Electric Field Effects on Brain Activity: Implications for Epilepsy and Burst Suppression.

Electric fields are now considered a major mechanism of epileptiform activity. However, it is not clear if another electrophysiological phenomenon, burst suppression, utilizes the same mechanism for its bursting phase. Thus, the purpose of this study was to compare the role of ephaptic coupling-the recruitment of neighboring cells via electric fields-in generating bursts in epilepsy and burst suppression. We used local injections of the GABA-antagonist picrotoxin to elicit epileptic activity and a general anesthetic, sevoflurane, to elicit burst suppression in rabbits. Then, we applied an established computational model of pyramidal cells to simulate neuronal activity in a 3-dimensional grid, with an additional parameter to trigger a suppression phase based on extra-cellular calcium dynamics. We discovered that coupling via electric fields was sufficient to produce bursting in scenarios where inhibitory control of excitatory neurons was sufficiently low. Under anesthesia conditions, bursting occurs with lower neuronal recruitment in comparison to seizures. Our model predicts that due to the effect of electric fields, the magnitude of bursts during seizures should be roughly 2-3 times the magnitude of bursts that occur during burst suppression, which is consistent with our in vivo experimental results. The resulting difference in magnitude between bursts during anesthesia and epileptiform bursts reflects the strength of the electric field effect, which suggests that burst suppression and epilepsy share the same ephaptic coupling mechanism.

Neonatal Anesthesia and Oxidative Stress.

Neonatal anesthesia, while often essential for surgeries or imaging procedures, is accompanied by significant risks to redox balance in the brain due to the relatively weak antioxidant system in children. Oxidative stress is characterized by concentrations of reactive oxygen species (ROS) that are elevated beyond what can be accommodated by the antioxidant defense system. In neonatal anesthesia, this has been proposed to be a contributing factor to some of the negative consequences (e.g., learning deficits and behavioral abnormalities) that are associated with early anesthetic exposure. In order to assess the relationship between neonatal anesthesia and oxidative stress, we first review the mechanisms of action of common anesthetic agents, the key pathways that produce the majority of ROS, and the main antioxidants. We then explore the possible immediate, short-term, and long-term pathways of neonatal-anesthesia-induced oxidative stress. We review a large body of literature describing oxidative stress to be evident during and immediately following neonatal anesthesia. Moreover, our review suggests that the short-term pathway has a temporally limited effect on oxidative stress, while the long-term pathway can manifest years later due to the altered development of neurons and neurovascular interactions.

Demographic Trends From 2005 to 2015 Among Physicians With Accreditation Council for Graduate Medical Education-Accredited Anesthesiology Training and Active Medical Licenses.

BACKGROUND: A temporary decrease in anesthesiology residency graduates that occurred around the turn of the millennium may have workforce implications. The aims of this study are to describe, between 2005 and 2015, (1) demographic changes in the workforce of physicians trained as anesthesiologists; (2) national and state densities of these physicians, as well as temporal changes in the densities; and (3) retention of medical licenses by mid- and later-career anesthesiologists. METHODS: Using records from the American Board of Anesthesiology and state medical and osteopathic boards, the numbers of licensed physicians aged 30-59 years who had completed Accreditation Council for Graduate Medical Education-accredited anesthesiology residency training were calculated cross-sectionally for 2005, 2010, and 2015. Demographic trends were then described. Census data were used to calculate national and state densities of licensed physicians. Individual longitudinal data were used to describe retention of medical licenses among older physicians. RESULTS: The number of licensed physicians trained as anesthesiologists aged 30-59 years increased from 32,644 in 2005 to 36,543 in 2010 and 36,624 in 2015, representing a national density of 1.10, 1.18, and 1.14 per 10,000 population in those years, respectively. The density of anesthesiologists among states ranged from 0.37 to 3.10 per 10,000 population. The age distribution differed across the years. For example, anesthesiologists aged 40-49 years predominated in 2005 (47%), but by 2015, only 31% of anesthesiologists were aged 40-49 years. The proportion of female anesthesiologists grew from 22% in 2005, to 24% in 2010, and to 28% in 2015, particularly among early-career anesthesiologists. For anesthesiologists with licenses in 2005, the number who still had active licenses in 2015 decreased by 9.6% for those aged 45-49 years, by 14.1% for those aged 50-54 years, and by 19.7% for those aged 55-59 years. CONCLUSIONS: The temporary decrease in anesthesiology residency graduates around the turn of the 21st century decreased the proportion of anesthesiologists who were midcareer as of 2015. This may affect the future availability of senior leaders as well as the future overall workforce in the specialty as older anesthesiologists retire. National efforts to plan for workforce needs should recognize the geographical variability in the distribution of anesthesiologists.

