| It is commonly accepted that the epidural space is a continuous compartment containing fat, lymphatics, arteries, loose areola connective tissue, spinal nerve roots and an extensive plexus of veins. However, recent studies have suggested that meningo-vertebral ligaments are present between the lumbosacral spinal canal wall and the surrounding dura. Meningo-vertebral ligaments have been described between the dura mater and the lumbosacral spinal canal by Benchao Shi. Meningo-vertebral ligaments scattered in the epidural space with adipose tissue on their surface and separated the epidural space into compartments of different sizes and shapes. Meningo-vertebral ligaments result in discontinuity of the epidural space and uneven distribution of injection, thereby contributing to unilateral or partial anesthesia after injection of local anesthetic. Meningo-vertebral ligaments exist in the posterior epidural space and connect to the venous plexus, which may contribute to placement failure of epidural catheter.According to reports, the overall failure rate of epidural block for labor analgesia was 1.7% and sometimes multiple replacements can not improve the effect of the analgesia. In general, a continuous and even distribution of local anesthetic within the epidural space bathing the appropriate nerve roots leads to successful labor analgesia. At times, replacement of the epidural catheter does not improve the distribution of epidural local anesthetic. An important reason may be the occurrence of compartments formed by epidural meningo-vertebral ligaments and adipose tissue.In the book of Gray’s Anatomy, the spinal cord was connected to a number of fiber bundles that were called Meningo-vertebral ligaments. The name of the dural dorsal ligament was more chaotic, foreign parts of the literature would be referred to the Hofmann ligament with the epidural space, the dorsal ligament of the epidural space was seldom studied. In the study of Geers, the epidural space was divided into the front and the back cavity with the nerve root, and the function of the membrane was different.In the latest study, the epidural space was divided into two parts, the anterior chamber of the Hofmann ligament and the dorsal ligament of the posterior chamber. Studies have shown that fetal epidural cavity was hoof tissue around the package, with the growth of fetus, the connective tissue is absorbed gradually and become irregular in shape. But nobody can clearly distinguish between the posterior and lateral, due to more posterior was absorbed than the anterior. Which resulted in the very little distribution of membrane vertebral ligament in the dorsal spinal cord of adult. Through the operation in epidural cavity L5 level, Solarogl found the dura mater and yellow ligament between connection ligament. Solarogl called it as ATA ligament. It was known as dural ligamentum flavum ligament from the study of Zhang Yimo.It was reported in the 40th edition of Gray’s anatomy, the spinal dura mater was connected to the posterior longitudinal ligament through the fiber bundle. Through these called meningo-vertebral ligament fibers, the dural canal was connected to the inner surface of the connection. Distribution of the ligament tissue was different in different parts of the spinal canal. Usually in the anterior spinal canal and lateral development it become more perfect. The funicular ligaments of the myelin sheath of nerve root are fixed to protect the nerve roots.Early in 1963, Luyendijk observed the lack of contrast agent in the central section of the dorsal spinal dural in epidural angiography. And the reasons attributed to that the midline region of the dorsal spinal dural were folded structures. He made the midline region of the dorsal spinal dural folds as an hypothesis, that these folds were connected between the inner wall of the spinal canal and spinal dura mater with special structure, and which plays an important function for fixed dura mater and spinal cord.In 1986, Blomberg had another new finding. Advanced endoscopic technique was used to observe the lumbar spinal epidural space structure. Through the endoscope, the lumbar spinal epidural space of the lumbar vertebral canal was observed. There were many different forms of filamentous or cord tissues, these tissues could even form a membranous appearance. The tissues were closely connected with the ligamentum flavum, and its distribution were very regular, which is mainly distributed in the back and side of the hard ridge. Through the connecting mechanism, the hard ridge film was firmly fixed on the back cavity of the hard ridge film, and which leaded to the obvious narrowing of the center line of the hard ridge film. The finding was contrary to the traditional view that the epidural space in the spinal canal was the widest point in the midline. Connecting structure of the midline area can partially explain the epidural anesthesia puncture accidental puncture of stiff backbone film phenomenon. Sometimes puncture needle did not puncture the penetration of the dura mater directly. Because the dural were pulled by the