Overinflation of the cuff and pressure on the neck reduce the preventive effect of supraglottic airways on pulmonary aspiration: an experimental study in human cadavers.

BACKGROUND: The oesophageal leak pressure is defined as the pressure which breaks the seal between the cuff of a supraglottic airway and the peri-cuff mucosa, allowing penetration of fluid into the pharynx and the oral cavity. As a consequence, a decrease in this variable increases the risk of reflux and can lead to pulmonary aspiration. The aim of this study was to analyse the effects of cuff overinflation and pressure on the neck on the oesophageal leak pressure of seven supraglottic airways. METHODS: Three laryngeal masks, two laryngeal tubes, and two oesophageal-tracheal tubes were tested in an experimental setting. In five human cadavers, we simulated a sudden increase in oesophageal pressure. To measure baseline values (control), we used an intracuff pressure as recommended by the manufacturer. The first intervention included overinflation of the cuff by applying twice the amount of pressure recommended. A second intervention was defined as external pressure on the neck. RESULTS: The oesophageal leak pressure was decreased for laryngeal masks (control, 28 cm H2O; overinflation, 9 cm H2O; pressure on the neck, 8 cm H2O; P<0.01) and for laryngeal tubes (control, 68 cm H2O; overinflation, 37 cm H2O; pressure on the neck, 39 cm H2O; P<0.01) and was unaffected for oesophageal-tracheal tubes (control, 126 cm H2O; overinflation/pressure on the neck, 130 cm H2O; n.s.). CONCLUSION: Cuff overinflation and pressure on the neck can enhance the risk of gastro-oesophageal reflux when using supraglottic airways. Therefore, both manoeuvres should be avoided in clinical practice.

Oesophageal seal of the novel supralaryngeal airway device I-Gel in comparison with the laryngeal mask airways Classic and ProSeal using a cadaver model.

BACKGROUND: Supraglottic airway devices are increasingly used in anaesthesia and emergency medicine. This study was designed to investigate the oesophageal seal of the novel supralaryngeal airway device, I-Gel (I-Gel), in comparison with two of the laryngeal mask airways, Classic (cLMA) and ProSeal (pLMA), in a model of elevated oesophageal pressure. METHODS: The three supralaryngeal airway devices were inserted into eight unfixed cadaver models with exposed oesophagi that had been connected to a water column producing both a slow and a fast oesophageal pressure increase. The pressure applied until the loss of oesophageal seal during a slow and fast pressure increase was measured. RESULTS: During the slow increase of pressure, the pLMA withstood an oesophageal pressure up to a median of 58 cm H(2)O, while the cLMA was able to block the oesophagus up to a median of 37 cm H(2)O, and I-Gel already lost its seal at 13 cm H(2)O. One minute after maximum pressure had been applied, the pLMA withstood an oesophageal pressure of 59 cm H(2)O, the cLMA of 46 cm H(2)O, and I-Gel airway of 21 cm H(2)O. A fast release of oesophageal fluid was accomplished through the oesophageal lumen of both the pLMA and I-Gel. CONCLUSIONS: Both the pLMA and cLMA provided a better seal of the oesophagus than the novel I-Gel airway. The pLMA and I-Gel drain off gastrointestinal fluid fast through the oesophageal lumen. Thus, tracheal aspiration may be prevented with their use. Further study is necessary.

Imaging of hamate bone fractures in conventional X-rays and high-resolution computed tomography. An in vitro study.

RATIONALE AND OBJECTIVES: To examine the ability to image fractures of the body and hook of the hamate bone in conventional X-rays and high-resolution computed tomography (HR-CT). MATERIALS AND METHODS: In an in vitro experiment using 18 cadaver hands, the hamate bone was fractured at different places. Before and after fracture, conventional X-rays were taken in different planes (anteroposterior, lateral, oblique, and carpal tunnel), and HR-CT was performed with 2-mm layer thickness in the axial, sagittal, and coronal plane. RESULTS: Taking into account all the conventional X-ray projections applied, the in vivo experiment revealed a sensitivity of 72.2%, a specificity of 88.8%, and an accuracy of 80.5%. For the HR-CT, the sensitivity was 100%, the specificity was 94.4%, and the accuracy was 97.2%. CONCLUSIONS: Fractures of the body and hook of the hamate cannot always be detected with certainty in the conventional X-ray image, even if different projectional planes are used. The HR-CT is the imaging procedure of choice for further clarification, and an axial or sagittal plane should be selected.

