| 1. |
- Södergren, Anna, et al.
(author)
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Responsiveness of platelets during storage studied with flow cytometry - formation of platelet subpopulations and LAMP-1 as new markers for the platelet storage lesion
- 2016
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In: Vox Sanguinis. - : Wiley-Blackwell Publishing Inc.. - 0042-9007 .- 1423-0410. ; 110:2, s. 116-125
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Journal article (peer-reviewed)abstract
- Background and ObjectivesStorage lesions may prevent transfused platelets to respond to agonists and arrest bleeding. The aim of this study was to evaluate and quantify the capacity of platelet activation during storage using flow cytometry and new markers of platelet activation. Materials and MethodsActivation responses of platelets prepared by apheresis were measured on days 1, 5, 7 and 12. In addition, comparisons were made for platelet concentrates stored until swirling was affected. Lysosome-associated membrane protein-1 (LAMP-1), P-selectin and phosphatidylserine (PS) exposure were assessed by flow cytometry on platelets in different subpopulations in resting state or following stimulation with platelet agonists (cross-linked collagen-related peptide (CRP-XL), PAR1- and PAR4-activating peptides). ResultsThe ability to form subpopulations upon activation was significantly decreased already at day 5 for some agonist combinations. The agonist-induced exposure of PS and LAMP-1 also gradually decreased with time. Spontaneous exposure of P-selectin and PS increased with time, while spontaneous LAMP-1 exposure was unchanged. In addition, agonist-induced LAMP-1 expression clearly discriminated platelet concentrates with reduced swirling from those with retained swirling. This suggests that LAMP-1 could be a good marker to capture changes in activation capacity in stored platelets. ConclusionThe platelet activation potential seen as LAMP-1 exposure and fragmentation into platelet subpopulations is potential sensitive markers for the platelet storage lesion.
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| 2. |
- Tynngård, Nahreen, et al.
(author)
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Effects of different blood components on clot retraction analysed by measuring elasticity with a free oscillating rheometer
- 2006
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In: Platelets. - : Informa UK Limited. - 0953-7104 .- 1369-1635. ; 17:8, s. 545-554
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Journal article (peer-reviewed)abstract
- Free oscillation rheometry (FOR) using the ReoRox® 4 instrument makes it possible, at bedside, to study the coagulation process in blood over time and gives information on clotting time and coagulum elastic properties. In order to find out how various factors influence the FOR analysis we studied the coagulation process and change of elasticity over time in non-anticoagulated and citrated blood samples, plasma samples with various platelet concentrations (0-200 109/l) and blood samples with various haematocrit (0-40%). Blood samples supplemented with fibrinogen were analysed to elucidate the importance of fibrinogen on elasticity. The importance of the GPIIb/IIIa receptor on platelets was investigated by comparing the elasticity development in blood samples in presence and absence of a GPIIb/IIIa receptor inhibitor, abciximab. Anticoagulation with citrate did not have major influence on the viscoelastic properties of the coagulum. Increasing number of platelets and increasing fibrinogen concentration resulted in higher elasticity while increasing haematocrit gave lower elasticity. Blood samples with GPIIb/IIIa receptor inhibitor had very low elasticity indicating the importance of functional GPIIb/IIIa receptors. In conclusion we consider FOR to be a useful method to study the elastic properties of the coagulum. Various factors such as the number of red blood cells and platelets as well as the fibrinogen concentration should be taken into consideration when evaluating the results. The ReoRox® 4 instrument had excellent measuring range and unusually small artefactual effects on clot elasticity induced by the instrument in comparison with published results on other instruments.
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| 3. |
- Tynngård, Nahreen, et al.
(author)
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Free oscillation rheometry detects changes in clot properties in pregnancy and thrombocytopaenia
- 2008
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In: Platelets. - : Informa UK Limited. - 0953-7104 .- 1369-1635. ; 19:5, s. 373-378
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Journal article (peer-reviewed)abstract
- Improved methods are needed to identify patients at risk for thrombotic or bleeding events. Free oscillation rheometry (FOR) is a technique that offers information on coagulation, based on contributions of all blood components, by measurement of clotting time and changes in clot elasticity. This is the first study that evaluates FOR parameters in subjects likely to represent hypercoagulability (pregnant women) and hypocoagulability (thrombocytopenic patients). Clotting time and blood clot elasticity were measured by FOR in blood samples obtained from women in different pregnancy trimesters (n = 58), in thrombocytopenic patients before and after a platelet transfusion (n = 20) and in healthy blood donors (n = 60). The clotting time was shorter and the clot elasticity higher in pregnant women compared to the non-pregnant female blood donors. The elasticity was higher in late pregnancy compared to early pregnancy. Compared to the blood donors, the thrombocytopenic patients had lower elasticity, which was increased by a platelet transfusion, but there was no difference in clotting time. The results suggest that FOR can provide new information on the haemostatic status of patients at risk of thrombotic or bleeding events as well as information on the haemostatic effect of a platelet transfusion.
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| 4. |
- Zwedberg, Sofia, et al.
(author)
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Midwives' experiences as preceptors and the development of good preceptorships in obstetric units
- 2020
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In: Midwifery. - : Elsevier BV. - 0266-6138 .- 1532-3099. ; 87
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Journal article (peer-reviewed)abstract
- Objective: To study midwives' experience in their role as a preceptor and their perception on how to best support midwifery students in obstetrics units. Obstetric units are an important learning area for student midwives but knowledge on how to become a good midwife preceptor is limited. Design: This qualitative study explores midwife preceptors' experience of supervising midwifery students in three obstetric units in Sweden. Following ethical approval seventeen midwife preceptors were inter- viewed and data were analysed thematically. Findings: Thematic analysis of the interviews resulted in the identification of two themes and five sub- themes: (1) self-efficacy in the preceptor role which involves (a) being confident in the professional posi- tion and (b) having the support of management and colleagues and (2) supporting the student to attain self-confidence and independence which entails (a) helping the student to grow, (b) facilitating reflection in learning situations, and (c) "taking a step back". Key conclusion: Good preceptorship occurs when midwives achieve full self-efficacy, when they master the preceptor role, and when they have enhanced their abilities to help, the student reach confidence and independence. Implications for practice: Health care organisations needs to develop and support midwifery preceptor- ships
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