Lecture 28: Shock and Hemorrhage Flashcards
Circulatory shock occurs when
The blood pressure falls so low that adequate blood flow to the tissues can no longer be maintained
Four types of circulatory shock
- Hypovolumic
- Vasogenic
- Cardiogenic shock
- Neurogenic
Hypovolemic shock is induced by
A fall in blood volume
Four ways hypovolemic shock can occur
- Hemorrhage
- Burns
- Trauma and surgery
- Severe diarrhea and vomiting
What’s the most common cause of hypovolumic shock
hemorrhage
What happens during hemorrhage
- Decreases the filling pressure of the circulation
- Decreased venous return
- Decreased cardiac output
- Shock
What happens during burns
- Loss of plasma in exudate from damaged tissue
- Loss in blood volume with little to no change in rbc concentration
- hemocencentration
- Increased blood viscosity
- Increased afterload on heart
- Loss of plasma volume
- Decreased venous return, decreased cardiac output
Exudate
A fluid with a high content of protein and cellular debris which has escaped from blood vessels and has been deposited in tissues or on tissue surfaces
Hemoconcentration
Increase in the proportion of formed elements in the blood, as a result of a decrease in its fluid content
Surgery and trauma shock can occur without the hemorrhage because
Contusion of the body can damafe capillaries enough to allow excess loss of plasma into tissues
Two types of vasogenic shock
- Septic shock
2. Anaphylaxis
Septic shock
- Endotoxin released by invading bacteria stimulates nitric oxide release by macrophages
- Thought to contribute to the severe hypotension characteristic of septic shock
Anaphylaxis
- Severe allergic reaction to an antigen
- Release in a large amount of histamine
Histamine promotes
- Profound vasodilation
- Increased permeability of capillaries which promotes protein and fluid loss, resulting in edema
Cardiogenic shock
Blood flow to tissues is no longer adequate to meet resting metabolic demands
Cardiogenic shock is most commonly due to
extensive infarction of the left ventricle
Why is cardiogenic shock sometimes called congested shock?
Associated with congestion of lungs
Neurogenic shock
Produced by loss of vascular tone due to inhibition of the normal tonic activity of the sympathetic vasoconstrictor nerves
-Often caused by brain/spinal cord injury and deep excruciating pain
Five effects of shock
- Decreased metabolism
- Muscular weakness
- Decreased body temperature
- Impaired mental function
- Reduced renal function
Usually a patient can continue to live for only a few hours if the cardiac output falls to as low as
40% below normal
One of the earliest symptoms of shock is
muscular weakness
Why is there reduced renal function in shock?
Diminishes urine output because of decreased filtration of fluid into Bowman’s capsule, due to a decrease in glomerular pressure
