Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HEMATOCRIT”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed2004

Hematocrit-lowering effect following inactivation of renin-angiotensin system with angiotensin converting enzyme inhibitors and angiotensin receptor blockers.

Several clinical and experimental observations suggest that an intact and activated renin-angiotensin system (RAS) may be an important determinant of erythropoiesis in a variety of clinical conditions, including hypertension, chronic renal insufficiency or failure, chronic obstructive pulmonary disease, and congestive heart failure. Accordingly, RAS inactivation may confer susceptibility to the hematocrit-lowering effects of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. Indeed, a dose-dependent decrease in hematocrit is observed within the first month of such therapy. In the majority of patients with hypertension decreases in hematocrit values after RAS inactivation are small and not clinically important. In extreme conditions, however, such as erythrocytosis after successful renal transplantation, secondary polycythemia of chronically hypoxemic COPD patients, erythrocytosis associated with renovascular hypertension, severe cardiac or renal failure, the hematocrit-lowering effect of angiotensin-converting enzyme inhibitors and angiotensin receptor blocker may be profound and even lead to or worsen anemia. Hematocrit reaches its nadir value within three months, and then it remains stable during long-term observations. After discontinuation of RAS blockade, hematocrit values rise gradually over the next three to four months towards the pretreatment levels. The mechanism(s) related to this phenomenon is not yet fully understood, but angiotensin II seems to be responsible for inappropriately sustaining secretion of erythropoietin despite hematocrit elevation and capable to directly stimulate the erythroid progenitors in bone marrow to produce erythrocytes.

Angiotensin Receptor Antagonists↗
PubMed2006

Hematocrit, independent of chronic kidney disease, predicts adverse cardiovascular outcomes in chinese patients with type 2 diabetes.

OBJECTIVE: Anemia and chronic kidney disease (CKD) are risk factors for cardiovascular diseases in diabetes. We examined the association between hematocrit, stratified by the presence of CKD, and cardiovascular events in a cohort of Chinese subjects with type 2 diabetes. RESEARCH DESIGN AND METHODS: A total of 3,983 patients who underwent assessment for diabetes complications were recruited. Subjects were categorized into five groups. Group I included subjects with hematocrit below the normal sex-specific range. The cutoff points for groups II-V were selected to represent the distribution of the hematocrit for each sex. CKD was defined by the estimated glomerular filtration rate <60 ml/min per 1.73 m(2). Cardiovascular events were defined as cardiovascular mortality and morbidity, including new onset of myocardial infarction, acute coronary syndrome, revascularization, heart failure, and stroke requiring hospitalization. RESULTS: A total of 294 subjects (7.4%) developed cardiovascular events during the median of 36.4 months. The rate of cardiovascular events was highest in subjects with low hematocrit (group I, 18.6%) compared with group V (3.4%, P < 0.001). The multivariate-adjusted hazard ratio for cardiovascular events diminished with increasing hematocrit (group I, 1.0; group II, 0.73 [95% CI 0.51-1.04]; group III, 0.57 [0.39-0.83]; group IV, 0.61 [0.39-0.95]; and group V, 0.36 [0.17-0.79]). After stratifying by the presence of CKD, the previously observed reduction in the risk of developing cardiovascular events with increasing hematocrit was abolished in the cohort with CKD but persisted in the non-CKD cohort. CONCLUSIONS: In Chinese subjects with type 2 diabetes, low levels of hematocrit and the presence of CKD are associated with increased risk of developing adverse cardiovascular events.

Adult↗
PubMed1990

Blood viscosity and optimal hematocrit in narrow tubes.

Blood viscosity in normal adults was measured in glass tubes with diameters of 50, 100 and 500 microns for a wide range of adjusted feed hematocrits (15-70%). Blood viscosity decreased at each of the adjusted feed hematocrits when going from a 500-micron tube to a 50-micron tube. The viscosity reduction increased with increasing hematocrit. The steepness in the hematocrit-viscosity curves decreased with decreasing tube diameter. Erythrocyte transport efficiency (hematocrit/blood viscosity) was calculated to estimate the optimal hematocrit for oxygen transport. Optimal hematocrit averaged 38% in 500-micron tubes, 44% in 100-micron tubes and 51% in 50-micron tubes. Our results suggest that the strong Fåhraeus-Lindqvist effect at high hematocrits may help to maintain oxygen transport in polycythemic patients as long as the driving pressure is sufficient.

