Publications by authors named "Paul Picton"

24 Publications

  • Page 1 of 1

Asymmetric neural dynamics characterize loss and recovery of consciousness.

Neuroimage 2021 Apr 10:118042. Epub 2021 Apr 10.

Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA; Center for Consciousness Science, University of Michigan Medical School, Ann Arbor, MI 48109, USA; Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA. Electronic address:

Anesthetics are known to disrupt neural interactions in cortical and subcortical brain circuits. While the effect of anesthetic drugs on consciousness is reversible, the neural mechanism mediating induction and recovery may be different. Insight into these distinct mechanisms can be gained from a systematic comparison of neural dynamics during slow induction of and emergence from anesthesia. To this end, we used functional magnetic resonance imaging (fMRI) data obtained in healthy volunteers before, during, and after the administration of propofol at incrementally adjusted target concentrations. We analyzed functional connectivity of corticocortical and subcorticocortical networks and the temporal autocorrelation of fMRI signal as an index of neural processing timescales. We found that en route to unconsciousness, temporal autocorrelation across the entire brain gradually increased, whereas functional connectivity gradually decreased. In contrast, regaining consciousness was associated with an abrupt restoration of cortical but not subcortical temporal autocorrelation and an abrupt boost of subcorticocortical functional connectivity. Pharmacokinetic effects could not account for the difference in neural dynamics between induction and emergence. We conclude that the induction and recovery phases of anesthesia follow asymmetric neural dynamics. A rapid increase in the speed of cortical neural processing and subcorticocortical neural interactions may be a mechanism that reboots consciousness.
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http://dx.doi.org/10.1016/j.neuroimage.2021.118042DOI Listing
April 2021

Brain network motifs are markers of loss and recovery of consciousness.

Sci Rep 2021 Feb 16;11(1):3892. Epub 2021 Feb 16.

School of Physical and Occupational Therapy, McGill University, Montreal, Canada.

Motifs are patterns of inter-connections between nodes of a network, and have been investigated as building blocks of directed networks. This study explored the re-organization of 3-node motifs during loss and recovery of consciousness. Nine healthy subjects underwent a 3-h anesthetic protocol while 128-channel electroencephalography (EEG) was recorded. In the alpha (8-13 Hz) band, 5-min epochs of EEG were extracted for: Baseline; Induction; Unconscious; 30-, 10- and 5-min pre-recovery of responsiveness; 30- and 180-min post-recovery of responsiveness. We constructed a functional brain network using the weighted and directed phase lag index, on which we calculated the frequency and topology of 3-node motifs. Three motifs (motifs 1, 2 and 5) were significantly present across participants and epochs, when compared to random networks (p < 0.05). The topology of motifs 1 and 5 changed significantly between responsive and unresponsive epochs (p-values < 0.01; Kendall's W = 0.664 (motif 1) and 0.529 (motif 5)). Motif 1 was constituted of long-range chain-like connections, while motif 5 was constituted of short-range, loop-like connections. Our results suggest that anesthetic-induced unconsciousness is associated with a topological re-organization of network motifs. As motif topological re-organization may precede (motif 5) or accompany (motif 1) the return of responsiveness, motifs could contribute to the understanding of the neural correlates of consciousness.
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http://dx.doi.org/10.1038/s41598-021-83482-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7887248PMC
February 2021

Trans-ocular brain impedance index for assessment of cerebral autoregulation in a porcine model of cerebral hemodynamic perturbation.

J Clin Monit Comput 2020 Jul 14. Epub 2020 Jul 14.

Department of Emergency Medicine, University of Michigan, 2800 Plymouth Road, Ann Arbor, MI, 26-323N48109, USA.

Cerebrovascular autoregulation (CA) is often impaired following traumatic brain injury. Established technologies and metrics used to assess CA are invasive and conducive for measurement, but not for continuous monitoring. We developed a trans-ocular brain impedance (TOBI) method that may provide non-invasive and continuous indices to assess CA. In this study, we monitored impedance metrics such as respiratory-induced impedance amplitude changes (dz) as well as a novel impedance index (DZx), which is a moving Pearson correlation between mean arterial pressure (MAP) and dz. Yorkshire swine were instrumented to continuously record ICP, MAP, and cerebral blood flow (CBF). TOBI was recorded by placement of standard ECG electrodes on closed eyelids and connected to a data acquisition system. MAP, ICP and CBF were manipulated utilizing an intravenous vasopressor challenge. TOBI indices (dz and DZx) were compared to the hemodynamic indicators as well as pressure reactivity index (PRx). During the vasopressor challenge, dz was highly correlated with ICP, CPP, and CBF (r =  < - 0.49, p < 0.0001). ICP, CPP, and CBF had a mean percent increase (standard deviation) from baseline of 29(23.2)%, 70(25)%, and 37(72.6)% respectively while dz decreased by 31(15.6)%. Receiver operator curve test showed high predictive performance of DZx when compared to PRx with area under the curve above 0.86, with high sensitivity and specificity. Impedance indices appear to track changes in PRx and hemodynamics that affect cerebral autoregulation. TOBI may be a suitable less invasive surrogate to PRx and capable of tracking cerebral autoregulation.
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http://dx.doi.org/10.1007/s10877-020-00556-1DOI Listing
July 2020

Intraoperative glycemic control in patients undergoing Orthotopic liver transplant: a single center prospective randomized study.

