Jason Chui

Cardiac Output and Cerebral Blood Flow: The Integrated Regulation of Brain Perfusion in Adult Humans.

Cerebral blood flow (CBF) is rigorously regulated by various powerful mechanisms to safeguard the match between cerebral metabolic demand and supply. The question of how a change in cardiac output (CO) affects CBF is fundamental, because CBF is dependent on constantly receiving a significant proportion of CO. The authors reviewed the studies that investigated the association between CO and CBF in healthy volunteers and patients with chronic heart failure. The overall evidence shows that an alteration in CO, either acutely or chronically, leads to a change in CBF that is independent of other CBF-regulating parameters including blood pressure and carbon dioxide. However, studies on the association between CO and CBF in patients with varying neurologic, medical, and surgical conditions were confounded by methodologic limitations. Given that CBF regulation is multifactorial but the various processes must exert their effects on the cerebral circulation simultaneously, the authors propose a conceptual framework that integrates the various CBF-regulating processes at the level of cerebral arteries/arterioles while still maintaining autoregulation. The clinical implications pertinent to the effect of CO on CBF are discussed. Outcome research relating to the management of CO and CBF in high-risk patients or during high-risk surgeries is needed.

The anesthetic considerations of intraoperative electrocorticography during epilepsy surgery.

Epilepsy surgery is a well-established therapeutic intervention for patients with medically refractory seizures. Success of epilepsy surgery depends on the accurate localization and complete removal of the epileptogenic zone. Despite the advances in presurgical localization modalities, electrocorticography is still used in approximately 60% to 70% of the epilepsy centers in North America to guide surgical resection of the epileptogenic lesion and to assess for completeness of surgery. In this review, we discuss the principles and intraoperative use of electrocorticography, the effect of anesthetic drugs on electrocorticography, and the use of pharmacoactivation for intraoperative localization of epileptogenic zone.

Day surgery craniotomy for unruptured cerebral aneurysms: a single center experience.

Background: Ambulatory day surgery is an evolving specialty in line with demands of modern medicine, health care services, and economics, but its role in neurovascular surgery remains controversial. The purpose of this study was to describe our experience of patients undergoing elective clipping of intact cerebral aneurysms as day surgery. Methods: This retrospective and prospective observational study was carried out as a cohort review of patients who underwent outpatient clipping of an intact intracranial aneurysm at the Toronto Western Hospital, University Health Network, between May 2009 and November 2012. Patients were categorized as success (discharged on the same day) or failure (requiring unplanned postoperative hospital admission) of day surgery. Data included the preoperative assessment of the patient, anesthetic management, postoperative care, and the incidence of perioperative complications. Outcomes were duration of hospital stay, and any problems preventing same-day discharge. Results: During the study period 25 patients aged 54±9 years underwent outpatient aneurysm repair. Seventeen patients (68%) successfully completed day surgery, and 8 patients (32%) were admitted to the hospital after surgery due to perioperative complications. Duration of hospital stay in the failure group ranged from 2 to 18 days. Conclusions: Our data demonstrates that surgical clipping of unruptured cerebral aneurysms may be performed in an outpatient setting. Careful selection of day surgery candidates and postoperative assessment for complications is needed. Further research is needed to identify potential risk factors and to target patient subgroups for successful ambulatory surgery.

Cerebrovascular reactivity to carbon dioxide under anesthesia: a qualitative systematic review.

