Narcotrend® and Bispectral Index® Monitor Are Superior to Classic Electroencephalographic Parameters for the Assessment of Anesthetic States during Propofol-Remifentanil Anesthesia

Background: A new electroencephalogram monitor, the Narcotrend(R), was developed to measure anesthetic depth. The authors compared the Narcotrend(R), the Bispectral Index(R), and classic electroencephalographic and hemodynamic parameters during anesthesia with propofol and remifentanil.

Methods: The authors investigated 25 patients undergoing laminectomy at different anesthetic states: awake, steady state anesthesia, first reaction during emergence, and extubation. Narcotrend(R) value; BIS; relative power (percent) in [delta], [theta], [alpha], and [beta]; median frequency; spectral edge frequency; and hemodynamic parameters were recorded simultaneously. The ability of the classic and processed electroencephalographic and hemodynamic parameters to predict the clinically relevant anesthetic states of awake, steady state anesthesia, first reaction, and extubation was tested using prediction probability.

Results: Only the Narcotrend(R) was able to differentiate between awake versus steady state anesthesia and steady state anesthesia versus first reaction/extubation with a prediction probability value of more than 0.90.     

Comparative evaluation of the Datex-Ohmeda S/5 Entropy Module and the Bispectral Index monitor during propofol-remifentanil anesthesia

BACKGROUND: Different analytical concepts were introduced to quantify the changes of the electroencephalogram. The Datex-Ohmeda S/5 Entropy Module (Datex-Ohmeda Division, Instrumentarium Corp., Helsinki, Finland) was the first commercial monitor based on the entropy generating two indices, the state entropy (SE) and the response entropy (RE). The aim of the current study was to compare the accuracy of SE and RE with the Bispectral Index(R) monitor (BIS(R); Aspect Medical Systems, Newton, MA) during propofol-remifentanil anesthesia. METHODS: The authors investigated 20 female patients during minor gynecologic surgery. SE, RE, BIS, mean arterial blood pressure, heart rate, and sedation level were recorded every 20 s during stepwise increase (target-controlled infusion, 0.5 microg/ml) of propofol until the patients lost response. Five minutes after loss of response, remifentanil infusion (0.4 microg . kg(-1) . min(-1)) was started. Spearman correlation coefficient and prediction probability were calculated for sedation levels with SE, RE, BIS, mean arterial blood pressure, and heart rate. The ability of the investigated parameters to distinguish between the anesthesia steps awake versus loss of response, awake versus anesthesia, anesthesia versus first reaction, and anesthesia versus extubation was analyzed with the prediction probability. RESULTS: SE correlates best with sedation levels, but no significant differences of the prediction probability values among SE, RE, and BIS were found. The prediction probability for all investigated steps of anesthesia did not show significant differences among SE, RE, and BIS. SE, RE, and BIS were superior to mean arterial blood pressure and heart rate. CONCLUSION: SE, RE, and BIS revealed similar information about the level of sedation and allowed the authors to distinguish between different steps of anesthesia. Both monitors provided useful additional information for the anesthesiologist.     

Application of Bispectral Index® and Narcotrend® Index to the Measurement of the Electroencephalographic Effects of Isoflurane with and without Burst Suppression

Background: The Narcotrend(R) monitor (MonitorTechnik, Bad Bramstedt, Germany) has recently been introduced as an intraoperative monitor of anesthetic state, based on a classification scheme originally developed for visual assessment of the electroencephalogram. The authors compared the performance of the Narcotrend(R) index (software version 4.0) to the Bispectral Index(R) (BIS(R), version XP; Aspect Medical Systems, Natick, MA) as electroencephalographic measures of isoflurane drug effect during general anesthesia.

Methods: The authors observed 15 adult patients scheduled to undergo radical prostatectomy with a combined epidural-isoflurane general anesthesia technique. At least 45 min after induction of general anesthesia, during a phase of constant surgical stimulation, end-tidal isoflurane concentrations were varied between 0.5 and 2.0 multiples of minimum alveolar concentration, and the BIS(R) and the Narcotrend(R) index were recorded. The prediction probability (PK) was calculated for the BIS(R) and the Narcotrend(R) index to predict isoflurane effect compartment concentration for each measure. The correlation analysis of the BIS(R) and the Narcotrend(R) index with the isoflurane effect compartment concentration was obtained by pharmacodynamic modeling based on two sigmoidal curves to account for the discontinuity in both indices with the onset of burst suppression.

