Fluid and Hemodynamic Disorders Flashcards
Edema
Excess fluid in tissues
Can be localized or systemic
Capillary hydrostatic pressure
Pressure in the capillary due to heart pumping and weight of blood
Capillary oncotic pressure
Pressure in the capillary due to proteins present in fluids (proteins in blood cannot cross a normal capillary wall)
Lymphatic system
A network of vessels separate from blood circulation that carries lymphatic fluid
Albumin
Maintains oncotic pressure
Made by the liver
Transports steriods, thyroid hormone, bilirubin, bile salts, fatty acids
Two main drivers of fluid movement across capillary wall:
Capillary hydrostatic pressure
Capillary oncotic pressure
Pericyte
Vascular supportive cell
How does the lymph fluid enter circulation?
Through the thoracic duct and right lymphatic duct
3 causes of localized edema
- Ischemia (irreversible cell injury): lysed cells release chemical mediators that cause leaky capillaries
- Infection: white blood cells release chemical mediators that cause leaky capillaries
- Lymphatic obstruction: obstruction or damage of small or large lymphatic vessels, usually by treatment for carcinoma
2 ways capillaries become leaky
- Endothelial cell retraction: ECs retract from each other in response to chemical mediators (can be reversible)
- Endothelial cell injury: more severe damage results in endothelial cell necrosis and detachment (not reversible)
3 causes of systemic edema
- Heart failure: left = lungs, right = legs
- Kidney disease: loss of albumin in urine, so retention of sodium and water
- Liver failure: not enough albumin produced
Ascites
Accumulation of fluid in the abdomen
How does heart failure cause systemic edema?
Increased hydrostatic pressure from impaired venous return
Heart failure
Heart is unable to pump enough blood to adequately perfuse tissues
Fluids will back up according to which ventricle is more affected
Left heart failure
Left ventricle is not working properly
Blood backs up into pulmonary veins
Right heart is still working
Blood has trouble moving through the capillary bed, so increased pressure on the venous end = less fluid leaves vessels
Can hear crackles with stethoscope at base of lungs
Right heart failure
Right ventricle is not functioning properly
Blood backs up into the vena cava
Problems arise in the capillary beds of the body
Increased hydrostatic pressure on the venous ends = no fluid moves
Patients can get ulcers from poor circulation
Treat with medications
Pitting edema
Pressing on skin will leave an indentation
See in RV failure
How does kidney disease cause edema?
In diseases kidneys, the glomerular basement membrane is damaged and albumin can cross it and be released into urine
Low blood concentration of albumin
Causes fluid to enter tissues and results in systemic edema
Oncotic pressure decreased, but hydrostatic pressure the same
2 things in liver failure
Not producing enough albumin
Not producing enough clotting factors
Why does liver failure cause edema?
Doesn’t produce enough albumin, so concentration is too low
Results in low oncotic pressure
Fluid will not return to capillary and will accumulate in tissues
2 main proteins in the coagulation cascade
Thrombin
Fibrin
Thrombo-embolus
A piece of thrombus that has broken off from where it formed and has travelled elsewhere in the body
3 major components that control thrombus formation
Endothelial cells: damaged endothelial cells cause platelets to adhere and form a plug
Platelets: aggregate and form a plug
Coagulation cascade: thrombin cleaves fibrinogen into fibrin which stabilizes the platelet plug
3 things pathologic thrombi can be caused by
- Endothelial cell injury
- Poor blood flow
- Hypercoagulable state
How does atrial fibrillation cause arterial thrombi?
Uncoordinated chaotic contraction of atrium results in areas of irregular blood flow
Thrombus can form on sites of poor blood flow in atrium
Often form on the surface of the left atrial appendage
2 major causes of arterial thrombi
Atherosclerosis
Atrial fibrillation
4 causes of venous thrombi
Venous stasis
Cancer
Pregnancy
Inherited Thrombophilia
How can pregnancy cause venous thrombus?
Pro-coagulant changes of pregnancy likely part of physiologic preparation for delivery (to prevent excessive hemorrhage during delivery)
How does inherited thromhophilia cause venous thrombus?
Some patients have genetic abnormalities in coagulation proteins that make them much more susceptible to venous thrombosis
Shock
Circulatory failure that results in poor tissue perfusion resulting in cellular hypoxia
3 ways to get shock
Cardiogenic shock: MI, other heart pathology
Hypovolemic shock: trauma (blood loss)
Septic shock: associated with systemic inflammatory response, usually infection (causes dilation of vessels)
Acute Respiratory Distress Syndrome
Damage to pulmonary capillary endothelium and alveolar epithelium causes edema to enter pulmonary alveoli
Damage secondary to many things
Common in patients with shock
Other causes: aspiration, pancreatitis, smoke of toxic gas inhalation
Acute phase: alveolar edema
Later phases: progression to hyaline membranes and thickened alveolar walls
Disseminated Intra-Vascular Coagulation
Complication of shock caused by excessive activation of coagulation and formation of thrombi in microvasculature of body
Causes consumption of coagulation factors and platelets and can then result in bleeding in other parts of the body
Ex: DIC in brain and kidneys and bleeding in GI tract
