Unusual Manifestations of the Trigeminocardiac Reflex During Awake Craniotomy: A Case Report and Review of the Literature.

The trigeminocardiac reflex (TCR) is triggered by stimulation of a branch of the trigeminal nerve and results in vagally mediated bradycardia, hypotension, apnea, and gastrointestinal hypermotility. In the operating theatre, patients susceptible to TCR are typically under general anesthesia; thus, cardiac abnormalities are the most common manifestation. Our case highlights the less common intraoperative manifestations of gastric hypermotility and apnea in a patient undergoing awake craniotomy for tumor resection. Prompt recognition, removal of stimuli, and airway management prevented catastrophic complications while facilitating completion of the procedure.

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.

Correlation Between Processed Electroencephalogram and Clinical Findings During Wake-Up Test in Prone Position for Scheduled Posterior Cervical Spine Surgery: A Case Report.

A 65-year-old man undergoing posterior cervical decompression and fusion demonstrated absent lower extremity evoked potential (EP) after prone positioning and before incision. Localized EP change pointed to either a technical or positional culprit. After excluding technical causes, we performed a wake-up test to rule out positioning as the culprit. During the test, we observed both symmetrical and asymmetrical hemispheric changes in density spectral array ß and γ bands that correlated with awakening, eye-opening, and extremity movements. By providing real-time information on brain state, processed electroencephalogram (EEG) can facilitate a safe wake-up test by showing high-power ß and γ activities that precede awakening.

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.

Correction to: Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary.

The article Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary, written by Stanley A. Skinner, Elif Ilgaz Aydinlar, Lawrence F. Borges, Bob S. Carter, Bradford L. Currier, Vedran Deletis, Charles Dong, John Paul Dormans, Gea Drost, Isabel Fernandez­Conejero, E. Matthew Hoffman, Robert N. Holdefer, Paulo Andre Teixeira Kimaid, Antoun Koht, Karl F. Kothbauer, David B. MacDonald, John J. McAuliffe III, David E. Morledge, Susan H. Morris, Jonathan Norton, Klaus Novak, Kyung Seok Park, Joseph H. Perra, Julian Prell, David M. Rippe, Francesco Sala, Daniel M. Schwartz, Martín J. Segura, Kathleen Seidel, Christoph Seubert, Mirela V. Simon, Francisco Soto, Jeffrey A. Strommen, Andrea Szelenyi, Armando Tello, Sedat Ulkatan, Javier Urriza and Marshall Wilkinson, was originally published electronically on the publisher's internet portal (currently SpringerLink) on 05 January 2019 without open access. With the author(s)' decision to opt for Open Choice the copyright of the article changed on 30 January 2019 to © The Author(s) 2019 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made. The original article has been corrected.

Loss of intraoperative neurological monitoring signals during flexed prone positioning on a hinged open frame during surgery for kyphoscoliosis correction: case report.

Various complications of prone positioning in spine surgery have been described in the literature. Patients in the prone position for extended periods are subject to neurological deficits and/or loss of intraoperative signals due to compression neuropathies, but positioning-related spinal deficits are rare in the thoracolumbar deformity population. The authors present a case of severe kyphoscoliotic deformity with critical thoracolumbar stenosis in which, during the use of a hinged open frame in the prone position, complete loss of intraoperative neural monitoring signals occurred while the frame was flexed into kyphosis to facilitate exposure and instrumentation placement. When the frame was reset to a neutral position, evoked potentials returned to baseline and the operation proceeded without complications. This case represents, to the authors' knowledge, the first report of loss of evoked potentials due to an alteration of prone positioning on a hinged open frame. When positioning patients in such a manner, careful attention should be directed to intraoperative signals in patients with critical stenosis and kyphotic deformity.

A Randomized Controlled Trial of Low-Dose Tranexamic Acid versus Placebo to Reduce Red Blood Cell Transfusion During Complex Multilevel Spine Fusion Surgery.

