DILUTING EFFECT OF COLLOIDS IN LOW SHEAR RATE CONDITIONS

Nowiny Lekarskie 2008, 77, 1, 25 29 ANNA MARCINKOWSKA-GAPIŃSKA, PIOTR KOWAL, ZBIGNIEW CHAŁUPKA DILUTING EFFECT OF COLLOIDS IN LOW SHEAR RATE CONDITIONS WPŁYW ROZCIEŃCZENIA KRWI PŁYNAMI KOLOIDOWYMI NA LEPKOŚĆ KRWI W ZAKRESIE NISKICH PRĘDKOŚCI ŚCINANIA Pracownia Reologiczna Klinika Neurologii Uniwersytet Medyczny im. Karola Marcinkowskiego w Poznaniu Kierownik Katedry: prof. dr hab. Wojciech Kozubski Summary Introduction. Hemodilution is one of the methods used in the treatment of peripheral circulatory disturbances. There is a lot of discussion about the influence of hemodilution and different kinds of fluids on the metabolism of the organism. Aim of the study. We investigated the influence of kind of colloid fluids used for transfusion on the rheological parameters of blood. Material and Methods. The blood viscosity measurements were performed with the use of a rotary-oscillatory rheometer Contraves LS 40. The investigation included measurements of blood viscosity and a haematocrit value at three stages: before, just after and two hours after transfusion. A group of 40 patients in the age between 45 and 75 years (60 years on average) was chosen for the investigation of the rheological parameters of blood in patients prepared for procedures in epidural anaesthesia. The choice was restricted to patients prepared for operations of scrotal or inguinal hernia. Patients suffering from vascular system diseases requiring long-term pharmacological treatment were automatically excluded from the group. In the first subgroup we used Dextran 40 (Polfa Kutno, Poland) with the recommended amount of 7 ml per kg body mass (up to the volume of 500 ml) and in the second subgroup 10% HES 200/05 (Fresenius AG, Germany) with the recommended amount of 4 ml per kg body mass (up to the volume of 500 ml). Results and Conclusion. Measurements of blood viscosity at the shear rate of 1 s-1 showed that this viscosity had the lowest value in the group of patients with HES 200/0.5 as a transfusion fluid (p 0.001). KEY WORDS: hemorheology, hemodilution, blood viscosity. Streszczenie Wstęp. Hemodylucja jest jedną z metod stosowanych w terapii krążenia obwodowego. Jest wiele dyskusji na temat wpływu hemodylucji oraz wyboru przetaczanego płynu na metabolizm organizmu. Cel pracy. W pracy badano wpływ przetaczanych płynów na własności reologiczne krwi. Materiał i metody. Lepkość krwi pełnej i osocza mierzono z wykorzystaniem oscylacyjno-rotacyjnego reometru Contraves LS-40. Badanie obejmowało pomiar lepkości krwi trzykrotnie pobranej od pacjenta: przed przetaczaniem, na koniec przetaczania i dwie godziny po przetoczeniu. Dla każdej próbki wyznaczano hematokryt metodą standardową. Łącznie badana grupa pacjentów liczyła 40 osób w wieku pomiędzy 45 a 75 lat (średnia wieku 60 lat), przygotowywanych do zabiegów operacyjnych. Pacjentów podzielono na dwie podgrupy, którym przetaczano odpowiednio: pierwszej Dextran 40 (Polfa Kutno, Polska) w ilości 7 ml na kilogram masy ciała do objętości 500 ml, a drugiej 10% HAES 200/0.5 (Fresenius AG, Niemcy) w ilości 4 ml na kilogram masy ciała do objętości 500 ml. Wyniki i wnioski. Pomiary lepkości krwi przy prędkości ścinania = 1 s-1 wykazały, że jest ona mniejsza w grupie pacjentów, którym podawano HAES (p ). SŁOWA KLUCZOWE: hemoreologia, hemodylucja, lepkość krwi. Introduction Hemodilution is one of the methods used in the treatment of peripheral circulatory disturbances. It is also used in preparation stages of operational treatment of patients with vascular disorders and to fill the intravascular volume during operation [1, 2]. Fluid therapy is also used to restore physical conditions required for a normal blood circulation and tissue perfusion. Another issue is the kind of fluid used for hemodilution. There is a lot of discussion about the influence of hemodilution and different kinds of fluids on the metabolism of the organism [1, 2, 3]. Although none, apart from a patient s own blood, of the fluids used to restore the intravascular volume is free from side effects, fluid therapy gives the possibility to stabilise the macro- and micro-circulation. Aim The aim of this work was to compare a diluting effect of two different colloidal fluids. Materials and methods A group of 40 patients in the age between 45 and 75 years (60 years on average) was chosen for the investigation of the rheological parameters of blood in patients prepared for procedures in epidural anaesthesia. The choice was restricted to patients prepared for operations of scrotal or inguinal hernia. Patients suffering from

