A surgical technique for a terminal intracranial hypertension model in pigs.

The life-threatening effects of intracranial hypertension on brain perfusion and cerebral metabolism are the subject of current research in different animal models. The purpose of this study was to describe an efficient, reliable and inexpensive surgical method for temporary elevation of intracranial pressure (ICP) in acutely instrumented pigs in a research setting. Therefore, a balloon catheter was inserted into the left lateral ventricle and an ICP sensor was placed in the parenchyma of the right cerebral hemisphere. Ten acutely instrumented pigs were studied while under deep terminal general anaesthesia. The step-by-step inflation of the intraventricular balloon allows one to achieve the desired ICP up to 46 mmHg and maintain it at this level. ICP values ranged from a median of 2 (1-2) mmHg to 43 (29-45) mmHg. To the authors' knowledge, this is the first detailed description of a minimally invasive surgical technique for temporary ICP elevation in pigs via stepwise inflation of an intraventricular balloon.

Clinical evaluation of a simultaneous closed-loop anaesthesia control system for depth of anaesthesia and neuromuscular blockade*.

We developed a closed-loop system to control the depth of anaesthesia and neuromuscular blockade using the bispectral index and the electromyogram simultaneously and evaluated the clinical performance of this combined system for general anaesthesia. Twenty-two adult patients were included in this study. Anaesthesia was induced by a continuous infusion of remifentanil at 0.4 µg.kg(-1) .min(-1) (induction dose) and then 0.25 µg.kg(-1) .min(-1) (maintenance dose) and propofol at 2 mg.kg(-1) 3 min later. The combined automatic control was started 2 min after tracheal intubation. The depth of anaesthesia was recorded using bispectral index monitoring using a target value of 40. The target value of neuromuscular blockade, using mivacurium, was a T1/T1(0) twitch height of 10%. The precision of the system was calculated using internationally defined performance parameters. Twenty patients were included in the data analysis. The mean (SD) duration of simultaneous control was 129 (69) min. No human intervention was necessary during the computer-controlled administration of propofol and mivacurium. All patients assessed the quality of anaesthesia as 'good' to 'very good'; there were no episodes of awareness. The mean (SD) median performance error, median absolute performance error and wobble for the control of depth of anaesthesia and for neuromuscular blockade were -0.31 (1.78), 6.76 (3.45), 6.32 (2.93) and -0.38 (1.68), 3.75 (4.83), 3.63 (4.69), respectively. The simultaneous closed-loop system using propofol and mivacurium was able to maintain the target values with a high level of precision in a clinical setting.

[Feedback control of depth of anesthesia during propofol administration. Bispectral index as the controlled variable]. / Regelkreisgesteuerte Narkosetiefe bei Propofolapplikation. Verwendung des Bispektralindex als Regelungsgrösse.

BACKGROUND: The objective of this study was to evaluate the performance of a new system for closed-loop control of propofol administration using the bispectral index (BIS) under total intravenous anesthesia in the index values of middle-to-deep depth of anaesthesia. METHODS: In this study 20 adult patients anesthetized with propofol and remifentanil were investigated. The propofol infusion was carried out using a fuzzy-PD+I controller with a target BIS value of 40. RESULTS: Closed-loop control was able to provide maintenance of anesthesia and adequate operating conditions for all patients. The following quality control criteria were calculated: median performance error (MDPE; 0.16%, SD +/-1.4%), median absolute performance error (MDAPE; 6.9%, SD +/-2.8%) and wobble (6.8%, SD +/-2.5%). CONCLUSION: The present study showed the clinical feasibility of the controller compared to existing devices regarding a high level of quality criteria of a model with an implemented fuzzy-PD+I structure controlling depth of hypnosis.

[Efficacy of sugammadex in the reversal of neuromuscular blockade induced by rocuronium in long-duration surgery: under inhaled vs. intravenous anesthesia]. / Eficacia de la reversión con sugammadex del bloqueo neuromuscular inducido por rocuronio en cirugía de larga duración. Comparación del efecto de la anestesia inhalatoria frente a intravenosa.