BMC Anesthesiol 2020 01 4;20(1). Epub 2020 Jan 4.

Department of Anesthesiology, Michigan Medicine, 1H247 UH, 1500 East Medical Center Drive, SPC 5048, Ann Arbor, MI, 48109-5048, USA.

Background: Perioperative hyperglycemia is associated with poor outcomes yet evidence to guide intraoperative goals and treatment modalities during non-cardiac surgery are lacking. End-stage liver disease is associated with altered glucose homeostasis; patients undergoing liver transplantation display huge fluctuations in blood glucose (BG) and represent a population of great interest. Here, we conduct a randomized trial to compare the effects of strict versus conventional glycemic control during orthotopic liver transplant (OLT).

Methods: Following approval by the Institutional Review Board of the University of Michigan Medical School and informed consent, 100 adult patients undergoing OLT were recruited. Patients were randomized to either strict (target BG 80-120 mg/dL) or conventional (target BG 180-200 mg/dL) BG control with block randomization for diabetic and nondiabetic patients. The primary outcomes measured were 1-year patient and graft survival assessed on an intention to treat basis. Graft survival is defined as death or needing re-transplant (www.unos.org). Three and 5-year patient and graft survival, infectious and biliary complications were measured as secondary outcomes. Data were examined using univariate methods and Kaplan-Meir survival analysis. A sensitivity analysis was performed to compare patients with a mean BG of ≤120 mg/dL and those > 120 mg/dL regardless of treatment group.

Results: There was no statistically significant difference in patient survival between conventional and strict control respectively;1 year, 88% vs 88% (p-0.99), 3 years, 86% vs 84% (p- 0.77), 5 years, 82% vs 78. % (p-0.36). Graft survival was not different between conventional and strict control groups at 1 year, 88% vs 84% (p-0.56), 3 years 82% vs 76% (p-0.46), 5 years 78% vs 70% (p-0.362).

Conclusion: There was no difference in patient or graft survival between intraoperative strict and conventional glycemic control during OLT.

Trial Registration: Clinical trial number and registry: www.clinicaltrials.gov NCT00780026. This trial was retrospectively registered on 10/22/2008.
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http://dx.doi.org/10.1186/s12871-019-0918-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6942664PMC
January 2020

Cerebrovascular Disease and Perioperative Neurologic Vulnerability: A Prospective Cohort Study.

Front Neurol 2019 28;10:560. Epub 2019 May 28.

Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, MI, United States.

Stroke is a devastating perioperative complication without effective methods for prevention or diagnosis. The objective of this study was to analyze evidence-based strategies for detecting cerebrovascular vulnerability and injury in a high-risk cohort of non-cardiac surgery patients. This was a single-center, prospective cohort study. Fifty patients undergoing non-cardiac surgery were recruited -25 with known cerebrovascular disease and 25 matched controls. Neurologic vulnerability was measured with intraoperative cerebral oximetry as the primary outcome. Perioperative neurocognitive testing and serum biomarker analysis (S-100β, neuron specific enolase, glial fibrillary acid protein, and matrix metalloproteinase-9) were measured as secondary outcomes. Cerebral desaturation events (an oximetry decrease ≥20% from baseline or <50% absolute value for ≥3 min) occurred in 7/24 (29%) cerebrovascular disease patients and 2/24 (8.3%) controls (relative risk 3.5, 95% CI 0.81-15.2; = 0.094). Cognitive function trends were similar in both groups, though overall scores (range: 1,500-7,197) were ~1 standard deviation lower in cerebrovascular patients across the entire perioperative period (-1,049 [95% CI -1,662, -436], < 0.001). No significant serum biomarker differences were found between groups over time. One control patient experienced intraoperative hypoxic-ischemic injury, but no robust biomarker or oximetry changes were observed. Cerebrovascular disease patients did not demonstrate dramatic differences in cerebral oximetry, cognitive trajectory, or molecular biomarkers compared to controls. Moreover, a catastrophic hypoxic-ischemic event was neither predicted nor detected by any strategy tested. These findings support the need for novel research into cerebrovascular risk and vulnerability.
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http://dx.doi.org/10.3389/fneur.2019.00560DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6558425PMC
May 2019

Brain imaging reveals covert consciousness during behavioral unresponsiveness induced by propofol.

Sci Rep 2018 09 4;8(1):13195. Epub 2018 Sep 4.

Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, MI, USA.

Detecting covert consciousness in behaviorally unresponsive patients by brain imaging is of great interest, but a reproducible model and evidence from independent sources is still lacking. Here we demonstrate the possibility of using general anesthetics in a within-subjects study design to test methods or statistical paradigms of assessing covert consciousness. Using noninvasive neuroimaging in healthy volunteers, we identified a healthy study participant who was able to exhibit the specific fMRI signatures of volitional mental imagery while behaviorally unresponsive due to sedation with propofol. Our findings reveal a novel model that may accelerate the development of new approaches to reproducibly detect covert consciousness, which is difficult to achieve in patients with heterogeneous and sometimes clinically unstable neuropathology.
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http://dx.doi.org/10.1038/s41598-018-31436-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6123455PMC
September 2018

Neurologic Considerations and Complications Related to Liver Transplantation.

Anesthesiology 2018 05;128(5):1008-1014

From the Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan.

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http://dx.doi.org/10.1097/ALN.0000000000002148DOI Listing
May 2018

Promoting a Restrictive Intraoperative Transfusion Strategy: The Influence of a Transfusion Guideline and a Novel Software Tool.

Anesth Analg 2018 09;127(3):744-752

From the Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan.

Background: The effect of neither transfusion guidelines nor decision support tools on intraoperative transfusion has been previously evaluated. The University of Michigan introduced a transfusion guideline in 2009, and in 2011, the Department of Anesthesiology developed a transfusion decision support tool. The primary aim of this study was to assess the associations of the transfusion guideline and the optional use of the software transfusion tool with intraoperative behaviors; pretransfusion hematocrit assessment (whether or not a hematocrit was checked before each red cell unit) and restrictive red cell use (withholding transfusion unless the hematocrit was ≤21%).

Methods: This was a before-after retrospective study without a concurrent control group of patients transfused 1-3 units of red cells intraoperatively. Three phases were studied to provide data both before and after the implementation of the transfusion guideline and the intraoperative software tool. Within each phase, trends of checking hematocrits before transfusion and restrictive transfusion were charted against time. F tests were used to measure differences of slopes. The difference between means of each phase was measured using Mann-Whitney U tests. Independent associations were measured using mixed-effects multivariable logistic regression. A secondary outcome analysis was conducted for 30-day mortality, myocardial infarction, renal injury, and their combination.

Results: The transfusion guideline was associated with increased pretransfusion hematocrit evaluation (67.4%, standard deviation [SD] 3.9 vs 76.5%, SD 2.7; P < .001) and restrictive transfusion practice (14.0%, SD 7.4 vs 33.3%, SD 4.4; P = .001). After adjustment for confounders, the guideline phase was independently associated with increased hematocrit checking (odds ratio, 1.72; 95% confidence interval, 1.46-2.03; P < .001) and restrictive red cell transfusion (odds ratio, 2.95; 95% confidence interval, 2.46-3.54; P < .001). The software tool was not associated with either transfusion behavior. There was no significant change in the rate of renal injury (16.06%), myocardial injury (4.93%), 30-day mortality (5.47%), or a composite (21.90%).

Conclusions: The introduction of a transfusion guideline was independently associated with increased intraoperative pretransfusion hematocrit assessment and restrictive transfusion. The use of a software tool did not further influence either behavior.
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http://dx.doi.org/10.1213/ANE.0000000000002704DOI Listing
September 2018

Factors Associated with Postoperative Prolonged Mechanical Ventilation in Pediatric Liver Transplant Recipients.

Anesthesiol Res Pract 2017 3;2017:3728289. Epub 2017 Jul 3.

Department of Anesthesiology, University of Michigan, Ann Arbor, MI, USA.

Introduction: Almost all pediatric orthotopic liver transplant (OLT) recipients require mechanical ventilation in the early postoperative period. Prolonged postoperative mechanical ventilation (PPMV) may be a marker of severe disease and may be associated with morbidity and mortality. We determined the incidence and risk factors for PPMV in children who underwent OLT.

Methods: This was a retrospective analysis of data collected on 128 pediatric OLT recipients. PPMV was defined as postoperative ventilation ≥ 4 days. Perioperative characteristics were compared between cases and control groups. Multivariable logistic regression analysis was used to calculate odds ratios for PPMV after controlling for relevant cofactors.

Results: An estimated 25% (95% CI, 17.4%-32.6%) required PPMV. The overall incidence of PPMV varied significantly by age group with the highest incidence among infants. PPMV was associated with higher postoperative mortality ( = 0.004) and longer intensive care unit ( < 0.001) and hospital length of stay ( < 0.001). Multivariable analysis identified young patient age, preoperative hypocalcemia, and increasing duration of surgery as independent predictors of PPMV following OLT.

