Flashcards in Topics A16-21 - Hemodynamic Disorders: Shock, Edema, Thrombosis, DIC, Embolism, Hemorrhages Deck (69)
Shock definition and some general features
Systemic hypoperfusion, with noted hypoxia, hypotension, and poor removal of waste products. Starts as reversible shock, but eventually becomes irreversible.
It is the final common pathway of many lethal events.
What are 3 causes of cardiogenic shock?
1. Pump failure: no proper contractility. Caused by arrhythmias or AMI
2. Diastolic failure: example is cardiac tamponade (bleeding inside pericardial sac -> compresses right side of heart and prevents it from filling in diastole)
3. Outflow failure: for example with pulmonary embolism, right side cannot push past it
What are two causes of hypovolemic shock?
1. Bleeding: severe hemorrhage is the classic hypovolemic shock, the basis for most concepts of shock. Physiologists killed so many dogs for this
2. Loss of plasma: for example burning leads to extravasation of plasma. Also severe dehydration.
Anaphylactic shock is described in what type of hypersensitive reaction?
Why (very generally) does shock occur here?
HS type I.
Shock occurs because an allergic reaction causes massive histamine release from mast cells and eosinophils, which causes far too much peripheral vasodilation for the body to maintain a healthy blood pressure. This will be in later topics, that's it for here
Why does spinal cord injury cause shock? What type of shock is this?
It's called Neurogenic Shock
Occurs because neural tone is necessary to contract peripheral blood vessels. Injury removes this neural tone, and so massive vasodilation occurs.
What is the most important shock today? - Why?
Septic shock, because of major risks for hospital-acquired infection and the many immuno-compromised patients (on steroids, chemotherapy, AIDS, etc...)
Robbins says it's the #1 cause of mortality in intensive care units and has a 20-25% mortality rate
What pathogenic molecules are normally in the background of septic shock?
PAMPs like LPS (from Gram neg bacteria). It's detected by macrophage PRRs, and macrophages initiate a cytokine storm that causes the major problems of septic shock
What are some important molecules that are released in the cytokine storm related to septic shock? (there are 5 that Matolcsy listed)
(Others: IL-6, IL-8, NO, PAF, complement activation, goes on and on and on)
What are the 3 major consequences of cytokine storm that occur in septic shock?
1. Increased thrombosis, causing DIC (disseminated intravascular coagulation)
2. Increased permeability: edema and hypovolemia
3. Vasodilation: causes hypotension (key feature of shock)
What do inflammatory cytokines of the cytokine storm do to the endothelium?
Inflammatory cytokines loosen endothelial tight junctions. The junctions then become leaky, causing fluid to flow out and edema to form.
How is metabolism altered during septic shock?
Release of insulin is decreased and peripheral insulin resistance increases, causing the blood glucose level to increase. This provides more fuel for bacteria and helps them proliferate.
Hyperglycemia also decreases neutrophil activity
What are 4 major organs effects during multiorgan failure?
1. Bowel becomes leaky with hypoxia, allowing intestinal bacteria to enter circulation
2. Lung: capillary endothelial cells are leaky, causing hyaline membrane disease and ARDS (adult respiratory distress syndrome)
3. Kidney: blood flow is shut off to it, vasoconstricted so blood flows elsewhere. Low urine output, poor filtration, build up of toxic metabolites in kidney, and acute tubular necrosis (ATN)
4. Heart: reduced contractility
What is the first of 3 stages of shock? (the Matolcsy classification, it's probably different in the books)
1. Initial progressive stage: most people just call this reversible shock. The shock is under control, compensatory mechanisms like increased sympathetic tone, renin-angiotensin system, etc help keep blood pressure relatively normal.
What is the 2nd of 3 stages of shock?
Progressive stage: shock begins to be out of control. Widespread hypoxia occurs. Anaerobic glycolsis causes lactic acidosis, low pH. All generates failure of peripheral circulation
What is the final stage in the 3 stages of shock?
Irreversible stage: damage is so severe that even if you were able to restore full hemodynamic function, the person would still die. Enzyme leakage has destroyed too much tissue, renal failure due to tubular necrosis, ischemic bowel has let bacteria into the circulation, etc.
What percentage of the body weight is water?
What amount of that is in the intracellular vs extracellular space?
60% BW is water
1/3 extracellular (mostly in interstitial space)
What is the difference between transudate and exudate?
Transudate: low-protein fluid (specific gravity <1.012). Occurs with volume or pressure overload or reduced plasma protein content
Exudate: protein-rich fluid (sp. gravity >1.012). Related to inflammation and increased vascular permeability
Why does liver failure cause general edema (not just from portal system backup)
What other organ problem may cause the same problem?
The damaged liver has low protein output, especially of albumin, meaning that the blood has reduced colloid osmotic pressure that pulls fluid back from the extravascular space.
Nephrotic syndrome may cause the same problem because the glomerular capillary wall is leaky and loses albumin in the urine
Edema can develop from increased hydrostatic pressure in either systemic or local ways. How?
Local: impaired venous return, like a deep vein thrombosis, means hydrostatic pressure builds up backwards in the leg and forces more transudate out of the capillaries
Systemic: increased venous pressure, such in heart failure lowering the return of blood back to the heart. Blood builds up in veins and backwards pressure increases (both pulmonary edema and peripheral edema develop)
What are 3 possible pathological causes of pulmonary edema, excluding inflammation? What's the most common one?
1. Reduced osmotic pressure
2. Lymph vessel occlusion
3. Increased venous hydrostatic pressure - this is the most common one, occurs with left-sided heart failure
How does pulmonary edema appear in autopsy?
Lungs are heavy due to increased fluid. Consistency is firm yet elastic. Large amounts of bubbly/frothy fluid can be pressed out of a cut surface
How does sodium retention relate to edema?
Sodium retention leads to water retention, which increases hydrostatic pressure due to expansion of intravascular volume.
The plasma will also have reduced osmotic pressure.
What are 6 mechanisms of edema?
1. Increased intravascular hydrostatic pressure
2. Decreased colloid osmotic pressure in vessels
3. Increased tissue colloid osmotic pressure
4. Decreased lymph drainage
5. Increased capillary permeability
6. Sodium and water retention
What are 3 causes of generalized edema?
2. Right-sided heart failure
3. Rh incompatibility: hydrops in fetus. All organs and interstitium take up fluid
What are the 3 stages of nutmeg liver? (Another apparent Matolcsy favorite question)
1. Dilated central veins
2. Congestion -> hypoxia -> yellowish hepatocytes
3. Later: "confluence" occurs where hepatocytes and liver plates are necrotized
What is a fancypants patho term for "congestion," like when blood accumulates in a region?
What are some generalized forms of congestion / passive hyperemia? (5 are listed, do what you can)
1. Right-sided heart failure
3. Congestive gastritis, duodenitis
4. Nutmeg liver
5. Dilated stellate veins
What are 3 localized forms of congestion / passive hyperemia?
1. Venous thrombosis
2. Venous compression
3. Torsion, as in testicular
What are 5 consequences of chronic congestion?
1. Organ enlargement
2. Induration: tissue becomes firm, also brown due to macrophages eating hemosiderin