Blood pressure and blood viscosity are not correlated in normal healthy subjects

Components of the Complete Blood Count as a Risk Predictor for Incident Hypertension in a Large Taiwanese Population Follow-up Study

BACKGROUND

Previous studies investigating the relationship between hypertension (HT) and hematological parameters report inconsistent results, and most them included a small number of participants or only conducted a cross-sectional analysis of 1 or 2 hematological factors. Moreover, no large cohort follow-up studies have investigated this topic. The aim of this longitudinal study was to explore associations between components of the complete blood count (CBC) and incident HT using data from a large Taiwanese biobank.

METHODS AND RESULTS

Hematological parameters including white blood cell (WBC) count, red blood cell (RBC) count, hemoglobin, hematocrit (HCT), and platelet count were evaluated. We included 21,293 participants who did not have HT at baseline and followed them for a mean period of 3.9 years. During follow-up, 3,002 participants with new-onset HT (defined as incident HT) were identified. Univariable analysis revealed that high WBC count, high RBC count, high hemoglobin, high HCT, and low platelet count were associated with incident HT. Multivariable analysis after adjusting potential confounding factors found high WBC count (odds ratio [OR], 1.057; 95% confidence interval [CI], 1.028 to 1.087; P<0.001) and high HCT (OR, 1.023; 95% CI, 1.010 to 1.036; P<0.001) were still significantly associated with incident HT.

CONCLUSIONS

High WBC count and high HCT were associated with incident HT.

Positive Association between Hemoglobin Concentration and Blood Pressure in Adults: A Cross-Sectional Study Based on Rafsanjan Cohort Study

Introduction

Identification of factors associated with blood pressure (BP), including hemoglobin, can be used in diagnosing, controlling, and predicting the prognosis of patients. This study aims to investigate the cross-sectional association between hemoglobin concentration and BP in people aged 35-70 years in a cohort study of Rafsanjan, Iran.

Method

This cross-sectional study was conducted on 9398 urban and rural population of Rafsanjan adult cohort study as a part of the prospective epidemiological research studies in Iran (PERSIAN). Demographic information, medical history, history of smoking and alcohol intake, systolic and diastolic BP, and hemoglobin concentration were collected. A logistic regression test was performed to evaluate the relationship between hemoglobin concentration and BP in 4 unadjusted and adjusted models based on demographic indicators, clinical and laboratory findings using SPSS.24 software and SAS software version 9.2.

Results

The mean age of the participants was 49.78 ± 9.53 years, and 53.2% (5002 people) were women. Adjusted models 3 and 4 showed a positive association between BP and hemoglobin. For each unit increase in hemoglobin, the odds ratio (OR) of BP in the adjusted model 3 was 1.062 (95% CI: 1.005-1.121), and in the adjusted model 4, it was 1.090 (95% CI: 1.031-1.153).

Conclusion

Based on the results, the positive trend of BP and hemoglobin levels may indicate the need to pay more attention to these people as higher-risk groups for hypertension.

Blood Rheology Alterations in Patients with Cardiovascular Diseases

Blood rheology is an important determinant of blood flow but is probably one of the most neglected areas in clinical literature and practice. Blood viscosity changes according to shear rates and depends on cellular and plasma factors. RBCs' aggregability and deformability are the main determinants of local flow characteristics in areas with lower and higher shear rates, but plasma viscosity is the main regulatory factor of flow resistance in the microcirculation. In individuals with altered blood rheology, the mechanical stress to vascular walls induces endothelial injury and vascular remodelling, and promotes atherosclerosis. Increased values of whole blood viscosity and plasma viscosity are correlated with cardiovascular risk factors and adverse cardiovascular events. The long-term effects of physical exercise can produce a hemorheological fitness that protects against cardiovascular diseases.

Two Cases of Severe Hypertension in JAK2 Mutation-Positive Myeloproliferative Neoplasms

