Hypotension är vanligt förekommande vid anestesi och i den postoperativa fasen. Om blodtrycket sjunker till för låga nivåer eller pågår under för lång tid kan vitala organ som hjärta och njurar ta allvarlig skada. De flesta fall av hypotension behandlas idag retroaktivt. Med möjlighet att kunna upptäcka hypotension innan det uppstår skulle behandling kunna ske i ett förebyggande syfte och på så sätt minska tiden i hypotension för patienten. Med hjälp av maskininlärning går det att analysera blodtryckskurvor och kunna hitta vilka attribut i dem som kan förutse hypotension. Detta projekt har gått ut på att definiera och beräkna attribut för att i framtida arbeten kunna låta en maskininlärningsalgoritm analysera dem. Utöver detta har arbetet med signalbehandling skett för att kunna upptäcka bristande kvalitet på den analyserade signalen och kunna förbättra den vid behov. Målet att definiera och beräkna attribut har lyckats. Målet att kunna avgöra kvaliteten på signalen har lyckats delvis.

No description available.

京都大学 / 新制・論文博士 / 博士(医学) / 乙第13584号 / 論医博第2304号 / 新制||医||1070(附属図書館) / (主査)教授 江木 盛時, 教授 湊谷 謙司, 教授 江藤 浩之 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

No description available.

Introduction Postoperative medical complications are often preceded by a period with hypotension. Postoperative hypotension is poorly described in the literature. Data are needed to determine the incidence and risk factors for the development of postoperative clinically important hypotension after noncardiac surgery. Methods The incidence of postoperative clinically important hypotension was examined in a cohort of 40,004 patients enrolled in the VISION (Vascular Events in Noncardiac Surgery Patients Cohort Evaluation) Study. Eligible patients were ≥45 years of age, underwent an in-patient noncardiac surgery procedure, and required a general or regional anesthetic. I undertook a multivariable logistic regression model to determine the predictors for postoperative clinically important hypotension. Model validation was performed using calibration and discrimination. Results Of the 40,004 patients included, 20,442 patients were selected for the derivation cohort, and 19,562 patients were selected for the validation cohort. The incidence of clinically important hypotension in the entire cohort was 12.4% (4,959 patients) [95% confidence interval 12.1-12.8]. Using 41 variables related to baseline characteristics, preoperative hemodynamics, laboratory characteristics, and type of surgery, I developed a model to predict the risk of clinically important postoperative hypotension (bias-corrected C-statistics: 0.73) The prediction model was slightly improved by adding intraoperative variables (bias-corrected C-statistics: 0.75). A simplified prediction model using the following variables: high-risk surgery, preoperative systolic blood pressure <130 mm Hg, preoperative heart rate >100 beats per minute, and open surgery, also predicted clinically important hypotension, albeit with less accuracy (bias-corrected C-statistics 0.68). Conclusion Our clinical prediction model can accurately predict patients’ risk of postoperative clinically important hypotension after noncardiac surgery. This model can help identify which patients should have enhanced monitoring after surgery and patients to include in clinical trials evaluating interventions to prevent postoperative clinically important hypotension. / Thesis / Master of Science (MSc) / In patients undergoing noncardiac surgery, numerous patients will develop postoperative clinically important hypotension. This may lead to complications including death, stroke, and myocardial infarction. I performed a large observational study to examine which risk factors would predict clinically important postoperative hypotension. Once we have identified these risk factors, we will use them to conduct randomized trials in patients at risk of clinically important hypotension to determine if we can prevent major postoperative complications.

