PathologyHemostasis LectureTaught by Dr. Lewis

Important definitions1. Edema – collection of fluid 2. Effusion – collection of fluid in a body cavity3. Hydrothorax/pleural effusion – collection of fluid in lungs / alveolar air spaces4. Ascites – fluid in the peritoneum 5. Anasarca – swelling everywhere

a. Usually do to low plasma proteinsb. Either not making albumin or are peeing it out (glomerulonephritis)

6. Hyperemia and congestion – too much blood / fluid a. Hyperemia is an active process – due to altered inflow into a tissue – e.g. vasodilation in

skeletal muscleb. Congestion is a passive process – altered outflow from a tissue

i. Secondary due to a pathological conditionii. E.g. Congestive heart failure – blood collects

7. Clot and thrombusa. Clot is coagulation of blood in a non vascular space – e.g. paper cutb. Thrombus – collection and coagulation of blood in a vascular space – e.g. heart failure

8. Hematomaa. Bleeding into a tissue / collection of blood b. E.g. a bruise

Causes of Edema1. Increased hydrostatic pressure, due to things like:

a. Impaired venous flow caused by thrombosis, heart failure and scarringi. Deep vain thrombosis

1. Saw a few questions with someone sitting on an airplane for a long time, get one swollen foot = deep vain thrombosis in the affected leg

ii. Heart failure1. Swelling wont be limited to one foot, will be more systemic2. Kidney will try to compensate – kidney detects low flow -> rennin

system will increase aldosterone -> retain salt -> increase plasma volume but dump it all back into a failing heart

a. The increased plasma volume increases hydrostatic pressure -> edema

b. Arteriolar dilation in inflammation2. Decreased osmotic pressure due to things like:

a. Glomerulonephritis – pee out all your proteinb. liver disease – stop making albuminc. nutritional deficiencies

i. more so in third world countries1. no intake at all – body does what it can to retain whatever protein it has2. kwashiorkor – low to no protein intake, worse than above in regards to

swellingd. kidney will try to compensate here too (bc of low flow to the kidney), but all the fluid

that is retained just ends up leaving the vessels again bc haven’t corrected the underlying problem of low plasma protein – so will actually make the swelling worse

3. lymphatic obstruction due toa. neoplasia – actual metastatic cells clog up lymphatic vessels b. surgery – removal of axilary nodes in breast cancerc. radiationd. infections

i. microfilaria infection in developing world

1

1. elephantiasis of lower limbs and genetailia + enlarged inguinal nodes4. salt retention – water follows salt

a. any time renal flow is low get aldosterone secretion and salt retentionb. salt retention can also be due to dietc. in both cases, salt retention:

i. increases hydrostatic pressure (more fluid circulating through vessels)ii. decreases oncotic pressure (whatever proteins you had are diluted by the extra

fluid)5. Heart Failure – see slides 13 and 14

a. Left sided is more common than right sidedi. Left sided is due to atherosclerosis / heart disease – kill heart tissue bit by bit

ii. Characterized by build up of fluid in lungs (heart can’t pump it so blood backs up into lungs)

1. what do you see on a slidea. pinkish filled air spaces b. macrophages full of hemosiderin – eat red blood cells trapped

in the lungb. Right sided failure is usually caused by left sided failure

i. Left side fails -> pressure in lungs increases -> right side can’t overcome that pressure -> right side fails

ii. This is your most common clinical picture – biventricular CHFc. Cor Pulmonale

i. Pure right sided heart failureii. Due to pulmonary infections or embolisms

d. Differentiating between left sided heart failure and Cor Pulmonalei. In left sided heart failure main symptoms are due to pulmonary congestion and

pulmonary edemaii. In Cor Pulmonale, despite the name, pulmonary symptoms are minimal

1. Pt present with Systemic and portal venous congestion syndromea. Hepato and spleenomegally (blood backed up in portal system

bc right atrium is full)b. Lots of peripheral edema and ascites

e. Forward effects of heart failure – effect on the kidneysi. kidney detects low flow -> rennin system will increase aldosterone -> retain salt

-> increased plasma volume but dump it all back into a failing heartMorphology and Distribution of edema

1. Localized vs Anasarca2. Dependant edema – sign of heart failure, particularly right sided

a. Swelling of dependant places in the body b. Mediated by gravity which pools blood in certain areas of the body resulting in increased

hydrostatic pressure i. E.g. legs when standing

ii. Sacrum when recumbent – hospital bed3. Pulmonary edema – sign of left sided heart failure

a. Fluid fills alveolar air spaces, hindering gas exchange 4. Periorbital edema – usually sign of head trauma

a. Space around the eyes allows for fluid to accumulate 5. Brain edema – medical emergency

a. Give high dose steroids to reduce inflammationb. Fluid is poorly drained bc of lack of lymphatic drainage in brain

