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Elisabet U.m. Blix - One of the best experts on this subject based on the ideXlab platform.
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direct connections between the spinal Epidural Space and the venous circulation in humans
Regional Anesthesia and Pain Medicine, 2011Co-Authors: Charles W. Buffington, Larry Nichols, Pauline L Moran, Elisabet U.m. BlixAbstract:Background and Objectives: Our previous studies in pigs indicate that direct connections exist between the spinal Epidural Space and the venous circulation. We wondered if similar connections occur in humans and have extended our investigations to human cadavers awaiting autopsy. Methods: We studied 10 recently dead human bodies. We inserted 2 Tuohy needles into the Epidural Space of the lower thoracic spine at adjacent interSpaces. We infused saline with a constant-flow pump into 1 needle and measured the resulting pressure through the other. Epidural pressure increased to a steady plateau during fluid infusion, and this value was recorded at several flow rates. The pressure decay after flow stopped was also recorded. Then we infused radiopaque contrast, removed the needles, and obtained a computed tomographic scan of the spine from the foramen magnum to the coccyx. Results: Pressure in the Epidural Space increased to a plateau during saline infusion. Higher flow rates produced higher plateau pressures. Plots of plateau pressure versus infusion rate were linear in all bodies. The slope of the flow-pressure plot gave a steady-state resistance (543 ± 638 mm Hg·s/mL). The time constant of the pressure decay curve allowed calculation of initial capacitance (0.090 ± 0.062 mL/mm Hg). Contrast could be identified in veins around the spinal column in all bodies. Contrast was found most commonly in the deep veins of the neck (7 bodies) and in veins originating in the area of the brachial plexus (7 bodies). Contrast was found less commonly and in smaller amounts in veins draining into the azygous system (5 bodies) and the lumbar veins (5 bodies). No contrast was found in veins in the sacral area. Conclusions: A direct connection between the spinal Epidural Space and the venous circulation has been demonstrated in human cadavers. The connection is most commonly found in the cervical and upper thoracic spine.
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A macromolecular tracer indicates that the spinal Epidural Space connects directly to the venous circulation in pigs.
Regional Anesthesia and Pain Medicine, 2010Co-Authors: Charles W. Buffington, Elisabet U.m. BlixAbstract:Background and Objectives: Air injected into the Epidural Space of the spine reaches the heart within 15 secs, suggesting easy access to the bloodstream. We wished to quantify the washout of a macromolecular tracer (albumin labeled with Evans blue) from the thoracic Epidural Space. Methods: Eleven juvenile pigs were anesthetized with isoflurane and positioned on their sides. We injected a bolus of the tracer into the thoracic Epidural Space followed by serial saline infusions (total, 50-70 mL). We measured plasma concentrations of the tracer during washout. Finally, we injected Microfil (a liquid rubber compound that hardens on standing) into the Epidural Space and later inspected with a dissecting microscope the nerve roots and veins draining the spine. Results: More than half (60% ± 12%; range, 31%-79%) of the tracer injected in the Epidural Space was detected in the bloodstream. Microfil was detected in the veins draining the cervical or high thoracic spine, but never in veins draining the lumbar spine or sacrum. Conclusions: Because the macromolecular tracer cannot enter the bloodstream by absorption, these results indicate that pathways capable of handling bulk flow connect the spinal Epidural Space to the venous circulation. These pathways are located in the cervical and high thoracic spine of the pig.
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Hydrodynamics of the spinal Epidural Space in pigs: effects of death and exsanguinations.