26 Anna Marcinkowska-Gapińska i inni vascular system diseases requiring long-term pharmacological treatment were automatically excluded from the group. We also avoided the patients with anatomic conditions in the region of lumbar spine such that a multiple insertion of a needle was required. Such a choice of patients allowed for the elimination of the influence of factors other than the kind of fluid used for transfusion on the rheological parameters of blood. The patients were divided into two subgroups, 20 persons each, depending on the fluid used for transfusion. In the first subgroup the fluid was Dextran 40 (Polfa Kutno, Poland) with the recommended amount of 7 ml per kg body mass (up to the volume of 500 ml) and in the second subgroup 10% HES 200/05 (Fresenius AG, Germany) with the recommended amount of 4 ml per kg body mass (up to the volume of 500 ml). Small drops of blood pressure occurring during the anaesthesia were compensated with an increased rate of transfusion of different fluids. Different dosages of HES (4 ml/kg bw), Dextrane (7 ml/kb bw) may influence the decrease of hematocrit and blood viscosity. That this can be the case for HES was shown for different HES solutions in the past. Therefore, in our study we increased the volume of transfused HES to 500 ml for each patient, regardless of the body weight. Since for the two other fluids the limit of 500 ml was automatically achieved due to sufficient body weight, all patients received the same amount of liquid during the transfusion. Blood viscosity measurements were performed using a rotary-oscillatory rheometer Contraves LS 40 (Mettler Toledo, Switzerland). Three samples of blood (5 ml each) were taken from each patient into disposable syringes with anticoagulative substance (EDTA) at the entrance. The viscosity measurement protocol included the flow curve in the range of low shear rates (0.01 100 s-1, descending slope, 5 minutes, 30 points in log scale) at 37 C. For each blood sample the hematocrit value was measured using the standard method. The first blood sample was taken just before transfusion, the second one right after transfusion and the third one two hours after transfusion. The statistical analysis included: i) calculation of mean values of rheological parameters and their standard deviations, ii) performing Student s significance tests of the mean values to detect markedly different pairs. Results For each blood sample the hematocrit value was measured. The results of these measurements are summed up in Table 1. At the first stage (just before transfusion) the average hematocrit value in subgroups was identical, as expected. At the second stage (just after transfusion) we found a drop of the hematocrit value (dilution effect). At the third stage (two hours after transfusion) the hematocrit value recovered to the value close to he initial one reaching 91 ± 4% for he colloids. The average values of the whole blood viscosity measured at shear rate = 100 s-1 and chosen low shear rates ( = 1 s-1 and = 0,1 s-1) are presented in Tables 2, 3 and 4. The analysis of the viscosity measurement results for blood taken at three stages of operation showed that the transfusion lead to a strong drop of blood viscosity in the low shear range regardless of the kind of fluid used in therapy. This was reflected by the differences of the viscosity values for blood samples taken at stages one and two (immediately before and right after transfusion) (Fig. 1 and Fig. 2). The largest difference was observed in the group of patients receiving HES 200/0.5 (42 ± 4% drop at = 0.1 s-1). At the third stage of operation (2 hours after transfusion) the low-shear-rate blood viscosity values returned partially to their initial level (stage 1). Table 1. Mean hematocrit values in selected clinical subgroups. For all samples mean value and standard deviation are given. The braces in the table connect the pairs of significantly different values, p-values are given Tabela 1. Średnie wartości hematokrytu wraz z odchyleniami standardowymi w badanych podgrupach klinicznych. Klamra w tabeli łączy pary wartości istotnie różniące się. Liczby na klamrach oznaczają wartości poziomu istotności Stage of operation \ Subgroup 10 % HES 200/0,5 Dextran 40000 I beginning of transfusion 43,8 0,9 44,8 0,8 II end of transfusion 37,4 0,8 38,0 0,8 0,02 III two hours after transfusion 40,4 0,5 40,6 0,8 0,05 0,002 Table 2. Mean blood viscosity values [mpa s] measured at = 100 s-1 in selected clinical subgroups. For all samples mean value and standard deviation are given. The braces in the table connect the pairs of significantly different values, p-values are given Tabela 2. Średnie wartości lepkości krwi dla = 100 s-1 wraz z odchyleniami standardowymi w badanych podgrupach klinicznych. Klamra w tabeli łączy pary wartości istotnie różniące się. Liczby na klamrach oznaczają wartości poziomu istotności Stage of operation \ Subgroup 10 % HAES 200/0,5 Dekstran 40000 I beginning of transfusion 4,68 0,09 4,83 0,1 II end of transfusion 3,84 0,09 4,19 0,09 0,01 0,02 III two hours after transfusion 4,22 0,05 4,52 0,08 0,05 0,05

