Desplazamiento de los catéteres para bloqueo continuo del nervio supraescapular tras fisioterapia: estudio en cadáveres / Dislodgment of continuous suprascapular nerve block catheters after physiotherapy: A cadaver study

Antecedentes: Los bloqueos continuos de los nervios periféricos son de uso común para el manejo del dolor. Sin embargo, la incidencia de desplazamiento o migración del catéter es dudosa, pudiendo ser infraestimada y no denunciarse. Nuestro objetivo fue evaluar el posicionamiento del extremo del catéter supraescapular antes y después de la manipulación rutinaria y simulada mediante fisioterapia de hombro en un modelo cadavérico anatómico.MétodoSe colocaron 8 catéteres para bloqueo continuo y ecoguiado del nervio supraescapular en cadáveres frescos criopreservados. La tomografía computarizada (TC) confirmó la localización de la punta del catéter tras la inyección de 1ml de medio de contraste. Realizamos una serie de movimientos estandarizados de hombro durante una sesión simulada de fisioterapia de hombro en cadáveres. Tras ello, administramos 1ml de azul de metileno a través de los catéteres, y seguidamente realizamos disecciones para identificar con precisión la localización de las puntas del catéter y compararlas con su localización previa a la «fisioterapia».ResultadosLa imagen de la TC confirmó la localización en todos los casos de los extremos del catéter en la muesca supraescapular. Sin embargo, tras la fisioterapia, se encontró que 2 catéteres (25%) habían migrado y, en especial, uno fue localizado en el músculo supraespinoso y el otro en el músculo trapecio.ConclusiónNuestros hallazgos sugieren que el desplazamiento del catéter puede producirse en cerca del 25% de los casos tras la manipulación mediante fisioterapia simulada. Sin embargo, es necesaria más investigación para determinar la incidencia real de los desplazamientos del catéter en la práctica clínica. (AU)

Background: Continuous peripheral nerve blocks are commonly used for pain management. However, the incidence of catheter dislodgement or migration is unclear, and may be underestimated and underreported. Our objective was to assess suprascapular catheter tip positioning before and after routine simulated shoulder physiotherapy manipulation in an anatomical cadaver model.MethodEight ultrasound-guided continuous suprascapular nerve block catheters were placed in cryopreserved fresh cadavers. Computed tomography (CT) confirmed the location of the catheter tip after injection of 1ml of contrast medium. We performed a series of standardized shoulder movements during a simulated shoulder physiotherapy session in cadavers. Following this, we administered 1ml of methylene blue through the catheters, and then performed anatomical dissections to accurately identify the location of the catheter tips and compare them to their placement prior to the ‘physiotherapy’ResultCT imaging confirmed the location of the catheter tips at the suprascapular notch in all cases. However, following physiotherapy, 2 catheters (25%) were found to have migrated - specifically, 1 was located in the supraspinatus muscle, and the other was located in the trapezius muscle.ConclusionOur findings suggest that catheter dislodgement may occur in approximately 25% of cases following simulated physiotherapy manipulation. However, further research is needed to determine the read incidence of catheter dislodgement in clinical practice. (AU)

Dislodgment of continuous suprascapular nerve block catheters after physiotherapy: A cadaver study.

BACKGROUND: Continuous peripheral nerve blocks are commonly used for pain management. However, the incidence of catheter dislodgement or migration is unclear, and may be underestimated and underreported. Our objective was to assess suprascapular catheter tip positioning before and after routine simulated shoulder physiotherapy manipulation in an anatomical cadaver model. METHOD: Eight ultrasound-guided continuous suprascapular nerve block catheters were placed in cryopreserved fresh cadavers. Computed tomography (CT) confirmed the location of the catheter tip after injection of 1 ml of contrast medium. We performed a series of standardized shoulder movements during a simulated shoulder physiotherapy session in cadavers. Following this, we administered 1 ml of methylene blue through the catheters, and then performed anatomical dissections to accurately identify the location of the catheter tips and compare them to their placement prior to the 'physiotherapy'. RESULT: CT imaging confirmed the location of the catheter tips at the suprascapular notch in all cases. However, following physiotherapy, 2 catheters (25%) were found to have migrated - specifically, 1 was located in the supraspinatus muscle, and the other was located in the trapezius muscle. CONCLUSION: Our findings suggest that catheter dislodgement may occur in approximately 25% of cases following simulated physiotherapy manipulation. However, further research is needed to determine the read incidence of catheter dislodgement in clinical practice.

