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.

The effect of a checklist on the quality of post-anaesthesia patient handover: a randomized controlled trial

OBJECTIVE

Patient handover is an important element of continuity, quality and safety in patient care. Handover without standardized protocols is prone to information loss and might be a possible danger to patient safety. Checklists are established methods that help to structure complex processes in other high-risk fields such as aviation. In the past few years, their implementation has attracted research interest in medicine. We hypothesize that a checklist for handover between anaesthesiologist and post-anaesthesia care unit nurse will increase the amount of information transfer during patient handover after anaesthesia.

DESIGN AND SETTING

A total of 120 post-anaesthesia patient handovers were recorded on video and analyzed. Forty handovers before the implementation of the checklist and 80 after the implementation of the checklist, randomized into two groups: with and without the use of the checklist.

MAIN OUTCOME MEASURES

An overall number of items handed over, handover of specific items and duration of the handover were analyzed.

RESULTS

With the use of the written checklist, the overall items handed over increased significantly from a median of 32.4-48.7%. The duration of handover increased from a median of 86-121 s. Instructions about items that should be included in handovers, but without the use of a written checklist, was not associated with an increase in the number of items handed over or duration of the interview.

CONCLUSIONS

This study suggests that the use of a checklist for post-anaesthesia handover might improve the quality of patient handover by increasing the information handed over.

Vascular endothelial growth factor-stimulated cerebral microvascular endothelial cells mediate the recruitment of neural stem cells to the neurovascular niche

Endogenous and transplanted neural stem cells (NSC) are highly migratory and display a unique tropism for areas of neuro-pathology. However, signals controlling NSC motility in health and disease are still ill-defined. NSC appear to be intimately associated with the cerebral vasculature and angiogenesis is a hallmark of many neurological disorders. This has led us to investigate the influence of quiescent and angiogenically active human endothelial cells on human NSC migration. In vivo we observed frequent perivascular accumulation of human NSC in the proximity of cerebral microvessels upon induction of angiogenesis by cerebral infusion of vascular endothelial growth factor (VEGF) into the murine brain. We analyzed the in vitro effects of conditioned media from human endothelial cells before and after angiogenic stimulation with VEGF on the migration of human NSC in vitro. Non-stimulated endothelial cells induced a moderate chemotactic migration that was significantly enhanced after angiogenic activation by VEGF. In order to identify cytokines that may function as stimulators of NSC chemotaxis, we screened endothelial cell-conditioned media for the expression of 120 different cytokines. We identified PDGF-BB, RANTES, I-TAC, NAP-2, GROalpha, Ang-2, and M-CSF as endothelial cell-released chemoattractants for human NSC in vitro. VEGF-stimulated cerebral microvascular endothelial cells secreted higher levels of Ang-2 and GROalpha, which in part were responsible for the enhanced chemoattraction of NSC. Our findings support the hypothesis that the angiogenically active microvasculature modulates the local guidance of NSC through endothelial cell-derived chemoattractants.

Bispectral index and A-line AAI index as guidance for desflurane-remifentanil anaesthesia compared with a standard practice group: a multicentre study

BACKGROUND

This study was designed to investigate the impact of bispectral index (BIS) or A-line AAI index (based on middle-latency auditory evoked potential) monitoring on recovery times and drug consumption when compared with standard anaesthetic practice during desflurane-remifentanil anaesthesia.

METHODS

After having obtained approval from the institutional review board and written informed consent, 200 adult patients undergoing minor surgical procedures were randomized to receive a desflurane-remifentanil anaesthetic controlled either solely by clinical parameters or by BIS or AAI to the following target values: during maintenance of anaesthesia to a value of '50' (BIS) or '30' (AAI), 15 min before the end of surgery to '60' (BIS) or '45' (AAI). Recovery times and drug consumption were recorded by a blinded investigator.

