Hemodynamics (2/25, Rizea) Flashcards
Capillary fluid exchange is dependent on the balance of what two variables?
Balance of:
- hydrostatic pressure
- oncotic plasma protein pressure
- Fluid, salts, organic molecules move from intravascular space to the interstitial space (aka out of the capillary bed) when the hydrostatic pressure within the capillary bed (32 mmHg) exceeds the plasma colloid osmotic pressure (26 mmHg).
- Reverse: Fluid, salts, organic molecules move back into the vascular lumen (aka back into the venous end of the capillary bed) when the colloid osmotic pressure (26 mmHg) exceeds the hydrostatic pressure (20 mmHg)
What determines total extracellular fluid volume?
Total body sodium!
Renal sodium excretion es muy importante.
What is edema?
Accumulation of excess fluid in interstitial tissue or in cavities.
What are the 4 main mechanisms of edema (the pathogenesis)?
- Increased hydrostatic pressure
- Decreased plasm oncotic pressure
- Increased capillary permeability
- Lymphatic obstruction
What might cause a hydrostatic pressure increase and eventually lead to edema (3 causes)?
- Arteriolar dilation (example: inflammation)
- Increased venous pressure due to obstruction (example: venous thrombosis)
- Increased blood volume
What might cause a decrease in plasma oncotic pressure (3 causes)?
- Nephrotic syndrome (kidney disorder)
- Cirrhosis
- Malnutrition
What might cause an increase in capillary permeability (4 causes)?
- Acute inflammation
- Allergic Reactions
- Burns
- Shock
What might cause a lymphatic obstruction (3 causes)?
- Malignancy
- Fibrosis post radiation or inflammation
- Post surgery
What is the term for the fluid accumulation in serosal cavities?
Pericardial, pleural, or peritoneal effusion.
What might a transudative effusion indicate?
Transudative effusion = low protein. May indicate heart failure.
What might exudative effusion indicate?
Exudative effusion = high protein content. May indicate the presence of a tumor or inflammation.
Give 5 examples of localized edema:
- Inflammation
- Venous obstruction
- Lymphatic obstruction
- Allergic reaction
- Burns
Give 3 examples of generalized edema:
- Cardiac Failure
- Nephrotic syndrome
- Malnutrition
What does pulmonary edema suggest?
Left heart failure
What does lower limb edema suggest?
Right heart failure
What is cerebral edema a secondary symptom of?
Brain trauma, meningitis, infarcts, tumors
Define thrombosis:
The formation of an intravascular solid mass within the heart or intravascular system.
Created by the blood constituents: platelets, fibrin, entrapped red and white blood cells.
Adheres to luminal surface of the vessel
What are the 3 main predisposing factors for the formation of a thrombus?
- Endothelial damage
- Change in blood flow
- Change in blood coaguability
Name examples (5) of endothelial damage that may contribute to the formation of a thrombus:
- Trauma
- Inflammation
- Atherosclerosis
- Endocarditis
- Myocardial infarct
Name reasons (7) for a change in blood flow that may contribute to the formation of a thrombus:
- Narrowed arteries
- Aneurysms
- Cardiac arrhythmias
- Prolonged bedrest
- Postoperative
- Cardiac failure
- Myocardial infarction
Name 4 reasons for a change in blood coaguability that may contribute to the formation of a thrombus:
- Polycythemia (high hematocrit)
- Oral contraceptives
- Malignancy
- Coagulation abnormalities
What are the 5 outcomes of a thrombus?
- Propagation (growth) of the thrombus
- Occlusion of a vessel lumen
- Recanalization and organization
- Thromboembolism
- Fibrinolysis
What is the recanalization of a thrombus?
Recanalization is the ingrowth of endothelial cells, smooth muscle cells, and fibroblasts into the thrombus.
It provides capillary-sized channels through the thrombus for continuity of blood flow through the entire thrombus.
Define thromboembolism:
Part or all of the thrombus detaches and is transported elsewhere.
What is fibrinolysis?
Fibrinolysis is a natural process that breaks down fibrin clots.
For a newly formed thrombus, can use Rx to dissolve the newly formed thrombus.
What are two main clinical outcomes of a thrombus?
Ischemia and Infarction
Define embolism:
The transportation of a detached intravascular particle or mass in the bloodstream as far as its size will allow, where it becomes lodged and obstructs the vessel.
