Hemorrhage; types and causes

Hemorrhage is defined as the excess loss of blood due to 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:

Hemorrhage


ACCIDENTAL HEMORRHAGE

Accidental hemorrhage occurs in road accidents and industrial accidents, which are very common in the

developed and developing countries.

Accidental hemorrhage is of two types:

i. Primary hemorrhage, which occurs immediately after the accident

ii. Secondary hemorrhage, which takes place some time (about few hours) after the accident.

CAPILLARY HEMORRHAGE

Capillary hemorrhage is the bleeding due to the rupture of blood vessels, particularly capillaries. It is very

common in brain (cerebral hemorrhage) and heart during cardiovascular diseases. The rupture of the capillary is followed by spilling of blood into the surrounding areas.

INTERNAL HEMORRHAGE

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

blood accumulates in viscera.

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.

HEMORRHAGE DUE TO PREMATURE DETACHMENT OF PLACENTA

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

COMPENSATORY EFFECTS OF HEMORRHAGE

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

Acute Hemorrhage

Acute hemorrhage is the sudden loss of large quantity of blood. It occurs in conditions like accidents. Decreased blood volume in acute hemorrhage causes hypovolemic shock.

Chronic Hemorrhage

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

time. Internal bleeding occurs in conditions like ulcer. 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, series of compensatory reactions develop in the body to cope up with the blood loss.

Compensatory effects of hemorrhage are of two types.

A. Immediate compensatory effects

B. Delayed compensatory effects.

IMMEDIATE COMPENSATORY EFFECTS OF HEMORRHAGE

1. On Cardiovascular System

Reduced blood volume after hemorrhage decreases venous return, ventricular filling and cardiac output. In severe hemorrhage, there is 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 to 500 mL the blood pressure decreases slightly and soon it returns back to normal.

Mechanism involved in main tenance of blood pressure:

i. Usually when arterial blood pressure increases, the carotid and aortic baroreceptors are stimulated

and send impulses to brain resulting in decrease in blood pressure. During hemorrhage when the arterial

blood pres sure falls, baroreceptors become inactivated and stop discharging impulses.

ii. This increases the vasomotor tone leading to vasoconstriction. This type of reflex vaso constriction

occurs in all regions of the body except brain and heart.

iii. Vasoconstriction results in increase in the peripheral resistance

iv. Loss of blood also causes reflex constriction of veins

v. Venoconstriction enhances the venous return, ventricular filling and stroke volume

vi. Thus, because of increased peripheral resistance and stroke volume the arterial blood

pressure is restored

vii. One more factor is involved in this mechanism. Vasoconstriction occurs in the organs having

reservoir function such as skin, liver and spleen. Blood from these reservoir organs is directed into

systemic circulation. This may compensate the volume of blood that is lost during hemorrhage.

During severe hemorrhage

When hemorrhage is severe with loss of about 1,500 to 2,000 mL of blood, the arterial blood pressure falls to a great extend. It is because of decreased venous return and stroke volume.

In the heart, the reflex tachycardia increases the quantity of metabolic products in myocardium. These

metabolic products cause coronary vasodilatation.

2. On Skin

Vasoconstriction in skin, which occurs after hemorrhage decreases the cutaneous blood flow. It increases the deoxygenation of blood and large quantity of reduced hemoglobin is accumulated in cutaneous blood vessels. It results in greyish pallor color of 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

Arteriolar constriction decreases the capillary pressure. Therefore, tissue fluid enters capillaries. It

helps to compensate the blood loss. It also causes hemodilution.

4. On Kidneys

Constriction of afferent and efferent arterioles of kidneys after hemorrhage decreases the glomerular filtration rate (GFR) very much. Therefore, the urinary output decreases. The blood level of nitrogenous substances, particularly urea, increases resulting in uremia. Severe hemorrhage leads to 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 secretion

of renin from kidney and the subsequent formation angiotensin II. Angiotensin II helps in restoring blood

pressure by producing generalized vasoconstriction. It also increases release of aldosterone from adrenal

cortex. Aldosterone causes retention of sodium and this helps increasing the blood pressure. Angiotensins III and IV are also involved in restoring the blood pressure.

6. On Secretion of Antidiuretic Hormone

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 decrease in venous return, cardiac output and velocity

of blood flow. Hypoxia stimulates the chemoreceptors leading to increase in respiratory rate. The catecholamines, which are secreted in large quantities due to hemorrhage, increase the respiratory movements through reticular activating system (RAS).

9. On Nervous System

i. On brain

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

ii. On reticular formation

Catecholamines stimulate the RAS. It causes restlessness, anxiety and increased motor activity after hemorrhage. The respiratory movements are also accelerated due to stimulation of RAS.

iii. Fainting

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

iv. Cerebral ischemia

When the blood flow to 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.

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 increase in plasma volume, hemodilution

occurs. So, the concentration of plasma proteins and hemoglobin is low. Transport of fluid from tissues is

continued for long time after hemorrhage.

2. Restoration of Plasma Proteins

The reserve proteins stored in liver start mobilizing within few hours after hemorrhage. Liver also starts

synthesizing the plasma proteins. Restoration of plasma proteins occurs within 3 to 4 days. Plasma proteins help to retain the fluid transported from tissues to blood.

3. Restoration of Red Blood Cell Count and Hemoglobin Content

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

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