| 1. |
- Flodgren, Gerd, 1961-, et al.
(författare)
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Changes in interstitial noradrenaline, trapezius muscle activity and oxygen saturation during low-load work and recovery
- 2009
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 107:1, s. 31-42
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Tidskriftsartikel (refereegranskat)abstract
- Both physical as well as mental demands result in an increased activity in the sympathetic nervous system (SNS) with changes in blood-pressure and heart-rate. Through local release of catecholamines, e.g. noradrenaline (NAd) SNS exerts various actions at the muscle level. The aims of this study were to investigate the effects of low-load repetitive work alone and in combination with mental demands on local muscle interstitial noradrenaline concentration [NAd]i, muscle activity and oxygenation, assessed with microdialysis, surface electromyography, and near-infrared spectroscopy, respectively. Healthy females (n = 15) were exposed to (1) 30 min repetitive work (RW) and (2) 30 min repetitive work with superimposed mental load (RWML) on two different occasions. Muscle [NAd]i and muscle activity increased significantly in response to RW, but did not increase further during RWML. For RW, [NAd]i was found to be inversely correlated to muscle activity. Oxygenation decreased significantly during work, independently of occasion. Our findings indicate that low-load work causes significantly increased trapezius muscle [NAd]i in healthy females, and short periods of superimposed mental load do not add to this increase and further, that both muscle activity and oxygenation were unaffected by the superimposed mental load.
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| 2. |
- Gref, Margareta, 1950-, et al.
(författare)
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99mTc-diethylenetriamine penta-acetate plasma clearance in advanced renal failure by the mean sojourn time approach
- 2009
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Ingår i: Nuclear medicine communications. - 0143-3636 .- 1473-5628. ; 30:3, s. 202-205
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The single-sample 99mTc-diethylenetriamine penta-acetate (DTPA) clearance method by Christensen and Groth is recommended by the Radionuclides in Nephrourology Committee on Renal Clearance for use in adults with an estimated glomerular filtration rate (GFR) ≥30 ml/min. The purpose of this study was to test a new 99mTc-DTPA single-sample low clearance formula for GFR lesser than 30 ml/min. Methods: Twenty-one adult patients (29 investigations) were included. Reference clearance was calculated with both 51Cr-EDTA and 99mTc-DTPA according to Brøchner-Mortensen with samples drawn between 3 and 24 h. Single-sample clearance was calculated from a 24 h sample using the low clearance formula Equation (Uncited)Image Tools C(t) is the activity of the tracer in the plasma sample t minutes after the injection and Q0 is the injected amount. ECV is the extracellular volume in ml defined as the distribution volume of the tracer. ECV is estimated from the body surface area as ECV=8116.6×body surface area-28.2. Results: The mean difference between reference and 99mTc-DTPA single-sample clearance was -0.5 ml/min (SD 1.0 ml/min) for 99mTc-DTPA and -0.8 ml/min (SD 1.2 ml/min) for 51Cr-EDTA as reference clearance. Conclusion: In adult patients it is possible, even with GFR lesser than 30 ml/min, to get an accurate determination of 99mTc-DTPA plasma clearance from a single sample using the mean sojourn time approach. The blood sample should be obtained about 24 h after injection of the GFR tracer.
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| 3. |
- Gref, Margareta, 1950-
(författare)
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Formler för enprovs plasmaclearance
- 2000
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Ingår i: Njurarna och övre urinvägarna. - Lund : Studentlitteratur. - 9144009623 ; , s. 57-64
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Gref, Margareta, et al.
(författare)
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GFR determination in adults with a single-sample iohexol plasma clearance method based on the mean sojourn time
- 2007
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Ingår i: Nephrology, Dialysis and Transplantation. - : Oxford University Press (OUP). - 0931-0509 .- 1460-2385. ; 22:11, s. 3166-3173
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Tidskriftsartikel (refereegranskat)abstract
- Background. Glomerular filtration rate is a key parameter in kidney disease. The Radionuclides in Nephrourology Committee has recommended a single-sample method with 99mTc-DTPA based on the mean sojourn time. This study was done to develop the method for use with iohexol making the method more available. Methods. The single-sample formula was derived for group I (n = 48, Cl = 8–188 ml/min) and applied on group II (n = 47) and on group III (n = 123). In groups I and II, reference clearance was determined according to Sapirstein and in group III according to Brøchner-Mortensen. Results. The formula (a = (−6.49 × 10−6×t + 8.85 × 10−4)×t, b = 1.143 × t and c = ln[(C(t))×(ECV/Q0)](ECV) was derived for patients with estimated Cl > 30 ml/min with the best result if the single sample was obtained between 4 and 5 h. Extracellular volume was estimated as ECV =9985 × BSA − 3431. The formula ClS(24 h) = −ln[(C(t))×(ECV/Q0)](ECV)/(t) was developed for patients with estimated Cl <30 ml/min with a single sample at 24 h. With this combined approach SDdiff was 2.7 ml/min in group II and 3.1 ml/min in group III. Conclusions. An accurate determination of iohexol clearance can be obtained from a single plasma sample applying the mean sojourn time approach. A separate formula must be used for patients with low clearance values. Body surface area (BSA), injected amount of iohexol (Q0), time when the single sample is drawn (t) and the concentration of iohexol [C(t)] in the sample are needed for the calculations.