RESULTS

Compared with standard practice, patients with BIS or AAI monitoring needed similar desflurane concentrations (standard practice 2.9 [0.5] vol%, BIS 3.3 [0.9] vol%, AAI 2.6 [0.5] vol%), and had similar recovery times (open eyes 5.6 [2.5] min, 5.9 [3.4] min, 5.0 [3.1] min; extubation 6.3 [2.4] min, 6.6 [3.5] min, 5.6 [3.0] min; stating name 7.3 [2.4] min, 7.6 [3.5] min, 7.3 [6.6] min).

CONCLUSIONS

Compared with standard anaesthetic practice BIS and AAI guided titration to the used target ranges did not result in a reduction of desflurane consumption or recovery times during minor surgery with use of remifentanil.

Acute heart failure during spinal surgery in a boy with Duchenne muscular dystrophy

Patients with Duchenne muscular dystrophy (DMD) are at high risk of perioperative complications. DMD may be accompanied by heart failure resulting from dystrophic involvement of the myocardium, which can be subclinical in the early stages of the disease. This case demonstrates that a normal preoperative ECG and echocardiograph cannot exclude the development of heart failure during anaesthesia in DMD patients undergoing major surgery.

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, was developed to measure anesthetic depth. The authors compared the Narcotrend, the Bispectral Index, 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 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 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.

CONCLUSIONS

Modern electroencephalographic parameters, especially Narcotrend, are more reliable indicators for the clinical assessment of anesthetic states than classic parameters.

Single-channel amplitude integrated EEG recording for the identification of epileptic seizures by nonexpert physicians in the adult acute care setting

OBJECTIVE

Although several studies have shown the potential of amplitude integrated electroencephalography (aEEG) in detecting neonatal seizures, no publications have evaluated the diagnostic use of aEEG for the detection of seizures in adult patients.

METHODS

In this prospective blinded observational study, bifrontal single-channel electroencephalography (EEG) recordings were performed with a portable EEG monitor (CSM M3 ICU, Danmeter-Goalwick Holdings Limited, Odense, Denmark) during the out-of-hospital care of emergency cases. Four intensive care unit (ICU) physicians received training in the interpretation of aEEG recordings. After the training they evaluated the stored aEEG traces for the presence of epileptic seizure activity during the recording time. The physicians were blinded to the clinical data of the patients. The results obtained were compared with the clinical diagnosis and the evaluation of the raw EEG signal. The level of interrater agreement was quantified using Fleiss' ĸ.

RESULTS

The aEEG traces from 10 patients with generalized epileptic seizures and 46 patients without seizures were analysed. Overall, the nonexpert ICU physicians failed to identify recordings obtained from patients with seizures reliably, when compared with clinical diagnosis and the single-channel EEG results (mean sensitivity 40%, range 40-60%; mean specificity 89%, range 87-93%). Agreement between observers was high for the cases with seizures ( ĸ = 0.80 ± 0.13). Patients who suffered status epilepticus during the recordings were difficult to identify by most raters.

CONCLUSION

Recording of aEEG without access to the raw EEG data is not a reliable diagnostic tool for the identification of epileptic seizures in the hands of nonexpert ICU physicians.

Narcotrend, bispectral index, and classical electroencephalogram variables during emergence from propofol/remifentanil anesthesia

The aim of this study was to investigate modern and classical electroencephalographic (EEG) variables in response to remifentanil and propofol infusions. We hypothesized that modern EEG variables may indicate the effects of propofol but not of remifentanil. Twenty-five patients were included in the study after the end of elective spine surgery without any surgical stimulation. Baseline values were defined with remifentanil 0.3 microg. kg(-1). min(-1) and target-controlled infusion of propofol 3.0 microg/mL. EEG changes were evaluated 1, 3, 5, 7, and 9 min after the stop of remifentanil infusion, followed by a step-by-step reduction (0.2 microg/mL) every 3 min of target-controlled infusion propofol. Narcotrend (NT; classifying EEG stages from awake to deep anesthesia), bispectral index (BIS), EEG spectral frequency bands (%), 50% (Median) and 95% percentiles (spectral edge frequency), mean arterial blood pressure, heart rate, and oxygen saturation were detected at every time point. The end of remifentanil application resulted in significant increases in %alpha, spectral edge frequency, mean arterial blood pressure, and %theta and decreases in %delta (P < 0.05). NT, BIS, Median, heart rate, and oxygen saturation were unchanged. Decreases in propofol concentration were associated with statistically significant increases in NT and BIS (P < 0.05). Thus, the sedative-hypnotic component of propofol could be estimated by modern EEG variables (NT and BIS), whereas the analgesic component provided by remifentanil was not indicated. However, during conditions without surgical stimulation, neither NT nor BIS provided an adequate assessment of the depth of anesthesia when a remifentanil infusion was used.