[Pa s] [Pa s] Diluting effect of colloids in low shear rate conditions 27 Table 3. Mean blood viscosity values [mpa s] measured at = 1 s-1 in selected clinical subgroups. For all samples mean value and standard deviation are given. The braces in the table connect the pairs of significantly different values, p-values are given Tabela 3. Średnie wartości lepkości krwi dla = 1 s-1 wraz z odchyleniami standardowymi w badanych podgrupach klinicznych. Klamra w tabeli łączy pary wartości istotnie różniące się. Liczby na klamrach oznaczają wartości poziomu istotności Stage of operation \ Subgroup 10 % HES 200/0,5 Dextran 40000 I beginning of transfusion 19,45 0,84 21,0 0,99 II end of transfusion 10,76 0,53 13,3 0,84 0,02 0,002 III two hours after transfusion 13,63 0,39 16,4 0,82 0,05 Table 4. Mean blood viscosity values [mpa s] measured at = 0.1 s-1 in selected clinical subgroups. For all samples mean value and standard deviation are given. The braces in the table connect the pairs of significantly different values, p-values are given Tabela 4. Średnie wartości lepkości krwi dla = 0.1 s-1 wraz z odchyleniami standardowymi w badanych podgrupach klinicznych. Klamra w tabeli łączy pary wartości istotnie różniące się. Liczby na klamrach oznaczają wartości poziomu istotności Stage of operation \ Subgroup 10 % HES 200/0,5 Dextran 40000 I beginning of transfusion 38,8 3,2 41,5 2,8 II end of transfusion 22,4 1,6 26,2 2,6 0,02 III two hours after transfusion 29,1 1,7 33,4 3,5 0.1 0.01 HAES 200/0.5 Dextran 40 0,05 0.01 0.1 1 10 100 ' [s -1 ] 0,002 Fig. 1. Mean values of the viscosity of blood taken at the first stage of the clinical procedure (beginning of transfusion). Ryc. 1. Średnia wartość lepkości krwi pobieranej przed przetaczaniem. 0.1 0.01 HAES 200/0.5 Dextran 40 0.01 0.1 1 10 100 ' [s -1 ] Fig. 2. Mean values of the viscosity of blood taken at the second stage of the clinical procedure (end of transfusion). Ryc. 2. Średnia wartość lepkości krwi pobieranej tuż po przetaczaniu. Discussion The results presented above support the general opinion about the complexity of hemodynamic and hemorheological phenomena and arising from that problems with the choice of correct fluid [1, 3, 4, 5]. The values of particular hemorheological parameters depend equally on the research method, a type of apparatus, condition of the patient, pharmacological treatment and the kind of fluid used in transfusion [6]. As was mentioned in the Materials and Methods, we put a lot of effort to minimise the effect of all the unwanted factors listed above, focusing finally only on the effect of the kind of fluid used for transfusion. The subgroups of patients were checked to have the same average age (insignificant differences), equally random distribution of diseases. Two main hemorheological parameters, hematocrit value and low-shear-rate blood viscosity, were analysed at three stages of operation: just before transfusion, right after transfusion and two hours after transfusion. The severe dependency of whole blood viscosity on the hematocrit value was firstly described by H. Schmid-Schönbein [6]. The analysis of the hematocrit values shows that the subgroups were chosen correctly from the statistical point of view because the initial values of hematocrit values were equal for subgroups. Any differences at subsequent stages could, therefore, be attributed to the kind of fluid used for transfusion. The measurements of blood viscosity in the low shear range provided a way to investigate two effects: the effect of dilution on the flow resistance of blood (comparison between different stages within a subgroup) and the effect of the kind of fluid on the properties of red cells, mainly the rate of rouleaux formation [4, 7]. The comparison between the subgroups at the first stage of operation revealed no significant differences, as