midline connective tissue traction, the dural were teared by accident.According to reports, sometimes the epidural catheter were inserted into the vein by accident. The incidence rate of accidental injury of veins by lumbar epidural catheter was 5%-7%. It was found that the vertebral ligament was directly attached to the small artery and vein wall of the vertebral canal. The vertebral ligament were not in the form of syncline with the vascular wall. Previous studies have reported that small blood vessels were found in the tissue of the fetal specimens. During the process of the epidural anesthesia, if puncture needle accidentally injury the ligament that is connected to the blood vessels, the possibility of epidural hematoma increased. And most of the blood vessels connected to the membrane vertebral ligament were vertebral venous plexus. Because the spinal canal vein without valve, bleeding after injury is more difficult to be controlled, which will increase the risk of epidural hematoma and infection. The venous plexus of the spinal canal was located in the loose network of adipose tissue, and the blood flow was bidirectional.There were so many fat in the epidural of parturient that the epidural space became small. With the abdominal pressure increased, the pressure of the internal vertebral venous increased at the same time. Internal vertebral venous was very easy to be punctured by the needle or the epidural catheter during incubating the epidural catheter, which increased the risk of anesthesia. If not timely being discovered, local anesthetics were injected into intravascular may cause seizures, develop cardiovascular toxicity or even lead to cyclic failure or other life-threatening side effects. In clinical anesthesia, coagulation function in patients with low or thrombocytopenia should be paid special attention to. If the patient will be anesthetized in vertebral canal, Single spinal anesthesia technique should be considered. It’s necessary to avoid the damage of large epidural puncture needle to the venous plexus connected with the membrane of vertebral ligament, which may cause epidural hematoma.According to reports, the epidural catheter placement technology is one of the most difficult technology, although the overall success rate of nearly 90%, but the first time the success rate of only 60%. In the epidural space, there is a ligament in the vertebral ligament. When the catheter is placed in the middle of the ascending process, the tip of the epidural catheter may curl, which may be one of the reasons for the occurrence of this condition. Meningo-vertebral ligaments located within the epidural space may contribute to epidural catheter placement failure. The location of these structures can be unpredictable with 38% of meningo-vertebral ligaments located in the middle of the subdural cavity,32% in the left side subdural cavity, and another 30% next to right side of subdural cavity.At present, the research about the connection between the dura mater and spinal canal wall of vertebral ligament membrane structure is rare. To the lumbosacral portion of dural back connection structure of research, there is no consensus. It’s necessary to be further discussed. There is very important significance for spinal anesthesia in the presence of the lumbar and sacral ligament, which influences the success rate of puncture and intubation, and the effect of anesthesia. Which may increase the incidence of complications with anesthesia related. The effect of the lumbar and sacral ligament on spinal anesthesia can be described in the following aspects:Meningo-vertebral ligaments scattered in the epidural space with adipose tissue on their surface and separated the epidural space into compartments of different sizes and shapes, which resulted in discontinuity of the epidural space and uneven distribution of injection, thereby contributed to unilateral or partial anesthesia after injection of local anesthetic. The failure rate for neuraxial labor analgesia was reported as high as 12%. At times, replacement of the epidural catheter does not improve the distribution of epidural local anaesthetic. An important reason may be the occurrence of compartments formed by epidural meningo-vertebral ligaments and adipose tissue. The presence of epidural compartment structures suggest that when epidural anesthesia was not successful, anesthetists should try other anesthetic techniques such as a combined spinal epidural or general anesthesia rather than repeated catheterization.In the epidural space, there is a membrane vertebral ligament which are more concentrated in the center of the middle of the epidural space,and which leads to the narrowing of the epidural space. When the epidural catheter is placed in the middle of the ascending process, the tip of the epidural catheter may curl, which may lead to the difficulty of the catheter insertion. According to reports, the epidural catheter placement technology is one of the most difficult technology, although the overall success rate of nearly 90%, but the success rate of the first placement is only 60%.Sometimes