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| 5. |
- Gref, Margareta, 1950-
(författare)
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Glomerular filtration rate in adults : a single sample plasma clearance method based on the mean sojurn time
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Glomerular filtration rate (GFR) is a key parameter in evaluating kidney function. After a bolus injection of an exogenous GFR marker in plasma an accurate determination of GFR can be made by measuring the marker concentration in plasma during the excretion. Simplified methods have been developed to reduce the number of plasma samples needed and yet still maintain a high accuracy in the GFR determination. Groth previously developed a single sample GFR method based on the mean sojourn time of a GFR marker in its distribution volume. This method applied in adults using the marker 99m Tc-DTPA is recommended for use when GFR is estimated to be ≥ 30 mL/min. The aim of the present study was to further develop the single plasma sample GFR method by Groth including patients with severely reduced renal function and different GFR markers. Three different GFR markers 51Cr-EDTA, 99mTc-DTPA and iohexol were investigated. Formulas were derived for the markers 51Cr-EDTA and iohexol when GFR is estimated to be ≥ 30 mL/min. For patients with an estimated GFR < 30 mL/min a special low clearance formula with a single sample obtained about 24 h after marker injection was developed. The low clearance formula was proven valid for use with all three markers. The sources of errors and their influence on the calculated single sample clearance were investigated. The estimated distribution volume is the major source of error but its influence can be reduced by choosing a suitable sampling time. The optimal time depends on the level of GFR; the lower GFR the later the single sample should be obtained. For practical purpose a 270 min sample is recommended when estimated GFR ≥ 30 mL/min and a 24 h sample when estimated GFR < 30 mL/min. Sampling at 180 min after marker injection may be considered if GFR is estimated to be essentially normal.
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| 6. |
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| 7. |
- Mårtensson, Johan, et al.
(författare)
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Chromium-51-EDTA clearance in adults with a single-plasma sample
- 1998
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Ingår i: Journal of Nuclear Medicine. - 0161-5505 .- 1535-5667. ; 39:12, s. 2131-2137
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Tidskriftsartikel (refereegranskat)abstract
- In 1996, a committee on renal clearance recommended a mean sojourn time-based methodology for single-sample determination of plasma clearance of 99mTc-diethylenetriamine pentaacetic acid (DTPA) to be used on adults if the patient's glomerular filtration rate (GFR) is suspected to be >30 ml/min. The main purpose of this study was to derive a mean sojourn time-based formula for calculation of 51Cr-ethylenediamine tetraacetic acid (EDTA) clearance in adults. Methods: Two groups of patients with 51Cr-EDTA clearance (CI) between 16 and 172 ml/min were studied. In Group I (n = 46), reference CI was determined as a multi plasma sample, single-injection method (CISM). Sixteen blood samples were drawn from 0 until 5 hr after a single intravenous injection of 51Cr-EDTA. In Group II (n = 1046), reference CI was determined by the Brøchner-Mortensen four-sample clearance method (CIBM). The plasma timeactivity curves of Group I were used to derive two mean sojourn time-based formulas (Formulas 1 and 2) for calculation of a single sample clearance. Formula 1 was derived from the entire time activity curve, whereas the derivation of Formula 2 used only the final slope of the time-activity curve. The accuracy of the two formulas and the Christensen and Groth 99mTc-DTPA formula was tested on Group II. Results: Chromium-51-EDTA CI calculated by Formula 1 was almost identical to the CI calculated by the reference CI method (r = 0.982; SDdiff = 5.82 ml/min). Both 51Cr-EDTA CI calculated by Formula 2 and by the 99mTc-DTPA formula showed close correlation with the reference method (r = 0.976, r = 0.985, respectively) but systematically overestimated GFR for the whole range of clearance values by 3.5 and 3.2 ml/min (p < 0.001), respectively. Conclusion: It is possible to get an accurate determi nation of 51Cr-EDTA CI from a single-plasma sample in adults by the mean sojourn time methodology. The determination is marginally more accurate (p < 0.001) if using a formula derived from the entire plasma time-activity curve than from only the final slope. The single-sample formula derived for determination of 99mTc-DTPA CI tends slightly to overestimate GFR if used to calculate 51Cr-EDTA CI.
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