BACKGROUND AND OBJECTIVE: Sugammadex reverses neuromuscular blockade induced by aminosteroid agents by encapsulating these agents. The objective of this study was to compare the efficacy and safety of sugammadex to reverse a rocuronium-induced neuromuscular blockade in long-duration surgery in association with inhaled or intravenous anesthesia. PATIENTS AND METHODS: We performed a randomized, double-blind, multicenter trial of 20 ASA 1-3 patients aged between 18 and 69 years and scheduled for elective surgery lasting at least 120 minutes. Anesthesia was induced with remifentanil and rocuronium at a dosage of 0.6 mg x kg(-1), and neuromuscular function was monitored by means of acceleromyography. After randomization, anesthesia was maintained with sevoflurane or with propofol for total intravenous anesthesia. Patients in both groups also received an infusion of remifentanil for analgesia and rocuronium to maintain a block of greater than 90%. After surgery, sugammadex was administered at a dosage of 2 mg x kg(-1) on reappearance of the second train-of-four (TOF) twitch (T2) and the times until recovery of T4/T1 ratios of 0.7, 0.8, and 0.9 (main endpoints). Mean arterial pressure and heart rate were recorded at baseline and after 2, 5, 10, and 30 minutes (secondary outcome measures). RESULTS: Although less rocuronium was consumed in the sevoflurane group than in the propofol group and the time between the start of sugammadex administration until recovery of a TOF ratio of 0.9 was shorter for the sevoflurane group than for propofol group (mean [SD], 1.46 [0.30] minutes and 1.89 [0.62] minutes, respectively), these differences were not significant. No signs of recurarization or associated adverse effects were observed. CONCLUSIONS: Sugammadex effectively and safely reverses a rocuronium-induced neuromuscular blockade in less than 2 minutes in long-duration surgery performed under both inhaled and intravenous anesthesia. The interaction of neuromuscular blocking agents with sevoflurane appears not to affect the reversal time of sugammadex in such operations.

Eficacia de la reversión con sugammadex del bloqueoneuromuscular inducido por rocuronio en cirugía de larga duración. Comparación del efecto de la anestesia inhalatoria frente a intravenosa / Efficacy of sugammadex in the reversal of neuromuscular blockade induced by rocuronium in long-duration surgery: under inhaled vs. intravenous anesthesia

OBJETIVOS: Sugammadex revierte el bloqueo neuromuscularinducido por bloqueantes neuromuscularesaminoesteroideos mediante su encapsulación. En esteestudio comparamos la eficacia y seguridad de la reversióncon sugammadex del bloqueo mantenido con rocuronioen cirugía de larga duración con anestesia inhalatoriao intravenosa.PACIENTES Y MÉTODOS: Estudio multicéntrico, prospectivo,randomizado, doble ciego, en 20 pacientes (18-69 años), ASA I-III, programados para cirugía electivade igual o más de 120 minutos de duración. Se indujo laanestesia con propofol, remifentanilo y rocuronio 0,6mg.kg-1, monitorizándose la función neuromuscularmediante aceleromiografía. El mantenimiento se realizó,previa aleatorización, con sevoflurano o anestesia intravenosatotal con propofol, utilizándose en ambos gruposperfusión de remifentanilo para analgesia y rocuroniopara mantener un bloqueo ≥ 90%. Al finalizar la intervenciónse administró sugammadex 2 mg.kg-1 a la reapariciónde T2, midiendo el tiempo hasta la recuperaciónde un ratio T4/T1 de 0,7, 0,8, y 0,9 (variable principal).Se monitorizó la PAM y FC basal, y a los 2, 5, 10 y 30minutos (variables secundarias) de la reversión.RESULTADOS: El consumo de rocuronio y el tiempodesde el inicio de la administración de sugammadex hastaun ratio del TOF de 0,9 fue menor para el sevofluoranoque para propofol [media (DE)], 1,46 (0,30) min frentea 1,89 (0,62) min, sin diferencias significativas. Nohubo signos de recurarización ni efectos adversos relacionados.CONCLUSIONES: Sugammadex revierte de forma eficazy segura, en menos de dos minutos, el bloqueo mantenidocon rocuronio durante intervenciones de larga duración,tanto en anestesia inhalatoria como intravenosa.La interacción de los bloqueantes neuromusculares consevofluorano parece no influir en el tiempo de reversiónde sugammadex en este tipo de intervenciones (AU)