Background

Myeloproliferative neoplasms are a heterogeneous group of disorders resulting from the abnormal proliferation of one or more terminal myeloid cells—established complications include thrombosis and haemorrhagic events; however, there is limited evidence to suggest an association with arterial hypertension. Herein, we report two independent cases of severe hypertension in JAK2 mutation-positive myeloproliferative neoplasms. Case Presentations. Case 1: a 39-year-old male was referred to our specialist hypertension unit with high blood pressure (BP) (200/120 mmHg), erythromelalgia, and headaches. We recorded elevated serum creatinine levels (146 μM) and panmyelosis. Bone marrow biopsy confirmed JAK2-mutation-positive polycythaemia vera. Renal imaging revealed renal artery stenosis. Aspirin, long-acting nifedipine, interferon-alpha 2A, and renal artery angioplasty were employed in management. BP reached below target levels to an average of 119/88 mmHg. Renal parameters normalised gradually alongside BP. Case 2: a 45-year-old male presented with high BP (208/131 mmHg), acrocyanosis, (vasculitic) skin rashes, and nonhealing ulcers. Fundoscopy showed optic disc blurring in the left eye and full blood count revealed thrombocytosis. Bone marrow biopsy confirmed JAK2-mutation-positive essential thrombocytosis. No renal artery stenosis was found. Cardiac output was measured at 5 L/min using an inert gas rebreathing method, providing an estimated peripheral vascular resistance of 1840 dynes/s/cm⁵. BP was well-controlled (reaching 130/70 mmHg) with CCBs.

Conclusions

These presentations highlight the utility of full blood count analysis in patients with severe hypertension. Hyperviscosity and constitutive JAK-STAT activation are amongst the proposed pathophysiology linking myeloproliferative neoplasms and hypertension. Further experimental and clinical research is necessary to identify and understand possible interactions between BP and myeloproliferative neoplasms.

Association of Hemoglobin and Blood Pressure in a Chinese Community-Dwelling Population

This study investigated the relationship between hemoglobin (Hb) level and blood pressure in a Chinese community-dwelling population with normal glucose metabolism. Hb, fasting plasma glucose, glycated Hb A1c, hepatic and renal function, lipid, electrolytes, and anthropometric parameters were measured. Hb level was found to be positively correlated with systolic (SBP; r = 0.075, p < 0.001) and diastolic (DBP; r = 0.272, p < 0.001) blood pressure in the cohort. The relationship was not affected by age, BMI, serum creatinine (Cr), and low-density lipoprotein (LDL) in both males and females. Multivariate stepwise regression showed that age (β = 0.556, p < 0.001), BMI (β = 1.107, < 0.001), Hb (β = 0.082, p < 0.001), Cr (β = -0.032, p < 0.001), and LDL (β = 1.023, p < 0.001) were independent factors for SBP, and Hb (β = 0.168, p < 0.001), BMI (β = 0.519, p = 0.001), and LDL (β = 0.331, p < 0.001) for DBP. Hb level is positively associated with both SBP and DBP in a Chinese community-dwelling population with normal glucose metabolism.

Blood Viscosity, Glycemic Markers and Blood Pressure: A Study in Middle-Aged Normotensive and Hypertensive Type 2 Diabetics

Altered blood viscosity (BV) may affect blood pressure (BP) and develops further complications in diabetes. A case-control study was performed to examine the relationship of erythrocyte sedimentation rate (ESR), hematocrit, fibrinogen, and BV with glycemic markers and BP in middle-aged normotensive and hypertensive type 2 diabetic patients and healthy controls. A total of 145 participants between age group 30-50 years divided into three groups; controls (n = 60), type 2 diabetes mellitus (T2DM, n = 55), and T2DM with hypertension (T2DM + HTN, n = 30). ESR and hematocrit were determined by Wintrobe's method. Plasma fibrinogen was measured using Lempert method and BV calculated using Merill's formula. T2DM and T2DM + HTN patients had higher fasting plasma glucose (FPG), glycated hemoglobin (HbA1c), systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP), ESR, and fibrinogencompared to controls. In both male and female SBP, DBP, MAP, FPG, and HbA1c were significantly higher in T2DM and T2DM + HTN groups, compared to controls. Further, linear regression analysis revealed a positive association of ESR and fibrinogen with SBP, DBP, MAP, FPG, HbA1c, and positive diabetic status in all participants. Also, in the same analysis, BV showed a positive association with SBP, DBP, and MAP. The association of ESR and fibrinogenwith glycemic markers and BP in diabetes supporting the value of emerging marker's for early prediction of T2DM and hypertension.

