Influence Of Hematocrit Research Articles

Blood Glucose Determinations in Newborns: Four Instruments Compared

Four portable analyzers, HemoCue B-Glucose (I), Accu-Check III (II), One-touch II (III), and Glucometer Elite (IV), with different measuring principles were tested for their suitability for measuring blood glucose in neonates. Precision of all instruments is satisfactory. In the analysis of capillary blood from newborns, two instruments show an excellent accuracy; however, the scatter of the results for instrument (II) is about 1.6 times greater than for instrument (I). The inaccuracy of instruments (III) and (IV) is not acceptable from a clinical point of view. All devices show an influence of hematocrit, the magnitude of which varies between 5% (I) and 12% (III) for every 10% change of hematocrit. Instruments II and IV show that temperature has a marked influence on the readings; the same is true for oxygen in instrument IV. In conclusion, only instrument (I) has met the requirements of accurate and precise blood glucose determinations in neonates.

Cardiopulmonary bypass temperature, hematocrit, and cerebral oxygen delivery in humans

The neurologic effects of warm heart operations is a subject of popular interest. The purpose of this study was to examine the adequacy of cerebral oxygenation during normothermic cardiopulmonary bypass and better define the relationship between hematocrit, temperature, and brain oxygen delivery. Cerebral blood flow, metabolic rate, and oxygen delivery were measured in 60 patients randomized to normothermic (37 degrees C) or hypothermic (27 degrees C) cardiopulmonary bypass. The nitrous oxide saturation technique of Kety and Schmidt was used for cerebral blood flow determinations. Both temperature groups underwent moderate (31%) hemodilution. During normothermic cardiopulmonary bypass, cerebral blood flow increased secondary to hemodilution and decreased cerebral vascular resistance; a normal matching of oxygen demand and delivery was maintained. During hypothermic bypass, hemodilution and hypothermia had essentially equal, opposing effects on cerebral vascular resistance and blood flow. With hypothermia, brain oxygen demand and delivery were both reduced but not closely coupled. From the standpoint of global cerebral perfusion and oxygenation, our data support the practice of "warm" heart operations. It clarifies the marked influence of hematocrit on cerebral blood flow and delineates the interaction of temperature and hematocrit on cerebral oxygen delivery. It also suggests that additional investigation to better define "temperature-appropriate" hemodilution during cardiopulmonary bypass is indicated.

Influence of hematocrit and platelet count on impedance and reactivity of whole blood for electrical aggregometry

Previous studies have shown that differing qualities of blood specimen seem to influence whole blood electrical aggregometry (WBEA), making it difficult to standardize the method. The aim of this study was to investigate the impact of hematocrit (HCT) and platelet count (PLC) on in vitro platelet aggregation in citrated whole blood (CWB) in order to compensate for their possible effects on impedance aggregometry. Red blood cells and blood platelets were isolated from fresh citrated whole blood taken from 15 healthy donors (mean age = 26 years) and recombined to 20 physiologically relevant combinations of hematocrit and platelet count (HCT: 20–50, PLC: 100–500). Platelet aggregability was measured using WBEA with three different triggers. A special-purpose software package was used in this study, ensuring proper calibration, acquisition, and evaluation of analogue to digital converted data, allowing the calculation of a set of characteristic parameters of each impedance curve. Most of the linear regressions showed that all parameters significantly depend on HCT and PLC. Furthermore, we found interactions of both variables, making it impossible to focus on the effects of one of the investigated variables only. The outcome of this study is a set of dependences, allowing the calculation of regressions for in vitro aggregation in whole blood, enabling a comparison of blood of any quality with each other, regardless of the variables HCT and PLC. Together with the previously defined dependence of sample age on WBEA data, this step should help to make this technique a more reliable and practicable clinical tool, making it suitable for daily routine investigations.

Influence of hematocrit on erythrocyte aggregation kinetics for suspensions of red blood cells in autologous plasma.