28 Anna Marcinkowska-Gapińska i inni expected for a correct choice of patients. The behaviour of the viscosity at subsequent stages qualitatively followed the trend of the hematocrit values: first a significant drop was observed and then viscosity increased to some value below the initial one. In the low shear rate range blood viscosity is determined by only two main factors: a hematocrit value and the red cells aggregability (rouleaux formation). In view of practically equal hematocrit values, this effect can be interpreted only as a change of the red cells aggregability, which might be either a result of the red cell wall properties (e.g. stiffness) or the composition of blood plasma. Another interesting result was found in the comparison between the subgroups at the second stage of operation. The measured viscosity values were equal despite a significant difference in hematocrit values between the subgroups. We propose two possible explanations of this effect: either the use of Dextran 40 suppresses rouleaux formation or it promotes it to such an extent that rapidly sedimenting red cells produce an instrumental artefact in the low shear rate range of the experiment [4, 8, 9]. Both anticoagulative [3] and proaggregative [8] properties of Dextran have been reported which makes it difficult to make a final statement concerning the influence of Dextran. A comparison with other data is difficult also because of relatively small number of reports on blood properties in the low-shear-rate range. We think that a modified protocol of viscosity measurement, focused on the sedimentation phenomena, would be required to distinguish between the two cases. The main factor determining the aggregation of erythrocytes is the interaction of the red cells and fibrinogen. In physiological conditions there is a dynamic equilibrium between fibrinogen in free solution and fibrinogen adsorbed on the red cell membrane. It has been shown [10] that in certain disorders this equilibrium may be distorted, which should be considered in the interpretation of low-shear-rate viscosity data. The analysis of the blood viscosity values at different stages of operation within subgroups shows that in all subgroups there was a significant change from the first to the second stage of operation, while only in the first group (HES) a difference between the second and the third stage was significant. A general conclusion from the results of our study is that from the considered fluids the effect of HES was the strongest and lasted longer. By strength of the effect we mean the drop of both hematocrit value and the lowshear-rate blood viscosity at the second stage (right after transfusion). Such data point out that HES is a fluid with a long lasting action. Comparative studies of HES and Dextrans are more ambiguous [11]. Some results show no significant difference [12], other ones prove the superiority of HES [13, 14] or Dextrans [15]. The following conclusions can be formulated on the basis of results of our study: Conclusions

