-F4, and F3-F4) were similar to those of the "gold standards" (Cz'-FPz and C3'-C4') (pooled median, 45.6 ms with 25-75th percentiles, 44.0-47.8 ms, P = 0.308). The coefficients of variation (CV %) of the amplitudes were not statistically significantly different (P = 0.341). CONCLUSIONS: The use of alternative frontal reference leads (F3 and F4) for left posterior tibial nerve SEP monitoring yields signals of equal quality and reproducibility compared to signals with standard (FPz and C4') referencing. These alternative leads may substitute for traditional referencing when placement of FPz or C4' is precluded by the location of surgery.

Perspectives on Dexmedetomidine Use for Neurosurgical Patients.

The α2-adrenergic receptor agonist dexmedetomidine has sedative, anxiolytic, analgesic, and sympatholytic effects. The potential advantages of neuroprotection, minimal impact on neuronal function, stable hemodynamics, opioid and anesthesia sparing effects, and minimal respiratory depression during awake procedures render it an effective anesthetic adjuvant in various neurosurgical settings. However, both the benefits and drawbacks of the use dexmedetomidine in neuroanesthesia should be considered. This narrative review will summarize the applications of dexmedetomidine in various neurosurgical settings, highlighting evidence regarding both its common and controversial uses.