Hematocrit is the ratio of the volume of the red blood cell fraction (or all formed elements) to the total blood volume, expressed as a percentage. Simply put, this value, which is designated Ht, shows how viscous the blood is. If the hematocrit is elevated, it means it is thick.
Hematocrit is also called a special test tube (capillary) with divisions into which blood is collected and subjected to a centrifugation process for ten minutes at high speed. As a result, the formed elements are at the bottom, and the plasma is at the top. Today, in order to determine the hematocrit value, modern automatic devices are increasingly used - hemoanalyzers, which are more convenient to use and give a more accurate result.
Normally, Ht in an adult is about 40-45% of the total amount of circulating blood. The norms are different for women, men and children. An increase in hematocrit can be physiological or pathological.
The value of normal hematocrit in humans
The body of a healthy adult contains approximately 4.5-5 liters of blood. It contains formed elements and cells - red blood cells, platelets, leukocytes, as well as a liquid part called plasma.
Some blood components, for example, red blood cells, do not have all the necessary components of a human cell, losing them during the maturation process. Therefore, red blood cells and platelets are called blood cells, not cells.
In different categories of patients, the normal values of various parameters of the blood tested will differ. So, for most men, the hematocrit will be higher: 40-41%, and in some cases it can reach up to 51%, which is due to its slower renewal.
In healthy women, the hematocrit usually ranges from 36 to 42%. This is due to physiological features - due to regular menstrual bleeding, blood is renewed more often to replenish its volume. During pregnancy, from the 20th week, the indicator begins to decrease, which is also not considered a deviation.
In children, hematocrit differs at different age periods:
- 44-62% for newborns;
- 32-43% for babies up to three months;
- 36-43% for children under one year of age;
- 35-47% (up to 52% for boys) - in the first ten years.
In subsequent years, the hematocrit norm depends on gender and practically corresponds to the values of an adult.
Micronutrients for the hematopoietic system
Hematopoiesis - that is, hematopoiesis - is a set of stages in the transformation of a stem cell into one of the elements that make up the blood. Let us repeat that the role of vitamins B6, B9 and B12 and iron in these processes is a priority, and jumps in hct levels always one way or another lead to the conclusion about a lack of these substances.
In addition to these four, attention should be paid to other nutritional compounds.
- Vitamin E is a fat-soluble form and can accumulate in any tissue, but mainly in fat. Protects red blood cell membranes from damage due to oxidative stress;
- Vitamin C – adds iron to the process of hemoglobin synthesis, starting with the formation of red blood cells in the red bone marrow;
- Vitamin A (retinol) – helps transfer iron from “reserves”;
- Vitamin B2 (riboflavin) – helps not to remove the necessary iron prematurely through the genitourinary system;
- Vitamin D2 (ergocalciferol) - helps transport iron from storage cells to the red bone marrow, where hemoglobin is produced in the red blood cell;
- Copper - helps iron oxidize to the level of digestibility (ferrous);
- Omega 3 and Omega 6 fatty acids stimulate and regulate the formation of new cells in the process of erythropoiesis (the formation of red blood cells).
Often, if hct tests are questionable, you can turn to an additional blood test for vitamins and microelements that are involved in hematopoiesis. Based on detailed data, we can talk about developing a personal complex of micronutrients that will meet the needs within the framework of the individual characteristics of the body.
Methods for determining hematocrit
The indicator is determined as a percentage by calculating the amount of formed elements in whole blood. It is calculated using special instruments or manually.
Centrifugation using the Wintrobe method
The blood is exposed to centrifugal force for 10-30 minutes. The formed elements are heavier than plasma, so they settle to the bottom of the test tube. The hematocrit is determined by the ratio of sediment to the total volume of biomaterial.
Calculation of the indicator using the formula
The ratio of the number of red blood cells to the total blood volume can be calculated mathematically. To do this, the following indicators are required:
- total hemoglobin concentration (ctHB);
- red blood cell count (RBC);
- mean erythrocyte volume (MCV);
- mean erythrocyte hemoglobin concentration (MCHC).