6. Pitting edema – standard increased hydrostatic pressure / decreased osmotic pressure edemaa. Fluid filled with transudate

7. Non pitting edemaa. Caused by obstructed lymphatics

2

8. Hemorrhage, in increasing sizea. Petechiae (small pin point), purpura, >2cm = ecchymosisb. Hemothoraxc. Hematoma – bruise / collection of coagulated blood

9. Importance of blood volumea. Rapidly lose 20% or slowly lose more, its ok – any more loss and might go into shockb. Location is very important

i. Bleeding into a body cavity might be less severe than bleeding out1. Bleed in – reabsorb all the iron and heme 2. Bleed out – get anemia

ii. 65 year old man in hospital with anemia1. check for carcinoma of the colon – might be losing a lot of blood in shit

iii. 25 year old female with anemia1. give her some iron supplements

Hemostasis

1. Maintenance of flow and generation of plugs at bleeding sitesa. Most of the work is on flow maintenance, if it wasn’t we would clot to death

2. Pro flow factorsa. Endothelial PGI2 and NOb. Antithrombin 3

i. Inactivates thrombin (IIa) – generation of thrombin is the rate limiting step in the clotting cascade, converts fibrinogen to fibrin

ii. Heparin like molecules – increase activity of antithrombin 3c. Thrombomodulin

i. Binds to thrombin and facilitates activation of protein Cd. Protein c

i. Degrades activated clotting factors – Va and VIIIaii. Requires protein S from the endothelial cells

e. T-PA (tissue plasminogen activator??)i. Makes plasmin

ii. Plasmin splits fibrin iii. Only effective up to a certain point, once factor 13 is involved fibrin cannot be

split by plasmin (extensive cross linking has occurred due to actions of 13)3. Pro clotting factors

a. Injured endothelium becomes pro clotb. vWF facilitates platelet adhesion and aggregation

i. exposure of underlying ECM (especially collagen) is the strongest clotting activator

1. allows vWF to bind to collagen, platelets then bind to vWF2. note that vWF is always around, not produced upon injury

c. bacterial endotoxin (LPS) and cytokines like TNF and IL1 get the endothelium to make Tissue Factor - activates the extrinsic pathway

4. platelet functiona. first the platelet has to bind to the ECM – vWFb. once bound, platelet will secrete the contents of its granules

i. alpha granules1. fibrinogen, PDGF, TGFb, vWF, platelet factor 4 (heparin binding

chemokine – binds heparin so that it can’t increase antithrombin 3)ii. Dense bodies

1. ADP, Ca++, histamine, seratonin, epinephrine and TXA2 (vasoconstriction), phospholipid complex

iii. Expression of the phospholipid complexes is important1. Serve as binding sites for Ca++ and clotting factors

c. the granular contents now facilitate aggregationi. primary hemostatic plug formation induced by ADP and TXA2 (D. granules)

3

1. side note – formation of the primary hemostatic plug = bleeding timeii. to strengthen the plug, thrombin interacts with ADP and TXA2 to make

secondary hemostatic plugiii. thrombin is initially around in only small amounts, after secondary plug

formation it is secreted in larger amounts which cleaves fibrinogen (from alpha granules) into fibrin which “cements” the mass

d. how is clotting limited to sites of damage?i. vWF only binds to sites where ECM is exposed

ii. tissue factor and the phospholipids complex are only at the site of injury

the clotting cascade1. goal is to make thrombin – look at slide 302. have enzymes (the factors themselves), substrates (the next factor in the pathway), cofactors (can

be chelators – these speed up the reaction e.g. Citrate bdta which grabs Ca++, other cofactors = 8a and 5a) and phospholipid surface (assembly site)

a. Ca++ helps stick the thing together – carboxylation reactions key3. Basic outline

a. Extrinsic – 3,7,10b. Intrinsic – 12,11,9,10c. Common – starts at 10, 2, 1, 13d. Crosstalk – 10,7,9