Results: The prediction probabilities were indistinguishable (BIS(R) PK = 0.72 +/- 0.07 (mean +/- SD); range, 0.61-0.84; Narcotrend(R) index PK = 0.72 +/- 0.10; range, 0.51-0.87), as were the correlations between the electroencephalographic measures and isoflurane effect compartment concentrations (BIS(R) R2 = 0.82 +/- 0.12; Narcotrend(R) index R2 = 0.85 +/- 0.09). The pharmacodynamic models for the BIS(R) and the Narcotrend(R) index yielded nearly identical results.     

The Effects of Ketamine and Rocuronium on the A-Line® Auditory Evoked Potential Index, Bispectral Index, and Spectral Entropy Monitor during Steady State Propofol and Remifentanil Anesthesia

Background: The authors studied the effects of ketamine and rocuronium on the Bispectral Index, A-Line(R) auditory evoked potential index, state entropy, and response entropy during a calculated steady state anesthesia with propofol and remifentanil.

Methods: After ethics committee approval, 42 patients were allocated to four groups. Baseline measurements were performed after implementing a calculated steady state anesthesia with propofol and remifentanil. The control group received no additional medication. The ketamine group received a bolus and continuous infusion of ketamine. The rocuronium group received a bolus of rocuronium. The rocuronium-ketamine group received both. All data were stored during 15 min after baseline. After inspection of the raw data, the authors conducted an explorative statistical analysis.

Results: No significant changes were found in the control group for any of the monitors. Mean values decreased in the rocuronium group for the A-Line(R) auditory evoked potential index, Bispectral Index, and response entropy, but not for state entropy. In the ketamine group, the A-Line(R) auditory evoked potential index and Bispectral Index did not change significantly, but state and response entropy increased. In the rocuronium-ketamine group, the A-Line(R) auditory evoked potential index and Bispectral Index did not decrease as found in the rocuronium group. Response and state entropy increased significantly.     

Intrapatient Reproducibility of the BISxp® Monitor

Background: The Bispectral Index (BIS) reportedly reflects anesthetic depth. It is recommended that anesthetic agents should be titrated to maintain the BIS between 40 and 60 arbitrary BIS units during anesthesia. For anesthesia providers to follow this recommendation, the monitor should be predictably affected by different anesthetic agents and have good interpatient and intrapatient reproducibility. The authors hypothesized that when two BISxp(R) devices (Aspect Medical Systems, Newton, MA) are placed concurrently on the same patient, their readings are concordant throughout the anesthetic period.

Methods: Simultaneous BIS recordings from two BISxp(R) monitors were obtained during anesthesia at 5-s intervals from 12 participants.

Results: In total 22,860 concurrent paired BIS readings were obtained. For 10.7% of the time, there were sustained periods of 30 s or greater where the readings suggested a different depth of anesthesia. For 6% of the time, there were sustained periods of 30 s or greater where the readings differed by 10 or more arbitrary BIS units. The regression coefficient (R2) for the two devices was 0.65 (range, 0.35-0.92). There was zero bias between the devices, and the 95% limits of agreement ranged between -18 and +17.     

Epidural Lidocaine Decreases Sevoflurane Requirement for Adequate Depth of Anesthesia as Measured by the Bispectral Index ® Monitor

Background: Epidural anesthesia potentiates sedative drug effects and decreases minimum alveolar concentration (MAC). The authors hypothesized that epidural anesthesia also decreases the general anesthetic requirements for adequate depth of anesthesia as measured by Bispectral Index (BIS).

