| 1. |
- Abrahamsson, Pernilla, 1972-, et al.
(författare)
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An assessment of calibration and performance of the microdialysis system
- 2005
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Ingår i: Journal of Pharmaceutical and Biomedical Analysis. - : Elsevier. - 0731-7085 .- 1873-264X. ; 39:3-4, s. 730-734
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Tidskriftsartikel (refereegranskat)abstract
- To improve the reliability of microdialysis measurements of tissue concentrations of metabolic substances, this study was designed to test both the performance and the internal validity of the microdialysis methods in the hands of our research group. The stability of the CMA 600 analyser was tested with a known glucose solution in 72 standard microvials and in 48 plastic vials. To evaluate if variation in sampling time makes any difference in sample concentration (recovery), sampling times of 10, 20 and 30 min were compared in vitro with a constant flow rate of 1 microl/min. For testing of sampling times at different flow rates, an in vitro study was performed in which a constant sample volume of 10 microl was obtained. With the no net flux method, the actual concentration of glucose and urea in subcutaneous tissue was measured. The CMA 600 glucose analysis function was accurate and stable with a coefficient of variability (CV) of 0.2-0.55%. There was no difference in recovery for the CMA 60 catheter for glucose when sampling times were varied. Higher flow rates resulted in decreased recovery. Subcutaneous tissue concentrations of glucose and urea were 4.4 mmol/l and 4.1 mmol/l, respectively. To conclude, this work describes an internal validation of our use of the microdialysis system by calibration of vials and catheters. Internal validation is necessary in order to be certain of adequate sampling times, flow rates and sampling volumes. With this in mind, the microdialysis technique is useful and appropriate for in vivo studies on tissue metabolism.
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| 2. |
- Abrahamsson, Pernilla, 1972-, et al.
(författare)
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Comparison between outcome of surface and intraparenchymatous sampling using microdialysis in an experimental liver ischemia model
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Introduction. We recently have shown that samples from MD probes placed on the surface of the heart reflect metabolic events in the myocardium. This new interesting observation challenges us to consider whether surface application of MD applies to other parenchymatous organs and their surfaces. Material and methods. In thirteen anesthetized pigs transient liver ischemia was achieved by occlusion of arterial and venous inflow to the liver. Two probes on liver surface, and two in parenchyma were perfused with a flow rate of 1 µL/min (n=13). An identical set up was used for probes with a flow rate of 2 µL/min (n=9). Samples were collected for every 15 minute period during 60 minutes of baseline, 45 minutes of ischemia and 60 minutes of reperfusion. Lactate, glucose, pyruvate and glycerol were analysed in MD samples. We focused on relative changes in the present paper. Results. There was a strong agreement in relative lactate and glucose levels between probes placed on liver surface and parenchyma. No significant differences in relative changes of lactate and glucose levels were seen between samples from surface probes and probes in liver parenchyma during equilibration, baseline, ischemia or reperfusion with a flow rate of 1 µL/min. Conclusion. MD sampling applied on the liver surface is a new application area for the MD technique, and may be used to monitor liver metabolism both during physiological and pathophysiological conditions.