BACKGROUND: Multilevel spine fusion surgery for adult deformity correction is associated with significant blood loss and coagulopathy. Tranexamic acid reduces blood loss in high-risk surgery, but the efficacy of a low-dose regimen is unknown. METHODS: Sixty-one patients undergoing multilevel complex spinal fusion with and without osteotomies were randomly assigned to receive low-dose tranexamic acid (10 mg/kg loading dose, then 1 mg·kg-1·hr-1 throughout surgery) or placebo. The primary outcome was the total volume of red blood cells transfused intraoperatively. RESULTS: Thirty-one patients received tranexamic acid, and 30 patients received placebo. Patient demographics, risk of major transfusion, preoperative hemoglobin, and surgical risk of the 2 groups were similar. There was a significant decrease in total volume of red blood cells transfused (placebo group median 1460 mL vs. tranexamic acid group 1140 mL; median difference 463 mL, 95% confidence interval 15 to 914 mL, P = 0.034), with a decrease in cell saver transfusion (placebo group median 490 mL vs. tranexamic acid group 256 mL; median difference 166 mL, 95% confidence interval 0 to 368 mL, P = 0.042). The decrease in packed red blood cell transfusion did not reach statistical significance (placebo group median 1050 mL vs. tranexamic acid group 600 mL; median difference 300 mL, 95% confidence interval 0 to 600 mL, P = 0.097). CONCLUSIONS: Our results support the use of low-dose tranexamic acid during complex multilevel spine fusion surgery to decrease total red blood cell transfusion.

Awake Surgery for Brain Vascular Malformations and Moyamoya Disease.

OBJECTIVE: Although a significant amount of experience has accumulated for awake procedures for brain tumor, epilepsy, and carotid surgery, its utility for intracranial neurovascular indications remains largely undefined. Awake surgery for select neurovascular cases offers the advantage of precise brain mapping and robust neurologic monitoring during surgery for lesions in eloquent areas, avoidance of potential hemodynamic instability, and possible faster recovery. It also opens the window for perilesional epileptogenic tissue resection with potentially less risk for iatrogenic injury. METHODS: Institutional review board approval was obtained for a retrospective review of awake surgeries for intracranial neurovascular indications over the past 36 months from a prospectively maintained quality database. We reviewed patients' clinical indications, clinical and imaging parameters, and postoperative outcomes. RESULTS: Eight consecutive patients underwent 9 intracranial neurovascular awake procedures conducted by the senior author. A standardized "sedated-awake-sedated" protocol was used in all 8 patients. For the 2 patients with arteriovenous malformations and the 3 patients with cavernoma, awake brain surface and white matter mapping was performed before and during microsurgical resection. A neurological examination was obtained periodically throughout all 5 procedures. There were no intraoperative or perioperative complications. Hypotension was avoided during the 2 Moyamoya revascularization procedures in the patient with a history of labile blood pressure. Postoperative imaging confirmed complete arteriovenous malformation and cavernoma resections. No new neurologic deficits or new-onset seizures were noted on 3-month follow-up. CONCLUSIONS: Awake surgery appears to be safe for select patients with intracranial neurovascular pathologies. Potential advantages include greater safety, shorter length of stay, and reduced cost.

A Case Report of Onyx Pulmonary Arterial Embolism Contributing to Hypoxemia During Awake Craniotomy for Arteriovenous Malformation Resection.

A healthy 26-year-old man with cerebral arteriovenous malformation underwent staged endovascular embolization with Onyx followed by awake craniotomy for resection. The perioperative course was complicated by tachycardia and severe intraoperative hypoxemia requiring significant oxygen supplementation. Postoperative chest computed tomography (CT) revealed hyperattenuating Onyx embolization material within the pulmonary vasculature, and an electrocardiogram indicated possible right heart strain, supporting clinically significant embolism. With awake arteriovenous malformation resection following adjunctive Onyx embolization becoming increasingly employed for lesions involving the eloquent cortex, anesthesiologists need to be aware of pulmonary migration of Onyx material as a potential contributor to significant perioperative hypoxemia.

Factors associated with blood transfusion during intracranial aneurysm surgery.

STUDY OBJECTIVE: The purpose of this study was to identify risk factors associated with intraoperative blood transfusions in patients presenting for intracranial aneurysm surgery in the current era of more restrictive transfusion guidelines. DESIGN: Retrospective observational cohort study with stepwise, multivariate binary logistic regression analysis. SETTING: Tertiary care university teaching hospital. PATIENTS: Four hundred seventy-one consecutive patients undergoing intracranial aneurysm surgery at Northwestern Memorial Hospital (Chicago, IL) from 2006 to 2012. INTERVENTION: Red blood cell transfusion (retrospective observational). MEASUREMENTS: Demographic data, medical comorbidities, hemoglobin levels, Hunt-Hess grades, intracranial aneurysm characteristics, presenting intracranial bleeding states, estimated blood losses, transfused red blood cells, and blood products. MAIN RESULTS: Forty-six patients (9.5%) received intraoperative red blood cell transfusions. Preoperative risk factors associated with transfusions were highly related to aneurysm rupture, including such parameters as older age (P < .001), lower presenting hemoglobin level (P < .001), preoperative rupture (P < .001), and higher Hunt-Hess grade (P < .001). Intraoperative risk factors included larger aneurysm size (>10 mm; P = .03), intraventricular hemorrhage (P < .001), and intracerebral hematoma evacuation (P = .02). Binary logistic regression modeling identified age (P < .001), presenting hemoglobin level (P < .001), larger aneurysm size (>10 mm; P = .003), elevated Hunt-Hess grade (P = .021), and intraoperative rupture (P = .013) as independent predictors of intraoperative red blood cell transfusion. CONCLUSION: The incidence of intraoperative red blood cell transfusion in intracranial aneurysm surgery in our patient cohort was 9.5%, and the most significant factors associated with transfusion were presenting hemoglobin level less than 11.7 g/dL and age greater than 52 years. It would seem advisable that these patients undergo routine type and cross-matching of red blood cells before intracranial aneurysm surgery.

