Lecture 5, hemorrhage and hemostasis Flashcards
Hemorrhage
An abnormal escape of blood from an artery, a vein, an arteriole, a venule or a capillary network
- Caused by traumatic injury/medical condition
- External/internal
- Primary hemorrhage occurs soon after an injury
- Secondary hemorrhage follows an injury after a considerable lapse of
time - Arterial/venous/capillary/
parenchymatous
Arterial hemorrhage
- Ruptured artery
- Bright red colour (oxygen)
- Flow ordinarily in waves of spurts
- May be steady if artery is deep
- Spontaneous hemostasis rare
- Life-threatening
- Hardest to control
Venous hemorrhage
- Ruptured vein
- Rather dark red
- Steady, profuse bleeding
- Spontaneous hemostasis possible
- Level of danger dependant on the diameter of the vessel
- Potentially life-threatening
Capillary hemorrhage
- Ruptured capillaries
- Most common
- 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
Parenchymatous hemorrhage
- Injury to a parenchymal organ (liver, spleen, pancreas etc.), corpus
cavernosum (penis, clitoris), cancellous bone - Similar to capillary hemorrhage, bleeding more profuse
- Spontaneous hemostasis unlikely or time-consuming
- Potentially life-threatening
Blood volume of body weight
7-9%, in cats ~6,5%
Classification of hemorrhage, class I
HR, RR, BP normal, normal urine output, slightly anxious
Classification of hemorrhage, class II
Mild blood loss 15-30%
HR↑, RR↑(mild), BP normal, oligouria, confused, irritable, cool extremities
Classification of hemorrhage, class III
Moderate blood loss 30-40%
HR↑↑, RR↑, BP↓, oligouria, lethargic, cool extremities
Classification of hemorrhage, class IV
Severe blood loss >40%
HR↑↑↑, RR↑↑↑, BP↓↓, anuria; lethargic, comatose; cold extremities, cyanosis
Blood loss
Prognosis dependant on many factors (severity, rate, concurrent
disorders)
Medical attention in case:
* Bleeding does not stop
* Class II (recommended), Class III or IV (necessary)
Blood loss → hypovolemic shock →
death (1/2 - 2/3 of total blood volume lost)
Hemostasis
Complex process involving platelet activation and circulating clotting
factors. Causes blood from escaping the damaged blood vessel.
The balance of anti- and procoagulants keeps the blood in liquid form.
- Physiological hemostasis
- Artificial hemostasis
- Temporary (provisional)
- Definitive
- Vascular spasm
- Platelet plug formation
- Clot formation (coagulation)
How hemostasis happen?
- Injury → vasoconstrictors released from endothelium (endothelin) →
vasoconstriction at the site → (aggregation and) adhesion of platelets (plug formation) - 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
Ways to do provisional artificial hemostasis
Manual pressure
Tamponade
Pressure bandage
Hemostats (forceps)
Tourniquet
Ways to do definitive hemostasis
Mechanical
Physical
Chemical
Biological