The utility of three-dimensional optical projection tomography in nerve injection injury imaging.

The examination of nerve microarchitecture has hitherto been limited solely to two-dimensional imaging techniques. The objective of this study was to evaluate the ability of optical projection tomography to discern the nerve microarchitecture and injection injury in three dimensions. Five piglets were studied, whose median and lingual nerves were unilaterally injected post mortem with preset volumes of local anaesthetic, excised and subsequently made transparent with benzyl alcohol benzyl benzoate. Images were captured in three dimensions. The same contralateral nerves were used as controls. Using optical projection tomography, we observed differences between the internal organisation of the median and the lingual nerves, which potentially explain the variations in their susceptibility to injury. This was demonstrated in three dimensions as a disruption to the fascicles in the lingual nerve, and their displacement in the median nerve. This new technology offers potential for studying nerve microarchitecture topography and its tolerance to injection injury.

Electron microscopy of human peripheral nerves of clinical relevance to the practice of nerve blocks. A structural and ultrastructural review based on original experimental and laboratory data

ObjetivoEl principal objetivo fue describir la ultraestructura normal de los nervios periféricos y aportar todos aquellos aspectos relevantes para la práctica de los bloqueos anestésicos de los nervios periféricos.MétodoA partir de muestras de nervio ciático obtenidas de pacientes y muestras de saco dural, manguitos durales y nervios del plexo braquial disecados de cadáveres frescos se estudió la estructura del nervio periférico, incluyendo los fascículos y su composición topográfica, como así también la morfología de las cubiertas que revisten el nervio. Axones mielinizados, no mielinizados, fascículos, epineuro, perineuro y endoneuro fueron estudiados por microscopía óptica incluyendo métodos de inmunohistoquímica, y por microscopía electrónica de barrido y de transmisión. La estructura del perineuro, de los capilares intrafasciculares y su implicación en la barrera hematonerviosa fueron revisados.ResultadosCada uno de los elementos anatómicos fue analizado de forma individual, y los resultados fueron correlacionados con su impacto en la práctica clínica de la anestesia regional.ConclusionesLa práctica cotidiana de técnicas de anestesia regional y la visualización ecográfica de las estructuras nerviosas nos llevan a crear interpretaciones de la anatomía de los nervios cuyas repercusiones pueden ser importantes en la futura aplicación de la técnica. A este respecto, los resultados obtenidos en estudios ultraestructurales e histológicos están dirigidos a dar respuestas a esas dudas con origen en el entorno de las técnicas de la anestesia regional (AU)

AimThe goal is to describe the ultrastructure of normal human peripheral nerves, and to highlight key aspects that are relevant to the practice of peripheral nerve block anaesthesia.MethodUsing samples of sciatic nerve obtained from patients, and dural sac, nerve root cuff and brachial plexus dissected from fresh human cadavers, an analysis of the structure of peripheral nerve axons and distribution of fascicles and topographic composition of the layers that cover the nerve is presented. Myelinated and unmyelinated axons, fascicles, epineurium, perineurium and endoneurium obtained from patients and fresh cadavers were studied by light microscopy using immunohistochemical techniques, and transmission and scanning electron microscopy. Structure of perineurium and intrafascicular capillaries, and its implications in blood–nerve barrier were revised.ResultsEach of the anatomical elements is analyzed individually with regard to its relevance to clinical practice to regional anaesthesia.ConclusionsRoutine practice of regional anaesthetic techniques and ultrasound identification of nerve structures has led to conceptions, which repercussions may be relevant in future applications of these techniques. In this regard, the ultrastructural and histological perspective accomplished through findings of this study aims at enlightening arising questions within the field of regional anaesthesia (AU)

Electron microscopy of human peripheral nerves of clinical relevance to the practice of nerve blocks. A structural and ultrastructural review based on original experimental and laboratory data.