Conclusion: The incidence of PPMV is high and it was associated with prolonged ICU and hospital LOS and higher posttransplant mortality. Surgery duration appears to be the only modifiable predictor of PPMV.
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http://dx.doi.org/10.1155/2017/3728289DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5512041PMC
July 2017

Network Efficiency and Posterior Alpha Patterns Are Markers of Recovery from General Anesthesia: A High-Density Electroencephalography Study in Healthy Volunteers.

Front Hum Neurosci 2017 28;11:328. Epub 2017 Jun 28.

Center for Consciousness Science, University of Michigan Medical SchoolAnn Arbor, MI, United States.

Recent studies have investigated local oscillations, long-range connectivity, and global network patterns to identify neural changes associated with anesthetic-induced unconsciousness. These studies typically employ anesthetic protocols that either just cross the threshold of unconsciousness, or induce deep unconsciousness for a brief period of time-neither of which models general anesthesia for major surgery. To study neural patterns of unconsciousness and recovery in a clinically-relevant context, we used a realistic anesthetic regimen to induce and maintain unconsciousness in eight healthy participants for 3 h. High-density electroencephalogram (EEG) was acquired throughout and for another 3 h after emergence. Seven epochs of 5-min eyes-closed resting states were extracted from the data at baseline as well as 30, 60, 90, 120, 150, and 180-min post-emergence. Additionally, 5-min epochs were extracted during induction, unconsciousness, and immediately prior to recovery of consciousness, for a total of 10 analysis epochs. The EEG data in each epoch were analyzed using source-localized spectral analysis, phase-lag index, and graph theoretical techniques. Posterior alpha power was significantly depressed during unconsciousness, and gradually approached baseline levels over the 3 h recovery period. Phase-lag index did not distinguish between states of consciousness or stages of recovery. Network efficiency was significantly depressed and network clustering coefficient was significantly increased during unconsciousness; these graph theoretical measures returned to baseline during the 3 h recovery period. Posterior alpha power may be a potential biomarker for normal recovery of functional brain networks after general anesthesia.
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http://dx.doi.org/10.3389/fnhum.2017.00328DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5487412PMC
June 2017

Neurophysiologic Correlates of Ketamine Sedation and Anesthesia: A High-density Electroencephalography Study in Healthy Volunteers.

Anesthesiology 2017 07;127(1):58-69

From the Department of Anesthesiology (P.E.V., T.B.-B., U.L., D.L., H.K., E.J., V.T., A.M.M., B.S.K., P.P., G.A.M.), Center for Consciousness Science (P.E.V., T.B.-B., U.L., D.L., H.K., G.A.M.), and Neuroscience Graduate Program (G.A.M.), University of Michigan Medical School, Ann Arbor, Michigan; and the Department of Anesthesiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois (A.B.P.).

Background: Previous studies have demonstrated inconsistent neurophysiologic effects of ketamine, although discrepant findings might relate to differences in doses studied, brain regions analyzed, coadministration of other anesthetic medications, and resolution of the electroencephalograph. The objective of this study was to characterize the dose-dependent effects of ketamine on cortical oscillations and functional connectivity.

Methods: Ten healthy human volunteers were recruited for study participation. The data were recorded using a 128-channel electroencephalograph during baseline consciousness, subanesthetic dosing (0.5 mg/kg over 40 min), anesthetic dosing (1.5 mg/kg bolus), and recovery. No other sedative or anesthetic medications were administered. Spectrograms, topomaps, and functional connectivity (weighted and directed phase lag index) were computed and analyzed.

Results: Frontal theta bandwidth power increased most dramatically during ketamine anesthesia (mean power ± SD, 4.25 ± 1.90 dB) compared to the baseline (0.64 ± 0.28 dB), subanesthetic (0.60 ± 0.30 dB), and recovery (0.68 ± 0.41 dB) states; P < 0.001. Gamma power also increased during ketamine anesthesia. Weighted phase lag index demonstrated theta phase locking within anterior regions (0.2349 ± 0.1170, P < 0.001) and between anterior and posterior regions (0.2159 ± 0.1538, P < 0.01) during ketamine anesthesia. Alpha power gradually decreased with subanesthetic ketamine, and anterior-to-posterior directed connectivity was maximally reduced (0.0282 ± 0.0772) during ketamine anesthesia compared to all other states (P < 0.05).

Conclusions: Ketamine anesthesia correlates most clearly with distinct changes in the theta bandwidth, including increased power and functional connectivity. Anterior-to-posterior connectivity in the alpha bandwidth becomes maximally depressed with anesthetic ketamine administration, suggesting a dose-dependent effect.
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http://dx.doi.org/10.1097/ALN.0000000000001671DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5478453PMC
July 2017

Pleural Effusion Causing Cardiac Tamponade Following the Transition From Negative- to Positive-Pressure Ventilation During Aortic Aneurysm Repair.

J Cardiothorac Vasc Anesth 2016 Jun 1;30(3):736-40. Epub 2015 Sep 1.