Diluting effect of colloids in low shear rate conditions 29 The use of HES provided the longest effect of plasma volume increase. The results of low-shear-rate blood viscosity obtained for Dextran might support the opinion about proaggregative properties of this material. References 1. Kościelny J., Jung F., Kiesevetter H. et al.: Hemodilution New aspects in the management of circulatory blood flow. Improvement of macro and microcirculation, Springer- Verlag Berlin, Heilderberg 1992, pp. 8-89. 2. Szulc R., Zapalski S., Gaca M. i in.: Wykorzystanie tlenu przez tkanki w warukach hemodylucji powodowanej za pomocą roztworów hydroksyetylowanej skrobi i innych płynów. Pol. Prz. Chir., 1991, 63, 307-319. 3. Haljamae H.: Use of fluids in trauma. Int. J. Inten. Care, 1999, 6, 1, 21-29. 4. Lerche D., Bäumler H., Kucera W. et al.: Flow properties of blood and hemorheological methods of quantification, in: Physical Characterization of Biological cells. Basic research and clinic relevance. Ed. W. Scütt, H. Klinkmann, I. Lamprecht, T. Wilson, Verlag Gesundheit GmbH Berlin 1991, pp.189-214. 5. Rady M.: An Argument for Colloid Resuscitation for Shock. Acad. Emerg. Med., 1994, 1, 572-579. 6. Schmid-Schönbein H.: Microrheology of erythrocytes, blood viscosity, and the distribution of blood flow in the microcirculation. Int. Rev. Physiol., 1979, 9, 1-62. 7. Sandhagen B.: Assessment of Blood Rheology. Methodology and studies in healthy individuals, in patients with certain diseases and during liquid blood preservation. Acta Univ. Upsalensis, Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine 138, Uppsala, 1988, pp. 1-52. 8. Haass A., Kroemer H., Jäger H., Oest A., Schimrigk K.: Similar and Opposite Hemorheological Effects of Dextran 40 and Hydroxyethyl Starch in Hemodilution Therapy for Stroke, Cerebral Ischemia and Hemorheology, Ed. A. Hartmann and W. Kuschinsky, Springer-Verlag Berlin, Heilderberg 1987, pp. 487-495. 9. Marcinkowska-Gapińska A.: Zmiany właściwości reologicznych krwi u chorych po przebytym zawale serca, Ph.D. Dissertation, Karol Marcinkowski University of Medical Sciences in Poznań, 1997. 10. Kowal P.: Arterial hypertension decreases fibrinogen molecules contribution to the inter-red cells connection in stroke patients. Clin. Hemorheol. Microcirc., 21 (1999), 321-324. 11. Freyburger G., Dubreuil M., Boisseau M.R., G. Janvier G.: Rheological properties of commonly used plasma substitutes during preoperative normovolaemic acute haemodilution. Br. J. Anaesth., 1996, 76, 519-525. 12. Staedt U., Hütt M., Seufzer U. et al.: Vergleichende Untersuchungen unter der Hämo dilutionstherapie mit 10% HES 200/0,5 und 10% Dex 40, Therapie Woche, 1987, 37, Heft 31. 13. Kościelny J., Latza R., Pruss A., Kiesewetter H., Jung F., Meier C., Schimetta W.: Hypervolumetric hemodilution with HES 100/0.5 10% in patients with peripheral arterial occlusive desase (Fontaine, stage II): an open clinical and pharmacological phase IV study. Clin. Hemorheol. Microcirc., 2000, 22, 53-65.

30 Anna Marcinkowska-Gapińska i inni 14. Schneider R., Zeumer H., Jung F. et al.: Behandlung zerebraler Mikroangiopathien mit 10% HES 200/0,5, Medwelt 36 (1985), 545-549. 15. Köhler H., Zschiedrich H., Clasen R. et al.: Blood volume, colloid osmotic pressure and renal function in volunteers after infusion of middle-molecular 10% hydroxyethyl starch 200/0,5 and 10% dextran 40, in: Anaesthesist, Springer- Verlag 1989, pp. 2-6. Adres do korespondencji: Pracownia Reologiczna Katedry Neurologii UM w Poznaniu ul. Przybyszewskiego 49, 60-355 Poznań