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| 3. |
- Abrahamsson, Pernilla, 1972-
(författare)
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Methodological aspects on microdialysis sampling and measurements
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: The microdialysis (MD) technique is widely spread and used both experimentally and in clinical practice. The MD technique allows continuous collection of small molecules such as glucose, lactate, pyruvate and glycerol. Samples are often analysed using the CMA 600 analyser, an enzymatic and colorimetric analyser. Data evaluating the performance of the CMA 600 analysis system and associated sample handling are sparse. The aim of this work was to identify sources of variability related to handling of microdialysis samples and sources of error associated with use of the CMA 600 analyser. Further, to develop and compare different application techniques of the microdialysis probes both within an organ and on the surface of an organ. Material and Methods: Papers I and II are mainly in vitro studies with the exception of the No Net Flux calibration method in paper I where a pig model (n=7) was used to examine the true concentration of glucose and urea in subcutaneous tissue. Flow rate, sampling time, vial and caps material and performance of the analyser device (CMA 600) were examined. In papers III and IV normoventilated anaesthetised pigs (n=33) were used. In paper III, heart ischemia was used as intervention to compare microdialysis measurements in the myocardium with corresponding measurements on the heart surface. In paper IV, microdialysis measurements in the liver parenchyma were compared with measurements on the liver surface in association with induced liver ischemia. All animal studies were approved by the Animal Experimental Ethics Committee at Umeå University Sweden. Results: In paper I we succeeded to measure true concentrations of glucose (4.4 mmol/L) and Urea (4.1 mmol/L) in subcutaneous tissue. Paper II showed that for a batch analyse of 24 samples it is preferred to store microdialysis samples in glass vials with crimp caps. For reliable results, samples should be centrifuged before analysis. Paper III showed a new application area for microdialysis sampling from the heart, i.e. surface sampling. The surface probe and myocardial probe (in the myocardium) showed a similar pattern for glucose, lactate and glycerol during baseline, short ischemic and long ischemic interventions. In paper IV, a similar pattern was observed as in paper III, i.e. data obtained from the probe on the liver surface showed no differences compared with data from the probe in liver parenchyma for glucose, lactate and glycerol concentrations during baseline, ischemic and reperfusion interventions. Conclusion: The MD technique is adequate for local metabolic monitoring, but requires methodological considerations before starting a new experimental serie. It is important to consider factors such as flow rate, sampling time and handling of samples in association with the analysis device chosen. The main finding in this thesis is that analyses of glucose, lactate and glycerol in samples from the heart surface and liver surface reflect concentrations sampled from the myocardium and liver parenchyma, respectively.
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| 4. |
- Abrahamsson, Pernilla, 1972-, et al.
(författare)
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Optimised sample handling in association with use of the CMA 600 analyser
- 2008
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Ingår i: Journal of Pharmaceutical and Biomedical Analysis. - : Elsevier. - 0731-7085 .- 1873-264X. ; 48:5, s. 940-945
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Tidskriftsartikel (refereegranskat)abstract
- A large degree of variability for batched analysis of serially collected microdialysis samples measured with the CMA 600 analyser has been described. This study was designed to identify sources of variability related to sample handling. Standard concentrations of four solutes were placed in microdialysis vials and then stored and analysed at intervals. Results were analysed for variability related to vial and cap type, duration and temperature of storage, centrifugation and re-analysis. The main results were that centrifugation of samples reduced variability. When a batch of 24 samples was analysed, the use of crimp caps reduced evaporation. Samples in glass vials with crimp caps could be stored in a refrigerator for up to 14 days without large variability in concentration compared to plastic vials which demonstrated variability already when stored for more than 1 day. We conclude that variability in microdialysis results can occur in relation to storage and analysis routines if routines are not optimised concerning evaporation. Centrifugation before analyses, glass vials with crimp caps even during frozen storage, and attention to minimal times for samples to be uncapped during analysis all contribute to minimise variability in the handling and analysis of microdialysis samples.
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| 5. |
- Winsö, Ola, et al.
(författare)
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Thoracic epidural anaesthesia reduces insulin resistance and inflammatory response in experimental acute pancreatitis
- 2018
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Ingår i: Upsala Journal of Medical Sciences. - Abingdon : Taylor & Francis. - 0300-9734 .- 2000-1967. ; 123:4, s. 207-215
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: The activity of the sympathetic nervous system (SNS) is crucial at an early stage in the development of an inflammatory reaction. A study of metabolic events globally and locally in the early phase of acute pancreatitis (AP), implying hampered SNS activity, is lacking. We hypothesized that thoracic epidural anaesthesia (TEA) modulates the inflammatory response and alleviates the severity of AP in pigs.MATERIAL AND METHODS: The taurocholate (TC) group (n = 8) had only TC AP. The TC + TEA group (n = 8) had AP and TEA. A control group (n = 8) underwent all the preparations, without having AP or TEA. Metabolic changes in the pancreas were evaluated by microdialysis and by histopathological examination.RESULTS: The relative increase in serum lipase concentrations was more pronounced in the TC group than in TC + TEA and control groups. A decrease in relative tissue oxygen tension (PtiO2) levels occurred one hour later in the TC + TEA group than in the TC group. The maintenance of normoglycaemia in the TC group required a higher glucose infusion rate than in the TC + TEA group. The relative decrease in serum insulin concentrations was most pronounced in the TC + TEA group.CONCLUSION: TEA attenuates the development of AP, as indicated by changes observed in haemodynamic parameters and by the easier maintenance of glucose homeostasis. Further, TEA was associated with attenuated insulin resistance and fewer local pathophysiological events.
