Impact of Developmental Changes of GABAA Receptors on Interneuron-NG2 Glia Transmission in the Hippocampus

NG2 glia receive synaptic input from neurons, but the functional impact of this glial innervation is not well understood. In the developing cerebellum and somatosensory cortex the GABAergic input might regulate NG2 glia differentiation and myelination, and a switch from synaptic to extrasynaptic neuron-glia signaling was reported in the latter region. Myelination in the hippocampus is sparse, and most NG2 glia retain their phenotype throughout adulthood, raising the question of the properties and function of neuron-NG2 glia synapses in that brain region. Here, we compared spontaneous and evoked GABAA receptor-mediated currents of NG2 glia in juvenile and adult hippocampi of mice of either sex and assessed the mode of interneuron-glial signaling changes during development. With patch-clamp and pharmacological analyses, we found a decrease in innervation of hippocampal NG2 glia between postnatal days 10 and 60. At the adult stage, enhanced activation of extrasynaptic receptors occurred, indicating a spillover of GABA. This switch from synaptic to extrasynaptic receptor activation was accompanied by downregulation of γ2 and upregulation of the α5 subunit. Molecular analyses and high-resolution expansion microscopy revealed mechanisms of glial GABAA receptor trafficking and clustering. We found that gephyrin and radixin are organized in separate clusters along glial processes. Surprisingly, the developmental loss of γ2 and postsynaptic receptors were not accompanied by altered glial expression of scaffolding proteins, auxiliary receptor subunits or postsynaptic interaction proteins. The GABAergic input to NG2 glia might contribute to the release of neurotrophic factors from these cells and influence neuronal synaptic plasticity.

Dysfunction of NG2 glial cells affects neuronal plasticity and behavior

NG2 glia represents a distinct type of macroglial cells in the CNS and is unique among glia because they receive synaptic input from neurons. They are abundantly present in white and gray matter. While the majority of white matter NG2 glia differentiates into oligodendrocytes, the physiological impact of gray matter NG2 glia and their synaptic input are still ill defined. Here, we asked whether dysfunctional NG2 glia affect neuronal signaling and behavior. We generated mice with inducible deletion of the K⁺ channel Kir4.1 in NG2 glia and performed comparative electrophysiological, immunohistochemical, molecular and behavioral analyses. Kir4.1 was deleted at postnatal day 23-26 (recombination efficiency about 75%) and mice were investigated 3-8 weeks later. Notably, these mice with dysfunctional NG2 glia demonstrated improved spatial memory as revealed by testing new object location recognition while working and social memory remained unaffected. Focussing on the hippocampus, we found that loss of Kir4.1 potentiated synaptic depolarizations of NG2 glia and stimulated the expression of myelin basic protein while proliferation and differentiation of hippocampal NG2 glia remained largely unaffected. Mice with targeted deletion of the K⁺ channel in NG2 glia showed impaired long-term potentiation at CA3-CA1 synapses, which could be fully rescued by extracellular application of a TrkB receptor agonist. Our data demonstrate that proper NG2 glia function is important for normal brain function and behavior.

Cx43 carboxyl terminal domain determines AQP4 and Cx30 endfoot organization and blood brain barrier permeability

The neurovascular unit (NVU) consists of cells intrinsic to the vessel wall, the endothelial cells and pericytes, and astrocyte endfeet that surround the vessel but are separated from it by basement membrane. Endothelial cells are primarily responsible for creating and maintaining blood-brain-barrier (BBB) tightness, but astrocytes contribute to the barrier through paracrine signaling to the endothelial cells and by forming the glia limitans. Gap junctions (GJs) between astrocyte endfeet are composed of connexin 43 (Cx43) and Cx30, which form plaques between cells. GJ plaques formed of Cx43 do not diffuse laterally in the plasma membrane and thus potentially provide stable organizational features to the endfoot domain, whereas GJ plaques formed of other connexins and of Cx43 lacking a large portion of its cytoplasmic carboxyl terminus are quite mobile. In order to examine the organizational features that immobile GJs impose on the endfoot, we have used super-resolution confocal microscopy to map number and sizes of GJ plaques and aquaporin (AQP)-4 channel clusters in the perivascular endfeet of mice in which astrocyte GJs (Cx30, Cx43) were deleted or the carboxyl terminus of Cx43 was truncated. To determine if BBB integrity was compromised in these transgenic mice, we conducted perfusion studies under elevated hydrostatic pressure using horseradish peroxide as a molecular probe enabling detection of micro-hemorrhages in brain sections. These studies revealed that microhemorrhages were more numerous in mice lacking Cx43 or its carboxyl terminus. In perivascular domains of cerebral vessels, we found that density of Cx43 GJs was higher in the truncation mutant, while GJ size was smaller. Density of perivascular particles formed by AQP4 and its extended isoform AQP4ex was inversely related to the presence of full length Cx43, whereas the ratio of sizes of the particles of the AQP4ex isoform to total AQP4 was directly related to the presence of full length Cx43. Confocal analysis showed that Cx43 and Cx30 were substantially colocalized in astrocyte domains near vasculature of truncation mutant mice. These results showing altered distribution of some astrocyte nexus components (AQP4 and Cx30) in Cx43 null mice and in a truncation mutant, together with leakier cerebral vasculature, support the hypothesis that localization and mobility of gap junction proteins and their binding partners influences organization of astrocyte endfeet which in turn impacts BBB integrity of the NVU.