Blood Pressure and Haematological Indices in Twelve Communities in Ashanti, Ghana

Hypertension is the most important risk factor for cardiovascular mortality and morbidity in Sub-Saharan Africa. In western populations, high haemoglobin levels are associated with raised BP unlike in Sub-Saharan Africa where there is a paucity of data. Our study examines the association between haematological indices with BP variables. Weight, height, BP, and whole blood indices of viscosity (Hb, haematocrit, RBC count, and MCV) were measured in 921 adults (340 men, 581 women; aged 40-75) in 12 communities in Ghana. Mean values for Hb (12.3 g/dl ± 1.7 SD), haematocrit (36.7% ± 5.2), RBC (4.10 million/μL ± 0.64), and MCV were lower than reference values used in Sub-Saharan Africa. Mean BMI was 21.1 ± 4.1 indicating a lean population. Systolic BP increased by 1.0 mmHg (95% CI 0.5-1.5), p < 0.001, for women and 0.5 (0.1-1.0), p = 0.027, for men per unit increase in haematocrit. Similar relationships were found for Hb and RBC but not for MCV or platelets. The relationships were weaker when adjusted for BMI, 0.7 mmHg (0.2-1.2) in women and 0.5 (0.0-1.0) in men. Findings for diastolic BP were similar. Overall haematological indices were low. We have found a significant, positive relationship between BP, Hb, Haematocrit, and RBC count in our population.

Posttransfusion Increase of Hematocrit per se Does Not Improve Circulatory Oxygen Delivery due to Increased Blood Viscosity

BACKGROUND

Blood transfusion is used to treat acute anemia with the goal of increasing blood oxygen-carrying capacity as determined by hematocrit (Hct) and oxygen delivery (DO2). However, increasing Hct also increases blood viscosity, which may thus lower DO2 if the arterial circulation is a rigid hydraulic system as the resistance to blood flow will increase. The net effect of transfusion on DO2 in this system can be analyzed by using the relationship between Hct and systemic blood viscosity of circulating blood at the posttransfusion Hct to calculate DO2 and comparing this value with pretransfusion DO2. We hypothesized that increasing Hct would increase DO2 and tested our hypothesis by mathematically modeling DO2 in the circulation.

METHODS

Calculations were made assuming a normal cardiac output (5 L/min) with degrees of anemia ranging from 5% to 80% Hct deficit. We analyzed the effects of transfusing 0.5 or more units of 300 cc of packed red blood cells (PRBCs) at an Hct of 65% and calculated microcirculatory DO2 after accounting for increased blood viscosity and assuming no change in blood pressure. Our model accounts for O2 diffusion out of the circulation before blood arriving to the nutritional circulation and for changes in blood flow velocity. The immediate posttransfusion DO2 was also compared with DO2 after the transient increase in volume due to transfusion has subsided.

RESULTS

Blood transfusion of up to 3 units of PRBCs increased DO2 when Hct (or hemoglobin) was 60% lower than normal, but did not increase DO2 when administered before this threshold.

CONCLUSIONS

After accounting for the effect of increasing blood viscosity on blood flow owing to increasing Hct, we found in a mathematical simulation of DO2 that transfusion of up to 3 units of PRBCs does not increase DO2, unless anemia is the result of an Hct deficit greater than 60%. Observations that transfusions occasionally result in clinical improvement suggest that other mechanisms possibly related to increased blood viscosity may compensate for the absence of increase in DO2.

Cross-sectional and longitudinal association between hemoglobin concentration and hypertension: A population-based cohort study

We investigated the cross-sectional and longitudinal associations between hemoglobin concentration and hypertension in a Korean population.Between 2006 and 2013, we examined 4899 participants with mean age of 56.6 years (range 35-88 years) from a rural community. We excluded 298 participants with a history of myocardial infarction or stroke and 264 participants with very low hemoglobin levels (men: <13.3 g/dL; women: <11.6 g/dL). Finally, we performed a cross-sectional analysis on 1629 men and 2708 women. Longitudinal associations were evaluated in 654 men and 1099 women, after excluding 2584 people with hypertension at baseline and those who did not participate in follow-up examinations. Hypertension was defined as systolic blood pressure ≥140 mm Hg, diastolic blood pressure ≥90 mm Hg, or use of antihypertensive treatment.The mean hemoglobin level was significantly higher in people with hypertension than in those without hypertension (P = 0.002 for men, P = 0.006 for women). On cross-sectional analysis, the odds ratio (95% confidence interval) for hypertension per 1 standard deviation increase in hemoglobin concentration (1.2 g/dL) was 1.11 (1.05-1.18) before adjustment and 1.20 (1.09-1.32) after adjusting for age, sex, body mass index, kidney markers, lifestyle factors, and comorbidities. On longitudinal analysis, the relative risk (95% confidence interval) for incident hypertension per 1 standard deviation increase in hemoglobin concentration was 1.09 (0.96-1.23) before adjustment and 0.91 (0.78-1.08) after adjusting for age, sex, body mass index, lifestyle factors, baseline blood pressure, baseline comorbidities, and baseline kidney markers.This study suggests that hemoglobin per se does not cause hypertension development.

