Hemostasis 3 Flashcards
What is shock?
cardiovascular collapse
What causes shock? (3)
- insufficient cardiac output
- loss of circulating blood volume
- inappropriate vascular resistance (vasodilation)
Pathway of shock
- decreased cardiac output/effective circulating blood volume
- hypotension
- decreased tissue perfusion and cellular hypoxia
- shift to anaerobic metabolism
- cellular degeneration and death
Name the 3 types of shock
cardiogenic
hypovolemic
blood maldistribution
What can cause cardiogenic shock? (3)
myocardial infarction
cardiomyopathy
arrhythmias
What can cause hypovolemic shock? (2)
blood loss fluid loss (vomiting, diarrhea, severe burns)
What can cause blood maldistribution? (3)
sepsis
anaphylaxis
neurogenic
What are the 3 compensatory mechanisms against shock?
- increased heart rate and contractility
- peripheral vasoconstriction
- renal conservation of fluid
What is cardiogenic shock?
failure of the heart to adequately pump blood
Characteristics of cardiogenic shock
- increased HR and contractility increases myocardial O2 demand
- leads to cardiac failure and systemic hypoperfusion
- systemic hypoperfusion triggers inflammatory cascade
What is hypovolemic shock?
reduced circulating blood volume due to fluid loss
Characteristics of hypovolemic shock
- most often due to hemorrhage in domestic animals
- can be seen secondary to severe dehydration
What is septic shock?
components of microbes trigger release of excessive quantities of vascular and inflammatory mediators
Causes of septic shock
- LPS from gram negative bacteria
- less commonly, components of gram positive bacteria (peptidoglycan, lipoteichoic acid)
Effects of LPS in septic shock (7)
- activation of endothelial cells
- activation of inflammatory cells
- release of inflammatory cytokines
- activation of coagulation cascade
- inhibits production of anticoagulant substances
- activation of platelets
- activation of complement
General effects of septic shock (5)
- systemic vasodilation
- diminished myocardial contractility
- widespread endothelial injury
- activation of coagulation leading to DIC
- hypoperfusion leads to multi organ system failure
What is anaphylactic shock?
generalized type-1 hypersensitivity response
IgE mediated release of vasoactive substances from mast cells
General effects of anaphylactic shock
systemic vasodilation
increased vascular permeability
What is neurogenic shock?
widespread loss of vascular tone secondary to spinal cord injury or electrocution
Name the 3 stages of shock
- non-progessive stage
- progressive stage
- irreversible stage
What happens in the non-progressive stage of shock?
- increased cardiac output
- increased vasoconstriction
- blood flow maintained to certain tissues
- stimulation of renin-angiotensin-aldosterone system and release of ADH
What happens in the progressive stage of shock?
- pooling of blood
- hypoperfusion of tissues
- progressive cell injury
- anaerobic metabolism
- acidosis
- increased CO2
What is activated during the progressive stage of shock?
- inflammation
- coagulation
- complement
- fibrinolysis
What happens in the irreversible stage of shock?
- membrane transport fails
- lysosomal contents leak
- structural integrity of cells is lost
- cell necrosis
- multiple organ dysfunction/failure
- DIC
Clinical signs of shock (6)
hypotension weak pulses tachycardia decreased urine production hyperventilation hypothermia
Lesions of shock (5)
cellular degeneration and necrosis generalized congestion edema hemorrhage (petechia, ecchymoses) thrombosis
