Hemorrhage: Definition Types And Causes

Hemorrhage Definition

The term hemorrhage refers to excess loss of blood due to the rupture of blood vessels.

Types And Causes Of Hemorrhage

Hemorrhage occurs due to various reasons. Based on the cause, hemorrhage is classified into five categories:

1. Accidental hemorrhage
2. Capillary hemorrhage
3. Internal hemorrhage
4. Postpartum hemorrhage
5. Hemorrhage due to premature detachment of the placenta.

Read And Learn More: Medical Physiology Notes

1.  Accidental Hemorrhage

It occurs in road accidents and industrial accidents, which are very common in developed and developing countries.

Accidental hemorrhage is of two types:

1. Primary hemorrhage, which occurs immediately after the accident
2. Secondary hemorrhage, which takes place sometime (about a few hours) after the accident.

2. Capillary Hemorrhage

• Capillary hemorrhage is bleeding due to the rupture of blood vessels, particularly capillaries. It is very common in the brain (cerebral hemorrhage) and heart during cardiovascular diseases.
• The rupture of the capillary is followed by blood into the surrounding areas

3. Internal Hemorrhage

internal hemorrhage is bleeding in the viscera. It is caused by the rupture of blood vessels in the viscera. The blood accumulates in the viscera.

4. Postpartum Hemorrhage

Excess bleeding that occurs immediately after labor (delivery of the baby) is called postpartum hemorrhage. In some cases, it is very severe and leads to major complications.

5. Hemorrhage Due To Premature Detachment Of Placenta

In some cases, the placenta is detached from the uterus of the mother before the due date of delivery causing severe hemorrhage.

Effects Of Hemorrhage

Many effects are observed during and after hemorrhage. The effects are different in acute hemorrhage and chronic hemorrhage.

Acute Hemorrhage

Acute hemorrhage is the sudden loss of a large quantity of blood. It occurs in conditions like accidents.

The decreased blood volume in acute hemorrhage causes hypovolemic shock.

Chronic Hemorrhage

Chronic hemorrhage is the loss of blood either by internal or external bleeding over a long period of time.

Internal bleeding occurs in conditions like ulcers. External bleeding occurs in conditions like hemophilia and excess vaginal bleeding (menorrhagia).

Chronic hemorrhage produces different types of effects such as anemia.

Compensatory Effects

After hemorrhage, a series of compensatory reactions develop in the body to cope up with the blood loss.

Some of the compensatory reactions take place immediately after hemorrhage and others at a later period. Thus, the compensatory effects of hemorrhage are of two types.

1. Immediate compensatory effects
2. Delayed compensatory effects.

Immediate Compensatory Effects Of Hemorrhage On Cardiovascular System

Reduced blood volume after hemorrhage decreases venous return, ventricular filling, and cardiac output.

In severe hemorrhage, there is a fall in blood pressure also. However, when blood loss is slow or less, the arterial blood pressure is not affected much. If it is affected it is restored quickly.

During mild hemorrhage

During slow or mild hemorrhage when there is loss of a small amount of blood up to 350-500 mL the blood pressure decreases slightly and soon it returns back to normal.

The mechanism involved in the maintenance of blood pressure:

• Usually, when arterial blood pressure increases, the carotid and aortic baroreceptors are stimulated and send impulses to the brain resulting in a decrease in blood pressure. During hemorrhage when the arterial blood pressure falls, the baroreceptors become inactivated and stop discharging impulses.
• This increases the vasomotor tone leading to vasoconstriction. This type of reflex vasocons- friction occurs in all regions of the body except the brain and heart.
• Vasoc constriction increases the peripheral resistance
• Loss of blood also causes reflex constriction of veins
• Vasoconstriction enhances the venous return, ventricular filling,, and stroke volume
• Thus, because of increased peripheral resistance and stroke volume the arterial blood pressure is restored.
• One more factor is involved in this mechanism. Vasoconstriction occurs in the organs having a reservoir function.
• The organs having the reservoir function are mostly the skin, liver, and spleen.
• The blood from the reservoir organs is directed into the systemic circulation.
• This compensates for the volume of blood that is lost during hemorrhage.

During severe hemorrhage

• When hemorrhage is severe with loss of about 15002000 mL of blood, the arterial blood pressure falls to a great extent. It is because of decreased venous return and stroke volume.
• In the heart, the reflex tachycardia increases the of metabolic products in the myocardium. These rnoriboiic products cause coronary vasodilatation.