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| 6. |
- Åkesson, Oscar, et al.
(författare)
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Surface Microdialysis Detects Ischemia After Esophageal Resection : An Experimental Animal Study
- 2020
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Ingår i: Journal of Surgical Research. - : Elsevier. - 0022-4804 .- 1095-8673. ; 245, s. 537-543
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: After an esophageal resection, continuity is commonly restored by a gastric tube reconstruction and an intrathoracic anastomosis to the remaining proximal esophagus. Ischemia of the anastomotic region is considered to play a pivotal role in anastomotic leakage. Microdialysis (μD) is an excellent method to measure local biochemical substances and parameters in a specific organ or compartment aiming at early detection of ischemia. This animal study evaluates ischemia of the gastric tube reconstruction using a novel method-μD on organ surfaces. This promising method may have the potential to detect an anastomotic leakage before clinical symptoms develop.METHODS: Anesthetized normoventilated pigs were used. Surface microdialysis (S-μD) catheters and an intraparenchymal oxygen tension catheter were placed on the stomach. A gastric tube was made and the gastroepiploic artery was divided halfway along the greater curvature to produce severe ischemia at the top of the gastric tube. μD data from four locations (gastric tube, ileum and peritoneal cavity) were recorded every 20 min during the experiment. Tissue samples from all catheter sites underwent histopathological analysis. Intraparenchymal oxygen partial pressure, systemic blood tests, and hemodynamic parameters were recorded.RESULTS: S-μD data showed values indicating severe ischemia at the top of the gastric tube and intermediate ischemia at the level of transection of the gastroepiploic artery. Ischemia was verified by histopathological analysis of tissue samples and intraparenchymal oxygen tension data.CONCLUSIONS: S-μD can detect and grade severity of local ischemia in real time, in an animal model.
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| 7. |
- Åkesson, Oscar, et al.
(författare)
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Surface microdialysis measures local tissue metabolism after Ivor Lewis esophagectomy; an attempt to predict anastomotic defect
- 2023
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Ingår i: Diseases of the esophagus. - : Oxford University Press. - 1120-8694 .- 1442-2050. ; 36:8
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Tidskriftsartikel (refereegranskat)abstract
- Anastomotic defect (AD) after esophagectomy can lead to severe complications with need for surgical or endoscopic intervention. Early detection enables early treatment and can limit the consequences of the AD. As of today, there are limited methods to predict AD. In this study, we have used microdialysis (MD) to measure local metabolism at the intrathoracic anastomosis. Feasibility and possible diagnostic use were investigated. Sixty patients planned for Ivor Lewis esophagectomy were enrolled. After construction of the anastomosis, surface MD (S-MD) probes were attached to the outer surface of the esophageal remnant and the gastric conduit in close vicinity of the anastomosis and left in place for 7 postoperative days (PODs). Continuous sampling of local tissue concentrations of metabolic substances (glucose, lactate, and pyruvate) was performed postoperatively. Outcome, defined as AD or not according to Esophagectomy Complications Consensus Group definitions, was recorded at discharge or at first postoperative follow up. Difference in concentrations of metabolic substances was analyzed retrospectively between the two groups by means of artificial neural network technique. S-MD probes can be attached and removed from the gastric tube reconstruction without any adverse events. Deviating metabolite concentrations on POD 1 were associated with later development of AD. In subjects who developed AD, no difference in metabolic concentrations between the esophageal and the gastric probe was recorded. The technical failure rate of the MD probes/procedure was high. S-MD can be used in a clinical setting after Ivor Lewis esophagectomy. Deviation in local tissue metabolism on POD 1 seems to be associated with development of AD. Further development of MD probes and procedure is required to reduce technical failure.
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