Hemodynamics Flashcards
Hemodynamics is the correct ______ and ________ of blood and fluids within the body.
Flow and distribution
What two pressures maintain correct amounts of intravascular and extravascular volumes?
- hydrostatic pressures- pushing pressure out of vessel into extravascular and out of extravascular back into the vessel
- Osmotic pressure- pulling into the vessel or pulling into extravascular
What is abnormal distribution of fluid into the extravascular space?
Edema
What are the two reasons correct blood flow is crucial for tissues?
- they bring oxygen and nutrients
2. remove toxic metabolites
What results when blood is prevented from going to an organ?
Ischemia
Persistent _____ leads to cell death and the resultant area of necrotic cells is termed an _____.
ischemia leads to cell death, and the necrotic cells are an infarct
Define edema.
It is accumulation of fluid within interstitial tissue and or body cavities resulting from an net outward movement of fluid from the vessels
What are the five pathophysiologic causes of edema?
- increased hydrostatic pressure in the vessel
- decreased osmotic pressure in the vessel
- Lymphatic obstruction
- Sodium and water retention
- Inflammation
One of the pathophysiologic causes of edema is increased hydrostatic pressure in the vessels. What are four potential causes of this increased pressure?
- Heart failure- blood backs up in the veins forcing leakage from capillaries
- Cirrhosis of the liver- fibrous scars of the liver impair return of blood through the portal vein, increasing venous pressure
- Venous obstruction- tumor on the vein will backup the blood increasing leakage into interstitium from the capillary bed
- Arteriolar dilation due to heat can cause leakage
What are four causes of decreased osmotic pressure causing edema?
- Decreased albumin production from the liver (cirrhosis and other damage to liver)
- increased protein loss from kidney (glomerular disease)
- Malnutrition (too little protein)
- Protein-losing enteropathy like Crohn’s
What are the four major ways lymphatics can be obstructed? How does this cause edema?
- inflammation
- neoplastic
- Post-surgical
- post irradiation
Compressing the thoracic duct or lymphatic channels will decrease flow of toxic metabolites away from the tissue causing edema
What is the major cause of salt and water retention that leads to edema?
Renal failure where salt is retained, thus water is retained causing:
- increased hydrostatic pressure
- Decreased vascular osmotic pressure
This can occur because of high salt intake and renal insufficiency OR normal salt intake but increased renal tubular reabsorption
How does inflammation cause edema?
Inflammation increased blood flow and vascular permeability in infected tissue
What is a transudate?
What would be two pathological causes of transudate?
fluid that is low in cells and proteins that has a specific gravity less than 1.012
- cardiac failure
- loss of proteins via kidney
What is an exudate?
What would be a pathological cause of exudate?
It is a fluid high in cells and proteins that has a specific gravity greater than 1.012.
Inflammation causes exudate
What is dependent edema?
What would be a major cause?
Dependent edema is where fluid accumulation is dependent on gravity.
It occurs frequently with heart failure where the fluid is backed up in venous circulation. In standing people, fluid pools at the feet. If someone is lying down it pools in the center
What is pitting edema?
When you compress edema with your finger and it leaves an impression
What is anasarca?
What pathological condition is it often associated with?
Generalized edema of the whole body (sub-cutaneous and body cavity) usually caused by protein loss by the kidney (glomerular disease)
What are the clinical effects of soft tissue and extremity edema?
There is generally no significant damage (except delayed would healing and clearance of infection)
The main reason edematous extremities and soft tissue are of concern is because they are a clue to an underlying condition like kidney failure of cardiac failure.
What are the clinical effects of edema in the lungs?
fluid fills the alveoli and pleural cavity which:
- impairs the ability of the lung to oxygenate RBC
- provides an environment conducive for infection
What are the clinical effects of edema in the brain?
Edema causes the brain to expand and because the skull is an enclosed area, it can lead to flattened gyri and narrowed sulci.
Herniations are the result of the expanding brain
What is a herniation?
What are the three main areas where this occurs?
When the brain expands through available spaces
- subfalcine
- uncal
- cerebellar tonsillar
What is a subfalcine herniation?
When the cingulate gyrus herniates under the falx cerebri
What is an uncal herniation?
What are the clinical presentations of someone that may have an uncal herniation?
When the unci herniates under the tentorium and compresses:
- CN3 causing pupil dilation
- posterior cerebral artery (ipsi occipital lobe infarct)
What is a cerebellar tonsillar herniation?
What would be the clinical presentation of someone who had this?
It is when the tonsils herniate down the foramen magnum and compress the brainstem.
This shuts of respiratory and cardiac functions and causes death.
Which herniation is the most serious clinically?
Cerebellar tonsillar herniation because it can compress the brainstem and cause death
What role does the renin-angiotensin-aldosterone system and renal hypoperfusion play in edema?
When there is decreased flow to the kidneys, the renin-angiotensin-aldosterone system is activated to retain Na and water because of low persfusion. This exacerbates edema because of the retained fluid and Na causing increased hydrostatic pressure
Contrast generalized and dependent edema with respect to etiology.
Generalized edema (anasarca) is edema of the entire body and body cavities due to increased protein filtration by the kidneys (kidney failure) Dependent edema is fluid accumulation pulling in veins furthest from the heart commonly associated with heart failure
What is hyperemia?
