[Influence of rocuronium dose on the effectiveness of mask ventilation : A prospective, randomized clinical trial]. / Der Einfluss der Rocuroniumdosis auf die Effektivität der Maskenbeatmung : Eine prospektive, randomisierte, klinische Studie.

BACKGROUND: Mask ventilation could improve after administration of muscle relaxants if there is a functional obstruction of the airway, such as laryngospasm, vocal cord closure or opioid-induced muscle rigidity. On the other hand, muscle relaxants could worsen mask ventilation because they induce upper airway collapse; however, clinical studies showed that rocuronium (Roc) improved mask ventilation or it remained unchanged. In most cases Roc 0.06 mg/kgBW was used. OBJECTIVE: The optimal dose of Roc has not been studied; therefore, we studied the quality of mask ventilation with three different doses of Roc (0.3, 0.6 and 0.9 mg/kgBW) and compared them with a control group receiving saline. MATERIAL AND METHODS: In this prospective clinical trial 200 patients were randomized into 4 groups: NaCl (saline), Roc03 (Roc 0.3 mg/kgBW), Roc06 (Roc 0.6 mg/kgBW) and Roc09 (Roc 0.9 mg/kgBW). Mask ventilation was performed to reach a tidal volume (TV) of >5.0 ml/kgBW; maximum ventilation peak pressure (ppeak) was limited to 25 mbar. If this TV was not reached, mask ventilation was improved by better mask position, head position or/and usage of a Guedel tube (oropharyngeal airway). During mask ventilation ppeak and TV were recorded and the quality of mask ventilation was assessed with the Han and Warters scores. The quality of mask ventilation between the four groups was compared for all patients and a subgroup analysis was performed for patients of the study groups, who had to be ventilated with a Guedel tube and for obese patients (body mass index ≥26 kg/m2). A sample size calculation revealed that at least 38 patients were necessary for each group to detect a statistically significant difference between groups; it was assumed that Roc improved the efficacy of mask ventilation by 20% compared to saline (α = 0.05, 1-ß = 0.8). RESULTS: The administration of Roc significantly improved the TV/ppeak ratio compared to saline (p = 0.04); however, this effect was irrespective of the dose. In patients who were ventilated with the Guedel tube the TV/ppeak ratio increased after Roc03 (p ≤ 0.01) and after Roc06 (p < 0.02) compared to the saline group. In obese patients who were ventilated with the Guedel tube the TV/ppeak ratio increased after Roc03 (p ≤ 0.01), after Roc06 (p = 0.03) and after Roc09 (p = 0.02) compared to the saline group. There were no significant differences between the Roc groups; however, the effect was more pronounced in the Roc03 patients compared to the other Roc groups. The Han and Warters scores were not significantly different between the Roc groups and the saline group. CONCLUSION: The efficacy of mask ventilation was equal or improved after administration of Roc but did not become worse. Patients who were ventilated with a Guedel tube had higher TV/ppeak ratios after Roc03 and Roc06 compared to saline. Higher dosages (>Roc06), however, had no advantages concerning quality of mask ventilation. In obese patients who had to be ventilated with a Guedel tube, Roc also improved the efficacy of mask ventilation. We conclude that administration of Roc is effective in improving mask ventilation and this effect was seen after 30-60 s even after Roc03.

AF-1 a novel regulator of the redox equilibrium during aging.

Multicellular organisms generally undergo qualitative changes within time that are associated with progressive degeneration of biological functions, increased susceptibility to diseases, and increased probability to die within a given time period (aging). One of the major factors contributing to aging is accumulation of oxidative damage. We show that Aging Factor-1 (AF-1) negatively influences the redox balance during aging. AF-1 expression is greatly enhanced in various human cell types of aged individuals which leads to decreased stress resistance towards oxidative damage. We used Drosophila melanogaster as an in vivo model system. Functional knockdown of AF-1 in Drosophila melanogaster reveals a gender-specific effect on lifespan. Whereas female flies show a prolonged healthy lifespan, males show no difference (or even a shortened lifespan). Altogether our data suggest AF-1 expression during aging to be a mechanism that affects healthy aging and age-related stress resistance depending on the gender of the fly.

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.

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.

[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.