4. Extrinsic pathwaya. 3 (tissue factor) is released upon endothelial injury or exposure to LPS b. as a cofactor, 3 complexes with 7 to form 3/7ac. 3/7a activates 10 to 10a – generates a quick burst of thrombin (needed everywhere)

i. 3/7a also crosses over to intrinsic and activates 9a5. intrinsic pathway

a. exposure of collagen causes formation of a complex composed of:i. pre kallikrien, HMW kininogen, 11 and 12

b. pre kallikrien converted to kallikrienc. kallikrien activates 12 into 12ad. 12a

i. activates 11 to 11aii. activates more kallikrien from pre kallikrein (keeps rnx going)

e. 11a activates 9 to 9af. 9 activates 10 to 10a on the surface of platelets / phospholipids complex

i. for this last step, have to form the tenase complex on the phospholipid surface 1. small amount of thrombin from the extrinsic path activated 8a2. 8a serves as a receptor for 9a, 10, Ca++

a. once it is all together have the tenase complex, 10 -> 10aii. Ca++ and VitK

1. Calcium is a cofactor, Vit K is needed in carboxylation rxnsa. Activation of factors 2,7,9 and 10 so they can bind calcium

2. Vit K deficiency, everything is present but can’t activate 10aiii. Warfarin / coumidin – how does it work?

1. Warfarin is a vitamin K antagonist - anticoagulant2. It inhibits carboxylation reactions in the clotting cascade

a. activation of 2,7,9,103. If someone has overdosed on warfarin – give VitK

6. Common pathwaya. Starts with formation of a complex similar to the tenase complex above – this is also on

the phoshpholipid surface:i. Small amounts of thrombin from extrinsic actiaved 5a

ii. 5a serves as a cofactor/receptor 10a, 2 (prothrombin) and Ca++1. once the complex is formed 2 –=converted to 2a (THROMBIN)2. thrombin

4

a. will activate 1 – 1a (fibrin)b. will also activate 13 – 13a (fibrinase)

i. transglutaminase that cross links fibrin (stable) 7. summary notes on thrombin

a. most important for activating 1a (fibrin)b. also activates 11 and the cofactors 8a (for activating 10a) and 5a (for activating 2a)c. when combined with thrombomodulin it can activate Protein C (in the presence of

protein S)i. will cleave 5a and 8a – anticoagulant action

d. major endogenous inhibitor of thrombin formation= antithrombin 3i. also inhibits IIa, 9a, 10a, 11a, 12a

e. can be inhibited pharmaceutically by Heparin -> ups antithrombin 3 1000X8. summary of cofactors

a. Ca++ is needed all across the intrinsic pathi. (12a -> 11, 11a->9, 9a->10, 10a->2)

b. need 3 to activate 7c. need 8a to get 10a (also need the phospholipid layer)d. need 5a to get 2a (also need the phospholipids layer)

9. lewis’s “real” sequencea. not really separate pathways bc of the crossover (7,9 and 10)b. extrinsic gives you a quick burst of thrombin and then intrinsic amplifies the responsec. deficiency in 12 or 11

i. no big deal -> from 7 can get to 9

10. managing pts with clotting problemsa. acute treatment – someone is over clotting – give IV heparin, fast to take effect, long

recovery

5

b. chronic treatment – can take warfarin / coumidin orally, short to tske effect but with Vitsmin K can quickly recover

i. e.g. valve replacement ptsc. monitor pts PT time to make sure drugs are in balance

Thrombosis11. Virchows triad – three factors that promote thrombosis (endothelial damage, Stasis and

hypercoagulability)a. Endothelial damage

i. Things like: trauma, ischemia, atherosclerosis, endotoxins, cig smoke, type 3 HSR (compliment mediated damage)

ii. Once damaged 1. ECM gets exposed to plasma (start the whole cascade)2. Phenotypic changes to endothelium (go pro clot - stop making pro flow

factors PGI2 and NO)b. Stasis / turbulence

i. In stasis, anticoagulants diminished, procoagulants become concentrated1. Blood is not moving -> inhibitors are normally around in small

amounts and with no movement these all get used up -> pro coagulants can now act without interference

2. Why Atrail Fibrilation is so scary – causes stasis – stasis leads to thrombis – thrombis out the heart and into your brain

ii. Turbulence – very bad shit1. Can lead to stasis (whirlpools of blood that don’t follow normal flow)2. Bc of the stasis, endothelium is not being adequately supplied with 02 -

> ischemic damage3. The turbulence itself is physically damaging to the endothelium

Example – Deep vain thrombosis (lower limbs)4. Already have stasis bc this area is slow flow5. The valves create areas of turbulence right underneath them6. Perfect place for thrombosis

a. Is why pts have to walk around after surgery – DVT can lead to pulmonary emboli and sudden death

iii. Baby asprin a day1. Does NOT break up clots2. But prevents thrombus formation

c. Hypercoagulability - dehydrationi. Heparin induced thrombocytopenia

1. Heparin is supposed to be an anticoagulant but in some cases antibodies are developed to heparin/PF4 complex that cross react with platelets