A Predictive Model for Pediatric Postoperative Respiratory Failure: A National Inpatient Sample Study.

STUDY OBJECTIVE: To identify risk factors for pediatric postoperative respiratory failure and develop a predictive model. DESIGN: This retrospective case-control study utilized the US National Inpatient Sample (NIS) from 2012 to 2014. Significant predictors were selected, and the predicted probability of pediatric postoperative respiratory failure was calculated. Sensitivity, specificity, and accuracy were then calculated, and receiver-operator curves were drawn. SETTING: National Inpatient Sample data sets from years 2012, 2013, and 2014 were used. PATIENTS: Patients aged 17 and younger in the 2012, 2013, and 2014 NIS data sets. INTERVENTIONS: Candidate predictors included demographic variables, type of surgical procedure, a modified pediatric comorbidity score, presence of substance abuse diagnosis, and presence/absence of kyphoscoliosis. MEASUREMENTS: The primary outcome measure was the pediatric quality indicator (PDI 09), which is defined by the Agency for Healthcare Research Quality, and identifies pediatric patients with postoperative respiratory failure. MAIN RESULTS: The incidence of pediatric postoperative respiratory failure in each year's data set varied from 1.31% in 2012 to 1.41% in 2014. Significant risk factors for the development of postoperative respiratory failure included abdominal surgery ([OR] = 1.92 in 2012 data set, 1.79 in 2013 data set), spine surgery (OR = 7.10 in 2012 data set, 6.41 in 2013 data set), and an elevated pediatric comorbidity score (score of 3 or greater: OR = 32.58 in 2012 data set, 22.74 in 2013 data set). A predictive model utilizing these risk factors achieved a C statistic of 0.82. CONCLUSIONS: Risk factors associated with postoperative respiratory failure in pediatric patients undergoing noncardiac surgery include type of surgery (abdominal and spine) and higher pediatric comorbidity scores. A prediction model based on the identified factors had good predictive ability.

Association Between Participation and Performance in MOCA Minute and Actions Against the Medical Licenses of Anesthesiologists.

BACKGROUND: In January 2016, as part of the Maintenance of Certification in Anesthesiology (MOCA) program, the American Board of Anesthesiology launched MOCA Minute, a web-based longitudinal assessment, to supplant the former cognitive examination. We investigated the association between participation and performance in MOCA Minute and disciplinary actions against medical licenses of anesthesiologists. METHODS: All anesthesiologists with time-limited certificates (ie, certified in 2000 or after) who were required to register for MOCA Minute in 2016 were followed up through December 31, 2016. The incidence of postcertification prejudicial license actions was compared between those who did and did not register and compared between registrants who did and did not meet the MOCA Minute performance standard. RESULTS: The cumulative incidence of license actions was 1.2% (245/20,006) in anesthesiologists required to register for MOCA Minute. Nonregistration was associated with a higher incidence of license actions (hazard ratio, 2.93 [95% confidence interval {CI}, 2.15-4.00]). For the 18,534 (92.6%) who registered, later registration (after June 30, 2016) was associated with a higher incidence of license actions. In 2016, 16,308 (88.0%) anesthesiologists met the MOCA Minute performance standard. Of those not meeting the standard (n = 2226), most (n = 2093, 94.0%) failed because they did not complete the required 120 questions. Not meeting the standard was associated with a higher incidence of license actions (hazard ratio, 1.92 [95% CI, 1.36-2.72]). CONCLUSIONS: Both timely participation and meeting performance standard in MOCA Minute are associated with a lower likelihood of being disciplined by a state medical board.

Association between Performance in a Maintenance of Certification Program and Disciplinary Actions against the Medical Licenses of Anesthesiologists.

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: In 2000, the American Board of Anesthesiology (Raleigh, North Carolina) began issuing time-limited certificates requiring renewal every 10 yr through a maintenance of certification program. This study investigated the association between performance in this program and disciplinary actions against medical licenses. METHODS: The incidence of postcertification prejudicial license actions was compared (1) between anesthesiologists certified between 1994 and 1999 (non-time-limited certificates not requiring maintenance of certification) and those certified between 2000 and 2005 (time-limited certificates requiring maintenance of certification); (2) within the non-time-limited cohort, between those who did and did not voluntarily participate in maintenance of certification; and (3) within the time-limited cohort, between those who did and did not complete maintenance of certification requirements within 10 yr. RESULTS: The cumulative incidence of license actions was 3.8% (587 of 15,486). The incidence did not significantly differ after time-limited certificates were introduced (hazard ratio = 1.15; 95% CI, 0.95 to 1.39; for non-time-limited cohort compared with time-limited cohort). In the non-time-limited cohort, 10% (n = 953) voluntarily participated in maintenance of certification. Maintenance of certification participation was associated with a lower incidence of license actions (hazard ratio = 0.60; 95% CI, 0.38 to 0.94). In the time-limited cohort, 90% (n = 5,329) completed maintenance of certification requirements within 10 yr of certificate issuance. Not completing maintenance of certification requirements (n = 588) was associated with a higher incidence of license actions (hazard ratio = 4.61; 95% CI, 3.27 to 6.51). CONCLUSIONS: These findings suggest that meeting maintenance of certification requirements is associated with a lower likelihood of being disciplined by a state licensing agency. The introduction of time-limited certificates in 2000 was not associated with a significant change in the rate of license actions.