Auxiliary Subunits Control Function and Subcellular Distribution of AMPA Receptor Complexes in NG2 Glia of the Developing Hippocampus

Synaptic and axonal glutamatergic signaling to NG2 glia in white matter is critical for the cells' differentiation and activity dependent myelination. However, in gray matter the impact of neuron-to-NG2 glia signaling is still elusive, because most of these cells keep their non-myelinating phenotype throughout live. Early in postnatal development, hippocampal NG2 glia express AMPA receptors with a significant Ca²⁺ permeability allowing for plasticity of the neuron-glia synapses, but whether this property changes by adulthood is not known. Moreover, it is unclear whether NG2 glia express auxiliary transmembrane AMPA receptor related proteins (TARPs), which modify AMPA receptor properties, including their Ca²⁺ permeability. Through combined molecular and functional analyses, here we show that hippocampal NG2 glia abundantly express TARPs γ4, γ7, and γ8 as well as cornichon (CNIH)-2. TARP γ8 undergoes profound downregulation during development. Receptors of adult NG2 glia showed an increased sensitivity to blockers of Ca²⁺ permeable AMPA receptors, but this increase mainly concerned receptors located close to the soma. Evoked synaptic currents of NG2 glia were also sensitive to blockers of Ca²⁺ permeable AMPA receptors. The presence of AMPA receptors with varying Ca²⁺ permeability during postnatal maturation may be important for the cells' ability to sense and respond to local glutamatergic activity and for regulating process motility, differentiation, and proliferation.

Astrocytic GABA Accumulation in Experimental Temporal Lobe Epilepsy

An imbalance of excitation and inhibition has been associated with the pathophysiology of epilepsy. Loss of GABAergic interneurons and/or synaptic inhibition has been shown in various epilepsy models and in human epilepsy. Despite this loss, several studies reported preserved or increased tonic GABA_A receptor-mediated currents in epilepsy, raising the question of the source of the inhibitory transmitter. We used the unilateral intracortical kainate mouse model of temporal lobe epilepsy (TLE) with hippocampal sclerosis (HS) to answer this question. In our model we observed profound loss of interneurons in the sclerotic hippocampal CA1 region and dentate gyrus already 5 days after epilepsy induction. Consistent with the literature, the absence of interneurons caused no reduction of tonic inhibition of CA1 pyramidal neurons. In dentate granule cells the inhibitory currents were even increased in epileptic tissue. Intriguingly, immunostaining of brain sections from epileptic mice with antibodies against GABA revealed strong and progressive accumulation of the neurotransmitter in reactive astrocytes. Pharmacological inhibition of the astrocytic GABA transporter GAT3 did not affect tonic inhibition in the sclerotic hippocampus, suggesting that this transporter is not responsible for astrocytic GABA accumulation or release. Immunostaining further indicated that both decarboxylation of glutamate and putrescine degradation accounted for the increased GABA levels in reactive astrocytes. Together, our data provide evidence that the preserved tonic inhibitory currents in the epileptic brain are mediated by GABA overproduction and release from astrocytes. A deeper understanding of the underlying mechanisms may lead to new strategies for antiepileptic drug therapy.

BCG scarring and improved child survival: a combined analysis of studies of BCG scarring

Bacillus Calmette-Guérin (BCG) vaccine against tuberculosis (TB) is recommended at birth in TB-endemic areas. Currently, BCG vaccination programmes use "BCG vaccination coverage by 12 months of age" as the performance indicator. Previous studies suggest that BCG-vaccinated children, who develop a scar, have better overall survival compared with BCG-vaccinated children, who do not develop a scar. We summarized the available studies of BCG scarring and child survival. A structured literature search for studies with original data and analysis of BCG scarring and mortality were performed. Combined analyses on the effect of BCG scarring on overall mortality. We identified six studies covering seven cohorts, all from Guinea-Bissau, West Africa, with evaluation of BCG scarring amongst BCG-vaccinated children and follow-up for mortality. Determinants of BCG scarring were BCG strain, intradermal injection route, size of injection wheal, and co-administered vaccines and micronutrients. In a combined analysis, having a BCG scar vs. no BCG scar was associated with a mortality rate ratio (MRR) of 0.61 (95% CI: 0.51-0.74). The proportion with a BCG scar varied from 52 to 93%; the estimated effect of a BCG scar was not associated with the scar prevalence. The effect was strongest in the first (MRR = 0.48 (0.37-0.62)) and second (MRR = 0.63 (0.44-0.92)) year of life, and in children BCG-vaccinated in the neonatal period (MRR = 0.45 (0.36-0.55)). The effect was not explained by protection against TB. Confounding and genetic factors are unlikely to explain the strong association between BCG scarring and subsequent survival. Including "BCG scar prevalence" as a BCG vaccination programme performance indicator should be considered. The effect of revaccinating scar-negative children should be studied.

North American April tornado occurrences linked to global sea surface temperature anomalies

Annual tornado occurrences over North America display large interannual variability and a statistical linkage to sea surface temperature (SST) anomalies. However, the underlying physical mechanisms for this connection and its modulation in a rapidly varying seasonal environment still remain elusive. Using tornado data over the United States from 1954 to 2016 in combination with SST-forced atmospheric general circulation models, we show a robust dynamical linkage between global SST conditions in April, the emergence of the Pacific-North American teleconnection pattern (PNA), and the year-to-year tornado activity in the Southern Great Plains (SGP) region of the United States. Contrasting previous studies, we find that only in April SST-driven atmospheric circulation anomalies can effectively control the northward moisture-laden flow from the Gulf of Mexico, boosting low-level moisture flux convergence over the SGP. These strong large-scale connections are absent in other months because of the strong seasonality of the PNA and background moisture conditions.

Connexin-43 Gap Junctions Are Responsible for the Hypothalamic Tanycyte-Coupled Network

Tanycytes are hypothalamic radial glia-like cells that form the basal wall of the third ventricle (3V) where they sense glucose and modulate neighboring neuronal activity to control feeding behavior. This role requires the coupling of hypothalamic cells since transient decreased hypothalamic Cx43 expression inhibits the increase of brain glucose-induced insulin secretion. Tanycytes have been postulated as possible hypothalamic neuronal precursors due to their privileged position in the hypothalamus that allows them to detect mitogenic signals and because they share the markers and characteristics of neuronal precursors located in other neurogenic niches, including the formation of coupled networks through connexins. Using wild-type (WT), Cx30^−/– and Cx30^−/–, Cx43^fl/fl:glial fibrillary acidic protein (GFAP)-Cre (double knockout, dKO) mouse lines, we demonstrated that tanycytes are highly coupled to each other and also give rise to a panglial network specifically through Cx43. Using the human GFAP (hGFAP)-enhanced green fluorescent protein (EGFP) transgenic mouse line, we provided evidence that the main parenchymal-coupled cells were astrocytes. In addition, electrophysiological parameters, such as membrane resistance, were altered when Cx43 was genetically absent or pharmacologically inhibited. Finally, in the dKO mouse line, we detected a significant decrease in the number of hypothalamic proliferative parenchymal cells. Our results demonstrate the importance of Cx43 in tanycyte homotypic and panglial coupling and show that Cx43 function influences the proliferative potential of hypothalamic cells.