AIM: The goal is to describe the ultrastructure of normal human peripheral nerves, and to highlight key aspects that are relevant to the practice of peripheral nerve block anaesthesia. METHOD: Using samples of sciatic nerve obtained from patients, and dural sac, nerve root cuff and brachial plexus dissected from fresh human cadavers, an analysis of the structure of peripheral nerve axons and distribution of fascicles and topographic composition of the layers that cover the nerve is presented. Myelinated and unmyelinated axons, fascicles, epineurium, perineurium and endoneurium obtained from patients and fresh cadavers were studied by light microscopy using immunohistochemical techniques, and transmission and scanning electron microscopy. Structure of perineurium and intrafascicular capillaries, and its implications in blood-nerve barrier were revised. RESULTS: Each of the anatomical elements is analyzed individually with regard to its relevance to clinical practice to regional anaesthesia. CONCLUSIONS: Routine practice of regional anaesthetic techniques and ultrasound identification of nerve structures has led to conceptions, which repercussions may be relevant in future applications of these techniques. In this regard, the ultrastructural and histological perspective accomplished through findings of this study aims at enlightening arising questions within the field of regional anaesthesia.

Cerebrospinal fluid volume and nerve root vulnerability during lumbar puncture or spinal anaesthesia at different vertebral levels.

Cerebrospinal fluid (CSF) and nerve root volumes within the lumbosacral dural sac were estimated at various vertebral levels, in an attempt to determine any possible relevance to the incidence of nerve root trauma during lumbar puncture or spinal anaesthesia. Magnetic resonance images from seven patients were studied. Volumes were calculated by semi-automatic threshold segmentation combined with manual editing of each slice. The mean dural sac volume from S1 to T12 was 42.8±5.8 ml and the mean CSF volume 34.3±5.1 ml with the mean root volume being 10.4±2.2 cm(3). The mean CSF volume per vertebral segment ranged from 4.3±0.7 ml at L5, to 5.8±2.5 ml at L1, with high inter-individual variability. The mean root volume ranged from 0.6±0.1 cm(3) at L5 to 2.4±0.5 cm(3) at T12. The conus medullaris was located at L1 in four of the five patients scanned at upper lumbar levels, and at the lower border of L2 in the other. Vulnerability to nerve root damage was expressed as the Vulnerability Index (%), being defined as the ratio of root volume to dural sac volume (CSF volume + root volume). The value ranged between 7 and 14% at L5, increasing rostrally to 30 to 43% at T12. Caution is obviously required in high punctures to avoid contact with the conus medullaris, but the cauda equina is also vulnerable to contact with more caudal punctures and had a Vulnerability Index of about 25% at L4, that increased rostrally.

An anatomical study of the intradural space.

We have previously postulated that it is possible to accidentally insert an epidural needle or catheter into the substance of the dura during attempted epidural block, creating an intradural space. It appears that injection of local anaesthetic into an intradural space leads to an initially inadequate neuraxial block but further doses may produce an extensive life-threatening block. In the laboratory, 54 samples of human thoraco-lumbar dura were obtained from six cadavers and prepared for scanning electron microscopy. Images from these dehydrated specimens were assessed for the presence of spaces within the dura, and attempts were made to insert an epidural catheter, under optical microscopy, into the substance of the dura in 32 cases. Electron microscopy revealed the concentric laminae that compose the dura and the presence of artefactual spaces between some of these. It was possible to insert an epidural catheter into the substance of the dura in eight specimens, creating intradural spaces which remained following catheter removal. If this represents the clinical situation, it may help to explain previously reported cases of atypical neuraxial block and their associated radiological findings.

