Paul Picton

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

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.

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

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.

Comparison of intermediate vs subcutaneous cervical plexus block for carotid endarterectomy

BACKGROUND Carotid endarterectomy surgery can be performed under regional anaesthesia alone or under general anaesthesia. However, there are several types of regional block available and reported complication rates after superficial cervical plexus blocks are significantly lower than deep blocks. It is not known if subcutaneous and intermediate blocks are equally effective, although anatomical evidence suggests that the latter (where the injectate diffuses below the deep cervical fascia) might provide superior quality of intraoperative anaesthesia. METHODS Forty-four patients were randomized to receive either subcutaneous or intermediate cervical plexus blocks for carotid endarterectomy. The primary endpoint was supplemental lidocaine requirement during surgery. Secondary outcome measures included: total amount of fentanyl administered during surgery, recall of pain scores during surgery, complications, and patient and surgeon satisfaction. RESULTS There was no statistically significant difference for median (range) lidocaine supplementation between the subcutaneous and intermediate groups 65 (20-170) mg vs. 85 (30-345) mg, respectively; P=0.31. There were no statistical differences in the secondary outcome measures and no major complications during the study. CONCLUSIONS Intermediate and subcutaneous cervical plexus blocks are equally effective for carotid endarterectomy. This study adds to the body of evidence supporting the safe use of superficial blocks for this type of surgery.

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

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 (Fio2) has been demonstrated, and regional cerebral oxygenation (rSO2) has been shown to improve during carotid cross-clamping in awake patients by increasing Fio2. 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 Fio2 and end-tidal carbon dioxide (Petco2) on rSO2 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. rSO2 was measured using the INVOS 5100B monitor (Somanetics Corporation, Troy, MI). After carotid cross-clamping, Fio2 and minute ventilation were sequentially adjusted: 1) Fio2 30%, Petco2 30–35 mm Hg; 2) Fio2 100%, Petco2 30–35 mm Hg; and 3) Fio2 100%, Petco2 40–45 mm Hg. At each point, rSO2 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 Fio2: Administration of 100% oxygen while maintaining Petco2 in the range 30–35 mm Hg in unshunted patients resulted in an 8% increase (P = 0.008) in rSO2 on the operative side and a 6% increase (P = 0.011) on the nonoperative side compared with an Fio2 of 30%. In shunted patients, administration of 100% oxygen while maintaining the Petco2 in the range 30–35 mm Hg resulted in a 4% increase in rSO2 on both the operative side (P = 0.008) and the nonoperative side (P = 0.011) compared with an Fio2 of 30%. Increasing Petco2: In unshunted patients, there was a 6% (P = 0.008) increase in rSO2 on the operative side and a 5% increase (P = 0.024) on the nonoperative side at Petco2 40–45 mm Hg compared with Petco2 30–35 mm Hg maintaining Fio2 at 100%. In shunted patients, there was a 3% increase (P = 0.018) in rSO2 on the operative side and a 4% increase (P = 0.007) on the nonoperative side at Petco2 40–45 mm Hg compared with Petco2 30–35 mm Hg maintaining Fio2 at 100%. CONCLUSION: rSO2 is reliably improved during carotid cross-clamping by increasing Fio2 in patients undergoing CEA with general anesthesia. Additional improvement in rSO2 may be gained by increasing Petco2.

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

BackgroundVideolaryngoscopy 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.MethodsA 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.ResultsUse 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).ConclusionsUnsurprisingly, 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.

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

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.

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

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.

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.

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.

Network efficiency and posterior alpha patterns are markers of recovery from general anesthesia: A high-density electroencephalography study in healthy volunteers

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.

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

BackgroundBeach 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/designThis 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.DiscussionIf 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 registrationNCT01535274