Barreloid Borders and Neuronal Activity Shape Panglial Gap Junction-Coupled Networks in the Mouse Thalamus

The ventral posterior nucleus of the thalamus plays an important role in somatosensory information processing. It contains elongated cellular domains called barreloids, which are the structural basis for the somatotopic organization of vibrissae representation. So far, the organization of glial networks in these barreloid structures and its modulation by neuronal activity has not been studied. We have developed a method to visualize thalamic barreloid fields in acute slices. Combining electrophysiology, immunohistochemistry, and electroporation in transgenic mice with cell type-specific fluorescence labeling, we provide the first structure-function analyses of barreloidal glial gap junction networks. We observed coupled networks, which comprised both astrocytes and oligodendrocytes. The spread of tracers or a fluorescent glucose derivative through these networks was dependent on neuronal activity and limited by the barreloid borders, which were formed by uncoupled or weakly coupled oligodendrocytes. Neuronal somata were distributed homogeneously across barreloid fields with their processes running in parallel to the barreloid borders. Many astrocytes and oligodendrocytes were not part of the panglial networks. Thus, oligodendrocytes are the cellular elements limiting the communicating panglial network to a single barreloid, which might be important to ensure proper metabolic support to active neurons located within a particular vibrissae signaling pathway.

Synaptic input as a directional cue for migrating interneuron precursors

During CNS development, interneuron precursors have to migrate extensively before they integrate in specific microcircuits. Known regulators of neuronal motility include classical neurotransmitters, yet the mechanisms that assure interneuron dispersal and interneuron/projection neuron matching during histogenesis remain largely elusive. We combined time-lapse video microscopy and electrophysiological analysis of the nascent cerebellum of transgenic Pax2-EGFP mice to address this issue. We found that cerebellar interneuronal precursors regularly show spontaneous postsynaptic currents, indicative of synaptic innervation, well before settling in the molecular layer. In keeping with the sensitivity of these cells to neurotransmitters, ablation of synaptic communication by blocking vesicular release in acute slices of developing cerebella slows migration. Significantly, abrogation of exocytosis primarily impedes the directional persistence of migratory interneuronal precursors. These results establish an unprecedented function of the early synaptic innervation of migrating neuronal precursors and demonstrate a role for synapses in the regulation of migration and pathfinding.

Evolution and forcing mechanisms of El Niño over the past 21,000 years

The El Niño Southern Oscillation (ENSO) is Earth's dominant source of interannual climate variability, but its response to global warming remains highly uncertain. To improve our understanding of ENSO's sensitivity to external climate forcing, it is paramount to determine its past behaviour by using palaeoclimate data and model simulations. Palaeoclimate records show that ENSO has varied considerably since the Last Glacial Maximum (21,000 years ago), and some data sets suggest a gradual intensification of ENSO over the past ∼6,000 years. Previous attempts to simulate the transient evolution of ENSO have relied on simplified models or snapshot experiments. Here we analyse a series of transient Coupled General Circulation Model simulations forced by changes in greenhouse gasses, orbital forcing, the meltwater discharge and the ice-sheet history throughout the past 21,000 years. Consistent with most palaeo-ENSO reconstructions, our model simulates an orbitally induced strengthening of ENSO during the Holocene epoch, which is caused by increasing positive ocean-atmosphere feedbacks. During the early deglaciation, ENSO characteristics change drastically in response to meltwater discharges and the resulting changes in the Atlantic Meridional Overturning Circulation and equatorial annual cycle. Increasing deglacial atmospheric CO2 concentrations tend to weaken ENSO, whereas retreating glacial ice sheets intensify ENSO. The complex evolution of forcings and ENSO feedbacks and the uncertainties in the reconstruction further highlight the challenge and opportunity for constraining future ENSO responses.

[Measurement of carbon dioxide in emergency medicine]

Expiratory carbon dioxide (CO(2)) monitoring is a valuable tool in the prehospital setting. Recent reports of misplaced endotracheal tubes in the prehospital setting make it important to ensure that tube placement is verified by CO(2) monitoring. The Euronorm 2007:1789 made provision of capnometry mandatory for all medical vehicles. However, the frequency of utilization of CO(2) monitoring after securing the airway and in patients with respiratory insufficiency is low. This article covers the terminology, physiology, technology and clinical applications of CO(2) monitoring. Monitoring of cardiac output and the efficiency of cardiopulmonary resuscitation are described and the article also highlights the importance of CO(2) monitoring in patients with severe head trauma as well as restrictive and obstructive pulmonary disorders.

Adaptive coordination development in student anaesthesia teams: a longitudinal study

Although adaptive coordination has been highlighted by several studies, research dealing with how adaptive coordination develops is still rare. Thus, the aim of this study was to investigate the development of coordination mechanisms and their task-related adaptation in a longitudinal observation of medical simulation-based training of final year students. We recorded six anaesthesia teams during a sequence of four task scenarios, and each scenario comprised of a routine and a complication phase. After trained observers rated sub-tasks within each scenario for explicit and implicit coordination, statistical analysis revealed a statistically significant effect of previous scenarios on coordination development in the routine phases. While the amount of explicit coordination decreased, implicit coordination increased, revealing adaptive coordination as a skill developed through repeated group interaction. We conclude that anaesthesia training should consider cost- and patient safety-benefits of implicit and explicit coordination and focus on adaptive coordination.

PRACTITIONER SUMMARY

Group coordination is crucial to anaesthesia team performance. Results of this longitudinal observation of six anaesthesia teams during four medical simulation-based training scenarios document that teams develop adaptive patterns of coordination. This study also demonstrates that adaptive coordination is a trainable skill within crisis resource management training.

