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Intestine Microcirculation
Published in John H. Barker, Gary L. Anderson, Michael D. Menger, Clinically Applied Microcirculation Research, 2019
The study of intestinal microvascular function requires knowledge of the blood flow regulation, distribution of microvascular pressures to judge which vessels have the greatest effects on resistance, an index of tissue or blood oxygen tensions, and obviously, visual measurements of the inner diameter and numbers of microvessels. Relative changes in blood flow to the area of interest can be measured with Doppler ultrasound blood velocity probes on the intestinal arteries,5 calculated from measurements of flow velocity and vessel diameter in microvessels using the red cell cross-correlated velocity technique,2 and estimated from red cell flux (number of cells per unit time) using observed fluorescently labeled red blood cells in capillaries to vessels with inner diameters not greater than 25 µ.51 In large rats and larger species, actual flow can be measured using small flow probes, such as the electromagnetic or ultrasonic flow probe methods, placed on the intestinal artery. For flow probe systems, ligation of the inflow vessels along the bowel margin and the gut wall itself at both ends of the tissue field perfused by the selected artery is essential if data on flow per mass of tissue is needed.
Vascular
Published in Michael Gaunt, Tjun Tang, Stewart Walsh, General Surgery Outpatient Decisions, 2018
The blood supply of the intestinal tract is particularly rich in collaterals. Therefore, mesenteric ischaemia only occurs if two out of the three main intestinal arteries are occluded or severely stenosed. Isolated mesenteric artery disease is unlikely to result in mesenteric ischaemia unless previous abdominal surgery has been performed and the collateral pathways have been disrupted. The most important artery for intestinal blood supply is the SMA. Therefore, isolated stenosis of the coeliac or IMA rarely causes intestinal ischaemia.
Arteriography of the vascular beds
Published in Peter A. Schneider, Endovascular Skills: Guidewire and Catheter Skills for Endovascular Surgery, 2019
CO2 can be administered into the vascular system, is absorbed, and is excreted from the body by exhalation. When renal function is severely diminished, CO2 is the only contrast available that is not nephrotoxic. It has some very specific use issues that are discussed here. CO2 may not be used in the brain or heart and many operators are only comfortable using it in the infrarenal aorta and more distally. In the brain and the heart, where there is a moment-to-moment dependence on perfusion, the passage of gas through the arteriolar bed will temporarily diminish end organ flow and cause ischemic events. In the intestinal arteries, the risk is that an air lock will form that becomes stationary and prevents forward flow. In the lower extremities, CO2 is very well tolerated. Special settings at a high frame rate, usually six frames per second, are required to image CO2. This particular contrast forms a gas cloud in the vasculature. It rises against gravity and therefore the patient is placed in the Trendelenburg position when it is administered to decrease the likelihood that it could pass into the cerebral arteries. CO2 must be medical grade, the tank must be appropriately maintained, and the CO2 reservoir used during the endovascular procedure must not be contaminated with air. CO2 is used to fill a sterile, airtight bag; the bag has a one-way valve so that air cannot be entrained. The tubing is purged several times before use and is connected to the angiographic catheter. A small amount of CO2 is drawn into the syringe (about 5 cc) and slowly administered into the catheter. This clears the catheter of fluid to avoid a sudden jet of gas-propelled saline that could cause injury to the artery during injection. An aortoiliac arteriogram can be acquired with 20 cc of CO2. When the CO2 passes through normal arteries, the flow pattern of the gas is unpredictable. Therefore, in postprocessing, some type of longitudinal image stacking is usually required to form a reasonable arteriographic representation of the system being interrogated. When the CO2 encounters significant disease, the gas begins to fragment into bubbles and this makes it very challenging to properly evaluate severely diseased segments. CO2 is usually used in combination with dilute iodinated contrast in order to make a complete study. Between CO2 administrations, wait about 2 minutes for the contrast to pass. Each time the angiographic catheter is connected to the CO2 reservoir, the lines must be carefully purged of air and the catheter emptied of fluid prior to a CO2 angiographic run.
Gastroscopy assisted laser Doppler flowmetry and visible light spectroscopy in patients with chronic mesenteric ischemia
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 2019
Simen T. Berge, Nathkai Safi, Asle W. Medhus, Kim Ånonsen, Jon O. Sundhagen, Jonny Hisdal, Syed S. H Kazmi
It has previously been commented that intestinal ischemia may be patchy and the measurements of microcirculation with LDF and VLS may miss the anatomical locations with reduced microcirculation [9]. However, in our study, we found that a significant stenosis or occlusions in the intestinal arteries seem to result in an on average global reduction in microcirculation of the stomach and intestine in the patients with CMI. This finding is despite the development of an extensive collateral circulation in these patients [1]. Taken into consideration that these measurements are performed in a resting/fasting state, one may presume that during episodes of increased metabolic demand, for example during/after a meal, the deficit in the microcirculation in the patients with CMI may be more pronounced. A study on VLS after luminal feeding has been performed and did, however, not display these changes [19]. This study has limitations due to the mere approximation of the natural digestion. Furthermore, to reduce the risk of aspiration, the authors performed the measurements after the expected peak in postprandial hyperemia and may possibly missed the expected changes in the microcirculation.
Nonthrombotic proliferative vasculopathy associated with antiphospholipid antibodies: A case report and literature review
Published in Modern Rheumatology, 2019
Jeong Seok Lee, Hyojin Kim, Eun Bong Lee, Yeong Wook Song, Jin Kyun Park
The majority of the reported cases had a poor outcome with death or permanent organ loss (amputation of the affected extremity in cases 1 and 2). This is contrasted by the relative good outcome in our patient. One possible explanation is that, his NTPV-aPL was confined to few pulmonary arteries. Since pulmonary circulation has a large functional reserve, occlusion of few arteries would not result in a life-threatening infarct. By contrast, involvement of end artery such as peripheral or intestinal arteries without collateral circulation would lead to critical ischemia with permanent organ loss or death. A delay in diagnosis could be a reason for the poor outcome of NTPV patients because this disease entity might be under-recognized. Since the pathophysiologic process is poorly understood, an effective treatment has not been defined to date. In classical APS, aPL bind to and activate endothelial cells, leading to the activation of a coagulation cascade with subsequent thrombus formation. Consequently, anticoagulation therapy has proven effective [1].
The mesentery: an ADME perspective on a ‘new’ organ
Published in Drug Metabolism Reviews, 2018
Aneesh A. Argikar, Upendra A. Argikar
From a vascularization point of view, the abdominal aorta (aorta in the abdominal cavity) divides in to superior and inferior mesenteric arteries. The superior and inferior mesenteric arteries supply oxygenated blood to the intestines. These arteries pass through the mesentery and branch several times until they reach the intestines. The superior mesenteric artery branches into colic arteries, intestinal arteries, and ileocolic artery. The inferior mesenteric artery branches into colic artery, sigmoidal arteries, and rectal artery (Marieb and Hoehn 2012). A detailed representation of the mesenteric vascular flow is shown in Figure 2.