The hemoconcentration is the increase in hematocrit concentration in response to the decrease in plasma volume. That is, although there is an increase in hematocrit, the number of red blood cells is not modified..
Hemoconcentration occurs in the event of fluid loss or due to an imbalance in their distribution within the body. The imbalance causes plasma extravasation to the extravascular or interstitial space. It occurs in dehydrated patients, in large burns, in dengue hemorrhagic fever or in patients with systemic capillary leak syndrome..
Hemoconcentrated patients usually have hemoglobins above 17 g / dl. In the neonatal period there may be a physiological hemoconcentration, but after this period, such a high level of hemoglobin (> 20 g / dl) is alarming and dangerous.
Thus, hematocrit values above 65% represent a risk factor for suffering from hyperviscosity syndrome..
Cases of hemoconcentration due to decreased plasma fluid must be differentiated from patients with elevated hematocrit from other causes. That is, due to disorders in the production of the red series in bone marrow, such as polycythemia or polyglobulia.
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There are many causes that can lead to an abundant loss of fluid, or the extravasation of intravascular plasma fluid to the extravascular space, generating hemoconcentration in the patient.
Among the main causes are: dehydration, dengue hemorrhagic fever, severe and extensive burns, heart failure, systemic capillary leak syndrome, and eclampsia..
Dehydration can occur in cases of severe diarrhea and vomiting, without fluid replacement. Also in intense exercise with excessive sweating.
The loss of fluid causes a decrease in plasma volume and the consequent haemoconcentration.
Dengue is a viral infection caused by an arbovirus of the Flaviviridae family. The virus enters the patient by the bite of a hematophagous vector called Aedes aegypti.
The severe form of the disease occurs when there is reinfection by another serotype other than the first. The first infection leaves heterologous antibodies. These antibodies favor the replication of the virus and the increase in viremia in the second infection, causing a serious picture of the disease called dengue hemorrhagic fever..
The disease is characterized by an increase in the secretion of cytokines that favors the extravasation of the plasma to the extravascular space, producing hemoconcentration.
On the other hand, the virus causes the destruction of multiple types of cells, including T lymphocytes and platelets, which translates into a decrease in the patient's immunity and the appearance of significant bleeding..
Hemoconcentration and blood loss can lead to hypovolemic shock that can lead to death..
In the burned patient, a series of events occur that clarify why hemoconcentration occurs and how hypovolemic shock can occur.
When the skin burns, there is alteration of capillary permeability due to the increase in the concentration of histamine. This occurs moment after the incident. This causes the albumin to move into the interstitial space. Subsequently, the high concentration of proteins accumulated in the interstitial fluid further favors the attraction of water..
Likewise, there is less venous reabsorption due to the decrease in oncotic pressure. All of the above contributes to the formation of a large interstitial edema.
In addition, in the burned patient there is loss of liquid by massive evaporation. Burned skin is unable to retain moisture and, on the contrary, gives off water vapor. Through this route, up to 7 liters per day can be lost in patients with a large area of affected skin (≥ 50%)..
The loss of fluid, both through evaporation and edema, causes an electrolyte imbalance at the plasma level characterized by a decrease in sodium (hyponatremia) and an increase in potassium (hyperkalemia).
Hyperkalemia triggers a series of signs and symptoms in the patient, such as: fatigue, decreased muscle tone, cardiac arrest, paralytic ileus, among others. All these fluid depletion events can lead to hypovolemic shock..
On the other hand, there is massive destruction of red blood cells with the appearance of anemia. However, the hematocrit is elevated, that is, there is hemoconcentration due to platelet accumulation and fluid loss.
Hemoconcentration causes a slowing down of the circulatory system, favoring the formation of thrombi.
Grau et al. Studied patients with heart failure who were admitted to a health center. The treatment established in these patients is based on the administration of diuretics, which leads to a significant loss of fluid that can cause hemoconcentration in the patient..
To calculate the degree of hemoconcentration, they measured the difference in hemoglobin (DHb) of the patients at the time of admission and then after 3 months of treatment. The authors used the following formulas:
(DHb) = Hb (at 3 months) - Hb (at admission)
% DHb = (DHb × 100) / Hb at admission
The authors concluded that patients who presented hemoconcentration had a better prognosis, with less probability of readmission and death..
It is a rare and infrequent disease. Only 150 cases have been reported so far globally. This syndrome is characterized by the presence of hypotensive episodes, accompanied by hypoalbuminemia and hemoconcentration..
Hemoconcentration increases the viscosity of the blood and this causes blood circulation to slow down, which can cause peripheral hypoxia and dehydration at the neuronal level, as well as hypovolemic shock. In the case of pregnant women with severe pre-eclampsia, these types of episodes can occur.
Currently, it has been proposed to consider the hematocrit value as a predictive value of suffering eclampsia in pregnant women with symptoms of pre-eclampsia. Hematocrit values higher than 36% would suppose a poor prognosis in these patients.
A differential diagnosis should be made between hemoconcentration due to fluid loss and cases of increased hematocrit due to hyperproduction of red blood cells..
There are diseases that cause an increase in the production of red blood cells, among them are: primary and secondary polycythemia.
Polycythemia vera or primary is a bone marrow disorder, where there is an overproduction of red blood cells, with normal or slightly low erythropoietin values.
While secondary polycythemia is caused by overproduction of erythropoietin, which stimulates the marrow to overproduce red blood cells..
This occurs in response to situations of constant hypoxemia, such as: in methemoglobinemia, in congenital heart disease, in heart failure, in patients living in high altitude areas, in carboxyhemoglobinemia, among other causes..
Also in patients with erythropoietin-producing tumors, such as nephroblastoma, hepatoma, hemangioblastoma, and pheochromocytoma.
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