Hemorrhage and hemostasis Flashcards
Hemorrhage (bleeding) is defined simply as
an abnormal escape of blood from an
artery, a vein, an arteriole, a venule or a capillary network.
Arterial/venous/capillary/parenchymatous etc.
Hemorrhage is caused by (2)
Caused by traumatic injury or medical condition
Can be External/internal
Primary hemorrhage occurs when?
Secondary hemorrhage occurs when?
Primary hemorrhage occurs soon after an injury.
Secondary hemorrhage follows an injury after a considerable lapse of time.
Describe Arterial hemorrhage
- Ruptured artery
- Bright red color (oxygen)
- Flow ordinarily in waves or spurts
- May be steady if artery is deep
- Spontaneous hemostasis rare
- Life-threatening
- Hardest to control
describe Venous hemorrhage
- Ruptured vein
- Rather dark red
- Steady, profuse bleeding
- Spontaneous hemostasis possible
- Level of danger dependent on the diameter of the vessel
- Potentially life-threatening
Describe capillary hemorrhage
- Ruptured capillaries
- Most common type of bleeding
- Mix of arterial and venous blood (fairly bright)
- Trickle of blood (small drops at a time)
- Spontaneous hemostasis likely
- Usually not life-threatening
- Easiest to control
Describe Parenchymatous hemorrhage
- Injury to a parenchymal organ (liver, spleen, pancreas etc.), corpus cavernosum (penis, clitoris), cancellous bone (=spongy/trabecular)
- Similar to capillary hemorrhage, but bleeding more profuse
- Spontaneous hemostasis unlikely or time-consuming
- Potentially life-threatening
Blood volume is typically estimated to be what percentage of body weight?
Blood volume 7-9% of body weight
(in cats ~6,5%)
Classification of hemorrhage
Class I (minimal blood loss): -15%
* HR, RR, BP normal, normal urine output; slightly anxious
Class II (mild blood loss): 15-30%
* HR↑, RR↑(mild), BP normal, oliguria; confused, irritable; cool extremities
Class III (moderate blood loss): 30-40%
* HR↑↑, RR↑, BP↓, oliguria; lethargic; cool extremities
Class IV (severe blood loss): >40%
* HR↑↑↑, RR↑↑↑, BP↓↓, anuria; lethargic, comatose; cold extremities, cyanosis
Classification of hemorrhage, Class I:
Class I (minimal blood loss): -15%
* HR, RR, BP normal, normal urine output; slightly anxious
Classification of hemorrhage,
Class II:
Class II (mild blood loss): 15-30%
* HR↑, RR↑(mild), BP normal, oliguria; confused, irritable; cool extremities
Classification of hemorrhage,
Class III
Class III (moderate blood loss): 30-40%
* HR↑↑, RR↑, BP↓, oliguria; lethargic; cool extremities
Classification of hemorrhage,
Class IV
Class IV (severe blood loss): >40%
* HR↑↑↑, RR↑↑↑, BP↓↓, anuria; lethargic, comatose; cold extremities, cyanosis
Blood loss Prognosis dependent on
many factors (severity, RATE (of loss: fast vs slow), concurrent disorders).
Medical attention in case:
* Bleeding does not stop
* Class II hemorrhage ((mild blood loss): 15-30%) (recommended intervention)
* Class III or IV (moderate & severe loss; intervention necessary)
Hemostasis can be either
physiological (Complex process involving platelet activation and circulating clotting
factors)
or
artificial (Temporary (provisional), definitive)
- Vascular spasm
- Platelet plug formation (is temporary)
- Clot formation (coagulation)
describe what?
physiological hemostasis!
Physiological Hemostasis (simplified) (3)
Injury →
endothelium releases vasoconstrictors (endothelin) →
vasoconstriction at site →
(aggregation &) adhesion of platelets
(plug formation)
alternatively
A. vasoconstriction (after injury)
B. primary hemostasis (hemostatic plug made from platelets)
C. secondary hemostasis (fibrin polymerization)
D. thrombus and antithrombotic events
Thromboplastin (combination of phospholipids and tissue factor) catalyzes the conversion of
prothrombin (nonactive) to thrombin →
thrombin causes fibrinogen to polymerize →
polymerized fibrin forms long strands of tough unsoluble protein that are bound to the
platelets →
formation of a hemostatic clot
thrombin causes fibrinogen to
polymerize → polymerized fibrin forms
long strands of tough unsoluble protein that are bound to the platelets → formation of a hemostatic clot
polymerized fibrin forms long strands of tough unsoluble protein that are bound to the
platelets → formation of a hemostatic clot
What is the intrinsic pathway?
Is one of the two main pathways involved in the blood coagulation process. It is called “intrinsic” because the components necessary for its initiation are found within the bloodstream itself.
This pathway is activated by damage to the blood vessel ENDOthelium, exposure to collagen, or other negatively charged surfaces. Factor XII or Hageman.
a series of sequential enzymatic reactions that ultimately lead to the conversion of prothrombin to thrombin, which then converts fibrinogen into fibrin, forming a blood clot.
The key components of the intrinsic pathway include factors XII, XI, IX, and VIII, as well as prekallikrein and high molecular weight kininogen.
The intrinsic pathway plays a role in amplifying the coagulation process initiated by the extrinsic pathway and is particularly important in maintaining hemostasis in response to internal vascular injuries.
What is the extrinsic pathway?
Initiated by factors external to the bloodstream, particularly tissue damage. The key event in the extrinsic pathway is the release of tissue factor (also known as factor III) from damaged tissue.
Once tissue factor is exposed to blood, it forms a complex with factor VII, leading to the activation of factor VII.
This activated factor VII then initiates a cascade of enzymatic reactions that ultimately result in the conversion of prothrombin to thrombin, which then converts fibrinogen into fibrin, forming a blood clot.
The extrinsic pathway works in conjunction with the intrinsic pathway.
Provisional artificial hemostasis
Provisional meaning temporary.
- Manual pressure
- Tamponade
- Pressure bandage
- Hemostats (forceps)
- Tourniquet
Definitive artificial hemostasis types (4)
- Mechanical (e.g. ligation)
- Physical (low temp, high temp)
- Chemical (topical vs systemic, spongostan vs vit K etc.)
- Biological (omentum, coag factor transfusion)