Methods: After premedication with 0.02 mg/kg midazolam and 1 [mu]g/kg fentanyl, 30 patients aged 20-65 yr were randomized in a double-blinded fashion to receive general anesthesia with either intravenous saline placebo or intravenous lidocaine control (1-mg/kg bolus dose; 25 [mu]g [middle dot] kg-1 [middle dot] min-1). A matched group was prospectively assigned to receive epidural lidocaine (15 ml; 2%) with intravenous saline placebo. All patients received 4 mg/kg thiopental and 1 mg/kg rocuronium for tracheal intubation. After 10 min of a predetermined end-tidal sevoflurane concentration, BIS was measured. The ED50 of sevoflurane for each group was determined by up-down methodology based on BIS less than 50 (MACBIS50). Plasma lidocaine concentrations were measured.

Results: The MACBIS50 of sevoflurane (0.59% end tidal) was significantly decreased with lidocaine epidural anesthesia compared with general anesthesia alone (0.92%) or with intravenous lidocaine (1 %;P < 0.0001). Plasma lidocaine concentrations in the intravenous lidocaine group (1.9 [mu]g/ml) were similar to those in the epidural lidocaine group (2.0 [mu]g/ml).     

脑电双频指数用于小儿镇静及麻醉深度监测的研究进展

大量研究证实,脑电双频指数(BIS)与较大小儿的镇静及麻醉深度有较好的相 关性,与麻醉药物浓度呈负相关,能较好地评价意识水平。但对于婴儿,BIS监测的有效性尚 有待于进一步研究。     

A Comparison of the 24-Gauge Sprotte® and Gertie Marx® Spinal Needles for Combined Spinal-Epidural Analgesia during Labor

Background: Prior experience with the combined spinal-epidural technique (CSE) for labor analgesia demonstrated a high (up to 14%) failure rate because of failure to obtain cerebrospinal fluid (CSF) or lack of response to appropriate doses of intrathecal sufentanil. The current study was designed to test whether a longer needle with a shorter side port (Gertie Marx(R) needle; 127 mm long) would eliminate failures to obtain CSF compared with the needle we had used previously (Sprotte(R) needle; 120 mm long).

Methods: Seventy-three parturients were randomly assigned to have a CSE performed with one of these two needles. After identifying the epidural space with an 18-gauge Touhy needle at the L2-L3 or L3-L4 interspace, the spinal needle was introduced through the Touhy needle until penetration of the dura was felt or until the needle was maximally inserted. If no CSF was obtained, the alternate needle was tried. After obtaining CSF, 10 [mu]g sufentanil diluted in 1.8 ml saline was injected. Verbal pain scores (0-10) were obtained every 5 min for 30 min.

Results: Failure to obtain CSF occurred six times in the Sprotte group compared with none in the Gertie Marx group (P < 0.05). In all six failures in the Sprotte group, the Gertie Marx needle subsequently proved successful in obtaining CSF. There were no differences in pain scores between the groups.     

Comparative Efficacy of Acustimulation (ReliefBand®) versus Ondansetron (Zofran®) in Combination with Droperidol for Preventing Nausea and Vomiting

Background: Antiemetic drugs are costly, are associated with variable efficacy, and can produce unwanted side effects when used for prophylaxis against postoperative nausea and vomiting. This clinical study was designed to compare the efficacy of transcutaneous electrical acupoint stimulation using a ReliefBand(R) to ondansetron (Zofran(R)) when utilized alone or in combination for preventing postoperative nausea and vomiting after plastic surgery.

Methods: A single-center, randomized, double-blind, placebo- and sham-controlled study design was conducted to compare three prophylactic antiemetic treatment regimens in 120 outpatients undergoing plastic surgery procedures with routine low-dose droperidol prophylaxis: (1) ondansetron (n = 40), 4 mg intravenous ondansetron and a sham ReliefBand(R); (2) acustimulation (n = 40), 2 ml intravenous saline and an active ReliefBand(R); and (3) combination (n = 40), 4 mg intravenous ondansetron and an active ReliefBand(R). The incidences of postoperative nausea and vomiting, as well as the need for "rescue" antiemetics, were determined at specific time intervals for up to 72 h after surgery. The outcome variables assessed included recovery times, quality of recovery score, time to resumption of normal diet, and patient satisfaction with the prophylactic antiemetic therapy.