The use of the Foley Airway Stylet Tool® to guide tracheal intubations through an intubating laryngeal mask airway

BACKGROUND

Blind insertion of endotracheal tubes through the intubating laryngeal mask airway (ILMA) is unsuccessful in almost 50% of cases on the first attempt, with an overall success rate of approximately 90%. We used a portable fiber optic device (Foley Airway Stylet Tool® FAST) to detect the reasons for failed intubations and tested its use in facilitating endotracheal tube placement.

METHODS

Thirty patients without anticipated intubation difficulties participated in the study. The fiber optic device was fastened with its tip at the end of the endotracheal tube, and both instruments were advanced through the previously inserted ILMA past the lifting bar. The view was scored in the following manner: I, full view of laryngeal inlet; II, partial vocal cords, arytenoids, epiglottis; III, epiglottis; IV, no laryngeal structures identifiable. The ILMA was adjusted for the best obtainable view, which was scored, and the endotracheal tube was inserted.

RESULTS

The initial laryngeal view was I in four patients, II in eighteen patients, III in one patient and IV in seven patients. The best view after corrective maneuvers was I in twenty-seven patients, II in two patients and IV in one patient. First attempt tracheal intubations were successful in twenty-seven (90%) patients; two patients required a second attempt.

CONCLUSION

A grade II view or worse indicated misalignment of the ILMA with the glottis. An endotracheal tube inserted blindly through the misaligned ILMA will impinge on and potentially damage laryngeal structures. The use of a portable fiber optic device can help reduce the failure rate of endotracheal intubations by utilizing ILMA in emergent situations.

[Extraglottic airway devices in the intensive care unit]

Extraglottic airway devices (EGA) are not only used in routine anaesthesia practice, they also have a distinct value for in-hospital and out-of-hospital difficult airway management. In the environment of the intensive care unit (ICU) EGA are not used on a regular basis. However, expertise and knowledge regarding EGA coming from the operating theatre or the out-of-hospital setting may also be of value for the ICU setting. This review presents the potential indications for EGA on the ICU for the management of difficult airway situations as well as during percutaneous tracheotomy. Furthermore, the possible advantages of EGA during postoperative recovery from anaesthesia as well as termination of controlled ventilation for intensive care patients are discussed.

Deepwater formation in the North Pacific during the Last Glacial Termination

Between approximately 17,500 and 15,000 years ago, the Atlantic meridional overturning circulation weakened substantially in response to meltwater discharges from disintegrating Northern Hemispheric glacial ice sheets. The global effects of this reorganization of poleward heat flow in the North Atlantic extended to Antarctica and the North Pacific. Here we present evidence from North Pacific paleo surface proxy data, a compilation of marine radiocarbon age ventilation records, and global climate model simulations to suggest that during the early stages of the Last Glacial Termination, deep water extending to a depth of approximately 2500 to 3000 meters was formed in the North Pacific. A switch of deepwater formation between the North Atlantic and the North Pacific played a key role in regulating poleward oceanic heat transport during the Last Glacial Termination.

[Out-of-hospital pediatric emergencies. Perception and assessment by emergency physicians]

BACKGROUND

Out-of-hospital (OOH) pediatric emergencies have a relatively low prevalence. In Germany the vast majority of cases are attended by non-specialized emergency physicians (EPs) for whom these are not routine procedures. This may lead to insecurity and fear. However, it is unknown how EPs perceive and assess pediatric emergencies and how they could be better prepared for them.

METHODS

All active EPs (n=50) of the Department of Anaesthesiology, Emergency and Intensive Care Medicine at the University Medical Centre of Göttingen were presented with a structured questionnaire in order to evaluate their perception and assessment of OOH pediatric emergencies.

RESULTS

The 43 participating EPs made highly detailed statements on the expected characteristics of OOH pediatric emergencies. Their confidence level grew with the children's age (p<0.03) and with their own experience (p<0.01). The EPs felt particular deficits in the fields of cardiopulmonary resuscitation (n=18) and trauma management (n=8). The preferred educational strategies included simulator-based training (n=24) as well as more exposure to pediatric intensive care and pediatric anesthesia (n=12).

CONCLUSIONS

Despite their own limited experience EPs can realistically assess the incidence and severity of pediatric emergencies. They felt the greatest deficits were in the care of infrequent but life-threatening emergencies. Three educational groups can be differentiated: knowledge and skills to be gained with children in hospital, clinical experience from adult care also applicable in children and rare diagnoses and interventions to be trained with manikins or simulators.

[Evaluation of the new supraglottic airway devices Ambu AuraOnce and Intersurgical i-gel. Positioning, sealing, patient comfort and airway morbidity]

BACKGROUND

Supraglottic airway devices (SGAD) have become more important in airway management over the past years and an objective comparison of the available devices is in order.

METHODS

In a prospective study the four SGADs LMA-Classic(cLMA), LMA-ProSeal (PLMA), Ambu AuraOnce and Intersurgical i-gel were compared in groups of 40 patients in ambulatory surgery, with respect to the feasibility of positioning, leak tightness, patient comfort and airway morbidity. The seal test of the airway devices was carried out with a specially constructed pneumotachograph.

RESULTS

Adequate placement on the first attempt was achieved in 92.5% with the cLMA, 85% with the PLMA, 92.5% with the AuraOnce and 82.5% with the i-gel (p>0.05). There were no clinically relevant differences in mean insertion times: cLMA 13.8 s (+/-3.4 s), PLMA 13 s (+/-3.2 s), AuraOnce 11.2 s (+/-2.7 s; p<0.05) and 13.9 s (+/-3.6 s) with the i-gel. A tight seal at a constant oropharyngeal pressure of 15 cmH(2)O was achieved in 85% of the cases (34 cases) with the cLMA, 90% (36 cases) with the PLMA, 97.5% (39 cases) with the AuraOnce and 72.5% (29 cases) with the i-gel (p<0.05). A tight seal at a constant oropharyngeal pressure of 20 cmH(2)O was seen in 62.5% with the cLMA, 60% with the PLMA, 67.5% with the AuraOnce and in 50% with the i-gel of the cases (p>0.05). Airway morbidity was not observed in any group. Significantly more patients complained of a sore throat after using the cLMA (p<0.05).