Relationships between systemic vascular resistance, blood rheology and nitric oxide in children with sickle cell anemia or sickle cell-hemoglobin C disease

Vascular function has been found to be impaired in patients with sickle cell disease (SCD). The present study investigated the determinants of systemic vascular resistance in two main SCD syndromes in children: sickle cell anemia (SCA) and sickle cell-hemoglobin C disease (SCC). Nitric oxide metabolites (NOx), hematological, hemorheological, and hemodynamical parameters were investigated in 61 children with SCA and 49 children with SCC. While mean arterial pressure was not different between SCA and SCC children, systemic vascular resistance (SVR) was greater in SCC children. Although SVR and blood viscosity (ηb) were not correlated in SCC children, the increase of ηb (+18%) in SCC children compared to SCA children results in a greater mean SVR in this former group. SVR was positively correlated with ηb, hemoglobin (Hb) level and RBC deformability, and negatively with NOx level in SCA children. Multivariate linear regression model showed that both NOx and Hb levels were independently associated with SVR in SCA children. In SCC children, only NOx level was associated with SVR. In conclusion, vascular function of SCC children seems to better cope with higher ηb compared to SCA children. Since the occurrence of vaso-occlusive like complications are less frequent in SCC than in SCA children, this finding suggests a pathophysiological link between the vascular function alteration and these clinical manifestations. In addition, our results suggested that nitric oxide metabolism plays a key role in the regulation of SVR, both in SCA and SCC.

Influence of serological factors and BMI on the blood pressure/hematocrit association in healthy young men and women

The association between mean arterial blood pressure (MAP) and hematocrit (Hct) as a surrogate for blood viscosity was investigated in a young (average 20.0±2.3 years), healthy population of 174 men and 442 women. Health status was assessed by clinical examination and serological evaluation. Individuals with severe anemia or hemoconcentration, prior traumas or major surgical intervention, smokers, and pregnant or lactating women were excluded from the study. The MAP/Hct association was positive and significant (P=0.04) for women and negative, albeit not significantly so, for men. The MAP/Hct association was also evaluated in subgroups of the same population with a progressive step-by-step exclusion of: individuals with cholesterol >200 mg/dL; triglycerides >200 mg/dL; body mass index >25 kg/m(2); and glucose >100 mg/dL. This consecutively reduced the strength of the positive MAP/Hct association in women, which became negative - although not significantly so - when all anomalously high factors were excluded. The same trend was found in men. Our study indicates that previously reported positive trends in the relationship between the MAP and Hct in the population are not present in a young, healthy population of men or women that excludes individuals with the confounding factors of above normal serological values and BMI.

Association between the hemoglobin levels and hypertension in relation to the BMI status in a rural Japanese population: the Nagasaki Islands Study

OBJECTIVE

The hemoglobin levels and blood pressure has been reported in a few studies, and a positive association between the hemoglobin levels and the body mass index (BMI) status has also been documented. A higher BMI may therefore affect the association between the hemoglobin levels and hypertension. However, no published studies have examined this association in relation to the BMI status. The primary purpose of this study was to assess the association between the hemoglobin levels and hypertension in relation to the BMI status.

METHODS

A cross-sectional study of 3,203 non-anemic subjects (1,191 men and 2,012 women, 30-79 years old) who were undergoing general health checkups was conducted.

RESULTS

A positive association between the hemoglobin levels and hypertension was established for both men and women. For a one SD (standard deviation) increment in hemoglobin, the multivariable odds ratio (ORs) and 95% confidence interval (CIs) for hypertension were 1.21 (95%CI: 1.05-1.40) for men and 1.25 (95%CI: 1.13-1.39) for women. We also found that a significant association was confined to the participants with a BMI of <25 kg/m(2). Among the participants with a BMI of <25 kg/m(2), the multivariable ORs and 95% CIs for hypertension of a one SD increment in hemoglobin were 1.34 (95%CI: 1.12-1.60) for men and 1.31 (95%CI: 1.16-1.47) for women. Meanwhile, among those with a BMI of ≥25 kg/m(2), the corresponding values were 1.01 (95%CI: 0.79-1.30) and 1.09 (95%CI: 0.87-1.37).

CONCLUSION

An independent positive association between the hemoglobin levels and the risk of hypertension was observed for both non-anemic Japanese men and women, confined to participants with a BMI of <25 kg/m(2).