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