CONCLUSION

The tested SGADs were comparable with regard to ease of insertion, insertion times and airway morbidity. Considering leak tightness and patient comfort the PLMA and the AuraOnce fared better with regard to tightness of seal and patient comfort.

A controlled rapid-sequence induction technique for infants may reduce unsafe actions and stress

BACKGROUND

Classic rapid-sequence induction of anaesthesia (RSI-classic) in infants and small children presents a time-critical procedure, regularly associated with hypoxia. This results in high stress levels for the provider and may trigger unsafe actions. Hence, a controlled induction technique (RSI-controlled) that involves gentle mask ventilation until full non-depolarizing muscular blockade has become increasingly popular. Clinical observation suggests that RSI-controlled may reduce the adverse effects noted above. We aimed to evaluate both techniques with respect to unsafe actions and stress.

METHODS

In this controlled, randomized simulator-based study, 30 male trainees and specialists in anaesthesiology performed a simulated anaesthesia induction in a 4-week-old infant with pyloric stenosis. Two different RSI techniques, classic and controlled, were applied to 15 candidates each. We recorded the incidence of hypoxaemia, forced mask ventilation, and intubation difficulties. In addition, we measured individual stress levels by ergospirometry, salivary cortisol, and alpha-amylase, as well as a post-trial questionnaire.

RESULTS

Hypoxaemia always occurred in RSI-classic but not in RSI-controlled, repeatedly resulting in unsafe actions. Subjective stress perception and some objective stress levels were lower in the volunteers performing RSI-controlled.

CONCLUSIONS

Our data suggest that RSI-controlled, as compared with RSI-classic, leads to fewer unsafe actions and may reduce individual stress levels.

[Teaching and simulation. Methods, demands, evaluation and visions]

Since 1st October 2003 the new German "Approbationsordnung für Arzte" (Medical Licensing Regulations) requires an increasing amount of small group teaching sessions and encourages a multidisciplinary and more practical approach to the related topics. In 2004 the German Society of Anaesthesiology and Intensive Care Medicine has provided almost all anaesthesia faculties of German Universities with equipment for full-scale simulation. This article describes methods for a simulation-based medical education training program. Basic requirements for a successful training program using full scale simulators are the provision of an adequate logistical and material infrastructure, teacher attendance of train-the-trainer courses, implementation in the medical curriculum and an instructor-student ratio of 1:3, equivalent to that for bedside teaching. If these requirements were fulfilled, medical students scored the simulation scenarios "induction of anaesthesia", "acute pulmonary embolism", "acute management of a multiple trauma patient" and "postoperative hypotension" as 1.5, 1.6, 1.5 and 1.5, respectively, on a scale of 1-6. These scores were better than those given for other segments of the curriculum.

Intubating laryngeal mask airway for difficult out-of-hospital airway management: a prospective evaluation

BACKGROUND

Out-of-hospital airway management is a critical skill, demanding expert knowledge and experience. The intubating laryngeal mask airway (ILMA) is a ventilatory and intubating device which may be of value in this arena. We evaluated the ILMA for out-of-hospital management of the difficult airway.

METHODS

Twenty-one anaesthesia-trained emergency physicians (EPs) completed a training programme and used the ILMA in patients with difficult-to-manage airways. Indications for use of the ILMA included patients with difficult laryngoscopy, multiple intubation attempts, limited access to the patient's head, presence of pharyngo-laryngeal trauma, and gastric fluids or bleeding obscuring the view of the vocal cords.

RESULTS

During the study period, 146 of 2513 patients underwent tracheal intubation or alternate rescue airway insertion. In 135 patients, laryngoscopy was performed and Cormack-Lehane view was recorded as grade I in 72 (53.3%), II in 45 (33.3%), III in 10 (7.4%), and IV in 8 (5.9%). EPs encountered 11 patients (7.5%) with difficult-to-manage airways. ILMA insertion and ventilation was possible in 10 patients in the first and one patient in the second attempt. ILMA-guided tracheal intubation was successful in all patients, in 10 after the first and in 1 after two attempts.

CONCLUSIONS

In this study, ventilation and intubation with ILMA was successful in all patients with difficult-to-manage airways. Our data support the use of the ILMA as rescue device for out-of-hospital airway management by staff who have appropriate airway skills and have received appropriate training.

Laryngoscopic versus intubating LMA guided tracheal intubation by novice users—A manikin study

AIM OF THE STUDY

Airway control is a potentially lifesaving procedure but tracheal intubation by direct laryngoscopy is difficult. This pilot study was conducted to determine whether tracheal intubation was more rapid and the success rate higher using an intubating laryngeal mask airway.

MATERIAL AND METHODS

The success rates of 119 medical students without prior airway management experience in ventilating and then intubating the trachea of a Laerdal Airway Management Trainer with two different methods were compared. The methods were bag-mask ventilation (BM-V) followed by laryngoscopic intubation (LG-TI), and intubating laryngeal mask ventilation (ILMA-V) followed by ILMA-guided tracheal intubation (ILMA-TI). After an introductory lecture and demonstration, each student was allowed three attempts to intubate using each method in random order.

RESULTS

All participants were successful with BM-V and ILMA-V on the first attempt. Laryngoscopic tracheal intubation was achieved by 60 (50.4%), 31 (26.1%) and 12 (10.1%) participants on the first, second and third attempt, respectively, while 16 (13.4%) failed in all three attempts. In the ILMA-TI group, 107 (90.0%), 10 (8.4%) and 2 (1.6%) succeeded on the first, second and third attempt, respectively. None failed. The intergroup difference is highly significant (p<0.001). Male participants were more successful with LG-TI than female (p<0.01), but not with ILMA-TI.

CONCLUSION

Laryngoscopic orotracheal intubation is difficult for the untrained, but all participants were successful with ILMA-TI. These data suggest that alternative devices such as the ILMA should be included in the medical school curriculum for airway management.

Präklinisches Atemwegsmanagement in Norddeutschland

BACKGROUND

Out-of-hospital airway management confronts emergency medical teams with complex challenges. To date no specific data are available on the qualifications of emergency physicians (EPs) and the quality of emergency equipment in northern Germany.