Electron microscopic investigations on the growing tip of nerve fibres in the developing distal forelimb of the mouse.

The distal course of the sensory nerve fibres on the palmar side of the hand of 12-day-old mouse embryos was followed by serial ultrathin cross-sections of conventionally fixed tissue. Small nerves fibres are to be found in the space between the layer of the cutaneous blood vessels and the epidermis. A special arrangement of the tissue which is traversed by the nerve fibres is not visible. In most cases the nerve fibres are in intimate contact with fibroblasts. More distally the nerve fibres consist only of one axon encircled by a Schwann cell. The sheath of the Schwann cell decreases gradually, and finally disappears completely. The distal tips of the naked axons are a few microns ahead. In some cases they are considerably enlarged and contain only a fine fuzzy material without special cell organelles. Other axons may end in a more finger-like fashion, and contain also in the naked parts many cell organelles. Also the naked axons contact fibroblasts over long ranges. Collagen was not found aligned to the distal nerve fibres.

Electron microscopic investigations on the differentiation of Purkinje cells in the ontogenetic development of the chicken heart.

The ultrastructural development of subendocardial Purkinje cells of chicken left ventricle was investigated. In 9-day-old chick embryos the cell diameter and the organization of the cell organelles allow a distinction between Purkinje cells and ordinary myocardial cells In 14-day-old chick embryos, Purkinje cells show large accumulations of myosin filaments with interspersed ribosomes in addition to normomeric myofibrils. In these accumulations actin filaments seem to be absent. The deficiency of actin filaments is supposedly the reason for the random distribution of the myosin filaments. Purkinje cells of early chick embryos show areas with densely packed glycogen granules. In older embryos the glycogen concentration declines and only separate glycogen granules are visible. At hatching time the first subsarcolemmal leptomeric fibrils were observed in Purkinje cells. Leptomeric complexes arising in a close spatial relationship to the accumulations of myosin filaments and ribosomes can be seen in 2--4 week-old chickens. With the increasing age of the chickens, the size of these accumulations declines. Adult hens exhibit smaller accumulations, mainly in the neighborhood of leptomeric complexes. Purkinje cells show a distinct ontogenetic development. They are not simple embryonic remnants of ordinary myocardial cells.

Activity of acetylcholinesterase and unspecific cholinesterase during differentiation of somites in mouse embryos.

During the development of somites in mouse embryos, widespread activity of unspecific cholinesterase (BuChE) was demonstrated after prolonged incubation. Independent of their position, all somite cells and their derivatives (dermatome, myotome and sclerotome) exhibited enzyme activity in the perinuclear space and in the endoplasmic reticulum. The plasmalemma did not show any enzyme activity. Differentiation of the sclerotome into vertebrae was accompanied by a reduction of BuChE. However, a low enzyme reaction was still present in the first typical differentiated chondroblasts. Notochordal cells were detectable by their high BuChE content. This was also found in cells already showed severe degeneration. In addition to BuChE, acetylcholinesterase (AChE) was first visible of day 9 of embryonic development in newly formed myotubes of the myotomes. Some hypotheses on the functional significance of of embryonic BuChE are discussed in the light of these results.

[The imaging of hamate fractures in the conventional X-ray and CT: experimental results and clinical experiences]. / Darstellung von Os hamatum-Frakturen im konventionellen Röntgenbild und CT: experimentelle Ergebnisse sowie klinische Erfahrungen.