IMPLICATIONS

We investigated modern and classical electroencephalographic (EEG) variables during emergence from propofol/remifentanil anesthesia. Modern EEG variables indicate changes of infusion in propofol, but not in remifentanil. Thus, modern EEG variables did not provide an adequate assessment of depth of anesthesia when remifentanil was used.

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.

Identification of sensory blockade by somatosensory and pain-induced evoked potentials

BACKGROUND

To date, the anesthesia-induced blockade of nociceptive inputs is insufficiently reflected by commercially available electroencephalographic depth-of-anesthesia monitors. The aim of the current study was to evaluate the potential of somatosensory (SSEP) and intracutaneous pain evoked (iSEP) potentials during remifentanil and propofol anesthesia as electroencephalographic indicators of the nociceptive blockade.

METHODS

Ten healthy men were investigated in a double-blind crossover design during three sessions with remifentanil, propofol, and placebo administration. All dosages were increased in a step-by-step mode. SSEP and iSEP recordings were performed followed by subjective pain ratings and measurement of level of sedation (modified Observer's Assessment of Alertness and Sedation Scale). Changes from baseline in evoked potential components, pain ratings, and sedation scale were assessed by Bonferroni-Holms-corrected Wilcoxon tests.

RESULTS

Pain ratings were significantly reduced by remifentanil. Sedation scale was significantly reduced by propofol. Early SSEP components were not affected by medication. The amplitudes of the long latency SSEP components increased significantly with remifentanil, decreased with propofol, and did not change with placebo. The amplitudes of long latency components of the iSEP decreased significantly with both remifentanil and propofol and did not change with placebo.

CONCLUSION

Long latency components of the SSEP are differently affected by remifentanil and propofol administration. Further studies are needed to clarify whether they can serve as a specific indicator of the nociceptive blockade during anesthesia.

Clinical relevance of associated aneurysms with arteriovenous malformations of the posterior fossa

The aim of this study was to determine the frequency of aneurysms associated with arteriovenous malformations (AVMs) of the posterior fossa and their relation to hemorrhagic presentation in comparison to supratentorial AVMs. We performed a retrospective analysis of 474 patients with intracranial AVMs treated in our center from 1990 to 2010. Patients were analyzed for AVM size, drainage type and their clinical course with focus on vessel anomalies including AVM-associated aneurysms. Seventeen (30%) of 57 posterior fossa AVMs versus 46 (11%) of 417 supratentorial AVMs were associated with aneurysms. In six (10.5%) versus seven (1.7%) patients, respectively, flow-associated aneurysms were the source of hemorrhage. Infratentorial location of an AVM was a significant risk factor for the incidence (p < 0.001) and rupture (p < 0.001) of AVM-associated aneurysms. Feeding artery aneurysms in particular represented a risk factor for hemorrhage in the overall group of AVM patients, independently of the location (p < 0.001). The majority of patients with a posterior fossa AVM were treated by combined embolization and surgical removal within one procedure (n = 33, 58%). Feeding artery aneurysms were excluded by endovascular coiling or surgical clipping whenever feasible. Overall treatment-associated permanent morbidity in the subgroup of posterior fossa AVMs was 11% (n = 6) and mortality 4% (n = 2). Posterior fossa AVMs display a significantly higher frequency of associated aneurysms of the adjacent vessels that are correlated to the high bleeding rate compared to AVMs of the supratentorial compartment. We therefore recommend aggressive AVM treatment including the exclusion of associated aneurysms as a minimal therapeutic goal whenever possible.