MATERIALS AND METHODS

This study surveyed individual EPs at regional emergency dispatch centres about their personal knowledge and skills, and the procedures and equipment used in out-of-hospital airway management.

RESULTS

A total of 606 EPs from 59 of the 66 (89.4%) regional emergency dispatch centres surveyed responded and 56.1% of the EPs questioned were anesthesiologists. The other EPs were qualified in either internal medicine (22.6%), surgery (12.4%), general medicine (5.6%) or other specialties (3.3%). All (100%) of the EPs trained in anesthesia and 35.2% of the other EPs reported that they had performed more than 100 in-hospital endotracheal intubations (ETI). 93% of all EPs rated out-of-hospital ETI as more difficult than in-hospital ETI. A total of 33.0% of anesthesia-trained EPs and 6.1% of the other EPs used muscle relaxants for ETI in more than 20% of the cases. Of the anesthesia-trained EPs 38.1% used expiratory CO(2) monitoring to verify tube placement compared to 12.1% of the other EPs. A total of 97.8% of anesthesia-trained EPs reported having used an extra-glottic airway device more than 20 times compared to 11.1% of the other EPs. For the emergency equipment 44.4% included an extraglottic airway device, 57.8% a cricothyrotomy set and 27.1% CO(2) monitoring options.

CONCLUSION

Neither the emergency equipment nor the physicians' knowledge and skills were sufficient to meet the special demands of out-of-hospital airway management, particularly among non-anesthesiologists.

LMA CTrach™

BACKGROUND

The Intubating LMA was designed to facilitate blind intubation and to provide ventilation between two intubation attempts. However, blind intubation can be associated with a risk of oesophageal penetration, therefore, a flexible bronchoscope is frequently used to assist tracheal intubation. This leads to increased burdens on materials and personal resources and prolongs intubation times. Hence the LMA CTrach laryngeal mask airway (CTrach) was developed with an integrated fibreoptic system which can be connected to a monitor for visualisation of the larynx during intubation.

METHODS

We detail the initial experience gained with the practical handling of the CTrach and the application in 10 patients with difficult-to-manage airways. Laryngeal views were graduated in a CTrach-specific classification from grade I (clear view of the arytenoids, glottis and epiglottis) to grade IV (no part of the larynx can be identified). Adjusting manoeuvres were defined to improve the view of laryngeal structures.

RESULTS

All patients could be successfully ventilated with the CTrach. Ventilation quality was rated adequate in nine and possible in one patient. The initial distribution of the laryngeal view between grades I-IV was 1/2/1/6 and after adjusting manoeuvres to improve the laryngeal view the grade distribution was 3/5/0/2. Intubation through the CTrach was successful in all patients, nine at first and one at the second attempt.

CONCLUSION

In this small sample of patients with difficult-to-manage airways, the CTrach yielded high success rates for both ventilation and tracheal intubation. Adjusting manoeuvres can improve the laryngeal view further.

Evaluation of the CTrach™—an intubating LMA with integrated fibreoptic system †

BACKGROUND

The laryngeal mask airway CTrach (CTrach) is a variant of the intubating laryngeal mask airway. It provides visualization of the larynx during intubation and is designed to increase the success rates of ventilation and tracheal intubation.

METHODS

Sixty healthy anaesthetized and paralysed patients with normal airways were studied. The success rates of ventilation and intubation using CTrach were determined. Laryngeal view scoring ranged from grade I (full view of arytenoids and glottis), II (arytenoids and glottis partly visible), III (view of arytenoids, glottis or epiglottis blurred, or view clear with only epiglottis visible) to IV (no part of larynx identifiable). Adjusting manoeuvres were undertaken to improve the laryngeal view in grades II or worse.

RESULTS

CTrach insertion and ventilation was possible in all patients. Initial views were scored as grade I in 22 (36.7%), grade II in 14 (23.3%), grade III in 7 (11.7%) and grade IV in 17 (28.3%) patients. Adjusting manoeuvres were undertaken in 38 patients with grade II and worse (63.3%), resulting in improved views of grade I in 33 (55.0%), grade II in 18 (30.0%), grade III in 4 (6.7%) and grade IV in 5 (8.3%) patients. Tracheal intubation was successful in 58 (96.6%) patients at first attempt and in one at second. Tracheal intubation failed once.

CONCLUSIONS

In 60 patients with normal airways, the CTrach was used successfully for ventilation, with successful tracheal intubation in 59 patients. Tracheal intubation can be successful despite grade III or IV views.

Neue Perspektiven der simulatorunterstützten Ausbildung in Kinderanästhesie und Kindernotfallmedizin

Anaesthesia and emergency medical care for infants and toddlers is often associated with high clinical demands and specific challenges. Nevertheless, a significant proportion of interventions is performed by anaesthetists and emergency physicians with no specialised paediatric training and little experience in the management of anaesthetic incidents and emergencies specific to these age groups. Extensive studies have demonstrated a close inverse correlation between the level of specialisation and perioperative morbidity and mortality. However, clinical circumstances and the relatively small number of paediatric cases at many institutions often hinder the establishment of improved training concepts. Recently, high-fidelity infant simulators have become available, which permit authentic exposure to a large spectrum of scenarios in paediatric anaesthesia and emergency medicine. A multimodular concept of training, including such simulator-based techniques, may relieve the widespread shortage in clinical experience, and hence greatly facilitate improvement of quality of care and patient safety.

Akzidentelle Hypothermie in häuslicher Umgebung

In emergency medicine accidental hypothermia in non-traumatized patients is a rare situation. To emphasize the need for a precise preclinical temperature measurement, two cases of accidental hypothermia (28.2 degrees C and 29.3 degrees C core temperature) are presented which occurred under conditions that did not give a direct suspicion of hypothermia. In one case the immediate diagnosis lead to complete convalescence, the other patient died of multiple organ failure. The primary diagnosis, diagnostic methods and therapy as well as the primary treatment are discussed.