PURPOSE: Examination of the ability to image fractures of the body and hook of the hamate bone in conventional X-rays and HR-CT. MATERIAL AND METHODS: In an in vitro experiment on 18 cadaver hands, the hamate bone was fractured at different localisations. Before and after fracture, conventional x-rays were taken in different projectional planes: a.-p., lateral, oblique and carpal tunnel view, as well as an HR-CT with 2 mm layer thickness in the axial, sagittal and coronal plane. In addition, 15 clinically verified hamate bone fractures (two body and 13 hook of hamate fractures) were reviewed retrospectively to assess the value of the imaging procedures that led to diagnosis. RESULTS: Taking into account all conventional x-ray projections applied, the in vitro experiment yielded a sensitivity of 72.2%, a specificity of 88.8% and an accuracy of 80.5%. For CT, the sensitivity was 100%, the specificity 94.4% and the accuracy 97.2%. In retrospective clinical evaluation, 60% of the existing fractures were identified in the conventional x-ray images. The remaining fractures were detected by additional procedures like scintigraphy, conventional tomography and CT. CONCLUSION: For the diagnosis of fractures of the body and hook of the hamate HR-CT is the imaging procedure of choice, in which case an axial or sagittal plane should be chosen.

[Electrical nerve stimulation for plexus and nerve blocks]. / Elektrische Nervenstimulation für Plexus- und Nervenblockaden.

Despite the increasing use of ultrasound, electrical nerve stimulation is commonly used as the standard for both plexus and peripheral nerve blocks. Several recent randomized trials have contributed to a better understanding of physiological and clinical correlations. Traditionally used currents and impulse widths are better defined in relation to the distance between needle tip and nerves. Commercially available devices enable transcutaneous nerve stimulation and provide new opportunities for the detection of puncture sites and for training. The electrically ideal position of the needle usually is defined by motor responses which can not be interpreted without profound anatomical knowledge. For instance, interscalene blocks can be successful even after motor responses of deltoid or pectoral muscles. Infraclavicular blocks should be aimed at stimulation of the posterior fascicle (extension). In contrast to multiple single nerve blocks, axillary single-shot blocks more commonly result in incomplete anaesthesia. Blockade of the femoral nerve can be performed without any nerve stimulation if the fascia iliaca block is used. Independently of the various approaches to the sciatic nerve, inversion and plantar flexion are the best options for single-shot blocks. Further clinical trials are needed to define the advantages of stimulating catheters in continuous nerve blocks.

[The hip head-conserving management of traumatic medial cervical hip fractures with big-fragment screws: a biomechanical examination]. / Die kopferhaltende operative Versorgung der traumatischen medialen Schenkelhalsfraktur mit Grossfragmentschrauben -- eine biomechanische Prüfung.

AIM: With the growing number of elderly people in the population and the increasing incidence of proximal hip fractures the question of how to manage the medial hip head fracture is of increasing importance. Especially in Hungary and the Scandinavian countries surgeons prefer hip head-conserving therapy although the redislocation of this fracture and necrosis of the hip head opposes this point of view. METHOD: Encouraged by two theoretical and mathematical calculations, we tested two different possibilities to screw hip head fractures. RESULTS: Our results show that the hip head-conserving therapy with two cranial screws and a three-point-supported screw at Adam's arc has essential biomechanical advantages compared with the situation after conventional osteosynthesis. CONCLUSION: This result encourages us to prefer the minimally invasive head-conserving therapy of medial hip head fractures, especially for treatment of Pauwell's I and II injuries.

Expression of cholinesterase in the Schwann cells of peripheral nerves during development.

In peripheral nerves of mouse embryos Schwann cells exhibit a high activity of unspecific cholinesterase. At first (day 12 of embryonic development) this enzyme occurs in the nuclear envelope and in the granular endoplasmic reticulum. Thus, it is possible to differentiate between Schwann cells and fibroblasts which lack cholinesterase. Later on (day 16) the cholinesterase has shifted to the cell membrane of the Schwann cells. However, only that part of the plasmalemma which encircles single axons and the mesaxons exhibits an irregular deposition of the reaction end product. In newborns the first loops of the just formed myelin sheath are still stained. With maturation of the myelin sheath the enzyme activity disappears. The functional role of cholinesterase is unclear. Possible roles are discussed. The expression of cholinesterase in Schwann cells depends on the integrity of the axons. After a few hours, the cultivation of amputated limbs results in a reduction of the enzyme activity. After 1 day in culture cholinesterase disappears totally.

Innervation of the dermatomes in the neck of the mouse.