ARX-derived auditory evoked potential index and bispectral index during the induction of anesthesia with propofol and remifentanil

A new commercial auditory evoked potential (AEP) monitor (A-line AEP monitor) was developed to calculate an index (ARX AEP index; AAI) by automatically using the amplitudes and latencies of the AEP. We investigated 30 patients before spine surgery. AAI; bispectral index (BIS); relative (%) delta, theta, alpha, and beta; spectral edge frequency; median frequency; mean arterial blood pressure; heart rate; and oxygen saturation were obtained simultaneously during stepwise (1.0 micro g/mL) induction of target-controlled propofol concentration until 5.0 micro g/mL, followed by an infusion of 0.3 micro g. kg(-1). min(-1) of remifentanil. Every minute, the patients were asked to squeeze the observer's hand. Prediction probability (Pk), receiver operating characteristic, and logistic regression were used to calculate the probability to predict the conditions AWAKE, UNCONSCIOUSNESS (first loss of hand squeeze), and steady-state ANESTHESIA (5.0 micro g/mL of propofol and 0.3 micro g. kg(-1). min(-1) of remifentanil). Although a statistically significant difference among the conditions was observed for AAI, BIS, mean arterial blood pressure, median frequency, and %alpha, only AAI and BIS were able to distinguish UNCONSCIOUSNESS versus AWAKE and ANESTHESIA versus AWAKE with better than Pk = 0.90. The modern electroencephalographic variables AAI and BIS were superior to the classic electroencephalographic and hemodynamic variables to distinguish the observed anesthetic conditions.

IMPLICATIONS

The modern electroencephalographic ARX-derived auditory evoked potential index and the bispectral index were superior to the classic electroencephalographic and hemodynamic variables for predicting anesthetic conditions. Variables derived from the auditory evoked potential did not provide an advantage over variables derived from spontaneous electroencephalogram.

Topography of clonidine-induced electroencephalographic changes evaluated by principal component analysis

BACKGROUND

Principal component analysis is a multivariate statistical technique to facilitate the evaluation of complex data dimensions. In this study, principle component analysis was used to reduce the large number of variables from multichannel electroencephalographic recordings to a few components describing changes of spatial brain electric activity after intravenous clonidine.

METHODS

Seven healthy volunteers (age, 26 +/- 3 [SD] yr) were included in a double-blind crossover study with intravenous clonidine (1.5 and 3.0 microg/kg). A spontaneous electroencephalogram was recorded by 26 leads and quantified by standard fast Fourier transformation in the delta, theta, alpha, and beta bands. Principle component analysis derived from a correlation matrix calculated between all electroencephalographic leads (26 x 26 leads) separately within each classic frequency band. The basic application level of principle component analysis resulted in components representing clusters of electrodes positions that were differently affected by clonidine. Subjective criteria of drowsiness and anxiety were rated by visual analog scales.

RESULTS

Topography of clonidine-induced electroencephalographic changes could be attributed to two independent spatial components in each classic frequency band, explaining at least 85% of total variance. The most prominent effects of clonidine were increases in the delta band over centroparietooiccipital areas and decreases in the alpha band over parietooccipital regions. Clonidine administration resulted in subjective drowsiness.

CONCLUSIONS

Data from the current study supported the fact that spatial principle component analysis is a useful multivariate statistical procedure to evaluate significant signal changes from multichannel electroencephalographic recordings and to describe the topography of the effects. The clonidine-related changes seen here were most probably results of its sedative effects.