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BACKGROUND AND OBJECTIVE: Sugammadex reversesneuromuscular blockade induced by aminosteroidagents by encapsulating these agents. The objective ofthis study was to compare the efficacy and safety ofsugammadex to reverse a rocuronium-inducedneuromuscular blockade in long-duration surgery inassociation with inhaled or intravenous anesthesia.PATIENTS AND METHODS: We performed a randomized,double-blind, multicenter trial of 20 ASA 1-3 patientsaged between 18 and 69 years and scheduled for electivesurgery lasting at least 120 minutes. Anesthesia wasinduced with remifentanil and rocuronium at a dosage of0.6 mg·kg-1, and neuromuscular function was monitoredby means of acceleromyography. After randomization,anesthesia was maintained with sevoflurane or withpropofol for total intravenous anesthesia. Patients in bothgroups also received an infusion of remifentanil foranalgesia and rocuronium to maintain a block of greaterthan 90%. After surgery, sugammadex was administeredat a dosage of 2 mg·kg-1 on reappearance of the secondtrain-of-four (TOF) twitch (T2) and the times untilrecovery of T4/T1 ratios of 0.7, 0.8, and 0.9 (mainendpoints). Mean arterial pressure and heart rate wererecorded at baseline and after 2, 5, 10, and 30 minutes(secondary outcome measures).RESULTS: Although less rocuronium was consumed inthe sevoflurane group than in the propofol group and (..)(AU)

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Muscle relaxant use for tracheal intubation in pediatric anaesthesia: a survey of clinical practice in Germany.

OBJECTIVES: Aim of this Germany-wide study was to evaluate the use and application customs of neuromuscular blocking drugs (NMBDs) for tracheal intubation in children of age 5 years or younger. MATERIAL AND METHODS: In the year 2005, a total of 3260 questionnaires were sent out to all heads of anesthesia departments at all types of hospitals as well as ambulatory anesthesia centers in Germany. The fields covered by the questionnaire were regarding institutional size, amount of general anesthesia and specifically pediatric cases, number of intubations and NMBDs used, frequency of use of the individual relaxants and techniques utilized when administering muscle relaxants. RESULTS: Of the sent-out questionnaires 66.9% could be analyzed: 82% of hospitals use 1-3 muscle relaxants in children; 91% of the ambulatory anesthesia centers use a repertoire of 1-2 neuromuscular blockers for pediatric cases. However, general anesthesia with tracheal intubation in children is often induced without using any NMBD at all. Mivacurium is the predominantly used NMBD for pediatric intubation in Germany. In contrast, the use of succinylcholine is far less in ambulatory anesthesia centers than in hospitals. Despite controversial discussion, precurarization, priming, and timing are still utilized in German anesthesia practice. CONCLUSION: In Germany, mivacurium, with its favorable pharmacologic profile for short cases, is the predominantly used NMBD for pediatric tracheal intubation. Despite the known adverse effects of intubation without muscle relaxation, this technique is also wide-spread, especially among German anesthetists in ambulatory anesthesia centers. Surveys like these are important to determine a status quo of use and application customs of NMBDs in pediatric anesthesia and provide a basis for numerous other studies.

[Application of neuromuscular monitoring in Germany]. / Einsatz des neuromuskulären Monitorings in Deutschland.

The aim of the present study was to evaluate application customs of neuromuscular monitoring in hospitals and private practice. Of the 3,260 questionnaires sent out, 2,182 could be analyzed. Of these 54% were from anaesthetists in private practice, 41% from heads of hospital anaesthesia departments and 5% from heads of level 1 hospital anaesthesia departments. In 12.1% of the hospital departments and 66.7% of private practices, no neuromuscular monitoring was available at all. In both hospital departments and private practices, clinical signs were the most often applied criteria for timing of reinjection of myorelaxants as well as for evaluation of neuromuscular recovery.

Onset properties of mivacurium measured by mechanomyography depend on the twitch height of the adductor pollicis muscle.