Regional Anesthesia and Pain Medicine, 2009Co-Authors: Elisabet U.m. Blix, Charles W. BuffingtonAbstract:Background and Objectives: We have investigated how the vascular components of the spine determine the resistance and capacitance of the spinal Epidural Space and determined the magnitude of the longitudinal pressure gradient in the Space during fluid infusion. Methods: Pigs were studied during isoflurane anesthesia. Tuohy needles were inserted into midthoracic spine at adjacent interSpaces, one to measure pressure in the Epidural Space and one for fluid infusion. A third Tuohy needle was inserted in the lumbar Epidural Space. Fluid was infused at a constant flow (0.9-3.1 mL/min) until Epidural Space pressure reached a steady plateau, then the pump was shut off, and pressure returned to baseline over 5 to 6 mins. Resistance was calculated as the ratio of plateau pressure and flow. Initial (first 20-30 secs) and late (1-5 mins) capacitance was calculated. Measurements were made with the animal alive, 15 mins after its life was terminated by an intravenous injection of KCl, and then after exsanguination. Results: During fluid infusion, the pressure gradient between the lumbar and thoracic Epidural Space was small, on the order of 1 to 2 mm Hg. Death reduced resistance but not capacitance, whereas exsanguination reduced late capacitance but not resistance. Neither maneuver affected initial capacitance. Conclusions: There is a small longitudinal pressure gradient within the Epidural Space during fluid infusion. Hence, the major source of resistance occurs where fluid leaves the Epidural Space. Death reduced resistance, perhaps by depressurizing spinal arteries in the intervertebral foramina, but did not affect capacitance. Blood in Epidural veins is a major determinant of late Epidural capacitance.
Charles W. Buffington - One of the best experts on this subject based on the ideXlab platform.
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direct connections between the spinal Epidural Space and the venous circulation in humans
Regional Anesthesia and Pain Medicine, 2011Co-Authors: Charles W. Buffington, Larry Nichols, Pauline L Moran, Elisabet U.m. BlixAbstract:Background and Objectives: Our previous studies in pigs indicate that direct connections exist between the spinal Epidural Space and the venous circulation. We wondered if similar connections occur in humans and have extended our investigations to human cadavers awaiting autopsy. Methods: We studied 10 recently dead human bodies. We inserted 2 Tuohy needles into the Epidural Space of the lower thoracic spine at adjacent interSpaces. We infused saline with a constant-flow pump into 1 needle and measured the resulting pressure through the other. Epidural pressure increased to a steady plateau during fluid infusion, and this value was recorded at several flow rates. The pressure decay after flow stopped was also recorded. Then we infused radiopaque contrast, removed the needles, and obtained a computed tomographic scan of the spine from the foramen magnum to the coccyx. Results: Pressure in the Epidural Space increased to a plateau during saline infusion. Higher flow rates produced higher plateau pressures. Plots of plateau pressure versus infusion rate were linear in all bodies. The slope of the flow-pressure plot gave a steady-state resistance (543 ± 638 mm Hg·s/mL). The time constant of the pressure decay curve allowed calculation of initial capacitance (0.090 ± 0.062 mL/mm Hg). Contrast could be identified in veins around the spinal column in all bodies. Contrast was found most commonly in the deep veins of the neck (7 bodies) and in veins originating in the area of the brachial plexus (7 bodies). Contrast was found less commonly and in smaller amounts in veins draining into the azygous system (5 bodies) and the lumbar veins (5 bodies). No contrast was found in veins in the sacral area. Conclusions: A direct connection between the spinal Epidural Space and the venous circulation has been demonstrated in human cadavers. The connection is most commonly found in the cervical and upper thoracic spine.
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A macromolecular tracer indicates that the spinal Epidural Space connects directly to the venous circulation in pigs.
Regional Anesthesia and Pain Medicine, 2010Co-Authors: Charles W. Buffington, Elisabet U.m. BlixAbstract:Background and Objectives: Air injected into the Epidural Space of the spine reaches the heart within 15 secs, suggesting easy access to the bloodstream. We wished to quantify the washout of a macromolecular tracer (albumin labeled with Evans blue) from the thoracic Epidural Space. Methods: Eleven juvenile pigs were anesthetized with isoflurane and positioned on their sides. We injected a bolus of the tracer into the thoracic Epidural Space followed by serial saline infusions (total, 50-70 mL). We measured plasma concentrations of the tracer during washout. Finally, we injected Microfil (a liquid rubber compound that hardens on standing) into the Epidural Space and later inspected with a dissecting microscope the nerve roots and veins draining the spine. Results: More than half (60% ± 12%; range, 31%-79%) of the tracer injected in the Epidural Space was detected in the bloodstream. Microfil was detected in the veins draining the cervical or high thoracic spine, but never in veins draining the lumbar spine or sacrum. Conclusions: Because the macromolecular tracer cannot enter the bloodstream by absorption, these results indicate that pathways capable of handling bulk flow connect the spinal Epidural Space to the venous circulation. These pathways are located in the cervical and high thoracic spine of the pig.