A 3-dimensional extracellular matrix as a delivery system for the transplantation of glioma-targeting neural stem/progenitor cells

Neural stem/progenitor cells (NSPCs) display inherent pathotropic properties that can be exploited for targeted delivery of therapeutic genes to invasive malignancies in the central nervous system. Optimizing transplantation efficiency will be essential for developing relevant NSPC-based brain tumor therapies. To date, the real-world issue of handling and affixing NSPCs in the context of the neurosurgical resection cavity has not been addressed. Stem cell transplantation using biocompatible devices is a promising approach to counteract poor NSPC graft survival and integration in various types of neurological disorders. Here, we report the development of a 3-dimensional substrate that is based on extracellular matrix purified from tissue-engineered skin cultures (3DECM). 3DECM enables the expansion of embedded NSPCs in vitro while retaining their uncommitted differentiation status. When implanted in intracerebral glioma models, NSPCs were able to migrate out of the 3DECM to targeted glioma growing in the contralateral hemisphere, and this was more efficient than the delivery of NSPC by intracerebral injection of cell suspensions. Direct application of a 3DECM implant into a tumor resection cavity led to a marked NSPC infiltration of recurrent glioma. The semisolid consistency of the 3DECM implants allowed simple handling during the surgical procedure of intracerebral and intracavitary application and ensured continuous contact with the surrounding brain parenchyma. Here, we demonstrate proof-of-concept of a matrix-supported transplantation of tumor-targeting NSPC. The semisolid 3DECM as a delivery system for NSPC has the potential to increase transplantation efficiency by reducing metabolic stress and providing mechanical support, especially when administered to the surgical resection cavity after brain tumor removal.

A comparison between over-the-head and standard cardiopulmonary resuscitation performed by two rescuers: a simulation study

BACKGROUND

In cardiopulmonary resuscitation (CPR) of a patient with an unsecured airway performed by two health care professionals, two methods are possible: 1) Standard CPR according to the guidelines, with one rescuer performing chest compressions from the side and the other rescuer performing ventilations from over the head of the patient. Additional tasks (like attaching the electrocardiogram and defibrillator) must be performed by the second rescuer during the time between ventilations. 2) Over-the-head CPR, with one rescuer performing chest compressions and ventilations from over the head and the other rescuer performing additional tasks.

OBJECTIVES

The aim of this study was to compare the quality of CPR achieved by the two methods.

METHODS

After a standardized theoretical introduction and practical training, 106 medical students with limited knowledge and training in CPR participated in this randomized crossover study. Students performed a 2-min CPR test of standard CPR in both positions and over-the-head CPR alone on a manikin.

RESULTS

Standard CPR led to a significantly shorter hands-off-time over a 2-min interval than over-the-head CPR (median 25 s [interquartile range (IQR) 22-26 s] vs. 38 s [IQR 36-43 s], respectively, p < 0.001), and significantly more chest compressions (167 [IQR 158-176] vs. 142 [IQR 132-150], respectively, p < 0.001), more correct chest compressions (72 [IQR 11-136] vs. 45 [IQR 13-88], respectively, p = 0.004), inflations (10 [IQR 10-10] vs. 8 [IQR 8-8], respectively, p < 0.001), and correct inflations (5 [IQR 2-7] vs. 3 [IQR 1-4], respectively, p < 0.001).

CONCLUSIONS

In the case of a two-professional-rescuer CPR scenario, standard CPR enables a quantitatively better resuscitation than over-the-head CPR.

SNAP index and Bispectral index during different states of propofol/remifentanil anaesthesia

The accuracy of the new SNAP index with the Bispectral index (BIS) to distinguish different states of propofol/remifentanil anaesthesia was compared in 19 female patients who were undergoing minor gynaecological surgery. Comparisons of the SNAP index, BIS, spectral edge frequency, mean arterial blood pressure and heart rate were performed. The ability of all parameters to distinguish between the steps of anaesthesia -awake vs. loss of response, awake vs. anaesthesia, anaesthesia vs. first reaction and anaesthesia vs. extubation - were analysed with the prediction probability. The prediction probability to differentiate between two interesting nuances of anaesthetic states -loss of response vs. first reaction - was calculated. Only the BIS showed no overlap between the investigated steps of anaesthesia. Both the SNAP index and BIS failed to differentiate the nuances of anaesthesia. The SNAP index and BIS were superior to mean arterial blood pressure and heart rate and spectral edge frequency in distinguishing between different steps of anaesthesia with propofol and remifentanil and provided useful additional information.

