Blood flow Flashcards
% of persons body weight that is water
60
Definition of Edema
Accumulation of abnormal fluids in the interstitial / intercellular tissue → swelling of the
subcutaneous tissues
control mechanisms of edema
- Starling’s Law.
- Local factors
i) lymphatic obstruction.
ii) vascular permeability. - Systemic factors
i) cardiovascular function.
ii) overall fluid balance.
iii) salt retention.
Starlings law and the forces
movement of fluid between vessels and tissue is governed by the balance between 4 forces:
Hydrostatic pressure in vessel which measures
o 32 mmHg at arterial end
o 12 mmHg at the venous end.
Oncotic pressure = Colloid osmotic pressure (COP) of plasma (26 mmHg) which reflects the amount of
serum protein (albumin).
Interstitial pressure (tissue tension) = 3-4 mmHg.
Tissue fluid osmotic pressure (very low)
4 ways edema will occur w starling forces
- An increase in intravascular hydrostatic pressure: due to increased venous pressure
Clinical examples:
a. congestive heart failure: Right side failure –> peripheral edema or Left side failure –> lung
edema
b. deep venous thrombosis of lower legs (see the Case Study - A fall in colloid osmotic pressure of plasma: due to hypoproteinemia
Clinical examples:
o Liver disease as cirrhosis (liver failure): decrease synthesis of albumin
o Renal failure: loss of albumin in urine
o Malnutrition
. - Lymphatic obstruction: accumulation of interstitial fluid because of insufficient reabsorption and
deficient removal of proteins, the latter increasing the oncotic pressure of the fluid in the interstitial
space
Clinical examples:
o cancer
o inflammation
o postsurgical lymphedema - Sodium retention: causes both increase in hydrostatic pressure and reduced vascular osmotic
pressure
Clinical examples:
o kidney diseases
2 types of edema
- Localized edema: occurs due to
i) increased hydrostatic pressure due to vascular obstruction (local).
ii) Lymphatic obstruction: compression by tumour or inflammation (local). - Generalized edema: occurs due to:
i) increased hydrostatic pressure: i.e. heart failure.
ii) decreased oncotic pressure (colloid osmotic pressure) due to:
- loss of albumin in renal failure.
- decreased synthesis of albumin (liver failure).
iii) Sodium retention → Kidney disease.
Transudate vs exudate
Transudate
Results from disturbances in Starling forces
Protein <3 g/dl
Specific gravity <1.012
Exudate
results from damage to capillary wall
Protein >3 g/dl
Specific gravity >1.020
Thrombosis - what does it consist of
- formation of mass (clotted blood) in the heart or blood vessels.
The mass is called a “thrombus” and it consists of: Red blood cells White blood cells Platelets Fibrin
causes of thrombosis
Vessel wall damage/alteration: o injury → tear o inflammation Changes in blood flow: o turbulence (in an aneurysm or at site of arterial branching) o stasis (slow circulation). o lack of activity. o decreased cardiac output. o increased blood viscosity. Changes in blood composition (hypercoagulability): o ↑ platelets
Prognosis of thrombosis
Can increase in size and obstruct vessels.
Can breakdown and form emboli.
Can dissolve or be lyzed by fibrinolytic activity
Can become organized and may recanalize.
complications of thrombosis
Fragments of thrombus break off and result in thromboembolization/emboli.
Reduced blood flow to a tissue/organ resulting in ischemic injury or infarction
embolism
Occlusion of a blood vessel by a mass (embolus) transported to the site through the blood stream.
types of embolism
- Thrombi
-The most common type of emboli
- Thromboemboli arise from thrombi and range in size from microscopic to those which are large
enough to occlude major arteries
- Thromboemboli may occur in either arteries or veins - Gas (air) = gas bubbles in divers; may be accidentally introduced during invasive procedures
- Fat = often after fracture of large bones
- Tumor
- Others = foreign body = drug addicts
what is ischemia due to and what does it result in
due to: Inadequate blood supply to an area of tissue.
- The result is: Infarction → area of necrosis (death) produced by ischemia
causes of ischemia
- Decreased blood supply: (inadequate cardiac output).