Adult↗
PubMed1997

Do hematocrit and serum fibrinogen influence transcranial Doppler measurements?

To investigate the effect of hematocrit and serum fibrinogen on transcranial Doppler ultrasound (TCD) measurements, we performed, TCD tests and measured hematocrit and serum fibrinogen concentrations in 112 healthy adult volunteers. The mean velocities of the middle cerebral (r = -.37, p < .0001), internal carotid at siphon (r = -.14, p < .05) and cervical level (r = -.14, p < .05), vertebral (r = -.21, p < .005) and the basilar artery (r = -.33, p < .001) were significantly and inversely correlated with hematocrit, while serum fibrinogen weakly affected the mean velocities of the internal carotid artery. The subjects with low hematocrit (< or = 40%) showed significantly higher mean velocities of the middle cerebral, vertebral and basilar arteries than those with high hematocrit (> 40%). Considering the influence of the subject's age and gender, hematocrit is the strongest factor influencing the velocities of the middle cerebral and the basilar artery. These results suggest that hematocrit is an important variable for TCD measurements of the cerebral blood velocities and should be taken into account in TCD application.

Adult↗
PubMed1993

Clinical comparisons of continuous venous oxygen saturation and hematocrit monitors in pediatric surgery.

Continuous venous oxygen saturation and hematocrit values are important parameters in assessing patient status while on cardiopulmonary bypass. Two devices used to measure continuous venous oxygen saturation while on cardiopulmonary bypass were compared to a control. The Bentley Oxysat meter and the Medtronic MX2 Oxygen Saturation and Hematocrit System were compared to the ABL500 blood gas monitor. The continuous hematocrit readings from the MX2 system were compared to spun hematocrits. Twenty-nine pediatric patients ranging from 2.3kg-43.3kg were randomly selected. In-line optical transmission cells used were 1/4" or 3/8" depending upon the patient's blood flow requirements. A total of 163 data points were analyzed at different blood flow rates, temperatures, and hematocrits. The venous oxygen saturation values obtained from the Oxysat and the MX2 devices correlated well with the ABL500 over the entire range of blood flows, temperatures, and hematocrits. All correlation coefficients were greater than 0.89. The correlation between the MX2 device and the spun hematocrit varied with temperature ranges. The correlation coefficient tended to decrease with decreasing temperature. We conclude that these devices are important adjuncts to bypass as long as their limitations are understood.

Blood Gas Analysis↗
PubMed1999

Evaluation of acquired platelet dysfunctions in uremic and cirrhotic patients using the platelet function analyzer (PFA-100 ): influence of hematocrit elevation.

BACKGROUND AND OBJECTIVE: Patients with end-stage renal disease or advanced cirrhosis develop bleeding disorders characterized by defective interaction of platelets with damaged subendothelium. The anemia associated with both clinical entities has a negative influence on hemostasis. We evaluated alterations of platelet function in patients suffering from end-stage renal disease (n=21) or hepatic cirrhosis (n=20) using standard aggregometric techniques and the recently developed platelet function analyzer (PFA-100 ). The impact of low hematocrit was also analyzed. DESIGN AND METHODS: The hemostatic capacity of platelets was tested in the PFA-100 using citrated blood and standard cartridges containing collagen-ADP (COL-ADP) or collagen-epinephrine (COL-Epi). The hemodynamic influence of hematocrit was also evaluated in blood aliquots in which hematocrit was experimentally increased by adding red blood cells from the same patient. RESULTS: Aggregation studies demonstrated abnormal responses to several agonists in both group of patients. Closure times obtained by the PFA-100 for control blood samples were 87+/-3 sec for COL-ADP and 113+/-5 sec with COL-EPi cartridges. Closure times in uremic and cirrhotic patients with average hematocrits of 0.26 and 0.27 respectively were significantly prolonged (139+/-12 and 125+/-14 sec, respectively with COL-ADP and 194+/-29 and 151+/-15 sec with COL-Epi cartridges). A 5% increase in the hematocrit caused a reduction in the closure time to 111+/-7 sec (COL-ADP) and 143+/-14 sec (COL-Epi) in the uremic group and to 86+/-4 sec (COL-ADP) and 115+/-16 sec (COL-Epi) in the cirrhotic group. Our studies confirm the platelet dysfunction in uremic and cirrhotic patients. INTERPRETATION AND CONCLUSIONS: The PFA-100 device proved to be useful for testing alterations of primary hemostasis in these acquired disorders and was sensitive enough to detect modifications in hemostasis caused by elevations in hematocrit. Conventional aggregometric tests were able to identify the intrinsic platelet abnormality in uremic and cirrhotic conditions, while the PFA-100 seemed more sensitive in detecting the negative influence of the hematocrit reduction.