University of Michigan Medical School, Ann Arbor, MI.. Electronic address:

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http://dx.doi.org/10.1053/j.jvca.2015.08.034DOI Listing
June 2016

Influence of Ventilation Strategies and Anesthetic Techniques on Regional Cerebral Oximetry in the Beach Chair Position: A Prospective Interventional Study with a Randomized Comparison of Two Anesthetics.

Anesthesiology 2015 Oct;123(4):765-74

From the Department of Anesthesiology (P.P., A.D., A.A., M.N., A.S., M.H., G.A.M.) and Department of Orthopedic Surgery (B.S.M.), University of Michigan Medical School, Ann Arbor, Michigan.

Background: Beach chair positioning during general anesthesia is associated with cerebral oxygen desaturation. Changes in cerebral oxygenation resulting from the interaction of inspired oxygen fraction (FIO2), end-tidal carbon dioxide (PETCO2), and anesthetic choice have not been fully evaluated in anesthetized patients in the beach chair position.

Methods: This is a prospective interventional within-group study of patients undergoing shoulder surgery in the beach chair position that incorporated a randomized comparison between two anesthetics. Fifty-six patients were randomized to receive desflurane or total intravenous anesthesia with propofol. Following induction of anesthesia and positioning, FIO2 and minute ventilation were sequentially adjusted for all patients. Regional cerebral oxygenation (rSO2) was the primary outcome and was recorded at each of five set points.

Results: While maintaining FIO2 at 0.3 and PETCO2 at 30 mmHg, there was a decrease in rSO2 from 68% (SD, 12) to 61% (SD, 12) (P < 0.001) following beach chair positioning. The combined interventions of increasing FIO2 to 1.0 and increasing PETCO2 to 45 mmHg resulted in a 14% point improvement in rSO2 to 75% (SD, 12) (P <0.001) for patients anesthetized in the beach chair position. There was no significant interaction effect of the anesthetic at the study intervention points.

Conclusions: Increasing FIO2 and PETCO2 resulted in a significant increase in rSO2 that overcomes desaturation in patients anesthetized in the beach chair position and that appears independent of anesthetic choice.
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http://dx.doi.org/10.1097/ALN.0000000000000798DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4573359PMC
October 2015

Behavioral Modification of Intraoperative Hyperglycemia Management with a Novel Real-time Audiovisual Monitor.

Anesthesiology 2015 Jul;123(1):29-37

From the Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan.

Background: Hyperglycemia, defined as blood glucose (BG) levels above 200 mg/dl (11.1 mM), is associated with increased postoperative morbidity. Yet, the treatment standard for intraoperative glycemic control is poorly defined for noncardiac surgery. Little is known of the interindividual treatment variability or methods to modify intraoperative glycemic management behaviors. AlertWatch (AlertWatch, USA) is a novel audiovisual alert system that serves as a secondary patient monitor for use in operating rooms. The authors evaluated the influence of use of AlertWatch on intraoperative glycemic management behavior.

Methods: AlertWatch displays historical patient data (risk factors and laboratory results) from multiple networked information systems, combined with the patient's live physiologic data. The authors extracted intraoperative data for 19 months to evaluate the relationship between AlertWatch usage and initiation of insulin treatment for hyperglycemia. Outcome associations were adjusted for physical status, case duration, procedural complexity, emergent procedure, fasting BG value, home insulin therapy, patient age, and primary anesthetist.

Results: Overall, 2,341 patients had documented intraoperative hyperglycemia. Use of AlertWatch (791 of 2,341; 33.5%) was associated with 55% increase in insulin treatment (496 of 791 [62.7%] with and 817 of 1,550 [52.7%] without AlertWatch; adjusted odds ratio [95% CI], 1.55 [1.23 to 1.95]; P < 0.001) and 44% increase in BG recheck after insulin administration (407 of 791 [51.5%] with AlertWatch and 655 of 1,550 [42.3%] in controls; adjusted odds ratio [95% CI], 1.44 [1.14 to 1.81]; P = 0.002).

Conclusion: AlertWatch is associated with a significant increase in desirable intraoperative glycemic management behavior and may help achieve tighter intraoperative glycemic control.
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http://dx.doi.org/10.1097/ALN.0000000000000699DOI Listing
July 2015

Assessment of intraoperative awareness with explicit recall: a comparison of 2 methods.

Anesth Analg 2013 Apr 4;116(4):889-91. Epub 2013 Mar 4.

Division of Neuroanesthesiology, Department of Anesthesiology, University of Michigan Medical School, 1H247 UH/SPC-5048, 1500 East Medical Center Drive, Ann Arbor, MI 48109-5048, USA.

Background: Superiority of the modified Brice interview over quality assurance techniques in detecting intraoperative awareness with explicit recall has not been demonstrated definitively.

Methods: We studied a single patient cohort to compare the detection of definite awareness using a single modified Brice interview (postoperative day 28-30) versus quality assurance data (postoperative day 1).