INTRODUCTION: The influence of the twitch height of the adductor pollicis muscle during baseline measurements on the pharmacodynamic parameters of mivacurium was prospectively evaluated. PATIENTS AND METHODS: Fifty adult patients were anaesthetized with propofol and alfentanil. Neuromuscular function was monitored mechanomyographically by measuring the force of the adductor pollicis muscle following stimulation of the ulnar nerve. Following a stabilization period of 20 min, the individual twitch height of the adductor pollicis muscle was determined before a single bolus of mivacurium (75 microg kg-1) was administered. Patients were divided into two groups. The data of patients whose thumb adduction force was below the median value of all patients were the 'low force' group (9.1 +/- 1.4 N) and the data of all other patients were the 'high force' group (13.7 +/- 1.8 N). RESULTS: In the 'high force' group, maximum neuromuscular blockade of mivacurium was deeper (0.97 +/- 0.05 vs. 0.93 +/- 0.06; P < 0.05) and onset faster (2.9 +/- 1.1 min vs. 4.0 +/- 1.2 min; P < 0.05). Neuromuscular recovery did not differ between the groups. CONCLUSION: The different onset speeds reflect either different sensitivity to neuromuscular blocking agents with respect to patients' muscle power or a problem of the mechanomyographic measuring technique.

Incidence and duration of residual paralysis at the end of surgery after multiple administrations of cisatracurium and rocuronium.

In a randomised, controlled, double-blind, multicentre trial in 338 patients, we assessed the incidence of residual paralysis following administration of cisatracurium or rocuronium. The incidence at the end of surgery was significantly lower in patients treated with rocuronium (62 of 142 patients, 44%) than in those given cisatracurium (99 of 175 patients, 57%) (p < 0.05). In contrast, with rocuronium the mean (SD) time between skin closure and extubation was 28 (28) min vs 18 (19) min for cisatracurium, and the duration 0.9 (time from administration of last top-up dose to recovery of the train-of-four ratio to 0.9) was significantly longer and more variable for rocuronium than for cisatracurium. Thus, after repeated administration, the duration and variability of duration of action are greater with rocuronium compared with cisatracurium. These pharmacodynamic differences do not necessarily translate into a higher incidence of residual paralysis, because clinicians compensate for the longer duration of action and variability of rocuronium by terminating administration of the neuromuscular blocking earlier.

[Muscle relaxants in Germany 2005: a comparison of application customs in hospitals and private practices]. / Muskelrelaxanzien in Deutschland 2005: Ein Vergleich zwischen den Anwendungsgewohnheiten in Krankenhäusern und Praxen.

Aim of this study was to evaluate application customs of muscles relaxants in hospitals compared to their use in private practice. Of the 3,260 questionnaires sent-out, 66.9% could be analyzed. Of these 54% were from anesthetists in private practice, 41% from heads of hospital anesthesia departments and 5% from heads of level one hospital anesthesia departments. The first difference between private practices and hospitals was the number of available muscle relaxants: 87% of private practices use 1-3 relaxants, whereas 79% of hospitals use 3-5. Another apparent difference was the relationship between general anesthesia and the number of intubations: 60% of private practices have over 80% of general anesthesia cases, but only 50% of these patients are intubated. On the contrary, two thirds of the hospitals have 50-80% general anesthesia cases and 60-70% of patients are intubated. The main wish for an ideal muscle relaxant was independent of private practice or hospital, short onset time, followed by fast recovery. In accordance 74% of anesthetists in hospitals and 72% of anesthetists in private practice voiced the wish for a non-depolarizing succinylcholine substitute. The results of this nationwide survey suggest that time pressure in combination with an increased specialization of anesthetists in private practice are the main factors for availability and use of muscle relaxants in routine anesthesia.

[Depth of anaesthesia during intubation: comparison between propofol and thiopentone]. / Narkosetiefe bei Intubation : Vergleich zwischen Propofol und Thiopental.

