Bilateral measurement of bispectral index and mid-latency auditory evoked potentials in patients with unilateral brain lesions

Purpose

The impact of intracranial lesions on the results of bispectral index (BIS) and mid-latency auditory evoked potentials (MLAEP) remains unclear. We tested the hypothesis that MLAEP (latencies of wave Pa and wave Nb) obtained bilaterally from patients with unilateral brain lesions result in less bias than BIS values obtained from both sides.

Patients

Twenty patients with unilateral supratentorial lesions were included in the study.

Materials and Methods

Bispectral index and MLAEP were measured bilaterally using the BIS and AEP modules of the Monitor S/5 (GE, Helsinki, Finland). Significance of the difference in the number of patients with a clinically relevant bias (more than 10%) of BIS and MLAEP was calculated by Fisher exact test.

Results

Bispectral index was significantly in more patients different on the side of the lesion than latencies of wave Pa and Nb (18 patients for BIS, 1 patient for Pa, 3 patients for Nb, P < .0001). Mean bias was −18.8 ± 25.7 for BIS, 1.5 ± 3.4 milliseconds for wave Pa, and −1.5 ± 6.1 milliseconds for wave Nb (data given as mean ± SD).

Conclusions

Mid-latency auditory evoked potentials are less biased by intracranial lesions than BIS and seem to be superior to BIS for the monitoring of patients with intracranial lesions.     

Pr?operative Risikoevaluation aus an?sthesiologischer Sicht

Medical and technical progress together with demographic changes has led to a more complex perioperative care for patients. Accordingly, an optimal preoperative assessment in particular an adequate risk evaluation is more important than ever. A recently published joint recommendation of the German Society of Anaesthesiology and Intensive Care Medicine, the German Society of Surgery and the German Society of Internal Medicine aims to reduce considerable uncertainties in the preoperative risk evaluation especially with regard to??technical tests?? by providing transparent and comprehensive arrangements. Consequently, routine screening will be abandoned in favour of targeted patient and operation-oriented individual risk assessment. This approach will change the preoperative risk evaluation in a scientific, organisational and economic way. The following article on preoperative risk evaluation is based on the valuable and helpful recommendation and aims to provide additional important aspects from the perspective of anaesthesiologists.     

The place of premedication in pediatric practice

Behind the multiple arguments for and against the use of premedication, sedative drugs in children is a noble principle that of minimizing psychological trauma related to anesthesia and surgery. However, several confounding factors make it very difficult to reach didactic evidence-based conclusions. One of the key confounding issues is that the nature of expectations and responses for both parent and child vary greatly in different environments around the world. Studies applicable to one culture and to one hospital system (albeit multicultural) may not apply elsewhere. Moreover, the study of hospital-related distress begins at the start of the patient's journey and ends long after hospital discharge; it cannot be focused completely on just the moment of anesthetic induction. Taking an example from actual practice experience, the trauma caused by the actual giving of a premedication to a child who absolutely does not want it and may struggle may not be recorded in a study but could form a significant component of overall effect and later psychological pathology. Clearly, attitudes by health professionals and parents to the practice of routine pediatric premedication, vary considerably, often provoking strong opinions. In this pro–con article we highlight two very different approaches to premedication. It is hoped that this helps the reader to critically re-evaluate a practice, which was universal historically and now in many centers is more selective.     

Failure of Two Commercial Indexes and Spectral Parameters to Reflect the Pharmacodynamic Effect of Desflurane on EEG

Objective We compared two PK/PD models, one with and one without a plateau effect. Bispectral (BIS, Aspect Medical Systems, Natick, MA, version XP) and Narcotrend™ (NCT, MonitorTechnik, Bad Bramstedt, Germany, Version 4.0) indices were used as an electroencephalographic measure of desflurane drug effect. Methods With IRB approval and informed consent we investigated 20 adult patients scheduled for radical prostatectomy. At least 45 minutes after induction of general anaesthesia, end-tidal concentrations of desflurane was varied between 3 and 10 vol%. To evaluate the relationship between concentrations and EEG indices, two different pharmacodynamic models were applied: A conventional model based on a single sigmoidal curve, and a novel model based on two sigmoidal curves for BIS and NCT values with and without burst suppression. The parameters of the models␣were estimated by NONMEM V (GloboMax, Hanover, USA) by minimizing log likelihood. Statistical significance between the two models was calculated by the likelihood ratio test. Results The maximum end-tidal desflurane concentration during the two concentrations ramps was 10.0 ± 1.4 vol%. The mean BIS and NCT values decreased significantly but slightly with increasing end-tidal desflurane concentrations between 4 and 8 vol%. Therefore a two sigmoidal curves PK/PD model including a plateau describes the effects of desflurane on BIS and Narcotrend better than a single sigmoidal curve model. The difference between the log likelihood values of the new PK/PD model with two connected sigmoidal curves and the classical E _max model with one sigmoidal curve is 634 (P < 0.001) for the BIS monitor and 4089 (P < 0.001) for the NCT. Conclusions BIS and Narcotrend are not useful to differentiate pharmacodynamic changes in the EEG between 4 and 9 vol% desflurane. This study was presented in part at the American Society of Anesthesiologists meeting October 20, 2005 Atlanta. Kreuer S, Bruhn J, Ellerkmann R, Ziegeler S, Kubulus D, Wilhelm W. Failure of two commercial indexes and spectral parameters to reflect the pharmacodynamic effect of desflurane on EEG.     