Elongation of chordae tendineae as an adaptive process to reduce mitral regurgitation in functional mitral regurgitation.

AIMS: In functional mitral regurgitation (FMR), increased leaflet area has been described as a remodelling compensatory mechanism. We hypothesized that chordae tendineae elongation would also occur as part of this remodelling. In this study, the lengths of primary chords and measurements of mitral leaflets and annulus were compared with varying degrees of mitral regurgitation (MR). METHODS AND RESULTS: We studied 58 patients who underwent three-dimensional (3D) transoesophageal echocardiography, including 38 with FMR and 20 with normal mitral valves (NL). The FMR group was divided into two subgroups according to two-dimensional vena contracta width (VCW). Three-dimensional datasets from transgastric or mid-oesophageal approach were used to measure primary chordal length, coaptation length, inter-papillary muscle distances, and quantitative 3D measurements of the annulus and leaflets. Leaflet surface area was increased and coaptation length was decreased in FMR compared with NL. While no difference in other 3D measurement of annulus/leaflets was noted between the FMR subgroups, averaged chordal length was shorter in patients with more severe FMR. Chords of the anterior leaflet in FMR with larger VCW were shorter compared with both NL and FMR with smaller VCW. In contrast, the chords of the posterior leaflet were longer in FMR with smaller VCW compared with the other two groups. CONCLUSION: Our results suggest the posterior leaflet chords possibly remodel by elongating and contribute to reduced MR and that in a subgroup of FMR patients, the primary chords may remodel by shortening, resulting in augmented MR. This information could be useful in choosing strategy for FMR correction.

Leaflet-chordal relations in patients with primary and secondary mitral regurgitation.

BACKGROUND: The strategy for mitral valve (MV) repair has recently focused on the restoration of the submitral apparatus. However, the relationship between geometric changes of the submitral apparatus and the mitral leaflets has not been systematically investigated. The aim of this study was to determine the relationships among chordal length (CL) and LV size and leaflet surface area (LSA) in normal subjects, patients with primary (degenerative) mitral regurgitation (PMR), and patients with functional (secondary) mitral regurgitation (FMR). METHODS: A total of 72 patients who underwent three-dimensional transesophageal echocardiography, including: 27 with PMR with isolated P2 flail leaflet, 25 with FMR with greater than mild mitral regurgitation, and 20 with normal mitral valves. LSA was quantified at midsystole from full-volume midesophageal views. CL was calculated by averaging the lengths of eight primary chords from transgastric full-volume data sets using multiplanar reconstruction. RESULTS: Both CL and LSA in the PMR group were significantly longer compared with the FMR and normal control groups. No difference in CL was noted between patients with FMR and normal subjects. In all three groups, CL and LSA did not correlate with LV systolic or diastolic dimensions. Although CL did not correlate with LSA in the FMR group, a moderate correlation (R = 0.62) was observed in the PMR group. CONCLUSIONS: In patients with FMR with greater than mild mitral regurgitation, the chords retain normal length, despite LSA and LV enlargement. In patients with PMR with flail P2 scallops, CL elongation of primary chords is associated with larger LSA but not with LV dimensions. This information may have implications for clinical strategies for mitral valve repair surgery, including the submitral approach and percutaneous procedures.

Perioperative management of carotid endarterectomy: a survey of clinicians' backgrounds and practices.