The hematocrit number (HCT) is determined by one of the formulas:
- HCT (%)=(ctHB (mmol/l)*0.0485+0.0083)*100
- HCT (%)=0.1*MCV*RBC
- HCT (%)=ctHB/MCHC*100
Direct blood cell counting method
In a given volume of biomaterial, visible blood elements are counted manually or using hematological analyzers. The method is highly accurate, and the measurement process does not take much time - no more than five minutes, but the equipment required is very expensive.
Manual counting method
Blood collected using an anticoagulant is placed in a dry, clean tube and allowed to settle. In this case, the formed elements that have greater weight settle to the bottom of the container, and the light plasma rises to the top, forming two fractions of red and yellow colors, respectively. The hematocrit indicator can be determined by the divisions on the test tube. This method is the least accurate, its error is up to 20%, so it is currently not used in laboratories.
Preparation
Donating blood for a general analysis does not require special preparation, but to identify an adequate clinical picture of the formed elements and hematocrit, it is recommended to adhere to the following rules:
- Blood donation is performed on an empty stomach;
- stopping smoking in the morning on the day of the test (blood is donated in the morning);
- refusal of physical activity the day before and on the day of delivery of the biomaterial;
- prohibition of taking anticoagulants, antiplatelet agents and other drugs that affect the blood coagulation system 3 days before the study;
- abstaining (if possible) from stress and emotional experiences on the eve of the study;
- refusal to carry out diagnostic procedures (x-ray, ultrasound and other studies) the day before donating blood.
Sources:
- A.A. Kishkun, Doctor of Medical Sciences, Prof. Guide to laboratory diagnostic methods, - GEOTAR-Media, 2007.
- Mandy Flannery O'Leary, MD, MPH, FCAP. Hematocrit. — Laboratory Medicine, Medscape, 2014.
- Andrew S Artz, MD, MS. Anemia in Elderly Persons. - Hematology, Medscape, 2015.
When is a hematocrit test performed?
Most often, hematocrit is determined as part of a general (clinical) blood test. Therefore, at present this parameter of a clinical blood test is not prescribed separately. The hematocrit level changes when:
- disorder of the blood coagulation system;
- dehydration;
- anemia or polycythemia;
- bleeding.
Assessing the hematocrit level is important when determining indications for the need for blood transfusion or the effectiveness of blood transfusion, during hemodialysis, and some operations. To determine the hematocrit number, venous or capillary blood is taken.
Indications and preparation for analysis
The hematocrit indicator is always indicated in the results of a general blood test. This means that it can be assessed:
- During any medical examination or mandatory medical examination.
- In preparation for surgery.
- During hospitalization and before discharge.
But besides this, there are certain indications when it is necessary to determine the hematocrit. In this case, a direct measurement is performed: the plasma is separated by centrifuging the material and an accurate indicator is obtained. Indications for this:
- Bleeding.
- Blood clotting problems
- Dehydration of the body.
- Anemia.
- Polycythemia.
In order to get a reliable result, you should refuse food 6-10 hours before taking blood from a vein or from a finger. As a rule, the analysis is taken in the morning. It is also necessary to avoid drinking alcohol 2-3 days and refrain from smoking 2-3 hours before the procedure.
Increased hematocrit
An increase in hematocrit occurs with an increase in the number of blood cells - polycythemia - and a lack of fluid in the body. An increase in the indicator may indicate serious diseases accompanied by blood thickening and thrombotic complications.
Causes
Hematocrit increases due to stress, taking corticosteroid drugs and diuretics, traumatic shock accompanied by intense pain, as well as when climbing to high altitudes, smoking, or playing sports using anabolic steroids to gain muscle mass.
An increase in the indicator may indicate the following diseases:
- dehydration due to vomiting, profuse diarrhea, overheating or heat stroke, excessive sweating, insufficient fluids;
- heavy bleeding in the midst or immediately after it stops;
- pathologies accompanied by a decrease in blood plasma volume, for example, peritonitis, thrombosis, diabetes, burn disease;
- renal dysfunction - hydronephrosis, oncology, polycystic disease;
- vitamin B12 or iron deficiency anemia;
- leukemia;
- erythrocytosis;
- defects and coronary heart disease, heart failure;
- intestinal obstruction;
- bronchial asthma, pulmonary emphysema, obstructive bronchitis.
Symptoms
An increase in blood viscosity leads to thrombus formation. The latter can manifest itself in the form of tingling or various pains and numbness in the limbs. If the cause of increased blood viscosity is not determined in time, serious complications such as myocardial infarction, stroke, gangrene and even death may develop.