Adult↗
PubMed1992

Evaluation of threshold doses of drug action in the horse using hematocrit values as an indicator.

This study was designed to explore the use of hematocrit values as possible indicators of the threshold doses of adrenergic drugs in the performance horse. Acepromazine, detomidine, and fluphenazine were tested for their effects on hematocrit values, with the threshold dose for these effects investigated. Hematocrit values were shown to be quite sensitive to the administration of acepromazine with doses as low as 50 micrograms/horse producing detectable depressions in hematocrit values for up to 2 hours. Increasing the dose increased the magnitude of the effect, but did not appear to prolong it, while in contrast, reducing the dose to below 25 micrograms/horse totally eliminated the effect. The alpha-2 agonist detomidine produced a similar depression in hematocrit values, although doses of 10 micrograms/kg or approximately 5 mg/horse, were needed to produce a measurable effect. The anti-psychotic fluphenazine, which is believed to be an illegally administered drug in race horses, had no significant effect on hematocrit values when comparable doses were administered. In addition, the results of monitoring the hematocrit values of six horses for 48 hours suggested that the variations seen may be partially related to circadian factors, with peak values occurring in the afternoon hours.

Acepromazine↗
PubMedDate not supplied

Prediagnostic hematocrit values and subsequent cancer risk.

In this prospective study, the association between hematocrit values measured in 1965-68 and subsequent cancer incidence was studied among 7737 Japanese-American men in Hawaii. With an increase in hematocrit levels, there was an increasing risk for lung cancer, especially squamous or small cell type, and for kidney cancer. However, a statistically significant trend remained only for kidney cancer after adjusting for smoking history. The relative risk for kidney cancer was 4.94 (95% confidence interval, 1.03-23.63) for subjects with hematocrit values of 47 or higher compared with those with hematocrit values of 43 or lower. In contrast, the risk of oral-pharyngeal cancer decreased with increasing hematocrit levels. With adjustment for cigarette smoking and alcohol intake, the relative risk for oral-pharyngeal cancer was 0.20 (95% confidence interval, 0.04-0.88) for subjects with hematocrit values of 47 or higher compared with those with hematocrit values of 43 or lower. The association with kidney or oral-pharyngeal cancer was not affected by the time interval between examination and diagnosis of these cancers (< or = 10 and > 10 years). Erythropoietin production by kidney tumors and micronutrient deficiencies in oral-pharyngeal cancer cases may partially account for these results.

Adult↗
PubMed1990

Hematocrit values in the CAPD/CCPD population: a report of the National CAPD Registry.

A survey of the National CAPD Registry population was conducted to assess the distribution of hematocrit levels in a large group of peritoneal dialysis patients, to characterize the anemia of the population, and identify factors which relate to variation in hematocrit levels. A random sample of 812 patients was selected from the Registry population. Information was provided on 608 patients. Characteristics of sampled patients were similar to the Registry population as a whole. The mean hematocrit level in this cohort was 29.4% and the median was 29% Recent peritonitis, time on CAPD, folate therapy, androgen therapy, and iron therapy had no obvious influence on hematocrit distributions. Significantly higher hematocrits were seen in males, whites, and patients with polycystic kidney disease. Significantly lower hematocrits were seen in surgically anephric patients and in patients who had received transfusions 60 days before the survey. Eighty-nine percent of patients had not received a transfusion 60 days prior to the survey. Some patients, especially those with hematocrits below the median, might benefit from recombinant erythropoietin therapy.