The influence of hematocrit on red blood cell aggregation was investigated using a modified automated Myrenne Aggregometer System. Hematocrit values ranged from 20-70% at 10% increments, and were produced by resuspending washed red cells in autologous plasma. The Myrenne System produced seven kinetic parameters of red cell aggregation. The results indicate that hematocrit (Hct) had a strong and nonlinear effect on erythrocyte aggregability. At both low and high hematocrit, the aggregation intensity (AI) tends to decrease, reaching a plateau at 40% hematocrit. The disaggregation shear rate demonstrates an exponential relationship as In gamma TMIN = 3.29-0.0837 Hct. Time constants of the aggregation process such as T1/2, TSLOW and TFAST were rather inconsistent. The increase of hematocrit increased the rate of the fast phase aggregation and slightly slowed the secondary aggregation.

The influence of hematocrit, temperature and shear rate on the viscosity of blood from a high-energy-demand teleost, the yellowfin tuna Thunnus albacares

The high cardiac output, arterial blood pressure and cardiac energy demand of tuna make it likely that blood viscosity has an important influence on cardiovascular function. Furthermore, tuna regularly subject themselves to ambient temperature changes of 10°C or more during their daily vertical migrations. They can also maintain muscle temperatures several degrees Celsius above ambient and reach maximum muscle temperatures of approximately 15°C above ambient. The blood of tuna is, therefore, subjected to more frequent and rapid temperature changes than those that occur in other teleosts. Nothing is known, however, about the effects of temperature, shear rate or hematocrit on the viscosity of tuna blood. Viscosity of yellowfin tuna blood (hematocrits of 0­55 %) was measured at 15, 25 and 35°C and at shear rates of 45, 90, 225 and 450 s-1 using a cone-plate viscometer. As found for the blood of other vertebrates, viscosity increased with increasing hematocrit. Viscosity also increased nonlinearly with decreasing shear rate, until a shear rate of 90 s-1 was reached. There was no significant increase in viscosity when shear rate was decreased further, to 45 s-1. Because of the relatively flat hematocrit­viscosity curves, predicted optimal hematocrit curves were nearly flat above a hematocrit of approximately 30 %.

Influence of Hematocrit on Behavior of Ice Crystals and Human Red Blood Cells during Directional Solidification of Cell Suspensions.

Influence of Hematocrit on Behavior of Ice Crystals and Human Red Blood Cells during Directional Solidification of Cell Suspensions.

Sex-related and age-related differences in platelet function in vitro: influence of hematocrit

Even minor changes in the sodium citrate concentration of citrated plasma from young probands due to diverse hematocrit values were found to affect platelet functional activity following in vitro stimulation. There were no differences between men and women in the platelet aggregation and TXB 2 production of young probands with similar hematocrit values. Platelets from elderly persons virtually failed to respond to such changes in plasma sodium citrate. Mechanisms of increased platelet activity in the elderly are discussed. It is assumed that the age-related differences are caused by a more pronounced platelet response even to lower plasma calcium levels in citrated plasma.

Influence of hematocrit on quantitative analysis of "blood spots" on filter paper

Influence of hematocrit on quantitative analysis of "blood spots" on filter paper

Influence of hematocrit on tissue O2 extraction capabilities during acute hemorrhage.

This study was performed to test the hypothesis that tissue O2 extraction capabilities during hemorrhage may be greater when hematocrit (Hct) is initially reduced. Twenty-four anesthetized and splenectomized dogs were randomly assigned in three groups of eight dogs each: group 1 (Hct 40), 40-45% Hct; group 2 (Hct 30), 30-35% Hct; and group 3 (Hct 20), 20-25% Hct. In each animal, the desired Hct was obtained by normovolemic hemodilution using hydroxyethyl starch 450/0.7 and maintained throughout the experiment. O2 delivery (DO2) was progressively reduced by hemorrhage. At each step, DO2 and O2 consumption (VO2) were measured separately. Critical DO2 obtained from a plot of VO2 vs. DO2 was lower in the Hct 30 and Hct 20 groups than in the Hct 40 group [(in ml.min-1.kg-1) Hct 30, 7.9 +/- 2.2; Hct 20, 7.8 +/- 1.0; Hct 40, 10.4 +/- 1.1; P < 0.05]. Critical DO2 obtained from blood lactate levels was also significantly lower in the Hct 30 and Hct20 groups than in the Hct 40 group. Critical O2 extraction ratio was also greater in the Hct 30 and Hct 20 groups than in the Hct 40 group (Hct 30, 73.0 +/- 13.9%; Hct 20, 70.1 +/- 9.6%; Hct 40, 57.1 +/- 11.5%; P < 0.05). In the conditions of our study, moderate hemodilution was associated with an improvement of the O2 extraction capabilities of the body, probably related to the reduction in blood viscosity.