Reductions in baroreflex responsiveness have been thought to increase the prevalence of orthostatic hypotension in endurance trained athletes. To test this hypothesis, cardiovascular responses to orthostatic stress, cardiopulmonary and carotid baroreflex responsiveness, and the effect of cardiopulmonary receptor deactivation on carotid baroreflex responses were examined in 24 men categorized by maximal aerobic power (V02max) into one of three groups: high fit (HF, V0-2max=67.0±1.9 ml•kg^-1•min^-1), moderately fit (MF, V0-2max=50.9±1.4 ml•kg^-1•min^-1), and low fit (LF, V0-2max=38.9±1.5 ml•kg^-1•min^-1). Orthostatic stress was induced using lower body negative pressure (LBNP) at -5, -10, -15, -20, -35, and -50 torr. Cardiopulmonary baroreflex responsiveness was assessed as the slope of the relationship between forearm vascular resistance (FVR, strain gauge plethysmography) and central venous pressure (CVP, dependent arm technigue) during LBNP<-35 torr. Carotid baroreflex responsiveness was assessed as the change in heart rate (HR, electrocardiography) or mean arterial pressure (MAP, radial artery catheter) elicited by 600 msec pulses of neck pressure and neck suction (NP/NS) from +40 to -70 torr. Pressures were applied using a lead collar wrapped about the subjects' necks during held expiration. Stimulus response data were fit to a logistic model and the parameters describing the curve were compared using two-factor ANOVA. The reductions CVP, mean (MAP), systolic, and pulse pressures during LBNP were similar between groups (P<0.05). However, diastolic blood pressure increased during LBNP m all but the HF group. (P<0.05). The slope of the FVR/CVP relationship did not differ between groups, nor did the form of the carotid-cardiac baroreflex stimulus response curve change during LBNP. changes in HR elicited with NP/NS were not different between groups (£>0.05). The range of the MAP stimulus response curve, however, was significantly less in the HP group compared to either the MP or LF group (£<0.05). These data imply that carotid baroreflex control of HR is unaltered by endurance exercise training, but carotid baroreflex control of blood pressure is impaired significantly, predisposing athletes to faintness.

This thesis presents studies relating to the role of the gastrointestinal tract in postprandial blood pressure regulation. The areas that have been addressed include : ( i ) the methodological approaches to the evaluation of gastric emptying, blood pressure, splanchnic blood flow, intraluminal manometry and gut hormones and ( ii ) the pathophysiological mechanisms underlying postprandial hypotension, with a particular focus on ' gastric ' and ' small intestinal ' mechanisms and their potential therapeutic relevance. All of the studies have been either published or manuscripts have been prepared for publication. While scintigraphy represents the ' gold standard ' for the measurement of gastric emptying, recent studies suggest that three - dimensional ( 3D ) ultrasonography may also allow a precise measure of gastric emptying. Concurrent scintigraphic and ultrasonographic measurements of gastric emptying of liquids were performed in healthy young volunteers. There was a good correlation and agreement between scintigraphic measurements of gastric emptying and 3D ultrasonography after ingestion of both low - and high - nutrient drinks, indicating that 3D ultrasonography, provides a valid measure of gastric emptying of liquid meals in normal subjects. Postprandial hypotension, defined as a fall in systolic blood pressure of ≥ 20mmHg,occurring within two hours of a meal is now recognised as an important clinical problem, particularly in the elderly and in patients with type 2 diabetes. The mechanisms mediating postprandial hypotension are poorly understood. The effects of variations in concentration of intraduodenal glucose on the magnitude of the fall in blood pressure were evaluated in healthy elderly subjects. Blood pressure fell, and heart rate and blood glucose increased over time during infusions, however, there was no difference in blood pressure, heart rate or blood glucose concentrations between the study days. These observations suggest that glucose induced postprandial hypotension is a load rather, than concentration, dependent phenomenon. The effect of meal composition has been reported to influence the hypotensive response to a meal and information relating to the effects