The dorsal rami of the cervical and thoracic spinal nerves were investigated using both the in situ cholinesterase staining technique and cholinesterase staining on serial sections of plastic-embedded embryos. In most cases only the dorsal rami of the 2nd to 5th cervical spinal nerve possess cutaneous branches. The area innervated by the cutaneous branch of the dorsal ramus of the 5th spinal nerve borders on an area innervated by the cutaneous branch of the dorsal ramus of the 1st thoracic spinal nerve. The dorsal rami of the cervical spinal nerves 6-8 show no cutaneous branches. Therefore the gap in the series of the dorsal cutaneous branches is due only to the middle part of the nerves of the brachial plexus, which range from the 5th cervical nerve to the 1st thoracic nerve.

On the spatial relationship between fibroblasts and myogenic cells during early development of skeletal muscles.

The spatial relation between fibroblasts and myoblasts as well as myotubes in the extensor muscles of the forearm of mouse embryos was investigated with routine electron microscopic techniques. From day 13 of embryonic development onwards, fibroblasts and myogenic cells may be distinguished by their ultrastructure from each other. Above all the fibroblasts are characterized by their long cell processes. Specialized cell contacts between them are visible. Fibroblasts often encircle some myogenic cells indicating the division of the muscles into smaller bundles. Over long distances, the intercellular gap between both cell types is narrow and measures about 15 nm. Sometimes specialized intercellular junctions can be seen. They resemble simple desmosomes and seem to be mechanical cell junctions. After the establishment of the basal lamina around the myogenic cells such specialized cell contacts are no longer visible. It seems possible that the fibroblasts act as mechanical counterpart for the organization of the myogenic cells.

Specialized cell contacts in the developing nerves of mouse embryos.

In mouse embryos, special focal contacts between axons and Schwann cells, axons and fibroblasts as well as Schwann cells and fibroblasts are visible during the outgrowth of nerves. These rather seldom contacts exhibit a uniform structure. Axons and Schwann cells from small finger-like protrusions projecting into coated pits of Schwann cells and fibroblasts. The narrow intercellular space in the contact zone is crossed by fine filaments.

Development of the vascular supply in rat skeletal muscles.

The vascular development in the extensor muscles of rat forelegs from 12-day-old embryos up to 9-day-old animals was investigated with a light microscope using semithin plastic sections. On late day 12, blood vessels are distributed over the whole cross sectional area of the foreleg. On early day 13, a rearrangement of the blood vessels is visible. Now an avascular centre is enclosed by a vascularized tissue mantle, in which the muscle anlage starts developing. Few capillaries are visible within the muscle anlage. After differentiation of the muscle anlage into individual muscles the epimysium is passed by a netlike capillary plexus enwrapping the first avascular muscles. With the establishment of the perimysium on day 16 of embryonic development some capillaries are also visible within the individual muscles. The diameter of the capillaries is by far larger than the diameter of the myotubes. In older embryos the perimysium shows an increasing number of such large capillaries, whereas in the epimysium the capillaries are less frequent. In the perimysium a few additional capillaries with a small diameter of about 5 micron occur. On day 3 postpartum, small capillaries are also visible within the muscle fibre bundles. In the perimysium many large capillaries are still obvious. The vascular supply on day 9 postpartum, resembles that in adult muscles. The vascular supply of the muscles progresses from their periphery to more and more smaller compartments within the muscles, in close correlation to the establishment of the muscular connective tissue.

Development of muscles in the dorsal foreleg of rat embryos. A light microscopic study with the in situ cholinesterase staining technique.

The development of muscles from the dorsal side of the forelegs from 13- to 21-day-old rat embryos was investigated under a light microscope. The muscle blastemata and individual muscles were stained in situ with the cholinesterase technique. The first muscle blastemata are visible on the early day 13. It appears that mainly myotubes are stained. The antebrachial and brachial extensor muscles form separated anlagen which connect on the late day 13 in the proximal region of the extensor carpi ulnaris muscle. The individualization of the muscles in a muscle blastema takes place on days 13 and 14. On day 15 all extensor muscles are visible. However, at this time the inserting points of some of these muscles are not yet visible after staining with alcian blue. On the early day 16 the motor end-plates are conspicuous. Due to the content of unspecific cholinesterase in rat embryos the tendons are also stained on day 16. Muscles and tendons remain stainable until birth. In addition to the muscles also the nerves, especially the epifascial nerves, stain very well with the acetylcholinesterase reaction.