Results: The incidence of awareness based on the modified Brice interview was 19 per 18,847 or 0.1%. Fewer awareness cases (incidence 0.02%) were detected by the quality assurance approach (P < 0.0001).

Conclusion: The modified Brice interview is the preferred modality for assessing intraoperative awareness with explicit recall.
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http://dx.doi.org/10.1213/ANE.0b013e318281e9adDOI Listing
April 2013

The influence of basic ventilation strategies and anesthetic techniques on cerebral oxygenation in the beach chair position: study protocol.

BMC Anesthesiol 2012 Sep 20;12:23. Epub 2012 Sep 20.

Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.

Unlabelled:

Background: Beach chair positioning during general anesthesia is associated with a high incidence of cerebral desaturation; poor neurological outcome is a growing concern. There are no published data pertaining to changes in cerebral oxygenation seen with increases in the inspired oxygen fraction or end-tidal carbon dioxide in patients anesthetized in the beach chair position. Furthermore, the effect anesthetic agents have has not been thoroughly investigated in this context. We plan to test the hypothesis that changes in inspired oxygen fraction or end-tidal carbon dioxide correlate to a significant change in regional cerebral oxygenation in anesthetized patients in beach chair position. We will also compare the effects that inhaled and intravenous anesthetics have on this process.

Methods/design: This is a prospective within-group study of patients undergoing shoulder arthroscopy in the beach chair position which incorporates a randomized comparison between two anesthetics, approved by the Institutional Review Board of the University of Michigan, Ann Arbor. The primary outcome measure is the change in regional cerebral oxygenation due to sequential changes in oxygenation and ventilation. A sample size of 48 will have greater than 80% power to detect an absolute 4-5% difference in regional cerebral oxygenation caused by changes in ventilation strategy. The secondary outcome is the effect of anesthetic choice on cerebral desaturation in the beach chair position or response to changes in ventilation strategy. Fifty-four patients will be recruited, allowing for drop out, targeting 24 patients in each group randomized to an anesthetic. Regional cerebral oxygenation will be measured using the INVOS 5100C monitor (Covidien, Boulder, CO). Following induction of anesthesia, intubation and positioning, inspired oxygen fraction and minute ventilation will be sequentially adjusted. At each set point, regional cerebral oxygenation will be recorded and venous blood gas analysis performed. The overall statistical analysis will use a repeated measures analysis of variance with Tukey's HSD procedure for post hoc contrasts.

Discussion: If simple maneuvers of ventilation or anesthetic technique can prevent cerebral hypoxia, patient outcome may be improved. This is the first study to investigate the effects of ventilation strategies on cerebral oxygenation in patients anesthetized in beach chair position.

Trial Registration: NCT01535274.
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http://dx.doi.org/10.1186/1471-2253-12-23DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3499238PMC
September 2012

Prevention of intraoperative awareness with explicit recall in an unselected surgical population: a randomized comparative effectiveness trial.

Anesthesiology 2012 Oct;117(4):717-25

Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan 48109-5048, USA.

Background: Intraoperative awareness with explicit recall occurs in approximately 0.15% of all surgical cases. Efficacy trials based on the Bispectral Index® (BIS) monitor (Covidien, Boulder, CO) and anesthetic concentrations have focused on high-risk patients, but there are no effectiveness data applicable to an unselected surgical population.

Methods: We conducted a randomized controlled trial of unselected surgical patients at three hospitals of a tertiary academic medical center. Surgical cases were randomized to alerting algorithms based on either BIS values or anesthetic concentrations. The primary outcome was the incidence of definite intraoperative awareness; prespecified secondary outcomes included postanesthetic recovery variables.

Results: The study was terminated because of futility. At interim analysis the incidence of definite awareness was 0.12% (11/9,376) (95% CI: 0.07-0.21%) in the anesthetic concentration group and 0.08% (8/9,460) (95% CI: 0.04-0.16%) in the BIS group (P = 0.48). There was no significant difference between the two groups in terms of meeting criteria for recovery room discharge or incidence of nausea and vomiting. By post hoc secondary analysis, the BIS protocol was associated with a 4.7-fold reduction in definite or possible awareness events compared with a cohort receiving no intervention (P = 0.001; 95% CI: 1.7-13.1).

Conclusion: This negative trial could not detect a difference in the incidence of definite awareness or recovery variables between monitoring protocols based on either BIS values or anesthetic concentration. By post hoc analysis, a protocol based on BIS monitoring reduced the incidence of definite or possible intraoperative awareness compared with routine care.
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http://dx.doi.org/10.1097/ALN.0b013e31826904a6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3447261PMC
October 2012

Comparison of the glidescope, CMAC, storz DCI with the Macintosh laryngoscope during simulated difficult laryngoscopy: a manikin study.

BMC Anesthesiol 2012 Jun 21;12:11. Epub 2012 Jun 21.