Can an embolism be anything other than a solid particle?
Yes - it can be solid, liquid, or a gas.
Where do arterial emboli originate and travel?
Originate: left atrium
Enter systemic circulation (brain, intestine, legs, kidney, spleen…think: BILKS)
Where do venous emboli originate and travel?
Originate: Deep leg/pelvic veins
Travel to the pulmonary arterial system
What are the clinical scenarios that may arise from a venous emboli?
- Asymptomatic (majority of pulmonary emboli)
- Pulmonary infarction
- Massive pulmonary embolus = acute right Heart failure and sudden death
- Multiple pulmonary emboli = pulmonary hypertension & chronic right heart failure
What are the signs and symptoms of pulmonary infarction?
Cough, pleuritic chest pain, shortness of breath
Hemorrhagic, wedge-shaped infarcts
What causes an air embolism?
An example?
> 100 cc of air into the venous system can lead to sudden death.
The Bends: nitrogen embolism leading to decompression sickness. (At high pressure, N2 dissolves in blood. At a quick assent into lower pressure, the N2 “bubbles” out of blood and creates an embolism).
What causes a fat embolism?
Fat from bone marrow enters the blood stream and travels systemically to affect the lungs and brain.
Occurs following soft tissue crush injury (long bone fractures, cardiac resuscitation)
How might tumor emboli occur?
A tumor must invade into the vascular spaces.
Uses the vasculature to travel and can result in metastatic disease.
What are septic emboli?
Bacterial endocarditis!
Fragments of thrombi/vegetations with entrapped bacteria from these infected heart valves detach and may lodge in spleen or other organs and cause septic infarcts.
Define an infarction:
Occlusion of the arteries or obstruction of venous drainage.
May result in irreversible cell injury and death.
An infarcted area heals via fibrosis (scar!)
What are the 4 main factors that determine if an infarct develops?
- Presence/absence of collateral circulation or dual blood supply
- Rate of development of the obstruction
- Vulnerability of the tissue to hypoxia
- Oxygen carrying capacity of the blood
How does the presence/absence of collateral circulation or dual blood supply determine if an infarct will develop?
If collateral circulation or dual blood supply are present, the area affected may still receive sufficient blood supply to avoid necrosis.
How does the rate of development of the obstruction determine if an infarct will develop?
If the obstruction occurs slowly, there may be time for collateral circulation to establish in the area.
How does the vulnerability of the tissue to hypoxia determine if an infarct will develop?
For example, the brain is more susceptible than skeletal muscle
How does the oxygen carrying capacity of the blood determine if an infarct will develop?
An anemic patient is more likely to develop an infarction.
Define shock:
The clinical state associated with failure to maintain adequate perfusion of vital organs.
Characterized by
decreased effective cardiac output, hypotension, and
decreased tissue perfusion.
What are the three types of shock (HCS)?
- Hypovolemic shock
- Cardiogenic shock
- Septic shock
What is hypovolemic shock?
Can be caused by external fluid loss or internal fluid loss.
External fluid loss: from hemorrhage or dehydration
Internal fluid loos: from increased vascular permeability (burns, anaphylaxis)
What is cardiogenic shock?
Severe reduction in cardiac output due to primary cardiac disease.
(Myocardial infarct, arrhythmia)
What is septic shock caused by?
Gram (-) septicemia
What is the pathology of shock in these seven organs:
- kidney
- lung
- heart
- liver
- GIT
- pancreas
- adrenals
- kidney: acute tubular necrosis
- lung: diffuse alveolar damage
- heart: petechial hemorrhage, myocyte necrosis
- liver: centrilobular necrosis
- GIT: duodenal ulcer, hemorrhage
- pancreas: acute pancreatitis
- adrenals: hemorrhage (Waterhouse Friderichsen syndrome)
Define: atherosclerosis:
Plaque! Common sites: lower abdominal aorta, coronary & internal carotid arteries, brain
What is the pathogenesis of atherosclerosis?
- “Response to Injury Hypothesis”: endothelial cell damage creates a fatty streak on the vessel wall
- Deposition of extracellular lipid & fibrosis = plaque formation
- Plaque enlarges, causes pressure atrophy of the vessel’s muscle layer, and disrupts the elastic lamina. Wall weakens, vessels dilates, an aneurysm is born.