[New pathways in undergraduate medical education - first experiences with the cross section speciality emergency and intensive care medicine]

OBJECTIVE

On October 1 (st) 2003 Emergency Medicine was recognised for the first time as an independent cross section speciality in the new German "Approbationsordnung fuer Aerzte" (Medical Licensing Regulations). These amendments were made not only to increase the amount of small group teaching sessions but also to encourage a multidisciplinary and rather practical approach to the related topics. This article portrays the realisation of these objectives in form of a multidisciplinary module, as it has been established at University of Göttingen Medical School since the summer semester of 2004. We present the new curriculum, calculate the associated personnel resources and demonstrate the results of the structured evaluation given by the participating students.

METHODS

We linked the fields of emergency and intensive care medicine by splitting them up into submodules which the students had to run through according to a set rota. 162 students were allocated to 27 small groups. Every student received a total of 38.5 hours of teaching, with the workshops coming to 46.8 %. The workshops comprised of nine sessions, three in Emergency Medicine, four in Intensive Care Medicine and two at human patient simulators. In addition we scheduled a seminar and an accompanying lecture. The final examination was performed as an Objective Structured Clinical Evaluation (OSCE).

RESULTS

The realisation of the new module required a total of 1290 working hours for medical staff and 130 for our student aids. Compared to all other modules of Goettingen University Medical School the module here presented obtained the highest overall evaluation score by the medical students. Lessons with a high amount of practical involvement (i. e. Emergency Medicine and simulator-based workshops) were significantly better evaluated than rather formal teaching techniques, such as the lectures and the seminar. According to the students' self-assessment the simulator-based workshops were seen particularly valuable for the facilitation of knowledge transfer into clinical practice.

CONCLUSION

The determined realisation of the new German Medical Licensing Regulations requires considerable time resources. However, its evaluation by the medical students is strikingly positive.

[The applicability of the ProSeal laryngeal mask airway for laparotomies]

OBJECTIVE

The ProSeal laryngeal mask airway (PLMA) has some design features, which in contrast to the classic LMA allow separation of the respiration from the gastrointestinal canal, a higher leak pressure and a better position assessment. It can be debated if these instrumental improvements justify the application of the PLMA for elective abdominal surgery in cases without aspiration risk. Insertion of airway instruments and gastric tube with regard to insertion time and difficulties and frequency of side effects were to be compared for the tracheal tube and the PLMA. The pharyngolaryngeal morbidity for both methods was also of interest. It was approached with direct and indirect postoperative interview techniques.

METHODS

65 patients were investigated both at the university hospital and at the hospital Neu-Bethlehem in Goettingen. The surgical intervention was a surgical or gynecological laparotomy. Anaesthesia was performed with a standardized application of propofol, alfentanil and rocuronium. Glycopyrroniumbromide was applied to minimize salivation. A total of 34 patients received the PLMA, 31 were intubated. All of them were provided with a gastric tube.

RESULTS

The insertion of the PLMA took 70 seconds (21 - 234) on average, the intubation 57 seconds (35 - 145). Endotracheal intubation was accomplished in a shorter time period, but there was no significant difference in comparison with the PLMA-group (p = 0.1924). Insertion of the PLMA was significantly more difficult than oral intubation (p = 0.0006). The base of the tongue and the dorsal pharyngeal wall, but not the vocal cords or the epiglottis were visible in those cases, where the PLMA could not be positioned at all. Here the tip of the cuff was bended. The time period for positioning of the gastric tube was 38 seconds (15 - 75) in the PLMA- and 57 seconds (22 - 219) in the tracheal tube group. With these results the gastric tube positioning was accomplished in a significantly shorter time period in the PLMA-group (p = 0.0267), but not at a significantly higher level of difficulty for endotracheal intubation (p = 0,6247). In one case there was regurgitation through the drainage tube without aspiration before gastric tube placement. At the direct interview 16 patients in the PLMA-group and 23 of the tube group mentioned postoperative throat symptoms. The most frequent symptom was hoarseness (11 PLMA- and 18 intubated patients). There was no significant difference between PLMA- and tracheal tube application with regard to the total number of patients with pharyngolaryngeal morbidity and the frequency of single symptoms. The same is true for the degree of the symptoms. There was a tendency for a longer prevalence of throat symptoms after intubation, but no significant difference.

CONCLUSION

In this investigation the PLMA could be successfully applied for elective laparotomies in cases without the risk of aspiration. Proper patient selection and a deep level of anaesthesia are important. The advantage for patients receiving the PLMA is a smooth recovery without cough, but not so much a reduced amount of pharyngolaryngeal morbidity. From this observation it might be concluded that the invasiveness of the surgical intervention might also influence the tolerance for the airway instrument. The disadvantage in this study was the more difficult insertion of the PLMA compared with the oral intubation. Further studies with a larger number of patients must show if these first results of the "Proseal"-LMA for lararotomies are to be confirmed.

Simulation und Atemwegsmanagement

Despite the development of new devices and strategies to manage and secure the difficult airway, morbidity and mortality in anaesthesia due to airway problems such as difficult intubation or unrecognised failed intubation remain high. The problem seems to lie in the transfer of skills and strategies to daily clinical practice. Common methods for airway management training include theoretical instructions and hands-on sessions with manikins, animal models and cadavers. Simulation provides the opportunity to train skills and resolve specific situations embedded in a realistic scenario, facilitate the transfer of cognitive, psychomotor and affective abilities into daily clinical practice and help to improve behaviour in critical situations. This article outlines new training concepts in airway management with the help of simulation and simulators. We describe technical prerequisites and provide information on the implementation of difficult airway scenarios.

Strong hemispheric coupling of glacial climate through freshwater discharge and ocean circulation

The climate of the last glacial period was extremely variable, characterized by abrupt warming events in the Northern Hemisphere, accompanied by slower temperature changes in Antarctica and variations of global sea level. It is generally accepted that this millennial-scale climate variability was caused by abrupt changes in the ocean thermohaline circulation. Here we use a coupled ocean-atmosphere-sea ice model to show that freshwater discharge into the North Atlantic Ocean, in addition to a reduction of the thermohaline circulation, has a direct effect on Southern Ocean temperature. The related anomalous oceanic southward heat transport arises from a zonal density gradient in the subtropical North Atlantic caused by a fast wave-adjustment process. We present an extended and quantitative bipolar seesaw concept that explains the timing and amplitude of Greenland and Antarctic temperature changes, the slow changes in Antarctic temperature and its similarity to sea level, as well as a possible time lag of sea level with respect to Antarctic temperature during Marine Isotope Stage 3.