of triglyceride and protein on blood pressure is inconsistent. The comparative effects of isocaloric and isovolaemic intraduodenal infusions of glucose, triglyceride and protein on the magnitude of the postprandial fall in blood pressure and rise in heart rate and superior mesenteric artery blood flow were evaluated in healthy elderly subjects. There were comparable falls in systolic blood pressure and rises in heart rate, however, the maximum fall in systolic blood pressure occurred later after triglyceride and protein and the stimulation of superior mesenteric artery blood flow was less after protein. These observations suggest that the relatively slower systolic blood pressure response after triglyceride and protein may potentially reflect the time taken for digestion of triglyceride to free fatty acids and protein to amino acids. Acarbose is an antidiabetic drug that slows both gastric emptying and small intestinal glucose absorption. The effects of acarbose, on blood pressure, heart rate, gastric emptying of, and the glycaemic, insulin, glucagon - like peptide - 1 ( GLP - 1 ) and glucosedependent insulinotropic - polypeptide ( GIP ) responses to, an oral sucrose load were evaluated in healthy elderly subjects. Acarbose attenuated the fall in blood pressure and increase in heart rate induced by oral sucrose. Acarbose slowed gastric emptying and was associated with increased retention in the distal stomach. Stimulation of GLP - 1 may contribute to the slowing of gastric emptying and suppression of postprandial glycaemia by acarbose. These findings suggest that acarbose may represent a therapeutic option for the treatment of patients with postprandial hypotension. Recent studies indicate that gastric distension attenuates the postprandial fall in blood pressure. The effects of gastric distension on blood pressure and heart rate during intraduodenal infusion of glucose at a constant load and concentration were evaluated in healthy elderly subjects. Intragastric administration of water markedly attenuated the falls in systolic and diastolic blood pressure induced by intraduodenal glucose. Heart rate increased, with and without gastric distension, in response to intraduodenal glucose infusion but not after intraduodenal saline infusion. This study suggests that gastric distension may potentially be used as a simple adjunctive treatment in the management of postprandial hypotension. Studies employing nitric oxide synthase blockers have established, in animals, that nitric oxide mechanisms are important in the regulation of splanchnic blood flow and, hence, may effect postprandial blood pressure. The role of the nitric oxide synthase inhibitor, NG - nitro - L - arginine - methyl - ester ( L - NAME ), on gastric emptying, postprandial blood pressure, plasma insulin concentration and incretin hormone ( ie GIP and GLP - 1 ) release, following an oral glucose load, were evaluated in healthy elderly subjects. L - NAME attenuated the postprandial fall in blood pressure and increase in heart rate but had no effect on gastric emptying of glucose. L - NAME attenuated the glucose - induced rise in plasma insulin but had no effect on the incretin ( GIP and GLP - 1 ) hormone response to oral glucose. The study indicates that the magnitude of the fall in blood pressure and increase in heart rate and stimulation of insulin secretion induced by oral glucose in healthy elderly subjects are mediated by nitric oxide mechanisms by an effect unrelated to changes in gastric emptying, or the secretion of GIP and GLP - 1. Studies utilising 5 - hydroxytryptamine ( 5 - HT ) infusions in animals have demonstrated regional variations in intestinal blood flow suggesting a role for 5 - HT in postprandial haemodynamic responses. The effects of the 5 - hydroxytryptamine 3 ( 5 - HT3 ) antagonist, granisetron, on the blood pressure, heart rate, antropyloroduodenal motility and glycaemic responses to intraduodenal glucose infusion were assessed in healthy elderly subjects. Granisetron had no effect on blood pressure, heart rate or antral and pyloric motor responses but modulated the duodenal motor response, to intraduodenal glucose. This study indicates that while the cardiovascular response to intraduodenal glucose does not appear to be influenced by the stimulation of 5 - HT3 receptors, this receptor may be involved in the modulation of the duodenal motor activity. / Thesis (Ph.D.)--School of Medicine, 2006.