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Hydrodynamics of the spinal Epidural Space in pigs: effects of death and exsanguinations.
Regional Anesthesia and Pain Medicine, 2009Co-Authors: Elisabet U.m. Blix, Charles W. BuffingtonAbstract:Background and Objectives: We have investigated how the vascular components of the spine determine the resistance and capacitance of the spinal Epidural Space and determined the magnitude of the longitudinal pressure gradient in the Space during fluid infusion. Methods: Pigs were studied during isoflurane anesthesia. Tuohy needles were inserted into midthoracic spine at adjacent interSpaces, one to measure pressure in the Epidural Space and one for fluid infusion. A third Tuohy needle was inserted in the lumbar Epidural Space. Fluid was infused at a constant flow (0.9-3.1 mL/min) until Epidural Space pressure reached a steady plateau, then the pump was shut off, and pressure returned to baseline over 5 to 6 mins. Resistance was calculated as the ratio of plateau pressure and flow. Initial (first 20-30 secs) and late (1-5 mins) capacitance was calculated. Measurements were made with the animal alive, 15 mins after its life was terminated by an intravenous injection of KCl, and then after exsanguination. Results: During fluid infusion, the pressure gradient between the lumbar and thoracic Epidural Space was small, on the order of 1 to 2 mm Hg. Death reduced resistance but not capacitance, whereas exsanguination reduced late capacitance but not resistance. Neither maneuver affected initial capacitance. Conclusions: There is a small longitudinal pressure gradient within the Epidural Space during fluid infusion. Hence, the major source of resistance occurs where fluid leaves the Epidural Space. Death reduced resistance, perhaps by depressurizing spinal arteries in the intervertebral foramina, but did not affect capacitance. Blood in Epidural veins is a major determinant of late Epidural capacitance.
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Hydrodynamics of the spinal Epidural Space in pigs determined by constant-flow methods.
Regional Anesthesia and Pain Medicine, 2006Co-Authors: Charles W. Buffington, Elisabet U. M. NystromAbstract:Background and Objectives: Impressive quantities of fluid can be infused into the Epidural Space of the spine without causing dramatic or sustained increases in pressure. The Epidural Space is considered “leaky,” but questions remain about how fluid leaves the Epidural Space. We used constant-flow infusions of saline to gain insight into the hydrodynamics involved. Methods: We infused saline at a constant rate into the lumbar Epidural Space of 6 anesthetized pigs while measuring pressure at the adjacent interSpace. Three or 4 infusions were performed at different flow rates in each animal. Results: Epidural Space pressure in the absence of flow was consistently 2 to 3 mm Hg above right atrial pressure. During each infusion, pressure increased slowly to a steady plateau value between 15 and 70 mm Hg. When flow was stopped, pressure declined exponentially to the starting pressure. The presence of a plateau indicates that fluid leaving the Epidural Space ends up in a structure with high capacitance. Plateau pressures were linearly related to flow rate in each animal, indicating constant resistance to outflow. The flow-pressure relation showed neither a critical opening pressure nor moderating pressures with increased flow. Conclusions: Fluid leaves the porcine spinal Epidural Space through channels that are open at baseline rather than being recruited as Epidural pressure increases. This behavior is inconsistent with the view that the Epidural Space behaves like a Starling resistor.
M. Tsuji - One of the best experts on this subject based on the ideXlab platform.
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identification of the Epidural Space in children the application of a micro drip infusion set
Anaesthesia, 1991Co-Authors: M. Yamashita, M. TsujiAbstract:Summary We have used an intravenous micro-drip infusion set to identify the Epidural Space in 350 infants and children. The infusion set was prepared with saline and connected to the hub of an Epidural needle. Free dripping of saline was regarded as a sign that the needle tip had entered the Epidural Space. The overall success rate of this method was 97.7%.
Gao F Smith - One of the best experts on this subject based on the ideXlab platform.