Clonidine effects on pain evoked SII activity in humans

We investigated pain evoked activity in the human secondary sensory cortex (SII) following clonidine administration in six healthy volunteers using multi-channel magnetoencephalography (MEG). Pain was elicited by electrical shocks applied intracutaneously to the fingertip. Subjects rated pain intensity and perceptions of tiredness and passiveness by numerical ranking scales. Each subject underwent two investigations, one week apart from each other, with clonidine doses of 1.5 or 3.0microg/kg, administered intravenously in a random order and double-blinded. We applied a total number of seven blocks, each consisting of 60 painful stimuli, with one adaptation block, one pre-medication block, four post-medication blocks and one recovery block at the end of the session. MEG data were analysed by dipole reconstruction using CURRY(R) (Neuroscan, Hamburg) software package. Cortical activity in the contralateral SII cortex appeared with peak latencies of 118.5+/-10ms. This activity was significantly reduced by clonidine, in parallel with a reduction of pain intensity and enhancement of subjective tiredness and passiveness. There was, however, no significant correlation between MEG and subjective effects. Although both clonidine doses had similar effects, the higher dose induced longer changes. Results indicate that intravenous clonidine is able to relieve pain, but the exact mechanism of clonidine at the level of the SII cortex remains unclear. It is possible that clonidine interacts with the brainstem ascending system regulating vigilance and arousal which would explain the observed decrement of pain induced activity in SII. An additional more specific analgesic action at spinal level cannot be excluded.

[Measurement of the depth of anaesthesia]

One of the most important mandates of the anaesthesiologist is to control the depth of anaesthesia. An unsolved problem is that a straight definition of the depth of anaesthesia does not exist. Concerning this it is rational to separate hypnosis from analgesia, from muscle relaxation and from block of cardiovascular reactions. Clinical surrogate parameters such as blood pressure and heart rate are not well-suited for a valid statement about the depth of hypnosis. To answer this question the brain has become the focus of interest as the target of anaesthesia. It is possible to visualize the brain's electrical activity from anelectroencephalogram (EEG). The validity of the spontaneous EEG as an anesthetic depth monitor is limited by the multiphasic activity, especially when anaesthesia is induced (excitation) and in deep anaesthesia (burst suppression). Recently, various commercial monitoring systems have been introduced to solve this problem. These monitoring systems use different interpretations of the EEG or auditory-evoked potentials (AEP). These derived and calculated variables have no pure physiological basis. For that reason a profound knowledge of the algorithms and a validation of the monitoring systems is an indispensable prerequisite prior to their routine clinical use. For the currently available monitoring systems various studies have been reported. At this time it is important to know that the actual available monitors can only value the sedation and not the other components of anaesthesia. For example, they cannot predict if a patient will react to a painful stimulus or not. In the future it would be desirable to develop parameters which allow an estimate of the other components of anaesthesia in addition to the presently available monitoring systems to estimate sedation and muscle relaxation. These could be sensoric-evoked potentials to estimate analgesia and AEPs for the detection of awareness.

Monitoring methods: SNAP

The SNAP electroencephalogram (EEG) monitor, described as an interesting, innovative EEG tool that samples raw EEG signals and uses its own unique algorithm, analyses both high- (80-420 Hz) and low- (0-20 Hz) frequency components of the signal. This is termed the SNAP index, and it ranges from 100 (arbitrarily representing the fully awake state) to 0 to provide functional data points for patient management. The SNAP is the first commercial EEG-monitoring tool to use Personal Digital Assistant computer technology. The first version of SNAP index was introduced in 2002, and so far there has been little experience with the SNAP device reported in the literature. Compared with other EEG devices, there is no evidence that SNAP is superior to others in generating more specific information about 'depth of sedation'. Moreover, the influence of high-frequency electromyographic activity on the SNAP needs to be clarified.