The in situ staining of muscles during development with the cholinesterase technique.

Developing muscles from forelegs of 11- to 18-day-old mouse embryos were stained in situ for cholinesterase with the copper-ferrocyanide technique. The skin of the legs represents a diffusion barrier for the incubation medium. Therefore, in older embryos the skin was mechanically removed after trypsin digestion. In younger embryos the skin remained on the forelegs after trypsin treatment. With this technique it is possible to follow the establishment of the muscular pattern in the legs.

Pattern formation of the sensible nerves in the hand of mouse embryos with special reference to the posterior-anterior developmental gradient.

The development of the sensible innervation of the hand was investigated. For this reason normal forelimbs and limb bud cultures from 12- to 14-day-old mouse embryos were stained in toto using the cholinesterase technique. The dorsal side of the hand is mainly innervated by sensible branches of the radial and the musculocutaneous nerve, which penetrate the fascia in the region of the elbow. From here they grow in a distal direction forming the dorsal digital nerves. On the ventral side the median nerve grows in a subfascial compartment towards the palmar side of the hand. While passing the wrist the median nerve exhibits a frayed appearance. A net of branching and anastomosing small nerve fibre bundles is visible. This implies that on the palmar side of the metacarpal region of the hand-plate no specific highways for the growing nerve fibres exist. From late day 12 to early day 14 of embryonic development this diffuse nerve net is organized. In a posterior-anterior (ulnoradial) developmental gradient the common palmar digital nerves were formed, and these nerves divide at their tip into the proper digital nerves. However, the proper digital nerves again follow special pathways during their outgrowth.

Outgrowing nerves in the foreleg of a mouse embryo as viewed by three-dimensional reconstruction from electron micrographs.

Electron micrographs from serial cross-sections of 12-day-old mouse forelegs were digitized and three-dimensional reconstruction of the data was carried out on an Apple Macintosh Quadra 700 computer using a program especially designed for this purpose. Two nerve endings of the palmar net of the median nerve were visualized together with their accompanying Schwann cells and the surrounding processes of fibroblasts. Naked axons invade straightly into the embryonic connective tissue and serve as contact guidance for the Schwann cells to follow. Fibroblasts with long processes extend around the axons with a parallel orientation. Contacts between axons and fibroblasts are occasionally observed. It is unclear whether the parallel orientation of nerve endings and fibroblast extensions have any biological significance.

An abnormal pattern of blood vessels in the retroperitoneal space with a duplicated inferior vena cava in an adult: a case report.

During dissection a duplicated inferior vena cava (IVC) was found in an 82 year-old male. The IVCs were connected with each other by two anastomoses. The course of the other retroperitoneal veins also exhibited some alterations: Just below the diaphragm the azygos and the right ascending lumbar v. ran into the right IVC separately; the hemiazygos and the left ascending lumbar vv. joined before entering the left IVC. The testicular vv. ended normally on the right side in the right IVC, on the left side in the left renal vein. The embryologic basis of the pattern of these vessels is discussed and a short overview of the literature given. In the present case there were also some alterations in the course of the renal and testicular aa.

[Medullated ganglion cells in the guinea pig labyrinth]. / Die markhatigen Ganglienzellen im Labyrinth des Meerschweinchens.

The pericellular structures of the three ganglia situated in the petrous bone were investigated by light and electron microscopy in the guinea pig. All perikarya of the ganglion spirale cochleae and the ganglion vestibulare are surrounded by a myelin sheath which consists of 10-15 layers. Relative to their size, the cells of the ganglion spiral are characterized by a thicker myelin sheath than those of the ganglion vestibulare. The peripheral and central processes of the ganglion cells show a stronger myelination than the corresponding perikarya. The decrease in myelin from the nerve fibre to the perikarya does not proceed continuously but occurs only after the last interanular segment. At the peripheral processes, the myelin sheath ends a few micrometres before reaching the sensory epithelial layer. The perikarya of the ganglion geniculi nervi facialis are unmyelinated.