Influence of Lidocaine on Endotoxin-induced Leukocyte-Endothelial Cell Adhesion and Macromolecular Leakage in Vivo

Background: Endotoxin activates leukocyte-endothelial cell adhesion, vascular leakage, and changes in vascular microhemodynamics. The aim of this study was to determine whether lidocaine, which inhibits the activation of leukocytes, could attenuate microcirculatory disturbances during endotoxemia.

Methods: Thirty anesthetized male rats were randomly assigned to receive one of three treatments (n = 10 for each group): infusion of saline (control group), infusion of Escherichia coli endotoxin (LPS group: 2 mg [center dot] kg sup -1 [center dot] h sup -1 lipopolysaccharides) without lidocaine treatment, or infusion of endotoxin with lidocaine pretreatment 30 min before baseline measurements (lidocaine group: intravenous bolus of 2 mg/kg and continuous infusion of 2 mg [center dot] kg sup -1 [center dot] h sup -1). Leukocyte adherence, erythrocyte velocity (VRBC), and vessel diameters (Dv) were determined at baseline and at 60 and 120 min in mesenteric post-capillary venules using in vivo videomicroscopy. Macromolecular leakage was determined by measuring the extravasation of fluorescence-labeled albumin. Venular wall shear rate (tau) was calculated according to the equation tau = 8 [center dot] VRBC [center dot] Dv sup -1.

Results: Lidocaine significantly attenuated the increase of leukocyte adherence during endotoxemia. There were no significant differences of tau within or between the groups. Macro-molecular leakage exhibited the greatest increase in the LPS group. In the lidocaine group, it was significantly decreased but still increased compared with the control group.     

Epidural Epinephrine and Clonidine: Segmental Analgesia and Effects on Different Pain Modalities

Background: It is not known whether epidural epinephrine has an analgesic effect per se. The segmental distribution of clonidine epidural analgesia and its effects on temporal summation and different types of noxious stimuli are unknown. The aim of this study was to clarify these issues.

Methods: Fifteen healthy volunteers received epidurally (L2-L3 or L3-L4) 20 ml of either epinephrine, 100 micro gram, in saline; clonidine, 8 micro gram/kg, in saline; or saline, 0.9%, alone, on three different days in a randomized, double-blind, cross-over fashion. Pain rating after electrical stimulation, pinprick, and cold perception were recorded on the dermatomes S1, L4, L1, T9, T6, T1, and forehead. Pressure pain tolerance threshold was recorded at S1, T6, and ear. Pain thresholds to single and repeated (temporal summation) electrical stimulation of the sural nerve were determined.

Results: Epinephrine significantly reduced sensitivity to pinprick at L1-L4-S1. Clonidine significantly decreased pain rating after electrical stimulation at L1-L4 and sensitivity to pinprick and cold at L1-L4-S1, increased pressure pain tolerance threshold at S1, and increased thresholds after single and repeated stimulation of the sural nerve.     

Leitbild für die Leitstelle — Gefahren im Einsatz — Notfallmedizin im DRG-Zeitalter

Zusammenfassung Die 20. notfallmedizinische Jahrestagung der Arbeitsgemeinschaft Südwestdeutscher Notärzte (agswn) behandelte auch in diesem Jahr aktuelle berufspolitische Themen. Aktuelle Entwicklungen zur Verbesserung der Arbeitsabläufe in den Leitstellen wurden dargestellt, EDV-gestützte Systeme zur Notrufabfrage, die Vernetzung der Leitstellen und technische Verbesserungen der Leitstellensysteme genannt. Die Gefahren im Rettungsdienst waren ein weiterer Schwerpunkt der Tagung. Eine Ansteckungsgefahr bei Infektionstransporten bei MRSA-Patienten ist bei sachgemäßem Verhalten nicht zu befürchten. Weiterhin wurden die Möglichkeiten des terroristischen Einsatzes von biologischen Waffen realistisch deutlich relativiert. Amoklagen stellen dagegen eine nur schwer kalkulierbare Gefahrensituation dar. Als 3. Themenschwerpunkt wurden die besonderen Herausforderungen der Notfallmedizin im DRG-Zeitalter umrissen. Die Änderung des Einsatzspektrums und die Reduktion von Notarztstandorten erfordert die Bildung von Kompetenzzentren und eine hohe Qualifikation der Notärzte.