Bakgrund: Felaktiga torrvikter är ett problem inom hemodialysvården. Det kan orsaka vårdskada i form av komplikationer och lidande, med symtom som trötthet, blodtrycksfall och sendrag för dialyspatienter. Det finns ett behov av implementering av evidensbaserade metoder som minskar risken för fel i torrviktsbestämning. Bioimpedansmätning beskrivs i litteraturen som ett lovande hjälpmedel för bestämning av torrvikt Syfte: Undersöka effekten av bioimpedansledd torrviktskorrigering, på symtom som hemodialyspatienter kan erfara under och efter dialysbehandling. Metod: Experimentell intervention, i form av veckovis korrigering av torrvikt med vägledning av bioimpedansspektroskopi, utförd med single-case-design och multiple base- line. Urvalet bestod av sex strategiskt utvalda hemodialyspatienter. Resultat: Interventionen hade ringa effekt på förekomst av intradialytiska symtom. Bland studiens deltagare förelåg sällan samvariation mellan förekomst av blodtrycksfall och/eller sendrag och felaktig torrvikt. Däremot förelåg positivt samband mellan symtombörda och differens mellan predialytisk vikt och torrvikt. Bioimpedansmätningarna avslöjade dessutom kliniskt relevant varians i torrvikt över tid. Slutsats: Även om interventionen inte hade bevisad effekt på de beroende variablerna, är det inte uteslutet att noga monitorering av vätskebalans med bioimpedansmätare och korrigering av torrvikt kan förebygga uppkomst av intradialytiska symtom. I vissa subgrupper kan bioimpedansmätning också bidra till förbättrad blodtryckskontroll. Dialyspatienters torrvikt visade sig kunna variera med flera kilogram per vecka, varför fixerad torrvikt kan vara ett dilemma för vissa individer. Bioimpedansmätning bland hemodialyspatienter kan underlätta identifiering av individuella riskfaktorer för intradialytiska symtom och vara ett verktyg som bidrar till utvecklingen mot personcentrerad vård med större patientdelaktighet och individualiserade mål. / Background: Inaccurate dry weight is a problem in hemodialysis care. It can cause health damage in the form of suffering and complications such as fatigue, intradialytic hypotension (IDH) and cramps for dialysis patients. There is a need for implementation of evidence-based practices that reduce the risk of error in dry weight assessment. Bioelectrical impedance is described in literature as a promising tool for assessment of dry weight.Objective: Examine the effect of bioimpedance guided dry weight correction on symptoms that hemodialysis patients may experience during and after dialysis. Method: Experimental intervention in the form of weekly assessment of dry weight with the guidance of bioimpedance spectroscopy, performed with single-case design and multiple baseline. The sample consisted of six strategically selected hemodialysis patients. Results: The intervention had little effect on the prevalence of intradialytic symptoms. Among the study participants, the occurrence of IDH and / or cramps and inaccurate dry weight rarely correlated. However, there was positive correlation between symptoms and the difference between predialytic weight and dry weight. Bioimpedance measurement also revealed clinically relevant variance in dry weight over time. Conclusion: Although the intervention had no proven effect on the dependent variables, it is possible that careful monitoring of fluid balance with bioimpedance measurement and correction of dry weight can help prevent intradialytic symptoms. In certain subgroups bioelectrical impedance may also contribute to improved blood pressure control. Dialysis patients' dry weight was found to vary several kilograms per week; fixated dry weight may therefore be a dilemma for some individuals. Bioelectrical impedance among hemodialysis patients may facilitate identification of individual risk factors for intradialytic symptoms and be a tool that contributes to the development of person-centered care with greater patient participation and individualized goals.

This thesis presents studies relating to the role of the gastrointestinal tract in postprandial blood pressure regulation. The areas that have been addressed include : ( i ) the methodological approaches to the evaluation of gastric emptying, blood pressure, splanchnic blood flow, intraluminal manometry and gut hormones and ( ii ) the pathophysiological mechanisms underlying postprandial hypotension, with a particular focus on ' gastric ' and ' small intestinal ' mechanisms and their potential therapeutic relevance. All of the studies have been either published or manuscripts have been prepared for publication. While scintigraphy represents the ' gold standard ' for the measurement of gastric emptying, recent studies suggest that three - dimensional ( 3D ) ultrasonography may also allow a precise measure of gastric emptying. Concurrent scintigraphic and ultrasonographic measurements of gastric emptying of liquids were performed in healthy young volunteers. There was a good correlation and agreement between scintigraphic measurements of gastric emptying and 3D ultrasonography after ingestion of both low - and high - nutrient drinks, indicating that 3D ultrasonography, provides a valid measure of gastric emptying of liquid meals in normal subjects. Postprandial hypotension, defined as a fall in systolic blood pressure of ≥ 