Results: Use of the ReliefBand(R) in combination with ondansetron significantly reduced nausea (20 vs. 50%), vomiting (0 vs. 20%), and the need for rescue antiemetics (10 vs. 37%) compared with ondansetron alone at 24 h after surgery. Furthermore, the ability to resume a normal diet (74 vs. 35%) within 24 h after surgery was significantly improved when the ReliefBand(R) was used to supplement ondansetron (vs. ondansetron alone). Finally, the quality of recovery (90 +/- 10 vs. 70 +/- 20) and patient satisfaction (94 +/- 10 vs. 75 +/- 22) scores were significantly higher in the combination group versus the ondansetron group. There were no significant differences between the ReliefBand(R) and ondansetron when administered as adjuvants to droperidol for antiemetic prophylaxis.     

Quantifying the Effect of Antiplatelet Therapy: A Comparison of the Platelet Function Analyzer (PFA-100®) and Modified Thromboelastography (mTEG®) with Light Transmission Platelet Aggregometry

Background: Antiplatelet therapy with aspirin and clopidogrel is known to confer protection against ischemic events. Increasing numbers of patients are presenting for surgery while taking these drugs. This may lead to an increase in perioperative blood loss, particularly in those who have a heightened response to the drugs. Identifying these patients preoperatively would allow us to plan appropriate management.

Methods: The antiplatelet effect of aspirin and/or clopidogrel was measured using two point-of-care monitors: the platelet function analyzer (PFA-100(R); Dade, Miami, FL) and the modified thromboelastograph (mTEG(R); Haemoscope Corp., Niles, IL). This was compared with optical light transmission aggregometry.

Results: All people taking aspirin displayed a definitive aspirin effect on aggregometry (n = 20). Ninety percent of these were identified by modified thromboelastography (n = 18). Seventy percent were identified by the platelet function analyzer (n = 14). Fifty percent of people taking clopidogrel displayed a definitive response to the drug on aggregometry. Seventy percent of these were identified on modified thromboelastography (n = 7). None were identified by the platelet function analyzer. There was good agreement between the results of the aggregometry and modified thromboelastography in clopidogrel patients ([kappa] = 0.81).     

Comparison of Amsorb®, Sodalime, and Baralyme® Degradation of Volatile Anesthetics and Formation of Carbon Monoxide and Compound A in Swine In Vivo

Background: Consequences of volatile anesthetic degradation by carbon dioxide absorbents that contain strong base include formation of compound A from sevoflurane, formation of carbon monoxide (CO) and CO toxicity from desflurane, enflurane and isoflurane, delayed inhalation induction, and increased anesthetic costs. Amsorb(R) (Armstrong Ltd., Coleraine, Northern Ireland) is a new absorbent that does not contain strong base and does not form CO or compound A in vitro. This investigation compared Amsorb(R), Baralyme(R) (Chemetron Medical Division, Allied Healthcare Products, St. Louis, MO), and sodalime effects on CO (from desflurane and isoflurane) and compound A formation, carboxyhemoglobin (COHb) concentrations, and anesthetic degradation in a clinically relevant porcine in vivo model.

Methods: Pigs were anesthetized with desflurane, isoflurane, or sevoflurane, using fresh or partially dehydrated Amsorb(R), Baralyme(R), and new and old formulations of sodalime. Anesthetic concentrations in the fresh (preabsorber), inspired (postabsorber), and end-tidal gas were measured, as were inspired CO and compound A concentrations and blood oxyhemoglobin and COHb concentrations.

Results: For desflurane and isoflurane, the order of inspired CO and COHb formation was dehydrated Baralyme(R) >> soda-lime > Amsorb(R). For desflurane and Baralyme(R), peak CO was 9,700 +/- 5,100 parts per million (ppm), and the increase in COHb was 37 +/- 14%. CO and COHb increases were undetectable with Amsorb(R). Oxyhemoglobin desaturation occurred with desflurane and Baralyme(R) but not Amsorb(R) or sodalime. The gap between inspired and end-tidal desflurane and isoflurane did not differ between the various dehydrated absorbents. Neither fresh nor dehydrated Amsorb(R) caused compound A formation from sevoflurane. In contrast, Baralyme(R) and sodalime caused 20-40 ppm compound A. The gap between inspired and end-tidal sevoflurane did not differ between fresh absorbents, but was Amsorb(R) < sodalime < Baralyme(R) with dehydrated absorbents.     

