Hemodynamics Flashcards
What needs to be maintained in normal fluid homeostasis? Give examples of when these fail.
- vascular wall integrity (trauma causes focal defects in vessel wall)
- intravascular hydrostatic pressure (CHF causes alveolar capillary congestion and eventually pulmonary edema)
- osmolarity (cirrhosis causes low intravascular protein levels, leading to edema)
Define edema (what is the normal fluid balance?)
Accumulation of interstital fluid in subcutaneous tissues or body cavities (e.g. pleural cavity)
**Normally 2/3 intracellular and 1/3 extracellular body fluid
What is anasarca?
Very severe generalized edema
What causes edema?
Either increased hydrostatic pressure or decreased osmotic pressure (leads to net accumulation of fluid in interstitium)
What are some causes of increased hydrostatic pressure?
- Venous obstruction (e.g. DVT)
- Impaired venous return (e.g. CHF -> increased alveolar capillary pressure -> pulmonary edema)
- Arteriolar dilation (e.g. from heat or CNS dysfunction)
What are some causes of reduced osmotic pressure?
- Excessive loss of albumin from…
- nephrotic syndrome
- enteropathy (IBD, infections, etc)
- malnutrition
- liver disease (reduced synthesis of albumin)
What are three causes of lymphedema?
- Inflammation (e.g. lymphatic fibrosis from parasitic infection)
- Neoplastic
- Post-surgical/post radiation (most common)
What are three common locations edema is observed?
- Subcutaneous (from CHF/renal failure)
- Pulmonary (most commonly from left ventricular failure)
- Edema of the brain (focally from tumors or diffusely from viral infections)
Define hyperemia
Increase in blood volume within a tissue (due to increase blood flow and arteriolar dilation… an ACTIVE process)
e.g. conjunctivitis inflammation or in exercising skeletal muscles
Define congestion
Increase in blood volume within a tissue (due to decreased outflow of venous blood… a PASSIVE process)
e.g. systemically (liver/lung congestion due to CHF), or locally (obstruction of superior sagittal sinus of dura)
Define hemorrhage. What are some common causes?
Extravasation of blood from vessels and its accumulation within a space
Common causes:
- ruptured vessel (trauma, aneurysm)
- peptic ulcer
- chronic congestion (liver, lungs)
- predisposition to hemorrhage (decreased ability to clot)
Define hematoma
Accumulation of blood within a tissue (e.g. epidural/subdural, intracerebral, subcutaneous)
What are petechial hemorrhages?
Hemorrhages into skin, mucous membranes, or serosal surfaces (1-2 mm)
**associated with low platelet counts, platelet dysfunction, loss of vascular wall support, or local pressure
Define purpura
>3 mm hemorrhages associated with same disorders as petechiae
Define ecchymoses
>1-2 cm subcutaneous hematomas (bruises) associated with trauma
What are some main players in inhibiting thrombosis?
- Protein C (along with protein S) causes the proteolysis of factors Va and VIIIa -> shuts down clotting cascade
- Antithrombin III inactivates thrombin -> prevents fibrin formation (from fibrinogen)
Contrast primary and secondary hemostasis factors
- Primary (platelets adhere to wall)
- vasculature
- blood flow
- platelet count/function
- extracellular matrix proteins
- Secondary (clot formation)
- platelet plug
- coagulation factors (thrombin, fibrin)
What are the laboratory screening tests for primary and secondary hemostasis?
- primary hemostasis
- platelet count and function (PFA-100, aggregation studies)
- vWillebrand studies (antigen and activity)
- secondary hemostasis
- prothrombin time (PT -> extrinsic and common pathways)
- activated partial thromboplastin time (aPTT -> intrinsic and common pathways)
- fibrinogen activity
What is factor 5 leiden?
The most common inherited predisposition to thrombosis (a single point mutation in the cleavage site for protein C)
**mutation means protein C doesn’t work correctly and cannot break down factors Va and VIIIa -> increased clotting results
What is Virchow’s triad?