Active accumulation of blood due to increased flow and arteriolar dilation (inflammation, heat induced swelling)
What is congestion?
What are the two types of congestion?
Passive accumulation of blood due to impaired venous return.
- Acute passive congestion- occurs quickly and recently developed
- Chronic- congestion occurs over time and results in damage to the organ
In what situation (hyperemia, acute passive congestion, chronic passive congestion) would you see engorged vessels that are dilated?
Hyperemia and acute passive congestion
You are looking at a gross specimen that appears wet and oozing with blood.
You then look at a slide and see blood engorging the alveoli that are dilated.
This presentation could point to ________ or ___________.
How do you differntiate between these two situations?
It could be hyperemia or acute passive congestion and you would differentiate between these two using clinical correlation
What would you see on a slide of chronic passive congestion?
RBC broken down
Hemosiderin in cells
Macrophages
Inflammation and scarring
What would be the most common cause of chronic passive congestion in the lung?
Describe gross and microscopic morphology.
Left-sided heart failure would cause chronic passive congestion in the lung because blood backs up in the lungs due to the left ventricle not pumping fast enough
Gross: pigmented, heavy, firm lungs
Microscopic: Hemosiderin in macrophages and fibrosis of alveolar septa
What is “heart failure cells”?
Hemosiderin laden macrophages
What is the major cause of chronic passive congestion of the liver?
Right-sided heart failure which causes blood to back up in the liver
What is the morphology of chronic passive congestion of the liver?
- Gross
- Microscopic
- Nutmeg liver- shrunken and hemorrhagic central lobar areas (mottled red areas around central vein because they are last to get O2 and become ischemic)
- Fibrosis around central veins due to them being last to get O2 and first to become ischemic
What is a hemorrhage?
Extravasation (leaking) of blood from vessels into the extravascular space
What are the three types of hemorrhage?
- Petechial- pinpoint (1-2mm) on skin, mucous, serosal surface
- Purpura- (3-5mm)
- Ecchymosis (larger than a cm)
What are the common causes of petechial hemorrhage?
thrombocytopenia
platelet dysfunction
increased vascular pressure
clotting factor deficiencies
What are the common causes of purpural hemorrhage?
Same as petechial but including increased vascular fragility (elderly) and trauma
What are the common causes of ecchymosis?
trauma and fragility (usually associated with age)
Ecchymosis is bruising
What two factors determine severity of hemorrhage?
- Location of hemorrhage- (250ml from skin is insignificant but 5ml from brainstem can be fatal)
- Loss of blood (amount)- to die you need to lose 30% of blood
What is a hemothorax?
Hemorrhage in the pleural cavity
What is a hemoperocardium?
Hemorrhage in the pericardial cavity
What is a hemorrhage in the peritoneal cavity called?
Hemoperitoneum
What is an infarct?
Area of dead cells within an organ due to occlusion of arterial blood supply or venous drainage
What is the difference between hypoxia and ischemia?
Hypoxia is lack of oxygen to an organ
Ischemia is lack of blood which makes it more damaging than hypoxia because there is decreased oxygen AND decreased nutrients AND decreased removal of toxic metabolites
What is the most common cause of an infarct?
Arterial thrombus or embolism
What are the three major causes of infarct?
- Obstruction of a vessel (artery or vein)- thrombus, embolism, artherosclerosis, extrinsic compression
- Vessel damage
- Generalized hypotension (shock)
What are the four noted ways that a vessel can be obstructed (thus causing infarction)?
- Thrombus
- Embolism
- Vessel compression (tumor, twisted vessel)
- Atherosclerosis
What are the 3 main types of infarct?
Red, white and septic
What causes a red infarct?
What organs typically have red infarct?
Blood within the hemorrhage. This occurs in organs that have dual blood supply and/or loose parechymal tissue that allows for leakage of blood
Ex. Lungs
What is the most frequent cause of a red infarct?
Venous infarct because the artery still pumps blood to the tissue but it isn’t removed (no new O2 gets in because of the backup–> infarcted tissue)
What occurs when blood flow returns to an organ that had been ischemic?
Repurfusion injury
What is the gross presentation of red infarct and what is the microscopic presentation?
Gross- red and soft
Micro- coagulative necrosis (maintained cell shape, no nuclei)
What organs typically display white (anemic) infarction?
Organs with single blood supply (this is the end arterial flow with no collateral supply), and solid parenchyma.
Ex. Heart, liver, spleen
What is the morphology of white infarct?
- Gross
- Micro
- soft, white, tend to be wedge shaped at end of occluded vessel
- coagulative necrosis
What is septic infarct vs bland?
It is infected vs. non-infected
What are the two major causes of septic infarct?
- Embolization of bacterial vegetation (that has grown on heart valves, etc)
- Bacterial seeding of necrotic tissue
What is the morphology of a septic infarct?
It progresses from infarct to abscess
What are the four major factors that influence the development of an infarct?
- vascular supply - dual vs end-arterial
- Rate of development- does it allow time for collateral circulation?
- Vulnerability of cells to hypoxia- neurons die faster than myocytes
- Oxygen content of blood- anemic are more susceptible to infarct