Anemia↗
PubMed1990

Hematocrit and residual renal creatinine clearance in patients undergoing continuous ambulatory peritoneal dialysis (CAPD).

In a recent report, the relationship between renal creatinine clearance and hematocrit in patients with renal creatinine clearances, ranging from 55 to 8 mL per min. per 1.73 square meters of body surface area, was analyzed. The authors of this study have performed a cross-sectional analysis of the relationship of hematocrit to residual renal creatinine clearance in patients on continuous ambulatory peritoneal dialysis (CAPD). The authors of this study wanted to examine whether or not these hematocrits fall within extrapolations of the published 95% confidence limits for males and females with renal failure prior to end-stage renal disease and dialytic intervention. Authors also compared regression intercepts at residual creatinine clearances of 0. Most of the CAPD patients had hematocrits within the upper half or above the extrapolated 95% confidence limits for the predialysis population. Within the CAPD population, there were no significant correlations of hematocrit with residual creatinine clearance at these lower ranges. The degree of scatter in the CAPD population for hematocrit values was similar to that in the predialysis population. Residual creatinine clearance appears to be a crude index of the increasing severity of multiple factors that may contribute to the anemia. CAPD appears to maintain or improve hematocrit as renal mass and function decline.

Anemia↗
PubMed1989

Viscous resistance to blood flow in solid tumors: effect of hematocrit on intratumor blood viscosity.

Blood flow rate in a vascular network is proportional to the arteriovenous pressure difference and inversely proportional to the geometric and viscous resistances. We have recently shown that the geometric resistance to blood flow increases with increasing tumor size and/or decreasing arterial pressure. In this study, the viscous resistance to blood flow within tumor microvasculature was determined by alternately perfusing mammary adenocarcinoma [R3230AC; N = 12; tumor weight, 2.2 +/- 1.6 (SD) g] ex vivo with Krebs-Henseleit solution and with RBC suspensions at hematocrits between 1 and 60%. Our results demonstrate that: (a) intratumor blood viscosity increases with increasing hematocrit; and (b) for fixed hematocrits between 10 and 60%, the intratumor blood viscosity is significantly reduced (P less than 0.0001) compared to bulk viscosity measured at shear rates of 460 s-1 using a cone/plate viscometer. However, this reduction of intratumor blood viscosity is not as pronounced as in a previous study of skeletal muscle. Further comparison shows that as arterial pressure is lowered, intratumor blood viscosity increases at a greater rate and at lower hematocrits than in normal tissues. We attribute the increased viscous resistance in tumor microvasculature to (a) a less pronounced Fahraeus effect (i.e., reduction in hematocrit in small vessels) and a less pronounced Fahraeus-Lindqvist effect (i.e., reduction in blood viscosity in small vessels) in dilated tumor microvessels compared to normal microvessels; (b) low shear rates (i.e., velocity gradients) associated with tumor vessels which may facilitate rouleaux formation at moderate pressures and even at low hematocrits; and (c) vascular fluid losses of 5-14% which may also increase microvessel hematocrit. We also propose that intratumor blood viscosity may be even higher in vivo than ex vivo due to the presence of WBC and cancer cells in vivo; considerably more rigid than RBC, these cells may cause increased viscous resistance and transient vascular stasis in tumors. The implications of these results in tumor blood flow modulation using chemical and physical agents are discussed.

Adenocarcinoma↗
PubMed1989

Correlates of preoperative hematocrit value in patients undergoing coronary artery bypass.