Introduction: Controlling the arterial carbon dioxide tension (PaCO2) to reduce the cerebral blood flow (CBF) and the intracranial pressure is a common practice in neuroanesthesia. A change in CBF in response to change in PaCO2 is termed as cerebrovascular reactivity to carbon dioxide (CVR-CO2). Studies have shown that, both inhalational and intravenous anesthetic agents have variable effects on CVR-CO2 and the effect of anesthetic agents on CVR also varies with many physiological and pathologic conditions. The objectives of this review were to evaluate the effect of anesthetic agents on the CVR-CO2 in adults and to determine how this response is modified by other physiological and pathologic factors. Methods: We conducted a systematic search of the databases of Medline, Embase, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews using related term components for both CVR-CO2 and anesthesia. Our primary outcome of this review was to determine whether the CVR-CO2 is maintained under anesthesia. The other endpoints of this review are to determine the effect of other factors (age, sex, medical comorbidities, and cerebrovascular pathology) on the CVR-CO2 under anesthesia. Because of the methodological heterogeneity in the primary studies, quantitative analysis of the data was not possible, and therefore, we have summarized the data qualitatively. Results: Our search strategy yielded 1356 citations. After excluding nonpertinent papers, 38 studies were included for the systematic review. Nineteen randomized controlled trials and 19 observational studies met inclusion criteria and a total of 793 patients were studied. Transcranial Doppler was the most commonly used method for measuring CBF and changing the respiratory rate and/or minute ventilation were the most commonly used method to change the CO2 tension. CVR-CO2 is maintained with both inhalational and intravenous anesthetic agents within the range of concentrations used in clinical anesthesia. At doses leading to a broadly equivalent depth of anesthesia, the reactivity value was highest with isoflurane and the least with propofol. Individual agents differ in their degree of reactivity to hypercapnic and hypocapnic stimuli. CVR-CO2 is impaired in elderly patients when compared with young patients with both sevoflurane and propofol anesthesia. In patients with medical comorbidities, the CVR-CO2 impairment under anesthesia was associated with the severity of the underlying diseases and not the anesthetic agents. Conclusions: Our systematic review showed that within the clinical anesthesia concentrations, CVR-CO2 is maintained under both propofol and inhalational agents. However, most of the information available is from non-neurosurgical patients and these studies also suffer from significant methodological heterogeneity. Therefore, we were limited by the amount and the quality of data available for this review.

An update on the prone position: Continuing Professional Development.

PurposeThe purpose of this Continuing Professional Development module is to provide information needed to prepare for and clinically manage a patient in the prone position.Principal findingsProne positioning is required for surgical procedures that involve the posterior aspect of a patient. We searched MEDLINE® and EMBASE™ from January 2000 to January 2015 for literature related to the prone position and retrieved only original articles in English. We reviewed the advantages and disadvantages of various equipment used in prone positioning, the physiological changes associated with prone positioning, and the complications that can occur. We also reviewed strategies for the safe conduct and management of position-related complications.ConclusionIncreased age, elevated body mass index, the presence of comorbidities, and long duration of surgery appear to be the most important risk factors for complications associated with prone positioning. We recommend a structured team approach and careful selection of equipment tailored to the patient and surgery. The systematic use of checklists is recommended to guide operating room teams and to reduce prone position-related complications. Anesthesiologists should be prepared to manage major intraoperative emergencies (e.g., accidental extubation) and anticipate postoperative complications (e.g., airway edema and visual loss).RésuméObjectifL’objectif de ce module de développement professionnel continu est de présenter les informations nécessaires à la préparation et la prise en charge clinique d’un patient en position ventrale.Constatations principalesLe positionnement ventral est nécessaire pour les interventions chirurgicales sur la face postérieure d’un patient. Nous avons effectué des recherches dans les bases de données MEDLINE® et EMBASE™ s’étendant de janvier 2000 à janvier 2015 pour en extraire la littérature portant sur la position ventrale et avons retenu les articles originaux publiés en anglais. Nous avons passé en revue les avantages et les inconvénients de divers équipements utilisés pour le positionnement ventral, les changements physiologiques associés à la position ventrale, et les complications potentielles. Nous avons également passé en revue diverses stratégies pour la réalisation et la prise en charge sécuritaires des complications liées à la position ventrale.ConclusionUn âge avancé, un indice de masse corporel élevé, la présence de comorbidités et une durée de chirurgie prolongée semblent constituer les facteurs de risque les plus importants de complications associées au positionnement ventral. Nous recommandons une approche d’équipe structurée et une sélection minutieuse d’équipement en fonction du patient et de la chirurgie. L’utilisation méthodique de listes de contrôle (checklists) est recommandée afin de guider les équipes de salle d’opération et de réduire les complications liées à la position ventrale. Les anesthésiologistes doivent être prêts à faire face à des urgences peropératoires majeures (par ex. une extubation accidentelle) et à anticiper les complications postopératoires (par ex., un œdème des voies aériennes ou une perte de la vision).

