Hemodynamics

Question 1

What needs to be maintained in normal fluid homeostasis? Give examples of when these fail.

Answer 1

• 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)

Question 2

Define edema (what is the normal fluid balance?)

Answer 2

Accumulation of interstital fluid in subcutaneous tissues or body cavities (e.g. pleural cavity)

**Normally 2/3 intracellular and 1/3 extracellular body fluid

Question 3

What is anasarca?

Answer 3

Very severe generalized edema

Question 4

What causes edema?

Answer 4

Either increased hydrostatic pressure or decreased osmotic pressure (leads to net accumulation of fluid in interstitium)

Question 5

What are some causes of increased hydrostatic pressure?

Answer 5

• 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)

Question 6

What are some causes of reduced osmotic pressure?

Answer 6

• Excessive loss of albumin from…
  
  • nephrotic syndrome
  • enteropathy (IBD, infections, etc)
  • malnutrition
  • liver disease (reduced synthesis of albumin)

Question 7

What are three causes of lymphedema?

Answer 7

1. Inflammation (e.g. lymphatic fibrosis from parasitic infection)
2. Neoplastic
3. Post-surgical/post radiation (most common)

Question 8

What are three common locations edema is observed?

Answer 8

1. Subcutaneous (from CHF/renal failure)
2. Pulmonary (most commonly from left ventricular failure)
3. Edema of the brain (focally from tumors or diffusely from viral infections)

Question 9

Define hyperemia

Answer 9

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

Question 10

Define congestion

Answer 10

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)

Question 11

Define hemorrhage. What are some common causes?

Answer 11

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)

Question 12

Define hematoma

Answer 12

Accumulation of blood within a tissue (e.g. epidural/subdural, intracerebral, subcutaneous)

Question 13

What are petechial hemorrhages?

Answer 13

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

Question 14

Define purpura

Answer 14

>3 mm hemorrhages associated with same disorders as petechiae

Question 15

Define ecchymoses

Answer 15

>1-2 cm subcutaneous hematomas (bruises) associated with trauma

Question 16

What are some main players in inhibiting thrombosis?

Answer 16

1. Protein C (along with protein S) causes the proteolysis of factors Va and VIIIa -> shuts down clotting cascade
2. Antithrombin III inactivates thrombin -> prevents fibrin formation (from fibrinogen)

Question 17

Contrast primary and secondary hemostasis factors

Answer 17

• Primary (platelets adhere to wall)
  
  • vasculature
  • blood flow
  • platelet count/function
  • extracellular matrix proteins
• Secondary (clot formation)
  
  • platelet plug
  • coagulation factors (thrombin, fibrin)

Question 18

What are the laboratory screening tests for primary and secondary hemostasis?

Answer 18

• 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

Question 19

What is factor 5 leiden?

Answer 19

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

Question 20

What is Virchow’s triad?

Answer 20

Three primary abnormalities lead to thrombus formation:

1. endothelial injury
2. abnormal blood flow
3. hypercoagulability

Question 21

Define thrombosis

Answer 21

Formation of a blood clot within intact vessels

*may fragment and create emboli

Question 22

What are lines of Zahn?

Answer 22

Laminations apparent grossly and/or microscopically produced by alternating layers of platelets, fibrin, and RBCs

Question 23

What are some characteristics of a venous thrombosis?

Answer 23

• No associated inflammation
• 50% are asymptomatic
• Thrombi in superficial veins (saphenous) of legs rarely embolize -> cause loval swelling/pain/skin ulceration

Question 24

What are the possible fates of a deep vein thrombus?

Answer 24

• Resolution (only if given thrombolytic agent)
• Embolization to lungs
• Organization and recanalization
• Propagation towards heart (rare)

Question 25

Define embolus

Answer 25

A detached intravascular mass carried by blood to site distant from origin

Question 26

What are some types of emboli?

Answer 26

* Thromboembolism (most common) * Fat (long bone fractures, soft tissue damage/burns) * Air (obstetric procedure, divers) * Amniotic fluid * Tumor (metastasis through blood)

Question 27

What is the most common type of embolism?

Answer 27

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

Question 28

Define infarction

Answer 28

Area of ischemic necrosis caused by occlusion of either the arterial supply or the venous drainage of affected tissue

Question 29

Contrast a red infarct and a white infarct

Answer 29

* 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)

Question 30

Give examples of dual blood supply organs and end arterial circulation organs

Answer 30

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

Question 31

What is the difference between a hematoma and a hemorrhagic infarct?

Answer 31

A hemorrhagic infarct has blood _intermixed with necrotic tissue_ In a hematoma, blood is collected and _forms a solid mass_

Question 32

What is disseminated intravascular coagulation (DIC)?

Answer 32

* 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)

Question 33

Define shock (cardiovascular collapse)

Answer 33

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

Question 34

What are the major types of shock?

Answer 34

1. Cardiogenic (failure of myocardial pump) 2. Hypovolemic (inadequate blood/plasma volume) 3. Septic (many mechanisms including DIC) 4. Neurogenic shock (interruption of sympathetic vasomotor input with spinal cord injury) 5. Anaphylactic shock (IgE mediated hypersensitivity)

Question 35

What are the stages of shock?

Answer 35

* 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)

Question 36

What are some clinical manifestations of shock?

Answer 36

* 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**

Question 37

What is the common cause of septic shock?

Answer 37

Most often gram POS bacterial followed by gram NEG bacteria and fungi