DR NILESH KATE

MBBS,MD ASSOCIATE PROF

DEPT. OF PHYSIOLOGY

BLOOD VOLUME

OBJECTIVES Definition Physiological variations Pathological variations Measurement of blood

volume Factors regulating

blood volume Applied physiology

Wednesday, May 3, 2023

DEFINITION Blood volume is the amount of blood that

is circulating inside the circulatory system and stored in certain organs like spleen. It represents the TOTAL BLOOD in the body.

NORMAL VALUE = 80 ml/kg = 5 – 6 lit / 70kg body wt

PHYSIOLOGICAL VARIATIONSSex : female < male Muscular exercise : exercise : increases

High altitude : increasesPregnancy : increases Age : infants – more

compared to adultsSurface area of bodyBody weightAtmospheric temperaturePosture Emotion

PATHOLOGICAL VARIATION

PATHOLOGICAL INCREASE

1.Hemorrhage or blood loss

2. Fluid loss3. Haemolysis 4. Anemia5. Obesity6. Hypothyroidism

PATHOLOGICAL DECREASE

1. Hyperthyroidism 2. Hyperaldosteronism 3. Cirrhosis of liver 4. Congestive Cardiac

Failure

NORMOVOLEMIANORMOVOLEMIA HYPOVOLEMIAHYPOVOLEMIA HYPERVOLEMIAHYPERVOLEMIA

Simple Simple normovolemianormovolemia

Simple Simple HypovolemiaHypovolemia

Simple Simple HypervolemiaHypervolemia

Polycythemic Polycythemic normovolemianormovolemia

Polycythemic Polycythemic HypovolemiaHypovolemia

PolycythemicPolycythemic

HypervolemiaHypervolemia

Oligocythemic Oligocythemic normovolemianormovolemia

Oligocythemic Oligocythemic HypovolemiaHypovolemia

OligocythemicOligocythemicHypervolemiaHypervolemia

DETERMINATION OF BLOOD VOLUME

Direct method : Done only in animals.

Indirect method : Blood volume is calculated by two stages.

a) Estimating the RBC mass

b) Estimating the plasma volume

The substance which binds to red cells are used for this method

The substances are radioactive chromium

ESTIMATING THE RBC MASSRADIOACTIVE METHOD:VRBC = VD X Ra D

Ra R

VRBC = Red cell volume

VD = Volume of donor cells in ml

Ra D = Radioactivity of donor cells / ml Ra R = Radioactivity of recipient cells / ml

ESTIMATING THE RBC MASS BY RADIO ISOTOPE METHOD

GEIGERMULLER COUNTER RADIOACTIVITY OF RBC

INTRAVENOUS INJECTION

ESTIMATING THE PLASMA VOLUME

INTRAVENOUS INJECTION

A known quantity of dye is injected into the blood The amount of substance excreted is measured and from this blood volume is measured

Estimating the plasma volume

1. Indicator or Dye dilution method 2. Radio isotope method amt. of dye injected - amt. of dye excreted

Plasma volume = -------------------------------------------------------- mean conc. of dye / ml

Blood volume is determined by taking the Haematocrit and already calculated plasma volume

100 x plasma volume Blood volume = ------------------------------ 100 - pcv

REGULATION OF BLOOD VOLUME

Maintenance of blood volume depends on:Balance between water Adjustment of fluid and intake water loss interchange.

1.Regulation of volume (water level) 2.Regulation of RBC mass 3.Regulation of plasma proteins 4.Regulation of electrolytes

REGULATION OF VOLUME (WATER LEVEL)

1.Capillary fluid shift2.Osmoreceptors3.Volume receptors4.Baroreceptors 5.Renin Angiotensin System

CAPILLARY FLUID SHIFT More fluid filtered

into interstitial space – decreases blood volume

More fluid filtered across glomerulus – GFR increases

Wednesday, May 3, 2023

OSMORECEPTORSRise in blood volume

Fall in tonicity

Osmoreceptor inhibition

ADH release inhibited

No absorbtion of water from DCT and CD

Rise in urine output

Decline in blood volumeWhen blood volume decreases reverse changes takes place

ROLE OF VOLUME RECEPTORS

Receptors mainly present in great veins and atria respond to volume changes

ROLE OF VOLUME RECEPTORS

High blood volume

Activation of Activation of volume receptorsvolume receptors

sympathetic.dischargeTo kidney ADH SECRETION

SYMPATHETIC.DISCHARGE TO SYSTEMIC VESSELS

Urine output Water excretion Blood volumeUrine output

ROLE OF BARORECEPTORS High blood volume

High cardiac output

Rise in B.P

Activation of Baroreceptors

ROLE OF BARORECEPTORS

Activation of BaroreceptorsActivation of Baroreceptors

SYMPATHETIC.TONETO KIDNEY ADH SECRETION

SYSTEMIC VASODILATATION

URINE OUTPUT FLUID IN INTERSTITIAL SPACE

INHIBITION OF THIRST

URINE OUTPUT

RENIN-SITE OF PRODUCTION

Renin is produced in an inactive form called PRORENIN by the Juxtaglomerular cells of kidney .

The inactive renin is converted into active renin by kallikrein.

RENIN-SITE OF PRODUCTION

FORMATION OF RENIN AND IT’S ROLEGlomerular filtrate

Na+ and Cl- concentration in macula

Stimulate the JG cells to secrete Renin

Angiotensinogen Angiotensin Iconverting enzymes in lungs

Angiotensin II

Efferent vasoconstriction

G.F.R

Na+ and Cl- concentration

REGULATION OF RBC MASSLow blood volume

Hypoxia present

Liver Kidney

Erythropoietin

EP Sensitive stem cell

RBC production increases

RBC mass restored

REGULATION OF PLASMA PROTEINS

Loss of plasma proteins

Restoration of plasma proteins

In 4 hours in 24 hours

From tissue From liver

Factor regulating – High protein diet

REGULATION OF ELECTROLYTES

1. Na, K, Cl are mainly regulated by : a) Aldosterone b) ADH c) Natriuretic Hormone.2. Ca, PO4 ,Mg are regulated by: a) Parathyroid Hormone b) Calcitonin c) 1-25 (OH) 2 cholecalciferol

APPLIED PHYSIOLOGY DECREASED BLOOD VOLUME :1.Haemorrage2.Burns3.Dehydration 4.Myxoedema 5.Addisons disease

APPLIED PHYSIOLOGYINCREASED BLOOD VOLUME DUE TO IN WHOLE BLOOD: 1.Polycythemia Vera 2.Cushings syndrome 3.Thyrotoxicosis

APPLIED PHYSIOLOGY

INCREASED BLOOD VOLUMEDUE TO PLASMA VOLUME

4.Congestive cardiac failure5.Cirrhosis of liver

APPLIED PHYSIOLOGY

RECAP Definition Physiological variations Pathological variations Measurement of blood volume Factors regulating blood volume Applied physiology

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