- Obstruction of blood vessel by:
o thrombus
o embolus
o pressure (outside pressure)
o damage of the vessel wall:
→ inflammation
effects of ischemia
depends on degree of ischemia.
no effects → if there is alternate blood supply.
tissue death (infarction) → if severe and complete.
what is an infarction
An area of necrosis which typically produced by ischemia
- Infarct area is wedge-shaped
- Infarction is an irreversible process and healing occurs by fibrosis
types of infarction
White infarct
◦ Arterial occlusion
◦ Solid organs as Heart, spleen, kidney, brain
◦ Leg gangrene
Red infarct ◦ Venous or arterial occlusion ◦ Loose tissue as lung ◦ Dual blood supply ◦ Brain, intestine
hemorrhages
(bleeding): a discharge or escape of blood from the blood vessels into the surrounding tissues or to the exterior of the body or into a body cavity
causes of hemorrhage
- Trauma to large blood vessels due to surgical procedures or fracture
- Weakened artery (from atherosclerosis, e.g. abdominal aortic aneurysm; congenital weakness, e.g.
berry aneurysm in Willis circulation) - Infections (e.g. pulmonary tuberculosis)
- Invasive tumors (erosion of vessel wall)
- Hypertension (increase intraluminal blood pressure)
- Hemorrhagic diatheses (spontaneous hemorrhage): affecting capillaries (small blood vessels) including:
o Thrombocytopenia
o Severe decrease in number of platelets
o Deficiency of coagulation/clotting factors
hematoma vs purpura
Hematoma: bleeding into the soft tissues.
Purpura: diffuse, superficial hemorrhages in the skin, as large as 1 cm.
Ecchymosis vs petechia
Ecchymosis: a larger superficial hemorrhage (e.g. a ‘black’ eye); skin discoloration reflects products of
heme degradation from hemoglobin in the RBCs.
Petechia: a pinpoint hemorrhage (1-2 mm), usually in the skin; represent rupture of capillaries or
arterioles and mainly involving skin, mucous membranes and serosal surfaces.
hemothorax vs hemoperitoneum vs hemoarthrosis
Hemothorax / hemopericardium
o Collection of blood in the pleural cavities due to trauma or rupture of aorta
o Collection of blood in pericardial cavity around heart due to rupture of heart or the aorta
Hemoperitoneum
o Collection of blood in the abdominal cavity due to rupture of an aortic aneurysm or trauma to
liver, spleen, or aorta
Hemoarthrosis
o Collection of blood in joint
what is shock and what is it characterized by
Characterized by failure of the circulatory system to maintain an appropriate blood supply to the
microcirculation with resultant inadequate perfusion of vital organs.
- Generalized inadequate perfusion of all cells and tissue of vital organs
what is shock due to
Decreased blood volume
Decreased cardiac output
Redistribution of blood
types of shock
- Hemorrhagic/hypovolemic
- Cardiogenic
- Septic
- Anaphylactic/Neurogenic
hypovolumetric shock is due to ______ as a result of….
Due to loss of fluid from vascular compartment (decreased blood volume): as a result of
a. Loss of blood: Hemorrhage (external) or massive internal hemorrhage
b. Decrease Plasma volume: e.g. burns
c. Fluid loss: e.g. diarrhea ,excessive urine formation, sweating or vomiting
2 reasons for cardiogenic shock
- Inability of the heart to pump blood
a. Myocardial infarction
b. Pericardial tamponade (fluid accumulate in the pericardium around the heart) - Extensive impairment of cardiac output
a. pulmonary embolism
what is septic shock from
bacteremia
anaphylatic and neurogenic shock
a. Anaphylaxis : Allergic condition
b. Neurogenic: anaesthesia, injury of spinal cord
- Peripheral vasodilation - associated with anaphylaxis, neurogenic and septic shock (due to release of factors (cytokines, bacterial endotoxins, etc.) that cause dilation and increased
permeability of the vessels).
effect of shock
The result of decreased tissue perfusion is hypoxic or anoxic cell injury which may lead to further decline in cardiac output (for example as a result of renal failure, heart failure, further endothelial cell damage).