Influence of hematocrit on tumor oxygenation and sensitivity to radiation

Influence of hematocrit on tumor oxygenation and sensitivity to radiation

The influence of haematocrit and blood glucose on cerebral blood flow in normal and in diabetic rats.

Cerebral blood flow (CBF) was measured at varying haematocrit values in 8 streptozotocin-diabetic and in 7 control rats using the intracarotid 133Xe technique. A hyperbolic relationship between CBF and haematocrit was established for the individual rats in both groups. Diabetic animals showed a preserved CBF response to changes to haematocrit. In 10 normal rats, CBF was measured during acute hyperglycaemia induced by intraperitoneal glucose injection. A significant, inverse correlation was found between CBF and blood glucose. We conclude that the CBF response to changes in haematocrit and thereby in pO2 is preserved in experimental diabetes. Secondly, in acute hyperglycaemia CBF varies inversely with blood glucose, by mechanisms not fully understood.

The accuracy of pulse oximetry at two haematocrit levels.

The object of this study was to investigate the influence of haematocrit on the accuracy of pulse oximetry. Seven Swedish land race rabbits were studied. The oxygen saturation of haemoglobin was decreased step-wise using increasing fractions of nitrogen to the inspiratory gas. One pulse oximeter probe was attached on the front leg and another probe directly over the common carotid artery. The pulse oximeter readings (SpO2) were compared with simultaneous oxygen saturation analysis (SaO2) by a haemoximeter. The pulse oximeter measurements were performed at the haematocrit levels of approximately 40% and 11%, respectively. We found a good correlation between SpO2 and SaO2 in a wide range of the oxygen saturation, i.e. SaO2 26-100%. After haemodilution the correlation was improved in the range 86-100%, but not in the range 26-85%. No correlation between SpO2 and SaO2 was found when the sensor was attached directly over the artery during normal haematocrit levels. After haemodilution a better correlation was however obtained. These results indicate that the accuracy of pulse oximetry is dependent on the haematocrit level.

The Effect of Haematocrit on Reagent Strip Tests for Glucose

Four blood glucose reagent strips (BM-Test 1-44, Glucostix, Hypoguard GA, and Exactech), used in conjunction with measuring devices produced by the same manufacturer, were investigated with respect to the influence of haematocrit. The erythrocytes and plasma of fresh blood samples were separated, then remixed in different proportions to achieve a range of haematocrit values and the resulting specimens subjected to glucose assay. All the strip tests showed some influence of haematocrit, low haematocrits producing higher glucose results and vice versa, but some were much more affected than others. The Hypoguard GA was most affected and the BM-Test 1-44 least. In the worst case, glucose results differed by 49% from one end of the normal adult haematocrit range to the other.

Red cell trapping after ischemia and long-term kidney damage. Influence of hematocrit

The influence of the hematocrit (Hct) on the trapping of red blood cells (RBC) in the renal microvasculature and its effect on the long-term outcome following unilateral ischemia were investigated in the rat. The results showed that an increase in the duration of ischemia increased the RBC trapping, as measured by 51Cr-labeled erythrocytes, in a dose-dependent manner. At normal Hct (46%) the period of ischemia producing half-maximum RBC trapping was 45 minutes, whereas after hemodilution (Hct = 31%) or hemoconcentration (Hct = 60%) the corresponding periods were 80 and 25 minutes, respectively. Regarding the long-term outcome, 45 minutes of ischemia with a normal Hct was associated with a marked decrease in kidney weight, GFR and urine osmolarity after four weeks of recovery, which could be prevented to a large extent by hemodilution. Conversely, with hemoconcentration there was severe damage after only 25 minutes of ischemia. It is suggested that these long-term effects are attributable to RBC trapping in the microvasculature of the outer medulla, which may cause added ischemia in this area of the kidney. It is also suggested that cortical atrophy is secondary to the medullary injury, and is brought about to avoid extensive water and salt losses.

