Haemorrhage Flashcards
What is shock
Excessive blood loss leading to a decrease in blood volume and blood pressure, resulting in cells not having enough nutrients and oxygen
What is the immediate, short, medium and long term response to blood loss
Immediate - stop bleeding
Short- increase blood pressure
Medium- increase fluid volume
Long - replace blood constituents
What are the two steps in haemostasis
First is the vascular response. Second is the platelet response.
Vascular responses- the smooth muscle in the blood vessel will contract to reduce blood flow to that area. The endothelial cells also release substances that promote platelet aggregation
Platelet response is the platelets coming together to adhere and aggregate, for axing a platelet plug. Thromboxane released by the platelets via positive feedback causes further aggregation, sealing the damaged blood vessel
What produces thromboxane a2
It is a vasoconstrictor that is released by activated platelets.
Functions of thromboxane a2
Vasoconstriction
Promotes platelet aggregation
Bronchoconstriciton (constriction of smooth muscles in airways)
Inflammation
What is the plasma response of haemostasis
Coagulation cascade - intrinsic, extrinsic, common pathway involving clotting factors, vitamin K
Where are clotting factors made
Liver
Important clotting factors
Hageman factor 12
Which coagulation pathway is more important in clotting
Extrinsic pathway,
Intrinsic serves more to maintain the process once it has started
Which clotting factor is associated with extrinsic pathway
7
Which clotting factor is activated when blood comes into contact with sub-endothelial connective tissue outside the blood vessel
Hageman factor (12) in the intrinsic pathway
Is it the extrinsic or intrinsic pathway that has a role in thrombosis
Intrinsic pathway
Intrinsic pathway - vascular damage
Extrinsic pathway - connective tissue damage
Common pathway - fibrinogen to fibrin with the help of thrombin
Due to heavy blood loss, blood pressure falls. What happens to baroreceptors?
Baroreceptors decrease firing in response to Low blood pressure causing an increase in sympathetic nervous system activity
Does veins and arteries constrict or dilate when we haemorrhage
Constriction (response by baroreceptors)
Which hormones (non local )causes vasoconstriction and increases total peripheral resistance?
Angiotensin II
Vasopressin = ADH
Adrenaline
How do we restore blood volume (3 points)
Increase Reabsorption at kidneys
Increase thirst via hypothalamus
Shifting interstitial fluid back into blood vessels
What stimulates the hypothalamus
An increase in plasma osmolarity and a decrease is ECF volume
What is erythropoietin
It is a protein that is needed for the production of red blood cells
Where is EPO made
Erythropoietin is made in the KIDNEYS
What is hypovolaemic shock caused by
A huge decrease in blood volume
Eg severe bleeding or dehydration
What is anaphylactic/septic shock caused by
A huge decrease in total peripheral resistance due to widespread vasodilation
Hypovolaemic shock causes a decrease in cardiac output
Anaphylactic shock or septic shock causes a decrease in tpr
Map= co x tpr
How does capillary hydrostatic fall during haemorrhage to favour shifting interstitial fluid back into blood vessels?
Vasoconstriction by baroreceptors and symoahtthic nervous system caused the resistance to rise, increase in resistance means slower blood flow and lower hydrostatic pressure pushing fluid out of the capillary
Is there an increase or decrease in plasma osmolarity when we haemorrhage
Increase in plasma osmolarity