Comparison of the over-the-head, lateral and alternating positions during cardiopulmonary resuscitation performed by a single rescuer with a bag--valve--mask device

BACKGROUND

The 2005 guidelines for cardiopulmonary resuscitation (CPR) do not include a statement on performance of basic life support by a single healthcare professional using a bag-valve-mask device. Three positions are possible: chest compressions and ventilations from over the head of the casualty (over-the-head CPR), from the side of the casualty (lateral CPR), and chest compressions from the side and ventilations from over the head of the casualty (alternating CPR). The aim of this study was to compare CPR quality of these three positions.

METHODS

102 healthcare professionals were randomised to a crossover design and performed a 2-min CPR test on a manikin for each position.

RESULTS

The hands-off time over a 2-min interval was not significantly different between over-the-head (median 31 s) and lateral (31 s) CPR, but these compared favourably with alternating CPR (36 s). Over-the-head CPR resulted in significantly more chest compressions (155) compared with lateral (152) and alternating CPR (149); the number of correct chest compressions did not differ significantly (119 vs 122 vs 109). Alternating CPR resulted in significantly less inflations (eight) compared with over-the-head (ten) and lateral CPR (ten). Lateral CPR led to significantly less correct inflations (three) compared with over-the-head (five) and alternating CPR (four).

CONCLUSIONS

In the case of a single healthcare professional using a bag-valve-mask device, the quality of over-the-head CPR is at least equivalent to lateral, and superior to alternating CPR. Because of the potential difficulties in bag-valve-mask ventilation in the lateral position, the authors recommend over-the-head CPR.

Inhibition of thromboxane synthase activity improves glioblastoma response to alkylation chemotherapy

Thromboxane synthase (TXSA), an enzyme of the arachidonic acid metabolism, is upregulated in human glial tumors and is involved in glioma progression. Here, we analyzed the in vitro and in vivo effects of pharmacological inhibition of TXSA activity on human glioblastoma cells. Furegrelate, a specific inhibitor of TXSA, significantly inhibited tumor growth in an orthotopic glioblastoma model by inducing proapoptotic, antiproliferative, and antiangiogenic effects. Inhibition of TXSA induced a proapoptotic disposition of glioma cells and increased the sensitivity to the chemotherapeutic agent 1,3-bis(2-chloroethyl)-1-nitrosourea, significantly prolonging the survival time of intracerebral glioma-bearing mice. Our data demonstrate that the targeted inhibition of TXSA activity improves the efficiency of conventional alkylation chemotherapy in vivo. Our study supports the role of TXSA activity for the progression of malignant glioma and the potential utility of its therapeutic modulation for glioma treatment.

[Undergraduate teaching of anaesthesiology : a nationwide survey in Germany]

BACKGROUND

In 2003 anaesthesiology was implemented as a compulsory speciality of undergraduate teaching in Germany due to the revised regulations of medical education. Besides the preexisting subject of emergency medicine an obligatory course in anaesthesiology was introduced. Thus anaesthesiology has gained considerable importance in all medical faculties. To gain insight into the current status of undergraduate medical education in the university departments of anaesthesiology a nationwide survey at all university departments in Germany was initiated.

METHODS

In cooperation with the German Society of Anaesthesiology and Intensive Care Medicine (DGAI) a standardized questionnaire was developed and sent to 36 departments of anaesthesiology of all German medical faculties. Questions concerned the structure of the respective curriculum, learning goals, teaching, assessment and evaluation methods as well as facultative courses.

RESULTS

Of the 36 university departments of anaesthesiology, 35 returned the questionnaire. In 66% undergraduate education in anaesthesiology is part of the fourth or fifth year of medical training. In 91% of the faculties lectures were accompanied by teaching in small student groups. A simulator-based training is integrated either in anaesthesiology and/or in emergency medicine in 91% of the departments of anaesthesiology. In 69% of the departments contents of anaesthesia, critical care medicine, emergency medicine and pain management are an integral part of undergraduate teaching in anaesthesiology. The primary learning goals are directed towards general anaesthesia and there is less focus on topics of preoperative or postoperative care, such as preoperative risk evaluation, postoperative pain management and regional anaesthesia. Besides a multiple choice test (91%) oral (63%) and/or practical examinations (71%) are used as assessment tools. In 71% of the medical faculties the respective departments of anaesthesiology are leading and organising skills laboratories. In student evaluations anaesthesiology achieved best ranking in 66% of the medical faculties compared to other specialties. The possibility to take an elective course in anaesthesiology exists in 74% of the faculties. Half of these faculties organize this elective as a longitudinal course for one complete semester, the other half as a full time course over mostly 1 or 2 weeks. At present E-learning plays a minor role.