Department of Anesthesiology, The University of Michigan, 1500 E, Medical Center Dr,, 1H247, SPC 5048, Ann Arbor, MI, 48109-5048, USA.

Unlabelled:

Background: Videolaryngoscopy presents a new approach for the management of the difficult and rescue airway. There is little available evidence to compare the performance features of these devices in true difficult laryngoscopy.

Methods: A prospective randomized crossover study was performed comparing the performance features of the Macintosh Laryngoscope, Glidescope, Storz CMAC and Storz DCI videolaryngoscope. Thirty anesthesia providers attempted intubation with each of the 4 laryngoscopes in a high fidelity difficult laryngoscopy manikin. The time to successful intubation (TTSI) was recorded for each device, along with failure rate, and the best view of the glottis obtained.

Results: Use of the Glidescope, CMAC and Storz videolaryngoscopes improved the view of the glottis compared with use of the Macintosh blade (GEE, p = 0.000, p = 0.002, p = 0.000 respectively). Use of the CMAC resulted in an improved view compared with use of the Storz VL (Fishers, p = 0.05). Use of the Glidescope or Storz videolaryngoscope blade resulted in a longer TTSI compared with either the Macintosh (GLM, p = 0.000, p = 0.029 respectively) or CMAC blades (GLM, p = 0.000, p = 0.033 respectively).

Conclusions: Unsurprisingly, when used in a simulated difficult laryngoscopy, all the videolaryngoscopes resulted in a better view of the glottis than the Macintosh blade. However, interestingly the CMAC was found to provide a better laryngoscopic view that the Storz DCI Videolaryngoscope. Additionally, use of either the Glidescope or Storz DCI Videolaryngoscope resulted in a prolonged time to successful intubation compared with use of the CMAC or Macintosh blade. The use of the CMAC during manikin simulated difficult laryngoscopy combined the efficacy of attainment of laryngoscopic view with the expediency of successful intubation. Use of the Macintosh blade combined expedience with success, despite a limited laryngoscopic view. The limitations of a manikin model of difficult laryngoscopy limits the conclusions for extrapolation into clinical practice.
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http://dx.doi.org/10.1186/1471-2253-12-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3519500PMC
June 2012

The association of body mass index to postoperative outcomes in elderly vascular surgery patients: a reverse J-curve phenomenon.

Anesth Analg 2011 Jan 2;112(1):23-9. Epub 2010 Dec 2.

Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan 48109-0048, USA.

Background: The purpose of this investigation was to determine whether there is a relation between body mass index (BMI) classes and early postoperative outcomes in elderly patients undergoing vascular surgery. We hypothesized that being overweight or obese increases the risks of surgery.

Methods: Data from the American College of Surgeons' National Surgical Quality Improvement Program Participant Use Data File was used to identify the BMI (kg/m(2)) and 30-day outcomes of 25,337 patients aged ≥ 65 years undergoing vascular surgery from 2005 to 2007. Patients were stratified into 6 BMI classes: (1) underweight (BMI ≤ 18.5 kg/m(2)), (2) normal (BMI = 18.6-24.9 kg/m(2)), (3) overweight (BMI = 25-29.9 kg/m(2)), (4) obese class I (BMI = 30-34.9 kg/m(2)), (5) obese class II (BMI = 35-39.9 kg/m(2)), and (6) obese class III (BMI ≥ 40 kg/m(2)). Morbidity and mortality rates across all BMI classes were subjected to univariate and multiple logistic regression analyses.

Results: Mortality rates varied among the BMI classes: 9.4% underweight, 4.0% normal, 3.0 overweight and obese I, 3.3% obese II, and 4.6% obese III (P < 0.001). Major postoperative morbidity paralleled the risk of death. Independent preoperative factors associated with mortality included diabetes mellitus, chronic obstructive pulmonary disease, active congestive heart failure, recent weight loss, disseminated cancer, and an inability to function independently. Each of these factors was statistically more important than the BMI alone in defining an increased risk of surgery.

Conclusion: Increased BMI alone was not a major factor predicting perioperative 30-day mortality in this cohort of elderly surgical patients; the effect was a nonlinear one with a reversed J-curve response documenting the poorest outcomes in underweight, normal, and a slight increase in excessively obese patients.
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http://dx.doi.org/10.1213/ANE.0b013e3181fcc51aDOI Listing
January 2011

The influence of basic ventilation strategies on cerebral oxygenation in anesthetized patients without vascular disease.

J Clin Monit Comput 2010 Dec 9;24(6):421-5. Epub 2010 Nov 9.

Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, MI, USA.

Objectives: Optimizing cerebral oxygenation is of paramount importance in certain intraoperative situations. There is, however, a paucity of published data pertaining to changes in cerebral oxygenation seen with increases in the inspired fraction of oxygen (FIO2) or end-tidal carbon dioxide (PETCO2) in anesthetized patients without vascular disease. Here we tested the hypothesis that changes in FIO2 or PETCO2 correlate to a significant change in regional cerebral oxygenation (rSO2) in anesthetized patients without vascular disease.