the vertebral ligament was connected with the vascular wall. The lamina and the yellow ligament of the membrane are directly connected to the small artery and vein wall of the spinal canal. Previous studies have reported that small blood vessels were found in the tissue of the fetal specimens. If the puncture needle accidentally injury the ligament that is connected to the blood vessels, the risk of epidural hemorrhage will increase.The epidural catheter coiled into a circle, or knotted with low incidence, but the event may lead to serious consequences. If you do not pay attention to it, the violence during extubation may cause difficulty in decannulation or catheter fracture. During the process of the extubation, epidural catheter tip is connected between the dura and the yellow ligament barrier, may be one of the reasons for the occurrence of highly crimped epidural catheter.To further explore the anatomical causes of the failure of the epidural tube, reveal the lumbosacral epidural behind film vertebral ligament and putamen outside anesthesia catheter and reduce epidural tube failure rate, we simulated epidural catheter in cadavers. Then we observed the epidural vertebral ligament and correlation structure through endoscopic. The observed results were documented and photographed. Through our research, we have to increase the understanding of the structure of the epidural space, so that more anesthesia doctors know about the existence of the membrane vertebral ligament and the effect of the membrane vertebral ligament on spinal anesthesia.The most comprehensive review of obstetric neuraxial failures is a retrospective analysis of 19,259 deliveries that demonstrated an overall failure rate of 12%. Of these neuraxial techniques,46% became functional with simple manipulations. Overall,7.1% of patients receiving neuraxial analgesia had their catheters replaced and 1.9% had multiple replacements. In the end,98.8% of patients reported adequate labor analgesia. This rate compares favorably with that observed in an earlier study of 4240 obstetric regional blocks, which found a 13.1% replacement rate but 98% overall satisfaction. In this study, through the understanding of the anatomy of the epidural space in the spinal canal, the reasons for the failure of epidural anesthesia for labor analgesia were analyzed, and different methods were adopted. Our research work is mainly divided into the following three aspects.Chapter 1 The anatomical observation of the lumbosacral epidural space without opening the vertebral canal based on endoscopicObjective:Through advanced epidural cavity endoscope technology, the lumbar sacral epidural cavity was observed and took pictures without changing the original structure around in order to record and reveal the epidural epidural anesthesia anatomy structure and provide a theoretical basis for clinical anesthesia.Methods:30 normal adult cadaver specimens (aged 30-70 years old, average 57 years old) were provided by the Department of anatomy of Southern Medical University, excluding the lumbar sacral lesions, deformity and lumbar sacral spinal surgery. We opened the anterior wall of the thorax and abdomen through conventional methods and stripped the paraspinal muscle anatomy from T12-L1 intervertebral disc at the transected spinal with diameter less than 5mm endoscopic probe in order to explore the posterior spinal canal epidural cavity without changing the original anatomical structure around. The epidural space was observed and the observation results were taken pictures. After the observation by Endoscope mirror, we sawed the bilateral pedicle from L1-S1 segment with a chainsaw without damaging the connection structure between the inner wall of the spinal canal and spinal dura. Then the epidural cavity was opened and photographed.Results:A large number of different forms of vertebral ligaments connected posterior wall of spinal canal and dura mater were observed in all the samples which were mainly distributed in the back and side of the epidural space.30 cases could be observed in the midline of the ligament, the ligament was connected with the yellow ligament and dura mater. The role is fixing dura mater to the yellow ligament, at the same time the space of the epidural space was narrowed. Some of the films were very tough and robust, and a small number of the dural and the yellow ligaments were involved. The vertebral ligament was especially well developed in the vertebral column, and a few of them even formed a complete membrane appearance. Part of the membranous ligaments were very long, and some evened cross the two spinal segments. Part of the ligament strengthened greatly, it was difficult to be tore apart by a great force. Some ligaments developed very stout, even if forced to push, it were also very difficult to destroy the membrane vertebral ligament connected. In the epidural space, the inner wall of the spinal canal and the dura mater were observed to fill the venous vessels, some of which were directly connected with the membrane vertebral ligament.Conclusion:There were a large number of vertebral