2. Causes the platelets to agglutinate and stick to endothelium3. Thrombocytopenia – blood analysis shows low platelets bc are all stuck

to endothelium or destroyed4. Small molecular weight heparin – decrease this risk of this reaction

ii. Antiphospholipid antibodies – e.g. cardiolipin1. Cross react with platelets2. Due to lupus – secondary anti phopsholipid antibody syndrome (apas)3. Or non autoimmune – primary apas4. Symptoms

a. Recurrent arterial and venous thrombosisb. Cardiac valve vegetationsc. Thrombocytopeniad. Miscarriages – antibodies developed inhibit tPA which the

trophoblast needs to lodge into the uterusiii. Prosthesis – mechanical valvesiv. Sickle cell disease – red cells clog up arteries

6

v. Inherited states – not very common, suspect it in pts under 50 with no other reason for their hypercoagulability

1. Leiden mutation in factor 5a – most common inherited mutationa. Makes it resistant to Protein C degradation

2. Gain of function mutations in prothrombin3. Homocysteinemia

a. Homocystein inhibits anti thrombin 3 and thrombomodulinb. Treatment = vit b12

vi. Other causes1. Low fibrinolytic capacity (plasmin can’t split fibrin)

a. One of the factors that predisposes women on the pill to clot (others include Leiden mutation, protein c and s deficiencies)

12. Morphology of thrombia. Postmortem vs antemortem

i. Antemortem – blood moving around is well mixed (cellular elements and fluid) – thrombus is dark in color = current jelly

ii. Postmortem – cellular elements and fluid separate – thrombi will have light and dark regions – light = chicken fat

b. Arterial vs Venousi. Arterial – high pressure, hard to form thrombus, red cells are moving quickly so

many DO NOT get stuck – thrombus is lighter in color1. Lines of zaun

a. Suggest arterial thrombib. Can see lines where red cells are not part of the clot and lines

where red cells are part of the clot – called laminationii. Venous – lower pressure, easier to form thrombi, red cells get lodged in the

thrombi – thrombus is darkerc. Mural thrombi – wall thrombi

i. Are formed in the walls of the heart chambers or aorta – can cause strokes13. Fate of thrombi

a. Propagation – the clot growsi. Heparin, warfarin / coumadin, baby asprin can all prevent this

b. Dissolutioni. Fibrinolytic / plasmin activity

c. Organization and recanalization – 24-48hoursd. Embolization

i. Piece breaks off and gets stuck somewhere else

Emboli1. Pulmonary emboli – see pics slide 54 - 67

a. Frequent cause of sudden death b. Majority stem from DVTc. May or may not cause infarction of tissue

i. Lung has a dual blood supply – same with liver d. Worst type is a saddle embolism

i. Starts in lower legii. Massive embolus that travels up, at the bifurcation of pulmonary artery one end

goes to the right and the other goes to the left – both lungs done 2. Fat emboli – pics 68 and 69

a. Occur due to crushing injuries b. Fat enters circulation, activates platelets and injures the endotheliumc. Fat is stained with sudan black

7

3. Amniotic Fluid Emboli – pic 71a. Complication that can occur when mothers blood is exposed to amniotic fluidb. Findings – squamous cells and hair cells (both from amnion) in lung arterioles c. Damage is caused by the biochemical rxns that induce shock in the mother - vasodilationd. If the mother survives the initial shock, often die from DIC (see below for def’n) due to

release of thrombogenic substances from the amnion4. Gas embolism

a. Most frequent cause – decompression sickness in divers and casson workers (NO2)b. Can occur during orthopedic surgery

i. Vessels in bone matrix are not collapsible – so when you cut bone air can get sucked into the vessels

1. Can be prevented / minimized if pts heart is above the operating siteii. Doesn’t occur in soft tissue bc vessels are collapsible

c. Injections – almost impossible – need 100cc of air to do some damage5. See slide 736. Arterial emboli

a. Most arise from mural thrombi in the wall of the left hearti. Left heart -> aorta -> anywhere in the body

b. Can be caused by abdominal aortic aneurismi. In aneurisms get stasis, turbulence and thrombosis

ii. Mostly below the origin of renal arteries and so emboli tend to just lodge in the lower leg somewhere – might have to cut off the toe

c. Atherosclerotic plaquei. Can break off and lodge somewhere

ii. Most dangerous is in the common carotid – travel to the braind. Damaged valves

i. Bad shit grows on them that can embolize – can end up anywhereii. Mitral and aortic are under more stress and so more prone to damage