Multidose Adenosine Used to Facilitate Microsurgical Clipping of a Cerebral Aneurysm Complicated by Intraoperative Rupture: A Case Report.

In some cases of cerebral aneurysm clipping, direct clip application to the aneurysm neck may be difficult or the aneurysm may rupture unexpectedly. In these cases, a clip may be temporarily applied to the parent artery to reduce aneurysmal wall tension, facilitate permanent clip placement, or control bleeding if the aneurysm ruptures. In certain circumstances, even applying a temporary clip may be challenging. We present a case in which the aneurysm ruptured and IV administration of adenosine was required to facilitate clipping. This case suggests that administering multiple consecutive precalculated doses of adenosine may be a safe method to manage aneurysmal rupture.

Insertion of intra-oral electrodes for cranial nerve monitoring using a Crowe-Davis retractor.

Acoustic neuroma resection is an example of a neurosurgical procedure where the brainstem and multiple cranial nerves are at risk for injury. Electrode placement for monitoring of the glossopharyngeal and hypoglossal nerves during acoustic neuroma resection can be challenging. The purpose of this report is to illustrate the use of a device for intra-oral electrode placement for intraoperative monitoring of the glossopharyngeal and hypoglossal nerves. A 60-year-old male presented for acoustic neuroma resection. Under general anesthesia, a Crowe-Davis retractor was used to open the mouth, providing access to the posterior pharynx. For glossopharyngeal monitoring, two bent subdermal needle electrodes were inserted just lateral to the uvula. Two additional electrodes were inserted on the lateral tongue to monitor the hypoglossal nerve. Cranial nerves monitoring was conducted utilizing both free running and triggered electromyography of the trigeminal and facial nerves in addition to the lower cranial nerves. The tumor was resected successfully. Monitoring of the cranial nerves (including the glossopharyngeal and hypoglossal nerves) revealed no concerning responses. The Crowe-Davis retractor and the technique described allowed insertion of electrodes for neural monitoring, contributing to neural preservation.

Intraoperative Monitoring: Recent Advances in Motor Evoked Potentials.

Advances in electrophysiological monitoring have improved the ability of surgeons to make decisions and minimize the risks of complications during surgery and interventional procedures when the central nervous system (CNS) is at risk. Individual techniques have become important for identifying or mapping the location and pathway of critical neural structures. These techniques are also used to monitor the progress of procedures to augment surgical and physiologic management so as to reduce the risk of CNS injury. Advances in motor evoked potentials have facilitated mapping and monitoring of the motor tracts in newer, more complex procedures.

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.

Intraoperative neurophysiological monitoring during spine surgery with total intravenous anesthesia or balanced anesthesia with 3% desflurane.