In order to study the depth of anaesthesia during endotracheal intubation, 30 patients received either thiopentone or propofol for anaesthesia induction. The BIS value as a parameter for the depth of anaesthesia and the rate pressure product (RPP) were acquired online. Patients who received thiopentone for anaesthesia induction showed significantly higher BIS values at the moment of intubation and reached BIS values >60 significantly more frequently than patients receiving propofol. The RPP in the propofol group lay significantly below that of the thiopentone patients. For all patients there was an mean increase in BIS values of 8 index points and an increase in the RPP. Therefore, BIS values around 50 should be achieved before intubation in order to avoid the critical BIS value for awareness of >60 despite the increase caused by the intubation procedure. Within 24 h of intubation all patients were interviewed for possible signs of awareness. None of the patients was able to remember the intubation or reported other experiences that indicated an unconscious awareness. Nevertheless, the progress of BIS values in a standardized intubation as performed in the normal clinical routine, shows that the use of thiopentone for initiating anaesthesia results in a very flat level of anaesthesia during intubation. The risk for patients to experience awareness should therefore, not be underestimated. Therefore, when using thiopentone it is recommended to also use a rapid acting muscle relaxant or to select a high ED95 to compensate for the flat level of anaesthesia. Alternatively, repetetive boluses of the hypnotic shortly before intubation should be considered or to revert to propofol. The dosage and pharmacokinetics of the analgesic should also be taken into consideration because an insufficient analgesia leads to a faster flattening of the depth of anaesthesia.

Comparison of invasive and less-invasive techniques of cardiac output measurement under different haemodynamic conditions in a pig model.

BACKGROUND AND OBJECTIVE: Despite the introduction of various less-invasive concepts of cardiac output measurement, pulmonary arterial thermodilution is still the most common measurement technique. METHODS: This prospective controlled study was designed to compare different methods of cardiac output measurement simultaneously. Pulmonary arterial thermodilution, transpulmonary thermodilution (PiCCO), trans-oesophageal echo-Doppler probe (HemoSonic) and partial carbon dioxide rebreathing technique (NICO monitor) were evaluated against a peri-aortic transit-time flow-probe as reference method in a clinically relevant animal model. After approval from the Local Ethics Committee on Animal Research, the investigations were conducted in nine anesthetized domestic pigs. Systemic haemodynamics were modulated systematically by the application of catecholamines, caval occlusion and exsanguination. Statistical analysis was performed with Bland-Altman and linear regression. RESULTS: A total of 366 paired cardiac output measurements were carried out at a reference cardiac output between 0.5 and 7 L min(-1). The correlation coefficients for pulmonary arterial and transpulmonary thermodilution against reference were 0.93 and 0.95, for trans-oesophageal Doppler and partial rebreathing technique 0.84 and 0.77. Pulmonary arterial thermodilution and transpulmonary thermodilution showed comparable bias and limits of agreement. Where HemoSonic showed an overestimation of cardiac output at a higher precision, NICO overestimated low and underestimated higher cardiac output values. CONCLUSIONS: Our data suggest that pulmonary arterial thermodilution and PiCCO may be interchangeably used for cardiac output measurement even under acute haemodynamic changes. The method described by Bland and Altman demonstrated an overestimation of cardiac output for both thermodilution methods. HemoSonic and NICO offer non-invasive alternatives and complementary monitoring tools in numerous clinical situations. Trend monitoring and haemodynamic optimizing can be applied sufficiently, when absolute measures are judged critically in a clinical context. The use of the NICO system seems to be limited during acute circulatory changes.

[Feedback control of muscle relaxation with a varying on-off controller using cisatracurium]. / Regelkreisgesteuerte Muskelrelaxation mit einem modifizierten Zweipunktregler mit Cisatracurium.

BACKGROUND: Under clinical conditions constant neuromuscular blockade can also be maintained by a simple closed-loop system. However, delayed onset time, non-linearity of the dose-response curve and different sensitivity to muscle relaxants for each patient are limiting factors. METHODS: In 20 patients who underwent elective surgical procedures under continuous propofol/alfentanil anaesthesia and relaxation with cisatracurium, the maintenance of an electromyographically controlled cisatracurium block of 90% was achieved by a varying on-off control system. Using an own computer-aided measuring device, the course of the neuromuscular blockade and deviations from the desired neuromuscular block were registered. RESULTS: Over a period of 64.2+/-14.0 min, neuromuscular block could be controlled on average at a T(1)-level of 10% (90% block). The mean error of the deviation of the obtained neuromuscular blockade from the set-point was -1.6+/-0.9% on average. To maintain this neuromuscular blockade, a dose rate of 1.4+/-0.9 micro g x kg(-1) x min(-1) cisatracurium was necessary. CONCLUSIONS: It can be concluded that a simple closed-loop system allows the safe use of the intermediate term muscle relaxant cisatracurium for the performance of surgical procedures.

