hemodynamic pathology
DESCRIPTION
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Hemodynamic
Disorders
Humans• Body Water
– 75% of body weight in infant– 60% of body weight in adult male – 55% of body weight in adult female– the exact percentage depending upon:
• age – newborn = 75%, lean adult man = 60%, old age = 45%
• body size – obese = as little as 45%, very lean as much as 75%
• gender – lean adult man = 60%,
lean adult women = 50%
• Fluid compartments– Intracellular fluid
– Extracellular fluid• Interstitial fluid
• Blood plasma
• Lymph
Body fluid compartments
Intracellular fluid (67%)
Extracellular fluid (33%)
Interstitial fluid (80%)
Plasma (20%)
Other fluids
Body fluid compartments
Total Body Weight
40% solids
60% fluids
67% ICF
33% ECF
80% interstitial
fluid
20% plasma
• Intracellular (ICF)
• Extracellular (ECF)– Interstitial
– Plasma
Body Fluid Compartments
Figure 5-13: Body fluid compartments
Fluid Balance
Semi-permeable membranes separate the fluid compartments
Fluids are in constant motion between the 3 compartments
Fluids Are In Constant Motion
plasma
endothelium
tissue cells
arteriolar end
filtrationreabsorption
venularend
interstitial fluid
osmosis
Fluids Are In Constant Motion
• Forces acting across the capillary membrane
causing net movement of fluid among compartments
Edema Formation“Excess fluid in body tissue”
• Most cases in the extracellular fluid
compartment
• Can also occur in the intracellular fluid
compartment as well
• Extracellular - pitting edema
• Abnormal leakage of fluid from plasma to the interstitial space across the capillaries– Failure of lymphatics to return fluid from
the interstitium back into the blood
– *Excess capillary fluid filtration
Edema Formation
Factors that increases capillary filtration
– Caused by major imbalance of capillary filtration forces and/or lymphatic blockage
– Filtration = Kf * (Pc - Pif - c + if)• Kf=capillary filtration coefficient (product of
permeability and surface area of the capillary)• Pc=capillary hydrostatic pressure• Pif=interstitial hydrostatic pressure
c=capillary plasma colloid osmotic pressure
if=interstitial fluid colloid osmotic pressure
– Major factors: increased Pc and/or Kf and/or decreased c
Extracellular - pitting edema
• Lymphatic blockage– Filaria nematodes– Cancer
Wuchereria Bancroft
• Heart failure– No pump of blood from veins into arteries
(↑ venous and capillary pressure with ↑ capillary filtration)
– ↓ arterial pressure ↓ excretion of salt and water by kidneys (↑ blood volume and capillary hydrostatic pressure)
– ↑renin, angiotensin II and aldosterone secretion (more salt and water retention)
Extracellular - pitting edema
• Decreased kidney excretion of salt and water– Disease state (acute glomerulonephritis)
with failure to filtrate adequate amounts of fluid
• Decreased plasma proteins– Failure of body to produce normal amounts
of proteins– Leakage of proteins from plasma
Extracellular - pitting edema
• Decreased plasma proteins (con’t)
• Nephrotic syndrome (damage to the
membranes of the renal glomeruli). Serious
edema when plasma protein falls below
2.5g/100ml.
– Cirrhosis of the liver (hepatic tissue fibrosis). ↓
protein synthesis leading to ↓ colloid osmotic
pressure.
Edema Formation
• Intracellular - non-pitting edema
• Na+ pump depression: increases intracellular
Na+ osmolarity and causes water to move to
the inside of the cell• metabolism disturbance (↓ blood supply)
• nutrient supply disturbance
– Inflammation: ↑permeability to Na+ and other
ions leading to osmosis of water
Safety Factors Preventing Edema
• Low compliance of the tissues in the negative
pressure range
• Lymphatic capacity for increasing flow
• Washdown of interstitial protein
Low compliance of the tissues in the negative pressure range
• Hydrostatic pressure in most subcutaneous
tissues around - 3mmHg• Holds tissue together• Negative pressure range, the compliance is low• Above 0 mmHg compliance is high safety
against edema is lost
SF = 3 mm Hg
• Free fluid forms in the interstitial space only after the interstitial fluid pressure rises above 0 mmHg. Fluid is in a “Gel State” at negative pressures.
Lymphatic capacity for increasing flow• Return the circulation fluids and proteins
filtered from the capillaries into the interstitium
• Without this function, ↓ plasma volume and edema occurs
• Lymph flow increases 10-50 fold when fluid start to accumulate
SF = 7 mm Hg
Washdown of interstitial protein
• ↑ Fluid filtration, ↑ pressure, ↑ lymph flow• ↓ Protein concentration with ↑ lymph flow• ↓ Colloid osmotic pressure• Net result is ↓ net filtration across capillaries
SF = 7 mm Hg
Total Safety Factor
17 mm Hg
• The capillary pressure in a peripheral tissue
could theoretically rise by 17 mm Hg before
marked edema would occur
Fluid in Potential Spaces
• Potential Space - Normally empty with (-) pressure.
– Pleural, peritoneal, pericardial, synovial
• Fluid accumulates because of unbalance of capillary forces or lymphatic blockage due to infection or injury
• Effusion: edema fluid from subcutaneous space collects in the potential space
Edema fluid types
• TRANSUDATE
• Watery in nature
• Sp. Gr = 1.012 or <
• Low Proteins
• Low Colloids
• No cells
• EXUDATE
• Proteinesous in nature
• Sp. Gr = 1.020 & >
• High Protein content
• High colloid levels
• High cell cont
• May contain various enzymes & tissue markers
Hyperemia• Local increase in blood flow in a tissue due to
vasodilation of blood vessels in that area.(arteriolar dilation takes place)
• Causes– Local factors
Temp.↑, CO2↑, pH↓, chemicals
– Systemic FactorsANS, Hormones, chemical mediators
• Features– Tissue become pink / red color & hot
Congestion• Accumulation of blood in a capillary network in a
tissue due to obstruction or decreased venous outflow.
• Causes– Compression– Thrombo – embolism– Vasculitis/phelebitis
• Features– It leads to edema formation– Tissue appears bluish / dusky in color
Thrombo - Embolism
• Thrombosisformation of collected mass of blood inside cardiovascular system (mass=thrombus)
• Embolisma detached thrombus or its part which flows in CVS & occludes any blood vessel
• Both of these result in tissue Ischemia or Infarction
Thrombo – Embolism (contd…)
• Ischemiadecreased blood flow to any organ or tissue due to any cause (reverscible)Compression from outside or narrowing of lumen of blood vessel
• Infarctiondeath of tissue due to lack of blood supply due to any cause (irreverscible)90% infarcts are due to Thrombo-embolic events & almost all result in arterial occlusion in tissues