What is the second leading cause of death in the USA?
Ischemic heart disease (restriction of blood supply to a tissue).
What are the primary complications of atherosclerosis (the primary plaque)?
Narrow the lumen = ischemia/infarction (myocardial infarction, stroke, gangrene)
What are the secondary complications of atherosclerosis?
Thrombosis or thromboemboli
Hemorrhage into the plaque = lunal compromise
Pressure atrophy = aneurysm formation
How will dentists need to manage patients with ischemic heart disease?
- Sedate
- Stop procedure if: tachycardia, fatigue, chest discomfort
- Avoid hypoxia with anesthesia
- If they have an arrhythmia, avoid vasoconstrictors
- Be aware if the patient is on anticoagulants
- Keep nitroglycerin and O2 on hand in case of chest pain
How will dentists need to manage patients with cerebrovascular disease?
- No care (especially extractions) until have medical clearance
- Check for warfarin and high dose aspirin - no care while they are on them
- Avoid hypotension with the correct sedation
- Avoid general anesthesia
Define aneurysm:
Localized abnormal dilation of a vessel.
Weakening of the wall is due to:
developmental defects or systemic diseases
What are the complications of aneurysms?
Rupture
Thrombosis with thromboembolism
Occlusion of vessel branches (stenosis) = ischemia, infarction
Impingement on adjacent structures
What is a berry aneurysm?
Congenital
Develop as weakness in muscle layer of vessel wall
Often involved in the Circle of Willis
Common cause of subarachnoid hemorrhage
Present with sudden onset of severe headache
Prevalence may be sporadic or associated with polycystic kidney disease.
What is an atherosclerotic aneurysm?
Most common cause
Atherosclerotic plaques cause the damage to the vessel wall
Elderly males often affected, smokers, age
Site: lower abdominal aorta
Surgical intervention with graft placement
How will dentists need to manage patients with aneurysms?
Avoid: stress, hypoxia, increase in blood pressure
Give prophylactic antibiotics
Define vasculitis:
Inflammatory process involving blood vessels: arteries, veins, capillaries.
Often idiopathic, or often secondary to:
- immune mechanisms
- infectious agents
- radiation
- trauma
- toxins
What is the pathology of vasculitis?
Narrowing of the lumen Destruction of the internal elastic lamina Fibrosis Thrombosis Aneurysm formation
What is Giant Cell Arteritis (Temporal Arteritis)?
Arteritis = inflammation of walls of arteries
Granulomatous vasculitis
Most common type of arteritis affecting head and neck arteries
Affects elderly, particularly women
Present with headache, localized tenderness, visual symptoms
What is Wegener’s Granulomatosis Arteritis?
Granulomatous vasculitis
Affects lungs, upper respiratory tract & kidneys
Middle aged males
What is Polyarteritis Nodosa?
Idiopathic disease
Affects kidneys, heart, gastrointestinal tract
Middle aged males
Associated with HepB surface antigen - immune complexes deposit in vessels
How will dentists need to manage patients with vasculitis?
Immunosuppressive drugs
Wound healing may be impaired
Risk for infections
What is a granuloma pyogenicum?
Benign neoplasm
Polypoid nodule of granulation tissue on skin
Associated with trauma or pregnancy
What is Capillary/Cavernous Hemangioma?
Benign neoplasm
Thin walled capillaries form a nodule in the skin
Uncertain origin
What is an angiosarcoma?
Malignant endothelial neoplasm
Skin, soft tissue, breast, liver
Associated with thorotrast, a radiocontrast agent from 30’s and 40’s
What is Kaposi’s Sarcoma?
Vascular neoplasm
Loss of immunity as in AIDS
Skin patches/plaques
Define varicose veins:
Abnormally dilated tortuous veins due to chronically increased intraluminal pressures, weakened vessel support
Define Vein Thrombosis
Thrombi may occur in the superficial veins (thrombophlebitis)
Thrombi within deep leg or pelvic veins = Deep Vein Thrombosis. From prolonged bed rest, reduced cardiac output. Can lead to embolization to the lungs with high mortality (sitting on an airplane too long!)
What is a lymphagioma?
A benign lymphatic neoplasm.