Diluting effect of colloids in low shear rate conditions 31 Tables Table 1 Mean hematocrit values in selected clinical subgroups. For all samples mean value and standard deviation are given. The braces in the table connect the pairs of markedly different values, p-values are given. Tabela 1. Średnie wartości hematokrytu wraz z odchyleniami standardowymi w badanych podgrupach klinicznych. Klamra w tabeli łączy pary wartości istotnie różniące się. Liczby na klamrach oznaczają wartości poziomu istotności. Stage of operation \ Subgroup 10 % HES 200/0,5 Dextran 40000 I beginning of transfusion 43,8 0,9 44,8 0,8 II end of transfusion 37,4 0,8 38,0 0,8 0,02 0,002 III two hours after transfusion 40,4 0,5 40,6 0,8 0,05

32 Anna Marcinkowska-Gapińska i inni Table 2 Mean blood viscosity values [mpa s] measured at = 100 s -1 in selected clinical subgroups. For all samples mean value and standard deviation are given. The braces in the table connect the pairs of markedly different values, p- values are given. Tabela 2. Średnie wartości lepkości krwi dla = 100 s -1 wraz z odchyleniami standardowymi w badanych podgrupach klinicznych. Klamra w tabeli łączy pary wartości istotnie różniące się. Liczby na klamrach oznaczają wartości poziomu istotności. Stage of operation \ Subgroup 10 % HAES 200/0,5 Dekstran 40000 I beginning of transfusion 4,68 0,09 4,83 0,1 II end of transfusion 3,84 0,09 4,19 0,09 0,01 0,05 0,02 III two hours after transfusion 4,22 0,05 4,52 0,08 0,05

Diluting effect of colloids in low shear rate conditions 33 Table 3 Mean blood viscosity values [mpa s] measured at = 1 s -1 in selected clinical subgroups. For all samples mean value and standard deviation are given. The braces in the table connect the pairs of markedly different values, p- values are given. Tabela 3. Średnie wartości lepkości krwi dla = 1 s -1 wraz z odchyleniami standardowymi w badanych podgrupach klinicznych. Klamra w tabeli łączy pary wartości istotnie różniące się. Liczby na klamrach oznaczają wartości poziomu istotności. Stage of operation \ Subgroup 10 % HES 200/0,5 Dextran 40000 I beginning of transfusion 19,45 0,84 21,0 0,99 II end of transfusion 10,76 0,53 13,3 0,84 0,02 0,002 III two hours after transfusion 13,63 0,39 16,4 0,82 0,05

34 Anna Marcinkowska-Gapińska i inni Table 4 Mean blood viscosity values [mpa s] measured at = 0.1 s -1 in selected clinical subgroups. For all samples mean value and standard deviation are given. The braces in the table connect the pairs of markedly different values, p- values are given. Tabela 4. Średnie wartości lepkości krwi dla = 0.1 s -1 wraz z odchyleniami standardowymi w badanych podgrupach klinicznych. Klamra w tabeli łączy pary wartości istotnie różniące się. Liczby na klamrach oznaczają wartości poziomu istotności. Stage of operation \ Subgroup 10 % HES 200/0,5 Dextran 40000 I beginning of transfusion 38,8 3,2 41,5 2,8 II end of transfusion 22,4 1,6 26,2 2,6 0,02 0,002 III two hours after transfusion 29,1 1,7 33,4 3,5 0,05

Diluting effect of colloids in low shear rate conditions 35

36 Anna Marcinkowska-Gapińska i inni Tables Table 1. Mean hematocrit values in selected clinical subgroups. For all samples mean value and standard deviation are given. The braces in the table connect the pairs of markedly different values, p-values are given Tabela 1. Średnie wartości hematokrytu wraz z odchyleniami standardowymi w badanych podgrupach klinicznych. Klamra w tabeli łączy pary wartości istotnie różniące się. Liczby na klamrach oznaczają wartości poziomu istotności Stage of operation \ Subgroup 10 % HES 200/0,5 Dextran 40000 I beginning of transfusion 43,8 0,9 44,8 0,8 II end of transfusion 37,4 0,8 38,0 0,8 0,02 III two hours after transfusion 40,4 0,5 40,6 0,8 0,05 0,002 Stage of operation \ Subgroup 10 % HES 200/0,5 Dextran 40000 I beginning of transfusion 43,8 0,9 44,8 0,8 II end of transfusion 37,4 0,8 38,0 0,8 0,02 III two hours after transfusion 40,4 0,5 40,6 0,8 0,05 0,002