[Application of muscle relaxants for rapid-sequence induction of anaesthesia]. / Die Anwendung von Muskelrelaxanzien zur Blitzintubation in Deutschland.

The present study evaluates the use of muscle relaxants for rapid-sequence induction (RSI) and different application techniques (pre-curarisation, priming, timing) as a part of a nationwide survey in Germany. In 86.8% of anaesthesia departments succinylcholine is used for RSI and an average of 56.5% of respondents used only succinylcholine for RSI. Of all non-depolarising muscle relaxants rocuronium is the most frequently used alternative. Of the anaesthesia departments 2.6% use rocuronium regularly in patients with increased risk for aspiration of stomach contents; level one centres significantly more than others, 12.9% answered that pre-curarisation techniques were never used, whereas 45.6% use non-depolarising neuromuscular blocking drugs before giving succinylcholine in 80-100% of cases. Priming is not used by 64.4% of respondents, as opposed to 9.8% who utilise this technique regularly. The statements regarding timing are 71.1% and 5.4%, respectively. Alcuronium is used for RSI in departments in which the financial aspect is the primary decision criteria. Despite ist known side-effects and the on-going discussion over the past years, succinylcholine is still the most frequently used muscle relaxants for RSI. Priming is often declined by anaesthetists in Germany, most probably due to the absence of clear advantages and the possibility of severe complications. It is the opinion of the authors that timing but also drugs with a slow onset (e.g., alcuronium and Pancuronium) are obsolete in the context of RSI.

[The use of neuromuscular monitoring in Germany]. / Einsatz des neuromuskulären Monitorings in Deutschland.

AIM: As there are no reliable epidemiological data for the use of muscle relaxants in Germany,we conducted a mailing study. The aim of the study was to compare the use of muscle relaxants between German anaesthesia departments. In the present part of the presentation we focused on neuromuscular monitoring (NMM) and management of residual paralysis. METHODS: A total number of 2,996 questionnaires were sent to all registered anaesthesiological facilities in Germany and the return was 68.6% (2054 questionnaires). RESULTS: In 574 of the returned questionnaires (28%) the regular use of NMM was confirmed. Intraoperative monitoring of neuromuscular block and assessment of neuromuscular recovery were the most frequent applications of NMM, i.e. 25% and 18% of returned questionnaires, respectively. Clinical signs, however, are still the most popular way to estimate the degree of neuromuscular blockade. Moreover, routine reversal at the end of surgery with a neostigmin/atropine mixture was not practiced in 75% of the anaesthesia departments. CONCLUSIONS: This survey revealed that NMM is still very rarely used in daily clinical practice. Especially the seldom use of NMM to assess residual paralysis has to be improved.

[The use of muscle relaxants for routine induction of anesthesia in Germany]. / Anwendung von Muskelrelaxanzien zur Routineeinleitung in Deutschland.

The aim of this study was to evaluate the use of muscle relaxants during induction of anesthesia in patients without risk of aspiration of stomach contents. Of the 2,996 questionnaires sent out, 2,054 (68.6%) could be analysed and the results show that succinylcholine is used regularly in 13.6% of anesthesia departments. The next most commonly used muscle relaxants are atracurium, vecuronium and mivacurium, followed by cis-atracrium, rocuronium and pancuronium. Alcuronium is the least frequently used muscle relaxant. During induction of an elective anesthesia procedure, a priming technique is used by 19% of anesthesiologists, 22% utilize precurarization, and a timing technique is performed in 7.1%. The use of muscle relaxants for on-going relaxation follows the same pattern as for induction of neuromuscular blockade and succinylcholine is used in 1.4% if further relaxation is needed. The desire for specific qualities of muscle relaxants is correlated with higher use of the specific substance: short onset time for rocuronium, good controllability with mivacurium, no side-effects with cisatracurium and economical aspects with alcuronium. Of the participants 76.6% voiced the desire for a non-depolarizing replacement for succinylcholine.Private practices use mivacurium more often than hospitals, level one hospitals use rocuronium and cisatracurium more often. This survey could not show a definite standard of use in terms of muscle relaxants for an elective case.Precurarization, priming and timing are used frequently in patients not at risk of aspiration. This should be reduced by on-going teaching.

