1. What is Hemorrhage?
- Hemorrhage is the loss
of blood from the circulatory system.
- It may
occur externally (outside the body) or internally (within
body cavities or tissues).
- It leads
to hypovolemia → decreased blood pressure → shock if
severe.
2. Classification of
Hemorrhage (Based on Volume Loss)
|
Class |
% of Blood Loss |
Clinical Features |
|
I |
<15% |
Mild or no symptoms |
|
II |
15–30% |
Tachycardia, pale skin |
|
III |
30–40% |
Hypotension, confusion |
|
IV |
>40% |
Life-threatening, unconsciousness |
Total blood volume ≈ 5 liters in adults
3. Immediate Effects of
Hemorrhage
- ↓ Blood
volume (hypovolemia)
- ↓ Venous
return
- ↓ Stroke
volume
- ↓ Cardiac
output
- ↓ Blood
pressure
- ↓ Oxygen
supply to tissues
- May lead
to circulatory shock
4. Compensatory
Mechanisms to Maintain BP & Circulation
The body immediately tries to compensate for blood loss using neural,
hormonal, and renal mechanisms.
A. Neural Mechanisms
(Fast)
Baroreceptor Reflex:
- Baroreceptors
in carotid sinus and aortic arch sense ↓ BP
- Stimulate sympathetic
nervous system →
- Vasoconstriction
- ↑ Heart
rate (tachycardia)
- ↑ Cardiac
output
Chemoreceptor Reflex:
- Activated
by ↓ O₂ and ↑ CO₂
- Stimulate vasoconstriction
and increased respiration
B. Hormonal Mechanisms
(Slower)
- Renin-Angiotensin-Aldosterone
System (RAAS):
- ↓ Renal
perfusion → Renin released
- Angiotensin
II: vasoconstriction
- Aldosterone:
Na⁺ & water retention → ↑ blood volume
- Antidiuretic
Hormone (ADH) / Vasopressin:
- Released
from posterior pituitary
- Promotes water
reabsorption in kidneys
- Causes vasoconstriction
- Catecholamines:
- Adrenaline
& Noradrenaline from adrenal medulla
- ↑ HR,
vasoconstriction
C. Renal Mechanisms
(Long-Term)
- Decreased
perfusion triggers:
- Water
retention
- Salt
reabsorption
- Leads to restoration
of blood volume over hours to days
D. Capillary Fluid
Shift
- Interstitial
fluid moves into capillaries due to low BP (Starling forces)
- Temporary
compensation to increase plasma volume
5. Summary Table –
Compensation in Hemorrhage
|
Mechanism |
Effect |
|
Baroreceptors |
↑ HR, ↑ vasoconstriction |
|
RAAS Activation |
Vasoconstriction, Na⁺ & water retention |
|
ADH Release |
Water retention, vasoconstriction |
|
Sympathetic Nervous System |
↑ CO, vasoconstriction |
|
Renal Compensation |
Long-term volume restoration |
|
Capillary Fluid Shift |
Temporary ↑ plasma volume |
6. Clinical Signs of
Hemorrhage
- Cold, pale
skin
- Rapid,
weak pulse
- Low BP
- Rapid
breathing
- Dizziness
or fainting
- Oliguria
(↓ urine output)
7. Management Overview
(for Clinical Practice)
- Control
bleeding (pressure, surgery)
- Restore
volume (IV fluids, blood transfusion)
- Monitor
vitals
- Support
cardiac function
Mnemonic for
Compensation: "SHARC"
- Sympathetic
activation
- Hormonal
control (RAAS, ADH)
- Aldosterone
- Renal
response
- Capillary
shift