Three primary abnormalities lead to thrombus formation:
- endothelial injury
- abnormal blood flow
- hypercoagulability
Define thrombosis
Formation of a blood clot within intact vessels
*may fragment and create emboli
What are lines of Zahn?
Laminations apparent grossly and/or microscopically produced by alternating layers of platelets, fibrin, and RBCs
What are some characteristics of a venous thrombosis?
- No associated inflammation
- 50% are asymptomatic
- Thrombi in superficial veins (saphenous) of legs rarely embolize -> cause loval swelling/pain/skin ulceration
What are the possible fates of a deep vein thrombus?
- Resolution (only if given thrombolytic agent)
- Embolization to lungs
- Organization and recanalization
- Propagation towards heart (rare)
Define embolus
A detached intravascular mass carried by blood to site distant from origin
What are some types of emboli?
- Thromboembolism (most common)
- Fat (long bone fractures, soft tissue damage/burns)
- Air (obstetric procedure, divers)
- Amniotic fluid
- Tumor (metastasis through blood)
What is the most common type of embolism?
A pulmonary embolism (usually from a DVT)
*Most are asymptomatic but can cause serious consequences with “saddle” emboli at bifurcation of pulmonary arteries or multiple emboli
**Cause sudden death and pulmonary hemorrhage/infarction
Define infarction
Area of ischemic necrosis caused by occlusion of either the arterial supply or the venous drainage of affected tissue
Contrast a red infarct and a white infarct
- Red
- hemorrhagic
- classic example= lung infarct secondary to embolus
- occurs in loose tissues (allows blood to collect)
- occurs in dual circulation tissues
- occurs when flow is re-established and in venous occlusions
- White
- anemic (no blood)
- occurs in solid organs with end-arterial circulation (e.g. spleen, kidney)
Give examples of dual blood supply organs and end arterial circulation organs
dual blood supply organs
- lung (bronchial and pulmonary arteries)
- liver (hepatic arter, portal vein)
- forearm/hand (ulnar and radial arteries)
end arterial circulation organs
- kidney
- spleen
What is the difference between a hematoma and a hemorrhagic infarct?
A hemorrhagic infarct has blood intermixed with necrotic tissue
In a hematoma, blood is collected and forms a solid mass
What is disseminated intravascular coagulation (DIC)?
- Characterized by initial clotting (microangiopathy), resulting in organ ischemia, followed by bleeding tendencies
- “Consumption coagulopathy” (widespread clotting leads to consumption of factors/platelets
- Associated with severe illness (sepsis, trauma, cancer, burns, ischemia)
Define shock (cardiovascular collapse)
Systemic hypoperfusion caused by:
- reduced cardiac output (pump failure from infarct, embolism, arrhythmia)
- decrease in effective circulating blood volume (from hemorrhage, fluid loss, septic/neurogenic/anaphylactic shock)
**hypotension -> impaired perfusion/cellular hypoxia -> tissue injury -> death
What are the major types of shock?
- Cardiogenic (failure of myocardial pump)
- Hypovolemic (inadequate blood/plasma volume)
- Septic (many mechanisms including DIC)
- Neurogenic shock (interruption of sympathetic vasomotor input with spinal cord injury)
- Anaphylactic shock (IgE mediated hypersensitivity)
What are the stages of shock?
- Nonprogressive phase (initial)
- tachycardia, peripheral vasoconstriction, renal fluid conservation (via sympathetic stimulation)
- perfusion of organs maintained
- Progressive phase
- tissue hypoxia/lactic acidosis
- lowering of tissue pH and blunting of vasomotor response
- tissue hypoperfusion present
- Irreversible phase
- cellular/organ injury preventing survival
- excessive production of lactic acid (anaerobic glycolysis)
What are some clinical manifestations of shock?
- hypovolemic and cardiogenic:
- hypotension, tachycardia, tachypnea
- cool, clammy, and cyanotic skin
- septic shock:
- hypotension, tachycardia, tachypnea
- peripheral vasodilation initially leads to warm and flushed skin
What is the common cause of septic shock?
Most often gram POS bacterial followed by gram NEG bacteria and fungi
