Low rbc and hematocrit
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Understanding Low RBC and Hematocrit Levels: Causes and Implications
Low Hematocrit and Bleeding Time
Low hematocrit levels are often overlooked as a cause of prolonged bleeding time in anemic patients. Research indicates a clear relationship between hematocrit and bleeding time, suggesting that transfusion of red blood cells (RBCs) can correct prolonged bleeding times in these patients1. Two main hypotheses explain this phenomenon: RBCs help disperse platelets towards the blood vessel wall, promoting interaction and hemostasis, and RBCs release adenosine diphosphate (ADP) during hemolysis, which activates platelets1.
Hematocrit and Platelet Interaction
Experimental studies using the Baumgartner perfusion technique have shown that both RBC and platelet counts significantly influence platelet adhesion and aggregate formation on the subendothelium. At low hematocrit levels, platelet aggregate formation is impaired, especially when platelet counts are also low, indicating a negative synergistic effect2. This underscores the importance of maintaining both normal hematocrit and platelet counts for optimal hemostasis in anemic and thrombocytopenic patients2.
Hematocrit and Thrombus Formation
In vivo studies on primates have demonstrated that variations in hematocrit levels affect thrombus formation depending on local blood flow conditions. Under low flow conditions, lower hematocrit levels were associated with increased platelet thrombus volume, while higher hematocrit levels correlated with increased RBC incorporation into thrombi3. This suggests that hematocrit levels can either promote or inhibit thrombus accumulation based on the flow environment3.
RBC Aggregation and Blood Viscosity
RBCs tend to form aggregates under low shear rates, which affects blood viscosity. Studies using microfluidic systems have shown that at low hematocrit levels, RBC aggregate sizes increase significantly as shear rates decrease, leading to higher blood viscosity4. This non-Newtonian behavior of blood is crucial for understanding microcirculation dynamics, especially in conditions of low hematocrit4.
Hematocrit in Low Birth Weight Infants
In very low birth weight infants, hematocrit levels correlate well with circulating RBC volume, although there is some uncertainty in estimating RBC transfusion needs based on hematocrit alone5. This highlights the need for more precise methods to assess RBC volume in clinical settings for better management of anemia in these infants5.
Hematocrit and Platelet Accumulation
Elevated hematocrit levels enhance platelet accumulation following vascular injury, promoting thrombus formation. Experimental models have shown that higher hematocrit levels increase the rate of platelet deposition and thrombus growth, suggesting that maintaining normal hematocrit levels could reduce the risk of arterial thrombosis7.
Conclusion
Low RBC and hematocrit levels have significant implications for bleeding time, platelet interaction, thrombus formation, and blood viscosity. Understanding these relationships is crucial for the effective management of anemia and related conditions. Maintaining optimal hematocrit and platelet levels is essential for ensuring proper hemostasis and reducing the risk of thrombotic events. Further research and improved diagnostic methods are needed to better manage these conditions, especially in vulnerable populations such as very low birth weight infants.
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Most relevant research papers on this topic
The role of the hematocrit in bleeding.
Low hematocrit can prolong bleeding time in anemic patients, and transfusion of red blood cells may help correct this issue.
Experimental basis for the use of red cell transfusion in the management of anemic‐thrombocytopenic patients
Red cell transfusion is essential for optimal hemostasis in anemic and thrombocytopenic patients, as it normalizes both platelet count and hematocrit levels for optimal hemostasis.
Non-RCT
Highly CitedEffects of red blood cell concentration on hemostasis and thrombus formation in a primate model.
Low hematocrit levels in baboons can promote or inhibit thrombus formation depending on local flow conditions, but do not affect hemostasis.
Non-RCT
Animal StudyHighly CitedRed blood cell aggregates and their effect on non-Newtonian blood viscosity at low hematocrit in a two-fluid low shear rate microfluidic system
Lowering shear rate significantly increases red blood cell aggregate sizes, which in turn increase blood viscosity at low hematocrit, demonstrating non-Newtonian behavior in microcirculation.
In Vitro Study
Rigorous JournalHighly CitedHematocrit Correlates Well with Circulating Red Blood Cell Volume in Very Low Birth Weight Infants
The correlation between hematocrit and circulating red blood cell volume is strong in older stable very low birth weight infants, but clinically important uncertainty remains in estimating circulating RBC volume and transfusion needs.
Observational StudyMicrofluidic-Based Measurement Method of Red Blood Cell Aggregation under Hematocrit Variations
The proposed microfluidic-based measurement technique effectively measures red blood cell aggregation under continuous hematocrit variations, especially by quantifying the EAI.
Elevated hematocrit enhances platelet accumulation following vascular injury.
Elevated hematocrit promotes arterial thrombosis by enhancing platelet accumulation at the site of vessel injury, suggesting maintaining a normal hematocrit may reduce arterial thrombosis risk in humans.
Non-RCTAnimal StudyHighly CitedExome Genotyping Identifies Pleiotropic Variants Associated with Red Blood Cell Traits.
16 new RBC variants were identified, revealing new genes involved in human erythropoiesis and pleiotropy in complex human traits.
Meta-AnalysisRigorous JournalHighly CitedLocal Hematocrit Fluctuation Induced by Malaria-Infected Red Blood Cells and Its Effect on Microflow
Malaria-infected red blood cells cause temporary local hematocrit elevations and contribute to the increase of cell free layer in microvessels, affecting blood flow and hematologic diseases.
Rigorous JournalToward noninvasive measurement of blood hematocrit using spectral domain low coherence interferometry and retinal tracking.
The novel instrument combines spectral domain low coherence interferometry and retinal tracking to noninvasively measure blood hematocrit in human retinal vessels, with results within the normal clinical range.
In Vitro Study