Diluting effect of colloids in low shear rate conditions 37 Table 2. Mean blood viscosity values [mpa s] measured at = 100 s-1 in selected clinical subgroups. For all samples mean value and standard deviation are given. The braces in the table connect the pairs of markedly different values, p-values are given Tabela 2. Średnie wartości lepkości krwi dla = 100 s-1 wraz z odchyleniami standardowymi w badanych podgrupach klinicznych. Klamra w tabeli łączy pary wartości istotnie różniące się. Liczby na klamrach oznaczają wartości poziomu istotności Stage of operation \ Subgroup 10 % HAES 200/0,5 Dekstran 40000 I beginning of transfusion 4,68 0,09 4,83 0,1 II end of transfusion 3,84 0,09 4,19 0,09 0,01 III two hours after transfusion 4,22 0,05 4,52 0,08 0,02 0,05

38 Anna Marcinkowska-Gapińska i inni Table 3. Mean blood viscosity values [mpa s] measured at = 1 s-1 in selected clinical subgroups. For all samples mean value and standard deviation are given. The braces in the table connect the pairs of markedly different values, p-values are given Tabela 3. Średnie wartości lepkości krwi dla = 1 s-1 wraz z odchyleniami standardowymi w badanych podgrupach klinicznych. Klamra w tabeli łączy pary wartości istotnie różniące się. Liczby na klamrach oznaczają wartości poziomu istotności Stage of operation\subgroup 10% HES 200/0,5 Dextran 40000 I beginning of transfusion 19,45 0,84 21,0 0,99 II end of transfusion 10,76 0,53 13,3 0,84 0,02 III two hours after transfusion 13,63 0,39 16,4 0,82 0,002 0,05

Diluting effect of colloids in low shear rate conditions 39 Table 4. Mean blood viscosity values [mpa s] measured at = 0.1 s-1 in selected clinical subgroups. For all samples mean value and standard deviation are given. The braces in the table connect the pairs of markedly different values, p-values are given Tabela 4. Średnie wartości lepkości krwi dla = 0.1 s-1 wraz z odchyleniami standardowymi w badanych podgrupach klinicznych. Klamra w tabeli łączy pary wartości istotnie różniące się. Liczby na klamrach oznaczają wartości poziomu istotności Stage of operation \ Subgroup 10 % HES 200/0,5 Dextran 40000 I beginning of transfusion 38,8 3,2 41,5 2,8 II end of transfusion 22,4 1,6 26,2 2,6 0,02 III two hours after transfusion 29,1 1,7 33,4 3,5 0,05 0,002

40 Anna Marcinkowska-Gapińska i inni Figures Fig. 1. Mean values of the viscosity of blood taken at the first stage of the clinical procedure (begining of transfusion). Ryc. 1. Średnia wartość lepkości krwi pobieranej przed przetaczaniem. Fig. 2. Mean values of the viscosity of blood taken at the second stage of the clinical procedure (end of transfusion). Ryc. 2. Średnia wartość lepkości krwi pobieranej tuż po przetaczaniu.

[Pa s] Diluting effect of colloids in low shear rate conditions 41 0.1 0.01 HAES 200/0.5 Dextran 40 0.01 0.1 1 10 100 ' [s -1 ] Fig. 1. Mean values of the viscosity of blood taken at the first stage of the clinical procedure (begining of transfusion). Ryc. 1. Średnia wartość lepkości krwi pobieranej przed przetaczaniem.

[Pa s] 42 Anna Marcinkowska-Gapińska i inni 0.1 0.01 HAES 200/0.5 Dextran 40 0.01 0.1 1 10 100 ' [s -1 ] Fig. 2. Mean values of the viscosity of blood taken at the second stage of the clinical procedure (end of transfusion). Ryc. 2. Średnia wartość lepkości krwi pobieranej tuż po przetaczaniu.