Aportaciones morfológicas al origen de la cefalea postpuncióndural / No disponible

La hipotensión de líquido cefalorraquídeo y la tracción de estructuras encefálicas sensibles al dolor ha sido una de las hipótesis más reiterada para justificar la cefalea pospunción dural. En este trabajo se recogen resultados obtenidos de diferentes estudios realizados por nuestro grupo, que se completan con nuevas aportaciones. Se estudió con técnicas con microscopia óptica y electrónica la morfología de los componentes del saco dural espinal humano, las lesiones que se producían con agujas de punción lumbar de diferente diámetro y diseño de punta, y tras la disección de un encéfalo, se señalan detalles del trayecto aparente de los pares craneales que pueden ser traccionados cuando un paciente con hipotensión de líquido cefalorraquídeo está en posición erecta. Los resultados aportan detalles morfológicos que contribuyen al conocimiento de la fisiopatología de la cefalea pospunción dural (AU)

Hypotension caused by cerebrospinal fluid leakage and traction over certain brain structures has been blamed as the main reason for post-dural puncture headache (PDPH) In this paper we review different papers published by our group in which we show old and new data. We light and electron optic microscopy to study the morphology of the human dural sac plus the damage caused by different types of needles with different diameters. We dissected different brain specimens to show the path of the cranial nerves focusing on those that can be affected by traction during orthostatic position. These results show several morphology details that can contribute to the physiopathology of post-dural puncture headache (AU)

Three-dimensional magnetic resonance image of structures enclosed in the spinal canal relevant to anesthetists and estimation of the lumbosacral CSF volume.

Three-dimensional (3D) image-reconstruction of structures inside the spinal canal certainly produces relevant data of interest in regional anesthesia. Nowadays, all hospital MRI equipment is designed mainly for clinical diagnostic purposes. In order to overcome the limitations we have produced more accurate images of structures contained inside the spinal canal using different software, validating our quantitative results with those obtained with standard hospital MRI equipment. Neuroanatomical 3D reconstruction using Amira software, including detailed manual edition was compared with semi-automatic 3D segmentation for CSF volume calculations by commonly available software linked to the MR equipment (MR hospital). Axial sections from seven patients were grouped in two aligned blocks (T1 Fast Field Eco 3D and T2 Balance Fast Field Eco 3D-resolution 0,65 x 0,65 x 0,65 mm, 130 mm length, 400 sections per case). T2 weighted was used for CSF volume estimations. The selected program allowed us to reconstruct 3D images of human vertebrae, dural sac, epidural fat, CSF and nerve roots. The CSF volume, including the amount contained inside nerve roots, was calculated. Different segmentation thresholds were used, but the CSF volume estimations showed high correlation between both teams (Pearson coefficient = 0.98, p = 0.003 for lower blocks; Pearson 0.89, p = 0.042 for upper blocks). The mean estimated value of CSF volume in lower blocks (L3-S1) was 15.8 + 2.9 ml (Amira software) and 13.1 +/- 1.9 ml (software linked to the MR equipment) and in upper blocks (T11-L2) was 21 +/- 4.47 ml and 18.9 +/- 3.5 ml, respectively. A high variability was detected among cases, without correlation with either weight, height or body mass index. Aspects concerning the partial volume effect are also discussed. Quick semi-automatic hospital 3D reconstructions give results close to detailed neuroanatomical 3D reconstruction and could be used in the future for individual quantification of lumbosacral CSF volumes and other structures for anesthetic purposes.

Proyecto Redesra / No disponible

No disponible

[Structure of the arachnoid layer of the human spinal meninges: a barrier that regulates dural sac permeability]. / Morfología de la lámina aracnoidea espinal humana. Barrera que limita la permeabilidad del saco dural.