Total intravenous anesthesia (TIVA) with propofol and opioids is frequently utilized for spinal surgery when somatosensory evoked potentials (SSEPs) and transcranial motor evoked potentials (tcMEPs) are monitored. Many anesthesiologists would prefer to utilize low dose halogenated anesthetics (e.g. 1/2 MAC). We examined our recent experience using 3% desflurane or TIVA during spine surgery to determine the impact on propofol usage and on the evoked potential responses. After institutional review board approval we conducted a retrospective review of a 6 month period for adult spine patients who were monitored with SSEPs and tcMEPs. Cases were included for the study if anesthesia was conducted with propofol-opioid TIVA or 3% desflurane supplemented with propofol or opioid infusions as needed. We evaluated the propofol infusion rate, cortical amplitudes of the SSEPs (median nerve, posterior tibial nerve), amplitudes and stimulation voltage for eliciting the tcMEPs (adductor pollicis brevis, tibialis anterior) and the amplitude variability of the SSEP and tcMEP responses as assessed by the average percentage trial to trial change. Of the 156 spine cases included in the study, 95 had TIVA with propofol-opioid (TIVA) and 61 had 3% expired desflurane (INHAL). Three INHAL cases were excluded because the desflurane was eliminated because of inadequate responses and 26 cases (16 TIVA and 10 INHAL) were excluded due to significant changes during monitoring. Propofol infusion rates in the INHAL group were reduced from the TIVA group (average 115-45 µg/kg/min) (p<0.00001) with 21 cases where propofol was not used. No statistically significant differences in cortical SSEP or tcMEP amplitudes, tcMEP stimulation voltages nor in the average trial to trial amplitude variability were seen. The data from these cases indicates that 1/2 MAC (3%) desflurane can be used in conjunction with SSEP and tcMEP monitoring for some adult patients undergoing spine surgery. Further studies are needed to confirm the relative benefits versus negative effects of the use of desflurane and other halogenated agents for anesthesia during procedures on neurophysiological monitoring involving tcMEPs. Further studies are also needed to characterize which patients may or may not be candidates for supplementation such as those with neural dysfunction or who are opioid tolerant from chronic use.

Bilateral neurological deficits following unilateral minimally invasive TLIF: A review of four patients.

BACKGROUND: Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is commonly used for the treatment of degenerative lumbar spinal disorders. The rate of postoperative neurological deficits is traditionally low. New neurological postoperative complications may be underreported. We report our infrequent rate of MI-TLIF procedures complicated by postoperative weakness. METHODS: A database of 340 patients was evaluated, all of whom underwent MI-TLIF procedures performed between January 2002 and June 2012 by the senior author. We identified four cases (1.2%) whose postoperative course was complicated with bilateral lower extremity weakness. We retrospectively reviewed their past medical history, operative time, estimated blood loss, length of hospital stay, changes in intraoperative neurophysiological monitoring, and pre- and postoperative neurological exams. RESULTS: The average age of the four patients was 65.5 years(range: 62-75 years), average body mass index (BMI) was 25.1 (range: 24.1-26.6), and there were three females and one male. All patients had preoperative degenerative spondylolisthesis (either grade I or grade II). All patients were placed on a Wilson frame during surgery and underwent unilateral left-sided MI-TLIF. Three out of the four patients had a past medical history significant for abdominal or pelvic surgery and one patient had factor V Leiden deficiency syndrome. CONCLUSIONS: The rate of new neurological deficits following an MI-TLIF procedure is low, as documented in this study where the rate was 1.2%. Nonetheless, acknowledgement and open discussion of this serious complication is important for surgeon education. Of interest, the specific etiology or pathophysiology behind these complications remains relatively unknown (e.g. direct neural injury, traction injury, hypoperfusion, positioning complication, and others) despite there being some similarities between the patients and their perioperative courses.

West Nile virus infection and postoperative neurological symptoms: a case report and review of the literature.

The incidence of West Nile virus, which may cause a range of clinical presentations including subclinical infections, mild febrile illness, meningitis, or encephalitis, has increased over recent years. Rare complications, including optic neuritis, also have been reported. A patient who presented with preoperative asymptomatic West Nile virus developed fever, altered mental status and temporary vision loss after elective multilevel spine fusion surgery.

The implementation and efficacy of the Northwestern High Risk Spine Protocol.

OBJECTIVE: The aims of this study were to determine the efficacy and feasibility of implementation of the intraoperative component of a high risk spine (HRS) protocol for improving perioperative patient safety in complex spine fusion surgery. METHODS: In this paired availability study, the total number of red blood cell units transfused was used as a surrogate marker for our management protocol efficacy, and the number of protocol violations was used as a surrogate marker for protocol compliance. RESULTS: The 548 patients (284 traditional vs. 264 HRS protocol) were comparable in all demographics, coexisting diseases, preoperative medications, type of surgery, and number of posterior levels instrumented. However, the surgical duration was 70 minutes shorter in the new group (range, 32-108 minutes shorter; P < 0.0001) and the new protocol patients received a median of 1.1 units less of total red blood cell units (range, 0-2.4 units less; P = 0.006). There were only 7 (2.6%) protocol violations in the new protocol group. CONCLUSIONS: The intraoperative component of the HRS protocol, based on two Do-Confirm checklists that focused on 1) organized communication between intraoperative team members and 2) active maintenance of oxygen delivery and hemostasis appears to maintain a safe intraoperative environment and was readily implemented during a 3-year period.