OBJECTIVE: To examine current trends in anesthetic practice for management of carotid endarterectomy (CEA) and how practice may differ by groups of practitioners. DESIGN: An online survey was sent to the Society of Cardiovascular Anesthesiologists and Society of Neuroscience, Anesthesiology, and Critical Care e-mail list servers. Responses were voluntary. SETTING: Academic medical centers and community-based hospitals providing perioperative care for a CEA in the United States and abroad. PARTICIPANTS: Anesthesiologists who provide perioperative care for patients undergoing a CEA. INTERVENTIONS: None MEASUREMENTS AND MAIN RESULTS: Of 664 responders (13% response rate), most (66%) had subspecialty training in cardiovascular anesthesiology, had been in practice more than 10 years (68%), and practiced in the United States (US, 81%). About 75% of responders considered general anesthesia as a preferable technique for CA, and about 89% of responders provided it in real life, independent of subspecialty training. The most preferable intraoperative neuromonitoring was cerebral oximetry (28%), followed by EEG (24%), and having an awake patient (23%). Neuroprotection was not considered by 33% of responders, and upon conclusion of a case, 59% preferred an awake patient for extubation, while 15% preferred a deep extubation. Neuroanesthesiologists and non-US responders more often risk stratify patients for perioperative cerebral hyperperfusion syndrome, compared with cardiac anesthesiologists and US responders (p=0.004 and p<0.005, respectively). Additionally, reported management strategies vary substantially from anesthetic practice 20 years ago. CONCLUSIONS: Although there are areas of perioperative management in which there seems to be agreement for the CEA, there are also areas of divergent practice that could represent potential for improvement in overall outcomes. There are many potential reasons to explain divergence in practice by location or subspecialty training, but it remains unclear what the "best practice" may be. Future studies examining outcomes after carotid endarterectomy should include perioperative anesthetic management strategies to help delineate "best practice."

Relationship between anesthetic depth and venous oxygen saturation during cardiopulmonary bypass.

BACKGROUND: During cardiopulmonary bypass, mixed venous oxygen saturation (Svo2) is frequently measured to assess circulatory adequacy. Fluctuations in Svo2 not related to patient movement or inadequate oxygen delivery have been attributed clinically to increased cerebral oxygen consumption due to "light" anesthesia. To evaluate the relationship between anesthetic depth and Svo2, we prospectively measured bispectral index (BIS) and Svo2 values in patients undergoing cardiac surgery with cardiopulmonary bypass. METHODS: Adults scheduled for cardiac surgery with cardiopulmonary bypass were recruited for this prospective observational study. During bypass, BIS and Svo2 values were recorded every 5 min. To control for confounding effects of changes in other variables known to affect Svo2, temperature, hematocrit, bypass pump flow, muscle relaxant use, and intravenous and inhaled anesthetic doses were also recorded. Only periods with limited variation in other variables affecting Svo2 were analyzed. The relationship between BIS and Svo2 was evaluated using mixed linear regression. RESULTS: One thousand thirty-four data points were obtained in 41 patients. No overall association between BIS and Svo2 was observed, either in unadjusted analysis or adjusted for covariates. In data points with temperatures less than the median (T < 34.1 degrees C), a significant association between BIS and Svo2 was observed both in unadjusted (beta = -0.32, P = 0.01) and adjusted (beta = -0.27, P = 0.04) analyses. CONCLUSIONS: In patients undergoing cardiopulmonary bypass, we found no overall association between BIS and Svo2. A weak but statistically significant association between BIS and Svo2 was observed in patients with temperatures less than 34.1 degrees C. These data suggest that low Svo2 values on bypass are unlikely to be due to light or inadequate anesthesia. The relationship among temperature, BIS and Svo2 deserves further study.

Transoesophageal echocardiography and central line insertion.

We investigated the potential utility of transoesophageal echocardiography (TOE) in facilitating central venous catheter (CVC) insertion in patients undergoing cardiac surgery. Thirty five patients undergoing elective cardiac surgery and CVC insertion were prospectively included in the observational, single-centre clinical investigation. Following induction of general anaesthesia and tracheal intubation, the TOE probe was inserted and the bicaval view obtained prior to CVC insertion (site at discretion of the anaesthesiologist). Prospectively collected data included site and sequence of CVC insertion attempts, information regarding ease of guidewire insertion, whether or not guidewire was visualized via TOE, and other pertinent information. In 1 patient, the TOE bicaval view could not be readily obtained because of right atrial (RA) distortion. In 31 patients, the TOE bicaval view was obtained and CVC access was successful at the site of first choice (guidewire visualized in all). Three patients had noteworthy CVC insertions. In one, CVC insertion was difficult despite visualization ofguidewire in the RA. In another, multiple guidewire insertions met with substantial resistance and without visualization of guidewire in the RA. One patient was found to have an unanticipated large mobile superior vena cava thrombus that extended into the RA, which changed clinical management by prompting initial CVC insertion into the femoral vein (potentially avoiding morbidity associated with thrombus dislodgement). Our prospective observational clinical study indicates that routine use of TOE during CVC insertion may help avoid potential complications associated with this intervention. If both CVC insertion and TOE are going to be used in the same patient, the benefits of TOE should be maximized by routine visualization of the bicaval view during guidewire insertion.