CONCLUSIONS

This survey provides detailed information about the current status of undergraduate teaching of the university departments of anaesthesiology in Germany. The study shows a remarkable consistency of structure, contents and methods of education in anaesthesiology throughout all university departments of anaesthesiology. This information is the basis for triggering synergistic effects, for improving educational standards in anaesthesiology and for introducing a platform for developing modern learning media, e.g. through the scientific society DGAI.

Alaris AEP monitor's "Click Detection" does not help to detect inadvertent disconnection of headphones during anesthesia

Auditory evoked potentials (AEP) can be suppressed by anesthetics dose dependently, but may fail to be registered because of the absence of adequate auditory stimuli. The Alaris AEP monitor includes the "Click Detection" (CD) (generating the message "NO AEP" or "LOW AEP") to detect the loss of auditory stimuli. We investigated the accuracy of the CD in 17 patients awake (AWAKE) and during anesthesia (ANESTHESIA) with accurately placed headphones (HP) and after disconnected HP (No HP) over 5 min each, respectively. Alaris AEP ARX index, CD, and Bispectral Index were recorded each minute. Changes were evaluated with the Friedman and Wilcoxon test. Sensitivity (SEN) and specificity (SPE) and receiver operating characteristic curve were analyzed for the accuracy of the CD. During AWAKE after disconnection of the HP, Alaris AEP ARX index decreased significantly (P < 0.05). The CD was able to detect No HP after 2 min with a SEN of 88% and a SPE of 97%. During ANESTHESIA, no changes were found after HP disconnection. CD detected No HP with a SEN of 100% and a SPE of 20%. The CD of the Alaris AEP monitor is not able to detect unnoticed disconnection of HP during ANESTHESIA.

IMPLICATIONS

Signal transmission of auditory evoked potentials can be suppressed by anesthetics, but also by disconnection of headphones. In the present study, we demonstrate that even the Alaris AEP monitor with the very new feature "Click Detection" was not able to detect the loss of headphones during general anesthesia with propofol and remifentanil.

[SNAP-index and bispectral index during induction of anaesthesia with propofol and remifentanil]

OBJECTIVE

Measurement of "depth of anesthesia" is of enormous interest to the anesthesiologist. New monitor systems, based on the electroencephalogram (EEG) were developed. The aim of the present study was to compare the SNAP index and the Bispectral index during induction of anesthesia with propofol and remifentanil.

METHODS

After IRB approval and written informed consent we investigated 19 female patients during minor gynecologic surgery. Target controlled infusion (TCI) of propofol was increased in a step-by-step mode (0.5 micro g/kg) every 1 min until the patients lost response to the modified Observer's Assessment of Alertness/Sedation scale (MOAAS). 5 min after the patient lost response remifentanil 0.4 micro g/kg/min was started. Every 20 s SNAP index, BIS, spectral edge frequency, mean arterial blood pressure, heart rate and MOASS were recorded. Prediction probability ( P(K)) was used to analyze the relationship of MOAAS, TCI propofol, and all investigated parameters. Changes after start of remifentanil were analyzed with Friedman and Wilcoxon test.

RESULTS

SNAP index ( P(K) = 0.91) and BIS ( P(K) = 1.0) were able to distinguish reliably between MOAAS = 5 and MOAAS = 0. Start of remifentanil infusion resulted in statistically significant changes for all parameters except the SNAP index (p > 0,05).

CONCLUSIONS

SNAP index and BIS were reliable parameters to distinguish different levels of sedation, but SNAP index was not able to reflect the analgesic potency of remifentanil during propofol infusion.