OBJECTIVES: Drugs injected into the epidural space are known to penetrate the subarachnoid space by simple diffusion through the dural sac. We aimed to study the cellular ultrastructure of the arachnoid membrane and the type of intercellular junctions responsible for creating the barrier that regulates the passage of drugs through the dural sac in humans. MATERIAL AND METHODS: Fourteen tissue samples of arachnoid membrane were taken from 2 patients during procedures that required opening the lumbar dural sac. The samples were treated with glutaraldehyde, osmium tetroxide, ferrocyanide and acetone, and then embedded in resin. Ultrathin sections were stained with lead citrate for examination by transmission electron microscopy. RESULTS: The arachnoid membrane was 35 to 40 microm thick. The outer surface contained neurothelial cells (dural border cells) along the subdural compartment, while the internal portion was made up of a plane 5 to 8 microm thick with 4 to 5 arachnoid cells overlapping to form a barrier layer. The intercellular spaces on this plane were 0.02 to 0.03 microm wide; the arachnoid cells were bridged by specialized junctions (desmosomes and other tight junctions). CONCLUSIONS: Structural features of the arachnoid cells provide a barrier within the human dural sac. They occupy only the internal portion of the arachnoid membrane. Specialized intercellular junctions explain the selective permeability of this membrane.

Morfología de la lámina aracnoidea espinal humana. Barrera que limita la permeabilidad del saco dural / Structure of the arachnoid layer of the human spinal meninges: a barrier that regulates dural sac permeability

OBJETIVOS: Se ha demostrado que las moléculas inyectadas en el espacio epidural pasan desde éste al espacio subaracnoideo por difusión simple a través de la pared del saco dural. Nuestro objetivo fue estudiar la ultraestructura de células de la lámina aracnoidea y tipo de uniones especializadas responsables del efecto barrera que gobierna el tránsito de moléculas a través del saco dural humano. MATERIAL Y MÉTODO: Se estudiaron catorce muestras de la lámina aracnoidea obtenidas de dos pacientes durante intervenciones con apertura del saco dural lumbar. Las muestras se trataron con glutaraldehido, tetróxido de osmio, ferrocianuro, acetona, e incluyeron en resina. Los cortes ultrafinos se contrastaron con citrato de plomo, para poder ser observados con un microscopio electrónico de transmisión. RESULTADOS: La lámina aracnoidea posee un espesor de 35-40 μm. En su porción externa se hallan células neuroteliales del compartimento subdural, mientras que su porción interna está formada por un plano celular de 5-8 μm de espesor, constituido por la superposición de 4-5 células aracnoideas que forman la capa barrera. El espacio intercelular de este plano fue de 0,02-0,03 μm. Entre las células aracnoideas se encontraron uniones especializadas de membrana de tipo desmosomas y uniones estrechas. CONCLUSIONES: Las células aracnoideas poseen características estructurales que aseguran la función barrera del saco dural humano y no ocupan todo el espesor de la lámina aracnoidea, sólo su porción interna. La presencia de uniones especializadas de membrana entre sus células justifica la permeabilidad selectiva de esta lámina(AU)

OBJETIVES: Drugs injected into the epidural space are known to penetrate the subarachnoid space by simple diffusion through the dural sac. We aimed to study the cellular ultrastructure of the arachnoid membrane and the type of intercellular junctions responsible for creating the barrier that regulates the passage of drugs through the dural sac in humans. MATERIAL AND METHODS: Fourteen tissue samples of arachnoid membrane were taken from 2 patients during procedures that required opening the lumbar dural sac. The samples were treated with glutaraldehyde, osmium tetroxide, ferrocyanide and acetone, and then embedded in resin. Ultrathin sections were stained with lead citrate for examination by transmission electron microscopy. RESULTS: The arachnoid membrane was 35 to 40 μm thick. The outer surface contained neurothelial cells (dural border cells) along the subdural compartment, while the internal portion was made up of a plane 5 to 8 μm thick with 4 to 5 arachnoid cells overlapping to form a barrier layer. The intercellular spaces on this plane were 0.02 to 0.03 μm wide; the arachnoid cells were bridged by specialized junctions (desmosomes and other tight junctions). CONCLUSIONS: Structural features of the arachnoid cells provide a barrier within the human dural sac. They occupy only the internal portion of the arachnoid membrane. Specialized intercellular junctions explain the selective permeability of this membrane(AU)

[Reversal of acenocoumarol anticoagulation with activated factor VII in massive hemorrhage following rupture of a splenic artery pseudoaneurysm]. / Reversión del efecto del acenocumarol con factor VII activado en la hemorragia masiva tras rotura de aneurisma esplénico.