20mmHg,occurring within two hours of a meal is now recognised as an important clinical problem, particularly in the elderly and in patients with type 2 diabetes. The mechanisms mediating postprandial hypotension are poorly understood. The effects of variations in concentration of intraduodenal glucose on the magnitude of the fall in blood pressure were evaluated in healthy elderly subjects. Blood pressure fell, and heart rate and blood glucose increased over time during infusions, however, there was no difference in blood pressure, heart rate or blood glucose concentrations between the study days. These observations suggest that glucose induced postprandial hypotension is a load rather, than concentration, dependent phenomenon. The effect of meal composition has been reported to influence the hypotensive response to a meal and information relating to the effects of triglyceride and protein on blood pressure is inconsistent. The comparative effects of isocaloric and isovolaemic intraduodenal infusions of glucose, triglyceride and protein on the magnitude of the postprandial fall in blood pressure and rise in heart rate and superior mesenteric artery blood flow were evaluated in healthy elderly subjects. There were comparable falls in systolic blood pressure and rises in heart rate, however, the maximum fall in systolic blood pressure occurred later after triglyceride and protein and the stimulation of superior mesenteric artery blood flow was less after protein. These observations suggest that the relatively slower systolic blood pressure response after triglyceride and protein may potentially reflect the time taken for digestion of triglyceride to free fatty acids and protein to amino acids. Acarbose is an antidiabetic drug that slows both gastric emptying and small intestinal glucose absorption. The effects of acarbose, on blood pressure, heart rate, gastric emptying of, and the glycaemic, insulin, glucagon - like peptide - 1 ( GLP - 1 ) and glucosedependent insulinotropic - polypeptide ( GIP ) responses to, an oral sucrose load were evaluated in healthy elderly subjects. Acarbose attenuated the fall in blood pressure and increase in heart rate induced by oral sucrose. Acarbose slowed gastric emptying and was associated with increased retention in the distal stomach. Stimulation of GLP - 1 may contribute to the slowing of gastric emptying and suppression of postprandial glycaemia by acarbose. These findings suggest that acarbose may represent a therapeutic option for the treatment of patients with postprandial hypotension. Recent studies indicate that gastric distension attenuates the postprandial fall in blood pressure. The effects of gastric distension on blood pressure and heart rate during intraduodenal infusion of glucose at a constant load and concentration were evaluated in healthy elderly subjects. Intragastric administration of water markedly attenuated the falls in systolic and diastolic blood pressure induced by intraduodenal glucose. Heart rate increased, with and without gastric distension, in response to intraduodenal glucose infusion but not after intraduodenal saline infusion. This study suggests that gastric distension may potentially be used as a simple adjunctive treatment in the management of postprandial hypotension. Studies employing nitric oxide synthase blockers have established, in animals, that nitric oxide mechanisms are important in the regulation of splanchnic blood flow and, hence, may effect postprandial blood pressure. The role of the nitric oxide synthase inhibitor, NG - nitro - L - arginine - methyl - ester ( L - NAME ), on gastric emptying, postprandial blood pressure, plasma insulin concentration and incretin hormone ( ie GIP and GLP - 1 ) release, following an oral glucose load, were evaluated in healthy elderly subjects. L - NAME attenuated the postprandial fall in blood pressure and increase in heart rate but had no effect on gastric emptying of glucose. L - NAME attenuated the glucose - induced rise in plasma insulin but had no effect on the incretin ( GIP and GLP - 1 ) hormone response to oral glucose. The study indicates that the magnitude of the fall in blood pressure and increase in heart rate and stimulation of insulin secretion induced by oral glucose in healthy elderly subjects are mediated by nitric oxide mechanisms by an effect unrelated to changes in gastric emptying, or the secretion of GIP and GLP - 1. Studies utilising 5 - hydroxytryptamine ( 5 - HT ) infusions in animals have demonstrated regional variations in intestinal blood flow suggesting a role for 5 - HT in postprandial haemodynamic responses. The effects of the 5 - hydroxytryptamine 3 ( 5 - HT3 ) antagonist, granisetron, on the blood pressure, heart rate, antropyloroduodenal motility and glycaemic responses to intraduodenal glucose infusion were assessed in healthy elderly subjects. Granisetron had no effect on blood pressure, heart rate or antral and pyloric motor responses but modulated the duodenal motor response, to intraduodenal glucose. This study indicates that while the cardiovascular response to intraduodenal glucose does not appear to be influenced by the stimulation of 5 - HT3 receptors, this receptor may be involved in the modulation of the duodenal motor activity. / Thesis (Ph.D.)--School of Medicine, 2006.