Anesthetic management of patients undergoing intracranial bypass procedures.

Cerebral revascularization is used to augment or replace cerebral blood flow in patients at risk of developing cerebral ischemia. These include patients with moyamoya disease, occlusive cerebrovascular disease, skull base tumors, and complex aneurysms. Our aim in this review is to provide a comprehensive update of both surgical and anesthetic aspects of cerebral revascularization procedures. The anesthetic concerns for most patients presenting for different types of bypass procedures are similar and include the maintenance of adequate cerebral perfusion to prevent cerebral ischemia. Patients with complex aneurysms and tumors have additional considerations related to the surgical treatment of the underlying pathology.

A Novel Automated Somatosensory Evoked Potential (SSEP) Monitoring Device for Detection of Intraoperative Peripheral Nerve Injury in Cardiac Surgery: A Clinical Feasibility Study

OBJECTIVE Peripheral nerve injury (PNI) is a common and potentially devastating complication in cardiac surgery. Somatosensory evoked potential (SSEP) monitoring is one of the modalities for PNI; however, its application is limited by complicated logistics. This study aimed to assess the feasibility of using a novel, automated SSEP device (EPAD; SafeOp Surgical, Hunt Valley, MD) for detection of intraoperative PNI during cardiac surgery. DESIGN Prospective, observational study. SETTING Single university hospital. PARTICIPANTS Cardiac surgical patients. INTERVENTIONS After Ethics Board approval and written consent, study participants were monitored using the EPAD automated SSEP device during cardiac surgery. All patients with prolonged and abnormal SSEP changes were evaluated postoperatively, and if they were symptomatic, they were referred for further nerve conduction and electromyographic assessment. MEASUREMENTS AND MAIN RESULTS Of the 43 patients who consented to study inclusion, 33 were monitored successfully. With increasing clinical experience the authors encountered minimal technical issues, and satisfactory signals were obtained in most patients. Abnormal SSEP signal changes, which were encountered in 5 (15.2%) patients, were interpreted as impending PNI; 3 patients experienced prolonged signal changes (>1 h), and 2 (6.1%) of these developed symptomatic peripheral neuropathy that was confirmed with nerve conduction studies. CONCLUSIONS The EPAD automated SSEP device is a viable option for detecting PNI during cardiac surgery. A high incidence of intraoperative peripheral nerve compromise and a 6.1% incidence of postoperative peripheral neuropathy were observed. This study reports the clinical feasibility of using the EPAD automated SSEP device; additional studies are required to evaluate the diagnostic test accuracy and the outcome benefit of routine SSEP monitoring in cardiac surgical patients.

Atrioventricular disruption after mitral valve replacement: the role of intraoperative transesophageal echocardiography.