The influence of haematocrit on the cerebral circulation.

The influence of haematocrit on the cerebral circulation.

Influence of hematocrit on whole blood glucose levels: new evidence from marine mammals

The water content and glucose concentration in the whole blood of marine mammals were found to be correlated to red blood cell concentration. Because hematocrit (Hct) undergoes significant periodic shifts in these mammals during periods of apnea and/or diving, the measured values of whole blood glucose change due to alterations in Hct, independent of shifts in metabolite regulatory pathways. In contrast to humans, where red blood cell and plasma glucose concentrations are equivalent, in most other mammalian species red blood cell glucose concentration is much lower than that in plasma. Therefore, as Hct increases, the whole blood concentration of glucose must decrease in a linear manner, depending on the magnitude of the Hct change and the concentration of glucose in the blood cells. This study demonstrates that water and metabolite distribution must be considered when interpreting whole blood metabolite data. The results suggest that plasma or serum analysis of metabolites would avoid distribution problems. This is especially critical in species where Hct varies during the course of the experiment, as in exercising or diving mammals.

Influence of hematocrit on cardiopulmonary function after acute hemorrhage

Influence of hematocrit on cardiopulmonary function after acute hemorrhage

The influence of haematocrit on blood cyclosporin measurements in vivo.

The influence of haematocrit on blood cyclosporin measurements has been studied in 276 paired blood and plasma samples from 21 renal transplant patients. A highly significant correlation was found between blood and plasma cyclosporin concentrations, r = 0.8744, but the correlation between blood or plasma cyclosporin and haematocrit was not significant. The ratio of blood/plasma cyclosporin did not significantly increase with increasing haematocrit. It was concluded that in vivo the influence of haematocrit on the measurement of blood cyclosporin concentrations was negligible.

The influence of hematocrit on hemolysis by ultrasonically activated gas-filled micropores

In vitro studies of ultrasonic bioeffects typically employ cell number densities much lower than those present in vivo, which can lead to difficulties in interpretation and extrapolation. In this study, the influence of cell number density on the hemolytic effect of ultrasonic gas-body activation (a low-level form of cavitation) was investigated. Hydrophobic membranes with 4μm diameter gas-trapping micropores were immersed in saline suspensions of erythrocytes with hematocrits (HCT) from 0.001 to 0.3, and whole blood, and exposed to 1.7 MHz continuous-wave ultrasound in a 37°C saline-filled exposure bath. Significant hemolysis was observed for spatial peak intensities above about 45–90 mW/cm 2 for the 16 min exposures. The percentage of cells hemolysed tended to decrease with increasing hematocrit such that the number of cells hemolysed, which is proportional to the product of the hematocrit and the percent hemolysis, remained roughly constant. Readily observable in vitro effects may therefore become quite subtle when diluted, as for in vivo conditions, by large numbers of cells.

The prognostic value of haematocrit in acute stroke.

One hundred and twenty-two consecutive patients admitted with acute stroke in a carotid distribution had venous blood taken for haematocrit (Hct), haemoglobin (Hb), white cell count (WCC) and urea estimations. Patients were followed for 12 weeks to determine the influence of haematocrit upon fatality. There were 96 patients aged greater than or equal to 65 years and 26 patients less than 65 years. No association could be demonstrated between Hct levels and fatality at 4 or 12 weeks. Regression analysis demonstrated that only increasing age (P less than 0.05) and a raised WCC (P less than 0.005) were independent factors significantly associated with fatality at both 4 and 12 weeks. In the elderly stroke patient (greater than or equal to 65 years) only WCC was significantly associated with fatality (P less than 0.005). Haematocrit levels are of no prognostic value for fatality in acute stroke. A raised white cell count is an important and independent prognostic factor for fatality at both 4 and 12 weeks following stroke.