Chapter 4- Hemodynamic Disorders Flashcards
What is the most important cause of morbidity and mortality in western society?
Cardiovascular disease
What two pressures counteract each other within the vascular system?
Hydrostatic (BP)
Plasma colloid osmotic
What protein primarily drives colloid osmotic pressure?
Albumin
Under normal circumstances what direction is the net movement of fluid within the vasculature?
Small movement of fluid to interstitium (lymphatics drain)
What is edema?
Fluid in tissues
What are effusions?
Fluid build up within cavities
What is the difference between transudate and exudate?
Transudate- protein poor
Exudate- protein rich
What is anasarca?
Severe, systemic edema
What conditions can increase hydrostatic pressure?
DVT
CHF
Liver cirrhosis
Lymphatic obstruction
What conditions can reduce plasma osmotic pressure?
Nephrotic syndrome (albumin loss)
Reduced renal perfusion (reduced plasma volume)
Sodium retention (increased water retention)
What is subcutaneous edema dependent upon?
Gravity
What tissues does periorbital edema affect?
Loose connective tissue
Eg) eyelids
What is pulmonary edema characterized by?
Heavy lungs
Frothy, blood-tinged fluid
What are the risks associated with brain edema?
Cerebral blood flow impediment
Herniation
What is the morphology of generalized edema in the brain?
Narrow sulci, distended gyri
What does left sided heart failure cause?
Forces fluid back into lungs
What is the difference between hyperemia and congestion?
Hyperemia- active augmentation of blood flow due to arteriolar dilation, erythema
Congestion- passive fluid build up due to impaired tissue outflow, cyanosis
What are the two kinds of congestion?
- Systemic (CHF)
2. Local (isolated venous obstruction)
What is the difference between acute and chronic congestion?
Acute- distended vessels, grossly hyperemic organs
Chronic- focal hemorrhage, hemosiderin laden macrophages
What are heart failure cells?
Hemosiderin laden macrophages in the lungs
What does congestion in the lungs cause?
Interstitial edema and airspace transudates
How does congestion manifest in the liver?
Central vein and sinusoidal distension
Nutmeg liver
What is the function of hemostasis?
Maintenance of blood flow in a fluid state while inducing a rapid and localized hemostatic plug at the site of vascular injury
What are the phases of the hemostatic response?
- Vasoconstriction
- Primary hemostasis (plt plug formation)
- Secondary hemostasis (fibrin deposition)
- Clot stabilization and resorption (fibrin and plt contraction)
What is exposed upon vascular injury?
vWF
BM/ECM
What is the difference between adhesion and aggregation?
Adhesion- plts bind endothelium via vWF (GpIb)
Aggregation- plts bind each other via fibrinogen (GpIIb)
What starts the coagulation cascade?
TF exposure activates factor VII
What does the coagulation cascade result in?
Thrombin formation and the conversion of fibrinogen to fibrin
How do activated plts contribute to secondary hemostasis?
Thromboxane production- induces aggregation
Calcium binding- nucleation sites for coagulation factor complexes
What counter regulatory mechanisms prevent the clot from over growing?
vWF and TF aren’t exposed at intact endothelium
tPA
Anticoagulant factors
What is extravasation?
Leakage beyond the container
What is hemorrhagic diathesis?
Unusual susceptibility to bleed due to coagulopathy
What are the sizes of various hematomas?
Petechiae- 1-2mm
Purpura- <1cm
Ecchymoses- >1cm
What deficiencies are associated with aggregation and adhesion?
Aggregation- Glanzmann thrombasthenia (GpIIb)
Adhesion- Bernard-Soulier syndrome (GpIb) and von Willebrand disease (vWF)
PT is associated with which pathway of the coagulation cascade?
Extrinsic
What are the functions of thrombin?
- Fibrinogen to fibrin conversion
- Induction of plt activation and aggregation
- Pro-inflammatory effects (protease activated receptors)
4! Anticoagulant when normal endothelium present
What does intact endothelium produce to exert anticoagulant effects?
NO
Prostaglandin
tPA
What is the function of plasmin?
Breaks down fibrin, interferes with polymerization
Where does plasmin come from?
tPA cleaves plasminogen
What is the function of alpha-2-antiplasmin?
Binds and inhibits free plasmin
How does the endothelium prevent a hemostatic response when it is not required?
Plt inhibitory effects- plts are shielded from vWF and collagen (aggregation inhibited)
Anticoagulant effects- plts are shielded from TF (coagulation inhibited)
Fibrinolytic effects- tPA secretion
What is the difference between primary and secondary hemorrhagic disorders?
Primary- involves plts or vWD
Secondary- coagulation factor disorders
What are the components of Virchow’s triad that lead to thrombosis?
- Endothelial injury
- Abnormal blood flow
- Hypercoaguability
How do you distinguish between an arterial and venous thrombi?
Arterial- retrograde growth, occlusive
Venous- grow in the direction of blood flow
Where do mural thrombi occur?
Heart chambers or aorta
How are post-mortem clots different from thrombi?
Lack lines of Zahn
Gelatinous (dark red portions and yellow chicken fat portions)
What are vegetations?
Thrombi on heart valves
What are the different types of vegetations?
Infective endocarditis- blood borne infection
Nonbacterial- sterile, hypercoaguable states
Sterile verrucous endocarditis/Libman Sacks (SLE)
What are the possible fates of a thrombus?
- Propagation
- Embolization
- Dissolution
- Organization and recanalization
What is phlebothrombosis?
Superficial thrombi in varicose saphenous veins
Rarely embolize
What is Trosseau syndrome?
Tumour associated procoagulant disease
Cancer cells form migratory microvenous thrombi
What veins are usually associated with DVT?
Popliteal
Femoral
Iliac
What are two major causes of arterial thrombi?
- Atherosclerosis
2. MI
What is DIC?
Widespread fibrin microthrombi due to diffuse thrombin activation
Can cause circulatory insufficiency
What is an embolism?
Any mass carried by blood flow to a distant site
What are some complications of emboli?
Vascular occlusion
Ischemic necrosis
What is the most common form of embolism?
Pulmonary
What are the different types of emboli?
- Pulmonary
- Systemic (left/arterial)- intracardiac mural thrombi
- Fat and marrow- bone fractures
- Air- decompression sickness
- Amniotic fluid
What is Caisson disease?
Chronic form of decompression sickness, has emboli persist
What is a paradoxical embolism?
Venous embolus passes through a defect in the heart and enters systemic circulation
What can multiple pulmonary emboli lead to?
Hypertension and right ventricular failure
What is an infarction?
Area of ischemic necrosis caused by occlusion of supply or drainage
What is the most common cause of an infraction?
Arterial thrombosis/embolism
What does venous thrombosis commonly cause?
Congestion
How are infarcts classified?
Colour- red (venous) vs white (arterial)
Infection- septic (vegetation’s embolize)
What factors influence the development of infarcts?
Anatomic pattern of vascular supply (dual circulation, anastomosing, end arterial)
Rate of occlusion
Vulnerability to hypoxia
Oxygen content of the blood
What is shock?
Systemic hypoperfusion
What are the three kinds of shock and their causes?
- Cardiogenic- low cardiac output
- Hypovolemic- low blood volume
- Associated with systemic inflammation- outpouring of inflammatory mediators
What is the cause of septic shock?
Microbial injury leads to inflammatory response causing systemic vasodilation, hypercoaguable state and DIC
Multi-organ dysfunction
What are the phases of shock?
- Non-progressive- reflex compensatory mechanisms
- Progressive- hypoperfusion, electrolyte disturbances
- Irreversible- damage too severe