Differences among forced-air warming systems with upper body blankets are small. A randomized trial for heat transfer in volunteers

BACKGROUND

Forced-air warming is known as an effective procedure in prevention and treatment of perioperative hypothermia. Significant differences have been described between forced-air warming systems in combination with full body blankets. We investigated four forced-air warming systems in combination with upper body blankets for existing differences in heat transfer.

METHODS

After approval of the local Ethics Committee and written informed consent, four forced-air warming systems combined with upper body blankets were investigated in a randomized cross-over trial on six healthy volunteers: (1) BairHugger trade mark 505 and Upper Body Blanket 520, Augustine Medical; (2) ThermaCare trade mark TC 3003, Gaymar trade mark and Optisan trade mark Upper Body Blanket, Brinkhaus; (3) WarmAir trade mark 134 and FilteredFlow trade mark Upper Body Blanket, CSZ; and (4) WarmTouch trade mark 5800 and CareDrape trade mark Upper Body Blanket, Mallinckrodt. Heat transfer from the blanket to the body surface was measured with 11 calibrated heat flux transducers (HFTs) with integrated thermistors on the upper body. Additionally, the blanket temperature was measured 1 cm above the HFT. After a preparation time of 60 min measurements were started for 20 min. Mean values were calculated over 20 min. The t-test for matched pairs with Bonferroni-Holm-correcture for multiple testing was used for statistical evaluation at a P-level of 0.05. The values are presented as mean+/-SD.

RESULTS

The WarmTouch trade mark blower with the CareDrape trade mark blanket obtained the best heat flux (17.0+/-3.5 W). The BairHugger trade mark system gave the lowest heat transfer (8.1+/-1.1 W). The heat transfer of the ThermaCare trade mark system and WarmAir trade mark systems were intermediate with 14.3+/-2.1 W and 11.3+/-1.0 W.

CONCLUSIONS

Based on an estimated heat loss from the covered area of 38 W the heat balance is changed by 46.1 W to 55 W by forced-air warming systems with upper body blankets. Although the differences in heat transfer are significant, the clinical relevance of this difference is small.

Role of growth factors in rabbit articular cartilage repair by chondrocytes in agarose

OBJECTIVE

Novel approaches to intervention in joint diseases consist of the replacement of diseased cartilage by in vitro engineered, viable cells or graft tissues. Two major obstacles remain to be overcome: (1) Hyaline cartilage in vitro often loses differentiated traits. (2) Grafts frequently are not integrated satisfactorily into host cartilage and/or the tissue is remodelled in situ into functionally inferior fibrocartilage. Therefore, we have explored the possibility whether chondrocytes embedded into agarose gels provided better graft tissues in a repair model of full thickness defects in rabbit joint cartilage.

DESIGN

Experimental defects of knee joint cartilage was filled with articular chondrocytes cultured in agarose gels. Chondrocytes in vitro either remained unstimulated or were treated with several growth factors. Repair of the defects was assessed by histology and was scored between 0 (no healing) and 1 (perfect healing) as judged by the follwing parameters: intensity of proteoglycan staining, organization of the superficial zone, ossification at the border between repair cartilage and subchondral bone, tidemark formation in the repaired area, arrangement of chondrocytes, and integration of repair cartilage into host.

RESULTS

Treatment of chondrocyte cultures with bFGF had a stabilizing effect on the differentiated state of the cells in implanted grafts whereas bone morphogenetic proteins stimulated ingrowth of subchondral bone reducing repair cartilage thickness and preventing normal tide mark formation; TGF-beta did not significantly affect evaluation parameters in comparison with untreated controls.

CONCLUSION

Growth factor treatment resulted in an ambiguous quality of graft development. Only FGF had a clear beneficial effect to the graft tissues after 1 month. Further studies are required to define the precise conditions and sequence of growth factor treatment of in vitro engineered cartilage which benefits graft quality.

Construction and evaluation of a manikin for perioperative heat exchange

BACKGROUND

During surgery hypothermia can be avoided only if the heat exchange between the body surface and the environment can be controlled. To allow a systematic analysis of this heat exchange, we constructed and evaluated a copper manikin of the human body.

METHODS

The manikin consists of six tubes (head, trunk, two arms and two legs) painted matt-black to simulate the emissivity of the human skin. Hot-water mattresses are bonded to the inner surface of the copper tubes to set the surface temperature. Calibrated heat flux transducers were placed on the following points to determine the heat exchange coefficient for radiation and convection (hRC) of the manikin: Forehead, chest, abdomen, upper arm, forearm, dorsal hand, anterior thigh, anterior leg and foot. Room temperature was set to 22 degrees C. Surface temperature of the manikin was set between 22 degrees C and 38 degrees C. The hRC was determined by linear regression analysis as the slope of the temperature gradient between the manikin and the room versus the measured heat flux. Subsequently we studied five minimally clothed volunteers in a climate chamber. Initial chamber temperature was set to 29 degrees C and was lowered slowly to 12 degrees C. The hRC was determined as described above for each volunteer.

RESULTS

The hRC of the manikin was 11.0 W m(-2) degrees C(-1) and hRC of the volunteers was 10.8 W m(-2) degrees C(-1).

CONCLUSION

The excellent correlation of hRC between the volunteers and the manikin will allow the manikin to be used for standardised studies of perioperative heat exchange.

Radical transfer hydrosilylation/cyclization using silylated cyclohexadienes

[reaction: see text] A new method for mild metal-free hydrosilylation is described. Silylated cyclohexadienes are used as radical transfer hydrosilylating reagents for various double and triple bonds. A trialkylsilane is transferred from a cyclohexadiene moiety to an alkene. The hydrosilylation can be combined with a C-C bond formation as shown for the preparation of silylated cycloalkanes from the corresponding dienes.