Treatment
Treatment is carried out not for the changed hematocrit level itself, but for the conditions or diseases that caused these changes. In some situations, when serious causes for a slightly changed hematocrit level have been excluded, no treatment is required. But usually such situations are short-lived, in the case of physiological reasons for changes in hematocrit levels.
Reasons for increase not related to diseases
An increase in Ht can be physiological, that is, a deviation from the norm is not related to disease. The body reacts to any changes in order to adapt to new conditions and maintain balance. The reasons for a safe increase in the hematocrit level may be as follows:
- As a result of dehydration, or dehydration. In this case, the amount of circulating blood in the bloodstream decreases due to a decrease in plasma volume. This can happen with vomiting, diarrhea, overheating, heavy sweating, or insufficient fluid intake. In this case, the body is forced to take water from the bloodstream. Thus, the ratio of the volume of the erythrocyte fraction and the total volume changes, the blood becomes thicker due to a decrease in the amount of plasma.
- Hematocrit is higher than normal in newborns. At this age, the norm is 44-62%.
- Hypoxia is chronic. Oxygen deficiency in cells is most often observed in patients with diabetes and smokers. Red blood cells deliver oxygen to tissues and remove carbon dioxide from cells. During hypoxia, the body produces more red blood cells, trying to compensate for the lack of oxygen. A high level of hematocrit and hemoglobin in this case is associated only with an increase in the number of red blood cells, while the total amount of blood in the bloodstream remains unchanged.
- When you stay in the mountains for more than two days, the level of red cells in the blood always increases, and therefore the hematocrit, since at altitude the air is thinner and contains less oxygen. Ht may exceed normal values in peoples living in high mountain areas, but people will not experience any discomfort.
- Elevated Ht levels are typical for athletes using anabolic steroids.
Residents of high mountain areas experience a physiological increase in hematocrit due to chronic hypoxia
Decreased hematocrit
A decreased hematocrit occurs when the number of red blood cells or their size decreases - erythrocytopenia. The cause may also be the accumulation of water in the body when the blood becomes thinner - hyperhydration, as well as hyperproteinemia or the accumulation of proteins in the plasma, which contributes to fluid retention.
Causes
A decrease in hematocrit is facilitated by prolonged immobility, fasting or a strict diet, taking anticoagulants and antiplatelet agents, and intravenous infusions in large volumes; heavy drinking, chronic alcoholism, excessive salt intake, menstruation in women.
Also, a downward change in the indicator may indicate the following pathologies:
- iron-, B12- or folate-deficiency anemia;
- severe bleeding;
- impaired hemoglobin production in sickle cell anemia;
- fibrous degeneration of the liver - cirrhosis;
- disruption of the urinary system;
- hemolysis of erythrocytes - destruction of red blood cells due to hereditary mutation, autoimmune processes or toxic effects on blood cells;
- malaria, typhoid fever;
- oncological diseases of the bone marrow or its metastatic lesions from other organs;
- an increase in the amount of protein in plasma due to vomiting, diarrhea, blood cancer and other conditions.
During pregnancy, a decrease in hematocrit can be observed in the case of toxicosis, a very young age of the mother, multiple pregnancies, a short period of time between pregnancies, and also after the 20th week of gestation due to a physiological increase in fluid in the body.
Symptoms
A decrease in hematocrit in the blood is accompanied by hypoxia of various organs, since it is the red blood cells that normally carry oxygen throughout the body. This condition is manifested by the following symptoms:
- fast fatiguability;
- general weakness;
- drowsiness;
- increased heart rate and breathing;
- feeling of lack of air;
- headache, dizziness;
- decreased memory and concentration;
- hair loss;
- marbling or pallor of the skin.
Why is it dangerous?
What does it mean if the hematocrit is increased? How dangerous is this?
- The cause of an increased hematocrit may indicate a serious disease (for example, erythremia or kidney cancer).
- Hematocrit is a synonym for blood viscosity. The higher the viscosity, the slower the blood flows through the vessels, the higher the risk of stasis and blood clots. And thrombosis in small and medium-sized vessels means strokes, heart attacks, thrombophlebitis, thromboembolism. These are the most serious complications that most often lead to sudden death.