A 66-year-old man with a metallic valve and under treatment with acenocoumarol developed hypovolemic shock after rupture of a splenic artery pseudoaneurysm. We managed to reverse anticoagulation within 60 minutes by administering 20 mg of vitamin K and 4.8 mg of activated recombinant factor VII. No thromboembolic adverse events were observed. We discuss the pharmacologic effects of coumarin derivatives and their antagonists, as well as the use of activated factor VII in the reversal of anticoagulation by these drugs.

Clinical implications of epidural fat in the spinal canal. A scanning electron microscopic study.

BACKGROUND AND OBJECTIVES: This review of articles summarizes recent developments in relation to fat located in the epidural space and also in dural sleeves of spinal nerve roots in order to improve our understanding of the clinical effects of the epidural blockade. METHOD: Medline search was carried cross-matching of the following words: "epidural fat", "epidural space", "adipose tissue" and "fat cells" from 1966 to 2008 in which articles referring to different pathologies that alter the epidural fat were also reviewed. Techniques used by different authors included the use of samples from dissections, cryomicrotome sections, as well as light and electron microscopy. RESULTS: Fat in the epidural space has a metameric distribution along the spinal canal that can be altered in some pathological conditions. Epidural fat is not evenly distributed. At cervical level fat is absent while in the lumbar region, fat in the anterior and posterior aspects of the epidural space forms two unconnected structures. Fat cells are found also in the thickness of dural sleeves enveloping spinal nerve roots but not in the region of the dural sac. Epidural lipomatosis is characterized by an increase in epidural fat content. When a patient has a combination of kyphosis and scoliosis of the spine, the epidural fat distributes asymmetrically. Spinal stenosis is frequently accompanied by a reduction in the amount of epidural fat around the stenotic area. CONCLUSIONS: The epidural space contains abundant epidural fat that distributes along the spinal canal in a predictable pattern. Fat cells are also abundant in the dura that forms the sleeves around spinal nerve roots but they are not embedded within the laminas that form the dura mater of the dural sac. Drugs stored in fat, inside dural sleeves, could have a greater impact on nerve roots than drugs stored in epidural fat, given that the concentration of fat is proportionally higher inside nerve root sleeves than in the epidural space, and that the distance between nerves and fat is shorter. Similarly, changes in fat content and distribution caused by different pathologies may alter the absorption and distribution of drugs injected in the epidural space.

[Paresthesia and spinal anesthesia for cesarean section: comparison of patient positioning]. / Parestesias y anestesia subaracnoidea en cesáreas: estudio comparativo según la posición de la paciente.

OBJECTIVE: To determine the incidence of paresthesia during lumbar puncture performed with the patient in different positions. MATERIAL AND METHODS: A single-blind prospective study of patients scheduled for elective cesarean section, randomized to 3 groups. In group 1 patients were seated in the direction of the long axis of the table, with heels resting on the table. In group 2 they were seated perpendicular to the long axis of the table, with legs hanging from the table. In group 3 they were in left lateral decubitus position. Lumbar punctures were performed with a 27-gauge Whitacre needle. RESULTS: One hundred sixty-eight patients (56 per group) were enrolled. Paresthesia occurred most often in group 3 (P = .009). We observed no differences in blood pressure after patients moved from decubitus position to the assigned position. Nor did we observe between-group differences in blood pressure according to position taken during puncture. CONCLUSION: Puncture undertaken with the patient seated, heels on the table and knees slightly bent, is associated with a lower incidence of paresthesia than puncture performed with the patient seated, legs hanging from the table. Placing the patient's heels on the table requires hip flexion and leads to anterior displacement of nerve roots in the dural sac. Such displacement would increase the nerve-free zone on the posterior side of the sac, thereby decreasing the likelihood of paresthesia during lumbar puncture. A left lateral decubitus position would increase the likelihood of paresthesia, possibly because the anesthetist may inadvertently not follow the medial line when inserting the needle.