Disseminated intravascular coagulation (DIC)1. Consumptive coagulopathy

a. Fibrin thrombi all over the microvasculature that use up all of the platelets and coagulation factors

b. Leaves you prone to massive bleeding in other areas of the body2. Fibrinolytic system will be activated

a. Diagnostic sign – elevated fibrin split products ***i. Will also have low platelets and clotting factors on blood test

ii. Pt might have massive GI bleedingiii. SHISTOCYTES (fragmented RBCs..cut up by clotting factors/fibers/split

products)3. Very sick ppl get this and mortality rate is high

a. A complication of anything that uses up all your thrombin

Tests for bleeding disorders1. Bleeding time

a. A measure of platelet functionb. Measures the time required to make the primary hemostatic plug (ADP and TXA2)c. Prolonged if deficienct in vWF or have low / poorly functioning platelets

2. Prothrombin time (PT)a. Measures extrinsic pathway + commonb. Prolonged if factors:

i. 5, 10, 2 (prothrombin) or 1 (fibrinogen) are messed – ALL COMMONii. 7 = pure extrinsic

3. Partial thromboplastin time (PTT)a. Measures intrinsic pathway + commonb. Prolonged if factors:

8

i. 5, 10, 2 or 1 = all commonii. 12, 11, 9, 8 = pure intrinsic

4. Note that the above two tests are done in tests tubes, inhibitors are put in so that the pathways can be isolated

a. Both PT and PTT are elevated = problem with the common pathwayb. All the times are ok according to test tube but pt is still bleeding = vit K deficiency ?

Infarction – slides 80 - 841. Death of tissue due to ischemic necrosis2. Almost all caused by thrombotic or embolic events3. Red or pale but wedged shaped infarct 4. Factors:

a. Anatomy of blood supply – most important factori. Liver and lung have dual blood supply so infarct usually less severe

1. Same for hand and forearmii. Kidney and spleen have end arterial systems – only one artery going in – most

damage if occludedb. Rate of occlusion

i. The quicker it develops the more severe the infarctii. With slower forming blocks, body can adapt via collateral vascularization

c. Organ dependence on aerobic metabolismi. Brain and heart will die fast, neurons will die the fastest

d. Oxygen content of the blood i. Anemic pts and heart failure pts

Shock – 3 forms

1. Cardiogenic Shocka. This is pump failure, but not due to heart failure (chronic condition), more acute stuff:

i. Muscle damage due to infarctionii. Cardiomyopathies

iii. Extrinsic compressioniv. Arrhythmiasv. Outflow obstruction (pulmonary embolism)

2. Hypovolumic Shocka. Blood or fluid loss (hemorrhage, burns, vomiting, diarrhea)

3. Septic Shocka. High mortality rateb. Usually caused by endotoxin from gram negative bacteria (organisms don’t have to be

alive)c. The sequence for endotoxic shock

i. Bacterial wall product LPS (endotoxin) is released when bacterial wall is degraded during normal inflammatory response

1. Injection of massive amount of LPS alone can cause shockii. LPS attaches to circulating LPS binding proteins

iii. LPS protein complexes bind to cell surface receptor (CD14)iv. Then activate toll like receptors 4 (TLR4)

1. TLR4 activated on endothelial cells – become pro clota. Decreases synthesis of tissue factor pathway inhibitor

i. So factor 3 of the extrinsic pathway is easily activated

b. Decreases synthesis of thrombomodulini. So have less activity of Protein C

2. TLR4 activated on macrophagesa. Release of TNF, IL1 and then IL6 (in that order)b. Lots of this shit leads to:

9

i. Systemic vasodilation (hypotension)ii. Diminished myocardial contractility

iii. Endothelial injury and thrombosis (DIC)iv. Alveolar capillary damage (ARDS)

4. Stages of Shocka. Nonprogressive – body can handle the situation – compensatory mechanisms activatedb. Progressive – tissue hypoperfusion and shit starting to hit the fan (acidosis kicking in)c. Irreversible – ischemic damage to the point that reperfusion can’t rescue the tissue

5. The “nightmare” or shocka. Initially body does its best to maintain fluid volume and output to the tissue

i. Tachycardia, vasoconstriction, kidney starts retaining fluidb. Hypoxia though induces anaerobic metabolism and lactic acid production increases

i. Lactic acid induces vasodlation (adding to effects of TNF, IL1 and IL6)c. Body starts to shut down

i. Low cardiac output, hypoxia gets worse, hypoxic heart lowers output even moreii. ATN – acute tubular necrosis

1. Kidney is damaged and can’t retain fluid -> eventually no flow -> DEAD

10