Methods: This was a prospective pilot study approved by the IRB. We measured rSO2 using the INVOS 5100B monitor in ten anesthetized patients. Patients were excluded if they had a history of or risk factors for vascular disease, suffered from respiratory failure, or did not speak English. Following induction of anesthesia and intubation, FIO2 and minute ventilation were sequentially adjusted. At each set point, rSO2 was recorded and arterial blood gas analysis was performed. Each patient acted as their own control. A paired-sample t test was used to evaluate the change in rSO2 resultant upon each intervention.

Results: The baseline rSO2 was measured with patients awake, breathing room air and varied between 48 and 72%. While maintaining PETCO2 in the range 30-35 mmHg, rSO2 was 8% higher when 100% oxygen was delivered compared to FIO2 30% (P = 0.021). While maintaining PETCO2 in the range 40-45 mmHg, rSO2 was 7% higher when 100% oxygen is delivered compared to FIO2 30% (P = 0.032). While maintaining FIO2 at 100%, rSO2 was 2% higher when PETCO2 was in the range 40-45 mmHg compared to PETCO2 30-35 mmHg (P = 0.017). While maintaining FIO2 at 30%, rSO2 was not statistically different between PECO2 40-45 mmHg and PETCO2 30-35 mmHg.

Conclusions: Modulating oxygenation and ventilation in anesthetized patients without vascular disease leads to measurable changes in rSO2.
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http://dx.doi.org/10.1007/s10877-010-9265-xDOI Listing
December 2010

The influence of inspired oxygen fraction and end-tidal carbon dioxide on post-cross-clamp cerebral oxygenation during carotid endarterectomy under general anesthesia.

Anesth Analg 2010 Feb 2;110(2):581-7. Epub 2009 Dec 2.

Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA.

Background: Ten to fifteen percent of awake patients develop neurological deficits secondary to cerebral hypoperfusion after carotid artery cross-clamping. The reversal of such deficits by increasing the inspired oxygen fraction (Fio(2)) has been demonstrated, and regional cerebral oxygenation (rSO(2)) has been shown to improve during carotid cross-clamping in awake patients by increasing Fio(2). Paradoxical improvements in cerebral blood flow during carotid endarterectomy (CEA) at the time of cross-clamping and normalization of post-cross-clamp electroencephalographic abnormalities have been induced by hypocapnia. We performed this study to determine the influence of Fio(2) and end-tidal carbon dioxide (Petco(2)) on rSO(2) in patients undergoing CEA with general anesthesia during carotid cross-clamping.

Methods: Twenty patients were recruited. Ten underwent elective shunting. Patients received standardized general anesthesia. rSO(2) was measured using the INVOS 5100B monitor (Somanetics Corporation, Troy, MI). After carotid cross-clamping, Fio(2) and minute ventilation were sequentially adjusted: 1) Fio(2) 30%, Petco(2) 30-35 mm Hg; 2) Fio(2) 100%, Petco(2) 30-35 mm Hg; and 3) Fio(2) 100%, Petco(2) 40-45 mm Hg. At each point, rSO(2) was recorded from both operative and nonoperative sides, and arterial blood gas analysis was performed.

Results: Results from shunted and unshunted patients were analyzed separately. Increasing Fio(2): Administration of 100% oxygen while maintaining Petco(2) in the range 30-35 mm Hg in unshunted patients resulted in an 8% increase (P = 0.008) in rSO(2) on the operative side and a 6% increase (P = 0.011) on the nonoperative side compared with an Fio(2) of 30%. In shunted patients, administration of 100% oxygen while maintaining the Petco(2) in the range 30-35 mm Hg resulted in a 4% increase in rSO(2) on both the operative side (P = 0.008) and the nonoperative side (P = 0.011) compared with an Fio(2) of 30%. Increasing Petco(2): In unshunted patients, there was a 6% (P = 0.008) increase in rSO(2) on the operative side and a 5% increase (P = 0.024) on the nonoperative side at Petco(2) 40-45 mm Hg compared with Petco(2) 30-35 mm Hg maintaining Fio(2) at 100%. In shunted patients, there was a 3% increase (P = 0.018) in rSO(2) on the operative side and a 4% increase (P = 0.007) on the nonoperative side at Petco(2) 40-45 mm Hg compared with Petco(2) 30-35 mm Hg maintaining Fio(2) at 100%.

Conclusion: rSO(2) is reliably improved during carotid cross-clamping by increasing Fio(2) in patients undergoing CEA with general anesthesia. Additional improvement in rSO(2) may be gained by increasing Petco(2).
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http://dx.doi.org/10.1213/ANE.0b013e3181c5f160DOI Listing
February 2010