[Application of muscle relaxants in Germany. A survey of German anaesthesia departments]. / Anwendung von Muskelrelaxanzien in Deutschland. Eine Umfrage an Deutschen Anästhesieeinrichtungen.

AIM: The aim of this study was to evaluate the use and application of muscle relaxants and neuromuscular monitoring in Germany. METHODS: A total of 2,996 questionnaires were sent out to the heads of German anaesthesia departments and private anaesthesia practices. The questions covered frequency of muscle relaxants used,how they were used, and neuromuscular monitoring. Influences on the way muscle relaxants were used could be derived from the desire for specific properties of a muscle relaxant, the desire for different monitoring conditions and from the size of the institution. We correlated these features with application practice using logistic regression analyses. RESULTS: Of the 2,996 questionnaires 2,058 could be analysed (68.6%). Amongst those were 102 level one hospitals (5%) and 903 private practices (44%). The replies from 350 (17%) departments were based on surveyed data, 1,613 (78.5%) were based on estimations. The desire for certain properties of muscle relaxants correlated with the use in practice, as were the desire for a non-depolarizing replacement for succinylcholine, the size of the department and the frequency of use of neuromuscular monitoring. Over 50% of all German anaesthesia departments limited the use of muscle relaxants to three. The use of laryngeal masks reduced the use of muscle relaxants. CONCLUSIONS: The survey regarding use of muscle relaxants in Germany could for the first time give an overview on the use of anaesthesia-specific substances in Germany. From the different frequencies of use and use modalities,conclusions could be drawn towards a standard of application for the year 2000. Changes in this standard would raise the need for further trend surveys. The methods of statistical analysis and survey evaluation can be used as a base for further surveys.

[The syringe pump as actuator--a practical application problem of feedback control systems]. / Die Spritzenpumpe als Stellglied--Ein Problem im praktischen Einsatz regelkreisgesteuerter Systeme.

Based on a computer simulation programme, the accuracy of the Graseby 3400 syringe pump was tested for its use in a feedback control system of the neuromuscular block. Firstly, a calculation of errors to determine the difference between the target and actual flow rates was carried out. Next, the characteristic curves of the syringe pump were determined under different flow and sampling rates to correct the application software of the feedback controller with a view to obtaining the correct flow rates online. It was discovered that, particularly with short 12 s sampling rates, dose-dependent errors of almost 100% were provable. Therefore, the application of a robust controller and integration of the characteristic curves at the outlet of the controller software are required. For the adoption of syringe pumps in medical feedback control systems, definite determination of the actual infusion quantity using an exact calculation of errors is required. Especially in cases of short sampling rates in combination with low infusion quantities, the syringe pump comes almost to a standstill, which results in extreme differences between target and actual flow rates.

[Quantitative assessment of neuromuscular block of the orbicularis oculi muscle]. / Quantitative Erfassung der neuromuskulären Blockade des Musculus orbicularis oculi.

In a prospective clinical study neuromuscular block at the orbicular ocular muscle was examined qualitatively and quantitatively by an AMG approach. The signals were recorded, visualized and evaluated simultaneously under PC-support after TOF-stimulation in 20 s intervals. Fifty ASA I and II patients were included into the study. After oral premedication with midazolam 10-15 mg, anaesthesia was induced with propofol 2 mg/kg and alfentanil 0.02 mg/kg and maintained by means of propofol 6-8 mg/kg/h and alfentanil 0.02 mg/kg/h. After intubation and signal stabilization, mivacurium 0.75 mg/kg was administered and neuromuscular blockade was recorded online. The measured acceleration at the orbicular ocular muscle amounted 0.9 g on average. Maximal neuromuscular block was registered at 78.5% and the TOF-ratio of 0.8 was achieved after 14.1 min. The low values of the AMG-signals of the orbicular ocular muscle requiring very high technical demands on the measuring instrument. Additional problems arise through the considerable temporal expenditure for discovering the optimal location of stimulation. During the AMG monitoring the position dependence of the measured values of the sensors must be taken into consideration. These technical problems restrict the suitability of the AMG at the orbicular ocular muscle as a quantitative neuromuscular monitoring tool.