Explanation for working with teaching material.

PATHOLOGY OF THE RBC 1

Explanation for working with teaching material.

1. Examine the lecture information and guide.

2. Complete the table.

3. Give answers to the tests.

4. Give answers to situational tasks (analysis of blood).

5. Give answers to 2 questions from the list of the final control of the level of knowledge.

Addition to the lecture

Typical forms of pathology and reactive changes of the total volume, the ratio of the plasma and blood corpuscular elements.

The total blood volume in an adult comprises 5-8% of the body mass, i.e. on an average 4.5-5.l. The corpuscular elements comprise on an average 36-48% of the total blood volume (hematocrit or the hematocrit factor – the ratio of the corpuscular elements volume to the plasma volume; in men it ranges 40-48%, in women – 36-42%).

 Both the total blood volume and the ratio of corpuscular elements and plasma may change under the conditions of pathology. There are three basic groups of typical forms of impairments.

Normovolemia is the state when a normal blood volume is preserved, but the ratio of corpuscular elements and plasma changes.

There are:

1) Simple normovolemia – is the state when a normal blood volume and a normal ratio of corpuscular elements and plasma take place;

2) Oligocytemic normovolemia (hemodilution) is characterized by a normal blood volume and a decrease of the count of corpuscular elements (mainly of erythrocytes) that is accompanied by a drop of hematocrit below 36%.  It occurs in massive hemolysis of erythrocytes, suppression of hemopoiesis, after acute loss of blood, when the blood volume comes quickly to the norm at the expense of the tissue fluid entering vessels, while the erythrocyte count still remains decreased. This state is manifested by hypoxia. A considerable decrease of the erythrocyte count may cause slowing down of blood coagulation and a hemorrhagic syndrome, while a prolonged decrease of the leukocyte count – a decrease of anti-inflammatory and anti-tumor resistance.

 3) Polycytemic normovolemia (hemoconcentration) is characterized by a normal total blood volume, while the corpuscular elements count exceeds 48%. It may be caused by chronic hypoxic conditions. It is manifested by the impairment of microcirculation due to blood thickening, an increase of its viscosity, thrombus formation slowing down the blood flow, decrease of intensity of transcapillary exchange. In considerable policytemia, arterial hypertension may develop.

Hypervolemia (from Greek. hyper – over, exceeding the norm + volemia) – is the condition characterized by an increase of the total blood volume and most often by the impairment of the ratio of corpuscular elements and plasma.

1) Simple (normocytemic) hypervolemia – is an increase of the total blood volume, while a normal per cent ratio of the plasma and corpuscular elements is preserved. It takes place during a short period of time in transfusing great amounts of donor blood, on great physical exertions, in acute hypoxia, when environmental high temperature comes into effect, when deponed blood comes into the blood stream from the depot and interstitial fluid from tissues. Such condition may result in a decrease of the vascular tone, cardiac overloading, development of cardiac insufficiency.

2) Oligocytemic hypervolemia (hydremia) – an increase of the blood volume at the expense of mainly a fluid part, the hematocrit factor being below 36%. It occurs in the impairment of the excretory function and retention of fluid in the blood stream, pathologic thirst, excessive injection of physiologic solution or blood substituting solutions, in hyperproduction of an anti-diuretic hormone. As a result the blood circulation impairment may occur due to overstretching of vessels, cardiac cavities and microcirculation impairment.

3) Policytemic hypervolemia – is the condition, when the circulating blood volume increases mainly at the expense of corpuscular elements (erythrocytes) due to which the hematocrit factor exceeds 48%. It occurs in heart defects, chronic circulation insufficiency, alveolar hypoventilation, decrease of oxygen blood capacity and efficiency of biologic oxidation, exogenous (hypo- and normobarric)  hypoxia, as well as in erythremia (Vaquez’ disease) – leucosis with predominant damaging of the red marrow germ (see below). The disease is accompanied by an increase of blood viscosity, arterial blood pressure, increase of the cardiac loading followed by hypertrophy of the left ventricle, etc.

Hypovolemia (from Greek. hypо - supra, below the norm + volemia) – is the condition characterized by a decrease of the total blood volume and impairment of the ratio of corpuscular elements and plasma.

 1) In the majority of cases simple (normocytemic) hypovolemia is characterized by a decrease of CBV (circulating blood volume) in normal hematocrit. Its causes are acute hemorrhages, shock conditions, a vasodilatational collapse. In the last two cases there occurs deponing of a considerable amount of blood in venous (voluminous) vessels and a considerable decrease of CBV. The danger of this condition includes a decrease of arterial pressure, impairment of peripheral blood flow causing hypoxia and the impairment of tissue metabolism.

2) Oligocytemic hypovolemia is characterized by a decrease of the total blood volume with a predominant decrease of corpuscular elements and hematocrit below 36%. It is observed immediately after the blood loss, when its migration from the depot and tissue fluid hasn’t eliminated hypovolemia yet and the outlet of blood cells from hemopoietic organs – deficiency of erythrocytes, as well as in massive hemolysis of erythrocytes or suppression of their production in bone marrow. It is manifested by the disturbance of blood circulation in various vessels, decrease of the blood oxygen capacity due to erythropenia.

3) Policytemic hypovolemia (anhydremia) is observed in decreasing of the total blood volume due to a predominant decrease of the plasma volume, the hematocrit volume exceeding the normal one. The most frequent causes of this condition are various forms of dehydration, pernicious vomiting, profuse diarrhea, polyuria, intense perspiration, expansive burns, water fasting, hyperthermia, diabetes incipidus, etc. There are observed disturbances of the central, organ-tissue and microhemocirculation systems.

Pathogenic classification of anemias

I. Anemia due to increased blood loss.

1. Acute posthemorrhagic anemia.

2. Chronic blood loss.