November 2014 • Volume 119 • Number 5 An 81-year-old man with coronary artery disease and severe mitral regurgitation from myxomatous mitral valve disease was referred for surgery due to progressive congestive heart failure. He was scheduled to have mitral valve replacement (MVR) and coronary artery bypass grafting. His intraoperative transesophageal echocardiogram (TEE) revealed that the main mechanism of his mitral regurgitation was anterior leaflet prolapse. He had severe left ventricular (LV) dysfunction (ejection fraction 25%). There was right ventricular and tricuspid annular dilation with mild-tomoderate tricuspid regurgitation, but right ventricular function was preserved. After completion of the MVR (29 mm Hancock II, Medtronic, Mississauga, Canada) and coronary artery bypass grafting (4 grafts), the patient was weaned from cardiopulmonary bypass (CPB) with inotropic support. Immediate post-CPB TEE revealed paravalvular leak, a small hematoma in the interatrial septum (IAS) and global LV hypokinesia (ejection fraction 10%–20%) (Fig. 1; Video 1, Supplemental Digital Content 1, http://links.lww.com/AA/ A917). The initial diagnosis was myocardial ischemia due to coronary air. The surgeon decided to decannulate the aorta, and protamine was administered. The patient became more hypotensive, despite increasing inotropic requirements. The TEE showed worsening biventricular function, subtle rocking of the bioprosthetic MVR, and hematoma in the IAS (Fig. 2; Video 2, Supplemental Digital Content 2, http://links.lww. com/AA/A918). The patient remained hypotensive, and CPB was reinstituted for surgical exploration. A large hematoma was found in the posterior atrioventricular groove extending to the inferior vena cava. The surgeon attempted but failed to repair the disrupted atrioventricular groove, and the patient died on the operating table. Retrospective analysis of the intraoperative 3-D TEE imaging using Qlab software (Philips Medical Systems) revealed a crescentic gap around the posterior aspect of the MVR, consistent with atrioventricular separation (Fig. 3; Video 3, Supplemental Digital Content 3, http://links.lww.com/AA/A919). With the use of multiple 2D planes (MPR mode) reconstructed from a 3D data set, the extent of atrioventricular separation was more readily appreciated (Fig. 3). Atrioventricular disruption is a rare but fatal complication after MVR, with a reported incidence between 0.5% and 14% and mortality between 50% and 75%.1,2 Classification has been divided into 3 types based on the location of the tear. Type I is the most common type and is associated with MVR. Types II and III have been virtually abolished, primarily due to the introduction of surgical preservation techniques and low-profile mitral prostheses (Table 1). The main clinical presentation for atrioventricular disruption is either unstable hemodynamics after weaning from CPB or failure to wean from CPB. Frank rupture with massive bleeding from the LV can alert the clinicians to the diagnosis of LV rupture. However, LV failure and ventricular arrhythmias are usually nonspecific presentations in many cases. More specific signs, such as dissecting hematoma in the posterior atrioventricular groove, are often not

Presurgical evaluation of patients with epilepsy: the role of the anesthesiologist.

Patients with medically refractory epilepsy when referred for surgical treatment often undergo extensive investigations to determine whether surgical treatment is feasible. Surgical feasibility is determined by identifying the location and number of seizure foci and their relationship to eloquent areas of the brain. Good surgical outcome depends on complete resection of seizure foci without any damage to eloquent brain function. Various noninvasive and invasive techniques are used in the presurgical evaluation of patients with epilepsy that include imaging techniques, electrophysiologic studies, and tests to determine functional areas. Understanding of the principles of seizure localization and of the effects of anesthetic drugs on the various preoperative investigations is essential for patient management. In this review article, we discuss the role of the anesthesiologist in patient management during many of these investigations and the role of anesthetic drugs to aid in the localization of the seizure focus and of determining eloquent brain function.

Is Routine Chest X-Ray After Ultrasound-Guided Central Venous Catheter Insertion Choosing Wisely?: A Population-Based Retrospective Study of 6,875 Patients

BACKGROUND: A routine chest radiograph (CXR) is recommended as a screening test after central venous catheter (CVC) insertion. The goal of this study was to assess the value of a routine postprocedural CXR in the era of ultrasound‐guided CVC insertion. METHODS: This population‐based retrospective cohort study was performed to review the records of all adult patients who had a CVC inserted in the operating room in a tertiary institution between July 1, 2008, and December 31, 2015. We determined the incidence of pneumothorax and catheter misplacement after ultrasound‐guided CVC insertion. A logistic regression analysis was performed to examine the potential risk factors associated with these complications, and a cost analysis was conducted to evaluate the economic impact. RESULTS: Of 18,274 patients who had a CVC inserted, 6,875 patients were included. The overall incidence of pneumothorax and catheter misplacement was 0.33% (95% CI, 0.22–0.5) (23 patients) and 1.91% (95% CI, 1.61–2.26) (131 patients), respectively. The site of catheterization was the major determinant of pneumothorax and catheter misplacement; left subclavian vein catheterization was the site at a higher risk for pneumothorax (OR, 6.69 [95% CI, 2.45–18.28]; P < .001), and catheterization sites other than the right internal jugular vein were at a higher risk for catheter misplacement. Expenditures on routine postprocedural CXR were US