The patient's preoperative red cell volume and hematocrit value are among the strongest predictors of need for postoperative transfusion. We have determined the factors that correlate with preoperative hematocrit value. We performed multiple regression analysis with preoperative hematocrit value as the dependent variable. The factors that were significantly correlated with preoperative hematocrit value, in order of their decreasing contribution to variability, were sex, date of operation, preoperative hospital stay, weight, left ventricular end-diastolic pressure, age, smoking history, and recent myocardial infarction (less than 6 weeks). Factors that did not contribute significantly to predicting preoperative hematocrit value included ejection fraction, emergency operation, previous streptokinase use, number of coronary arteries diseased, body mass index (obesity), diabetes, height, body surface area, and history of percutaneous transluminal coronary angioplasty. The patient most likely to have a low preoperative hematocrit value can be characterized as a small, elderly, female nonsmoker with a recent myocardial infarction and elevated left ventricular end-diastolic pressure. The prevalence of low preoperative hematocrit value is increasing with time independent of other factors.

Aged↗
PubMed1988

Ingestion of grapefruit lowers elevated hematocrits in human subjects.

This study was based on in vitro observations that naringin isolated from grapefruit induced red cell aggregation and evidence that clumped red cells are removed from the circulation by phagocytosis. The effect on hematocrits of adding grapefruit to the daily diet was determined using 36 human subjects (12 F, 24 M) over a 42-day study. The hematocrits ranged from 36.5 to 55.8% at the start and 38.8% to 49.2% at the end of the study. There was a differential effect on the hematocrit. The largest decreases occurred at the highest hematocrits and the effect decreased on the intermediate hematocrits; however, the low hematocrits increased. There was no significant difference between ingesting 1/2 or 1 grapefruit per day but a decrease in hematocrit due to ingestion of grapefruit was statistically significant at the p less than 0.01 level.

Adult↗
PubMed1988

[Acute changes in hematocrit: their effect on flows in the great arteries of newborns].

To study the effect of acute hematocrit changes on the central circulation of human neonates, pulsed Doppler echocardiography was performed to evaluate flow velocities in the main pulmonary artery (PA) and the ascending aorta (Ao) five and seven hours of age in 16 polycythemic neonates (mean hematocrit of 68.1%), and in 12 normal neonates (mean hematocrit of 57.1%). All the polycythemic neonates were asymptomatic and underwent isovolumic partial exchange transfusion between five and seven hours of age to lower their mean hematocrit to 51.3%. Flow velocity integral per min (FVI/min) (cm/min), acceleration time (AT) (ms), and the ratio of pre-ejection period to ejection time (PEP/ET) were measured on the PA and Ao flow velocity tracings. Despite the significant differences in hematocrit, no significant difference was observed in any of their flow velocity indices at five hours age between the normal and polycythemic neonates. All flow velocity indices remained unchanged between five and seven hours of age in normal neonates. In polycythemic neonates, PA FVI/min and Ao FVI/min increased significantly between five and seven hours of age, reflecting increases in flow in both great arteries, while the difference between Ao FVI/min and PA FVI/min decreased, suggesting a reduction in a left-to-right shunt via the ductus arteriosus. Moreover, PA-AT increased and PA-PEP/ET decreased significantly, suggesting a decrease in pulmonary vascular resistance. These changes caused by an acute decrease in hematocrit resembled the changes in the central circulation previously reported to occur in normal neonates during the postnatal period. In conclusion, an acute decrease in hematocrit transiently accelerates physiological changes in the central circulation during the neonatal period.

Aorta↗
PubMed1987

Are physiological changes in capillary tube hematocrit related to alterations in capillary perfusion heterogeneity?