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prediction by computerised tomography of distance from skin to Epidural Space during thoracic Epidural insertion
Anaesthesia, 2002Co-Authors: J Carnie, J Boden, Gao F SmithAbstract:Summary In this single group observational study on 29 patients, we describe a technique that predicts the depth of the Epidural Space, calculated from the routine pre-operative chest computerised tomography (CT) scan using Pythagorean triangle trigonometry. We also compared the CT-derived depth of the Epidural Space with the actual depth of needle insertion. The CT-derived and the actual depths of the Epidural Space were highly correlated (r = 0.88, R2 = 0.78, p < 0.0001). The mean (95% CI) difference between CT-derived and actual depths was 0.26 (0.03–0.49) cm. Thus, the CT-derived depth tends to be greater than the actual depth by between 0.03 and 0.49 cm. There were no associations between either the CT-derived or the actual depth of the Epidural Space and age, weight, height or body mass index.
Kiranpreet Kaur - One of the best experts on this subject based on the ideXlab platform.
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Identification of Epidural Space using loss of resistance syringe, infusion drip, and balloon technique: A comparative study.
Saudi journal of anaesthesia, 2014Co-Authors: Suresh Singhal, Manju Bala, Kiranpreet KaurAbstract:There are various techniques to identify Epidural Space but superiority of one technique over other has not been adequately studied. We conducted a study to Compare and evaluate the three techniques for Epidural Space localization that is, loss of resistance (LOR) syringe technique, balloon technique and drip infusion technique. Seventy-five patients of either sex, belonging to American Society of Anesthesiologists physical status Class 1 or 2, between 20 and 50 years of age, scheduled to undergo lower abdominal and lower limb surgeries were randomly allocated to one of the three groups (n = 25 each) depending upon Epidural Space localization. In Group I, Epidural Space localization was done with LOR syringe technique. In Group II Balloon technique and in Group III drip infusion technique was used. Distance of the Epidural Space from skin, number of attempts, time taken for Epidural Space localization and quality of the block were the parameter recorded during the study. First attempt success rate for Epidural Space localization was highest in Group III (100%). The mean time taken for Epidural Space localization was least in Group III, and when compared with other groups it was found to be statistically significant with P = 0.016. Number of attempt for Space localization and success rate of the block was better in the majority of patients of Group III, but the difference was found to be statistically nonsignificant. Complication rate was almost negligible in all three techniques. We conclude that the time taken to localize the Epidural Space was least in drip infusion technique. As for number of attempts, quality of the block and complications is concerned, all the three techniques are comparable.
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Identification of Epidural Space using loss of resistance syringe, infusion drip, and balloon technique: A comparative study.
Saudi Journal of Anaesthesia, 2014Co-Authors: Suresh Kumar Singhal, Manju Bala, Kiranpreet KaurAbstract:Background and Objective: There are various techniques to identify Epidural Space but superiority of one technique over other has not been adequately studied. We conducted a study to Compare and evaluate the three techniques for Epidural Space localization that is, loss of resistance (LOR) syringe technique, balloon technique and drip infusion technique. Materials and Methods: Seventy-five patients of either sex, belonging to American Society of Anesthesiologists physical status Class 1 or 2, between 20 and 50 years of age, scheduled to undergo lower abdominal and lower limb surgeries were randomly allocated to one of the three groups (n = 25 each) depending upon Epidural Space localization. In Group I, Epidural Space localization was done with LOR syringe technique. In Group II Balloon technique and in Group III drip infusion technique was used. Distance of the Epidural Space from skin, number of attempts, time taken for Epidural Space localization and quality of the block were the parameter recorded during the study. Results: First attempt success rate for Epidural Space localization was highest in Group III (100%). The mean time taken for Epidural Space localization was least in Group III, and when compared with other groups it was found to be statistically significant with P = 0.016. Number of attempt for Space localization and success rate of the block was better in the majority of patients of Group III, but the difference was found to be statistically nonsignificant. Complication rate was almost negligible in all three techniques. Conclusion: We conclude that the time taken to localize the Epidural Space was least in drip infusion technique. As for number of attempts, quality of the block and complications is concerned, all the three techniques are comparable.