ligaments in the posterior wall of the spinal canal and spinal dura mater. These ligaments were fixed to the dura mater, which leaded to the narrow space of the center line of the epidural space. A small number of membranous vertebral ligaments show a membranous appearance, separating the epidural space into several parts. The distribution and morphological characteristics of the lumbar sacral ligament, may be the anatomical factors of the epidural block, unilateral block, the catheter discount, the difficulties of the catheter and the complications such as epidural hemorrhage.Chapter 2 The applied anatomic study of lumbar epidural catheter placementObjective:To provide anatomical basis for the lumbar epidural catheter placements, and improve the success rate of anesthesia and reduce complications.Methods:A total of 50 adult embalmed cadavers (aged 43-72, mean 55 years) were used to simulate the lumbar epidural catheter placement. Bone canal was cut by chainsaw from both sides of the pedicle, and the connection structure between dura and the front of the vertebral body was separated. Then the relationship of the position between lumbosacral epidural structure with epidural catheter were carefully observed, and the epidural anatomical structure were observed and photographed.Results:After opening the epidural space, the location of the catheter was observed and recorded. The catheter tip was attached to the meningo-vertebral ligaments and curled into a circle in three cases, with one catheter twisted into a "9" shape. In two other cases, the catheter tip was in close proximity to the nerve roots near the intervertebral foramen, and perforation of the vertebral venous plexus was observed in five cases. Meningo-vertebral ligaments and their attachment sites In the posterior epidural space, meningo-vertebral ligaments were observed in each of the 50 adult lumbar vertebral segments, with topographic variations between subjects and between levels. The shape of meningo-vertebral ligaments varied from a thin elongated strip to a thick tough sheet. Other meningo-vertebral ligaments formed a sagittal septum, and were oriented in a web. Dural ligaments are mainly distributed in the middle or near the middle of the epidural space. The dorsal meningo-vertebral ligaments in the lumbosacral region connect the dura to the ligamentum flavum or the lamina. The dorsal meningo-vertebral ligaments were associated more often with the ligamenta flava than the lamina. Some ligaments connected directly to the spinal vascular wall. Malposition of the epidural catheter was more often observed when sheet-type and median-sagittal meningo-vertebral ligaments were present._ In 50 cadavers, catheter in the epidural space curled into a circle in 3 cases, catheter inserted into intervertebral foramen in 2 cases, and epidural vein were injured in 5 cases. The dorsal meningo-vertebral ligaments in the lumbosacral region connect the dura to the ligamenta flava or the lamina, it have relevant with the failure of the catheter placement.Conclusion:Meningo-vertebral ligaments exist in the posterior epidural space and connect to the venous plexus, which may contribute to epidural catheter failure, uneven distribution of anesthesia and epidural hemorrhage. Our study provides anesthesiologist with a better understanding of the anatomy and may mitigate complications of lumbar epidural catheter placement.Chapter 3 The causes and methods of treatment failure of continuous epidural labor analgesiaObjective:To investigate the causes and methods of treatment failure of continuous epidural labor analgesia.Methods:958 nulliparous patients were taken epidural block in the L2-3 interspaces, An epidural catheter is threaded 4 cm into the epidural space, then continuous intravenous injection plus patient-controlled method of labor analgesia were performed. If the VAS score of pain is greater than 5, the analgesia determined to failure。Such methods were taken to rescue the analgesia as withdrawing the epidural catheter 1 to 2cm, or replacement of the catheter, or changing to combined spinal epidural anesthesia. The VAS score and 24h postpartum satisfaction were recorded.Results:114 cases of patients with anesthesia failure, the epidural catheter were threaded into blood vessels in 47 cases, the epidural catheter were blocked in 13 cases, 9 cases of epidural catheter bent, unilateral block or Partial block occurred in 31 cases, the epidural catheter migrated in 37 cases, the catheters left epidural cavity in 5 cases, and dural puncture occurred in 2 cases. The rate of epidural analgesia failure was 15%, of which 87 cases were rescued by simple adjustment,48 cases were rescued by replacement of the epidural catheter.921 cases of postpartum 24h maternal satisfaction score reached 8 points or more, the total satisfaction rate was 96.1%.Conclusion:Though the failure rate of epidural analgesia is as high as 15%, most of the failures could be rescued by withdrawing or replacing the catheter or changing with combined spinal epidural anesthesia. |
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