Average capillary tube hematocrit is hypothesized to be reduced below the mean systemic value as a result of heterogeneous distribution of blood flow among microvessels. Furthermore, capillary tube hematocrit changes with vasomotor state and these have been proposed to be due to concomitant changes in perfusion heterogeneity. We reasoned that if alterations in average capillary tube hematocrit were related to changes in perfusion heterogeneity, then mean capillary tube hematocrit should be inversely related both to the heterogeneity of capillary blood flows and to the heterogeneity of capillary hematocrit. These inferences were tested by comparing estimates of average capillary tube hematocrit (Ht) and the heterogeneities of capillary blood flow and Ht in vasoconstricted and vasodilated hamster tibialis anterior muscles. Ht was estimated from the number of red blood cells per unit capillary length (n/l); heterogeneity of capillary blood flow and heterogeneity of Ht were estimated by calculating the coefficient of variation of capillary red blood cell velocities (vrbc) and n/l, respectively. Average Ht varied with vasomotor state. However, there was no correlation between average Ht and the heterogeneity of vrbc, our index of capillary blood flow: in fact, the heterogeneity of vrbc was constant under all experimental conditions. The heterogeneity of Ht varied with vasomotor state, but not in inverse proportion to average Ht as was expected. From these observations we conclude that alterations in average capillary tube hematocrit are not due to concomitant alterations in perfusion heterogeneity.

Animals↗
PubMed1983

The effect of hematocrit on the clearance of small molecules during hemodialysis.

Data collected during the evaluation of a series of hemodialysers were analysed to see the effect of hematocrit on the clearance of urea and creatinine. All evaluations were performed on patients with a range of hematocrits with a mean close to 20%. The urea clearance of those in the upper half of the distribution curve (mean hematocrit 29.4%) was not significantly different from that of patients in the lower half of the distribution curve (mean hematocrit 16.9%) whether the clearance was studied at high or low blood flow rates and with hollow fibre or flat plate disposable hemodialysers. Likewise, there was no correlation between hematocrit and urea clearance by regression analysis. In contrast, the clearance of creatinine was affected by hematocrit being greater at lower hematocrit values. This difference was independent of blood flow rate and dialyser type and was confirmed by regression analysis.

Creatinine↗
PubMed1982

Glucose determinations in plasma and serum: potential error related to increased hematocrit.

This study reports the effect of increased hematocrit (packed cell volume) on the rate of decrease in plasma glucose during 6 h in blood specimens from seven newborns (cord blood) and heparin-treated blood specimens from eight adults. Mean hematocrits ranged frm 0.43 to 0.75 for the adults and from 0.51 to 0.81 for the infants. The decrease in glucose was related to time and to hematocrit. For example, in adults with a mean hematocrit of 0.43, glucose decreased from 890 +/- 40 mg/L to 570 +/- 30 mg/L (mean +/- SEM) at 6 h, whereas in adults with a mean hematocrit of 0.75, glucose decreased from 890 +/- 40 to 200 +/- 30 mg/L. In infants with a mean hematocrit of 0.51, glucose decreased from 1010 +/- 20 to 480 +/- 70 mg/L at 6 h; infants with a mean hematocrit of 0.81 had blood glucose decrease from 1010 +/- 20 to 50 +/- 30 mg/L. These results indicate that the incidence of hypoglycemia in infants with polycythemia may be overestimated, and emphasize the need for prompt handling of blood samples collected from newborns for glucose determinations.

Adult↗
PubMed1995

Analytical artifacts in hematocrit measurements by whole-blood chemistry analyzers.

Compact analyzers suited to near-patient testing estimate hematocrit by measuring the conductivity of undiluted blood. We evaluated the accuracy of hematocrit determination of one such analyzer (Instrumentation Laboratory BGE analyzer) against an automated cell counter (EPC) and packed cell volume (PCV) microhematocrit. When specimens (n = 34) from outpatient and ward patients were analyzed with all three methods, the BGE analyzer correlated well with both EPC and PCV hematocrit determinations (BGE = 1.00 PCV + 0.3%, S(y)/x = 2.0%), suggesting that all three methods are similar in performance for most patients. However, a patient with increased plasma osmolality showed significant decreases in BGE and PCV hematocrits relative to the EPC method. The differences in hematocrit measurements could be reproduced by adding solutes to blood in vitro or by modifying the plasma osmolality of rats in vivo. Samples from patients undergoing cardiac surgery, whose blood had large changes in protein concentration, showed discrepancies between hematocrits by conductivity and other methods; similar effects could be produced by changes in protein concentration or in vitro addition of polyethylene glycol. We conclude that conductivity measurements provide accurate hematocrit results for physiologically normal subjects but not for some intensive-care and surgical patients.

Animals↗