Utility of Whole Blood Hemostatometry Using the Clot Signature Analyzer® for Assessment of Hemostasis in Cardiac Surgery

Background: A hemostatic monitor capable of rapid, accurate detection of clinical coagulopathy within the operating room could improve management of bleeding after cardiopulmonary bypass (CPB). The Clot Signature Analyzer(R) is a hemostatometer that measures global hemostasis in whole blood. The authors hypothesized that point-of-care hemostatometry could detect a clinical coagulopathic state in cardiac surgical patients.

Methods: Fifty-seven adult patients scheduled for a variety of elective cardiac surgical procedures were studied. Anesthesia, CPB, heparin anticoagulation, protamine reversal, and transfusion for post-CPB bleeding were all managed by standardized protocol. Clinical coagulopathy was defined by the need for platelet or fresh frozen plasma transfusion. The Clot Signature Analyzer(R) collagen-induced thrombus formation (CITF) assay measured platelet-mediated hemostasis in vitro. The activated clotting time, platelet count, prothrombin time, activated partial thromboplastin time, and fibrinogen concentration were also measured.

Results: The postprotamine CITF was greater in patients who required hemostatic transfusion than in those who did not (17.6 +/- 8.0 min vs. 10.5 +/- 5.7 min, respectively;P < 0.01). Postprotamine CITF values were highly correlated with platelet and fresh frozen plasma transfusion (Spearman r = 0.50, P < 0.001 and r = 0.40, P < 0.005, respectively). Receiver operator characteristic curves showed a highly significant relation between the postprotamine CITF and intraoperative platelet and fresh frozen plasma transfusion (area under the curve, 0.78-0.81, P < 0.005) with 60-80% sensitivity, specificity, positive and negative predictive values at cutoffs of 12-14 min. Logistic regression demonstrated that the CITF was independently predictive of post-CPB hemostatic transfusion, but standard hemostatic assays were not.     

Comparative evaluation of Narcotrend, Bispectral Index, and classical electroencephalographic variables during induction, maintenance, and emergence of a propofol/remifentanil anesthesia

In the present study, we sought to compare the abilities of Narcotrend (NT) with the Bispectral Index (BIS) electroencephalographic system to monitor depth of consciousness immediately before induction of anesthesia until extubation during a standardized anesthetic. We investigated 26 patients undergoing laminectomy. Investigated states of anesthesia were: awake, loss of response, loss of eyelash reflex, steady-state anesthesia, first reaction, and extubation during emergence. NT, BIS, spectral edge frequency, median frequency, relative power in delta, theta, alpha, beta, and hemodynamics were recorded simultaneously. The ability of all variables to distinguish between awake versus loss of response, awake versus loss of eyelash reflex, awake versus steady-state anesthesia, steady-state anesthesia versus first reaction and extubation were analyzed with the prediction probability. Effects of remifentanil during propofol infusion were investigated with Friedman's and post hoc with Wilcoxon's test. Only NT and BIS were able to distinguish all investigated states accurately with a prediction probability >0.95. After start of remifentanil infusion, only hemodynamics changed statistically significantly (P < 0.05). NT and BIS are more reliable indicators for the assessment of anesthetic states than classical electroencephalographic variables and hemodynamics, whereas the analgesic potency of depth of anesthesia could not be detected by NT and BIS. IMPLICATIONS: The modern electroencephalographic monitoring systems Narcotrend and Bispectral Index are more reliable indicators for the assessment of anesthetic states than classical electroencephalographic and hemodynamic variables to predict anesthetic conditions from before induction of anesthesia until extubation during a standardized anesthetic regime with propofol and remifentanil. The analgesic potency of depth of anesthesia could not be detected by Narcotrend and Bispectral Index.