2. On Skin

• Vasoconstriction in the skin which occurs after hemorrhage decreases the cutaneous blood flow.
• It increases the deoxygenation of blood and a large quantity of reduced hemoglobin is accumulated in cutaneous blood vessels. It results in a grayish pallor color of the skin.
• Sometimes cyanosis develops in certain areas of the body. Skin also becomes cold due to less blood flow. Sweating is decreased.

3. On Tissue Fluid

The arteriolar constriction decreases the capillary pressure. Therefore, tissue fluid enters capillaries. It helps to compensate for the blood loss. It also causes hemodilution.

4. On Kidneys

• Constriction of afferent and efferent arterioles of kidneys after hemorrhage decreases the GFR very much. Therefore, the urinary output decreases.
• The blood level of nitrogenous substances particularly urea increases resulting in uremia.
• Severe hemorrhage leads to a fall in arterial blood pressure and damage of renal tubules resulting in acute renal failure.

5. On Renin Secretion

• Hypoxia produced after blood loss increases the secretion of renin from the kidney and the subsequent formation of angiotensin 2.
• Angiotensin 2 helps in restoring blood pressure by producing generalized vasoconstriction.
• It also increases the release of aldosterone from the adrenal cortex. Aldosterone causes retention of sodium and this helps increase the blood pressure.
• Angiotensins 3 and 4 also are involved in restoring blood pressure.

6. On Secretion of Antidiuretic Hormone

• ADH is released in large quantities immediately after the hemorrhage.
• It is probably due to increased osmolality of body fluid by aldosterone-induced sodium retention.
• ADH promotes water retention and helps in restoring osmolality and volume of ECF.

7. On Secretion of Catecholamines

Sympathetic activity increases due to blood loss, it causes secretion of large quantities of catecholamines which are also involved in restoring blood pressure by the vasoconstrictor effect.

8. On Respiration

• Hemorrhage causes stagnant hypoxia because of a decrease in venous return, cardiac output, and velocity of blood flow.
• Hypoxia stimulates the chemoreceptors leading to an increase in respiratory rate.
• The catecholamines, which are secreted in large quantities due to hemorrhage, increase respiratory movements through the reticular activating system.

9. On Nervous System

On brain

• Though hemorrhage causes vasoconstriction in many organs of the body, it causes vasodilatation in the brain. It is because of increased sympathetic activity.
• However, the blood flow to the brain is not affected very much after hemorrhage because of autoregulation.

On reticular formation

• The catecholamines stimulate the reticular activating system. It causes restlessness, anxiety, and increased motor activity after hemorrhage.
• The respiratory movements are also accelerated due to stimulation of the reticular activating system.

Fainting

• When hemorrhage is severe, cardiac output decreases and blood pressure falls.
• The autoregulation in the brain fails to cope with the hypotension. So, the blood flow to the brain decreases resulting in fainting.

Cerebral ischemia

When the blood flow to the brain is severely affected due to hypoxia, ischemia of the brain tissues develops within 5 minutes. It causes irreversible damage to brain tissues.

Delayed Compensatory Effects Of Hemorrhage

If hemorrhage is not severe, some delayed compensatory reactions occur. These reactions help to restore blood volume, blood pressure, and blood flow to different regions of the body.

The delayed reactions are:

1. Restoration of plasma volume
2. Restoration of plasma proteins
3. Restoration of red blood cell count and hemoglobin content.

1. Restoration of Plasma Volume

• During the period of hemorrhage itself, tissue fluid starts entering the blood because of low capillary pressure.
• So, the plasma volume increases.
• Because of the increase in plasma volume, hemodilution occurs. So, the concentration of plasma proteins and hemoglobin is low.
• Transport of fluid from tissues is continued for a long time after hemorrhage.

2. Restoration of Plasma Proteins

• The reserve proteins stored in the liver start mobilizing within a few hours after hemorrhage.
• The liver also starts synthesizing plasma proteins. Restoration of plasma proteins occurs within 3-4 days.
• The plasma proteins help to retain the fluid transported from tissues to the blood.

3. Restoration of Red Blood Cell Count and Hemoglobin Content

• Hypoxia that is developed after hemorrhage stimulates the secretion of erythropoietin from the kidney.
• Erythropoietin in turn stimulates red bone marrow causing erythropoiesis.
• However, the restoration of RBC count is a slow process. It takes about 4-6 weeks. Reticulocyte count increases in blood.
• Hemoglobin content also comes back to normal levels along with RBC count, if the diet contains an adequate quantity of iron and proteins.