metabolism of water and its clinical significance

Metabolism of water andits clinical significance

Dr. Rohini C Sane

Water and electrolyte Balance• The organism possesses tremendous capacity to survive against odds

and maintain homeostasis .

• This is particularly true with regard to water ,electrolyte and acid- base status of the human body.

• Kidney actively participates in regulation of water ,electrolyte and acid-base Balance in human body.

Water and electrolyte Balance

Water

Electrolyte Balance

Acid base

Functions of kidney

Importance of Water

Functions of water

1. Powerful solvent for ionic compounds & neutral molecules in organisms( aqueous medium for biochemical reactions )

2. Strong influence on state of dissociation of macro molecules

3. Influence on structural & functional components of cells ( the major body constituent)

4. Regulation of body temperature (high heat of vaporization helps in body cooling)

5. Vehicle for transport of solutes

Weight contribution by water in a human body (age wise)

Weight contribution by water in the human tissue

Daily Water transfer in human body

Splanchnic and central compartments related with water

Distribution of water in a human body (70kg)

CATEGORY WATER CONTENT -WEIGHT CONTRIBUTION (% )

HUMAN 60

MEN 55-70

WOMEN 45-60

COMPARTENT BODY WEIGHT (% ) VOLUME OF H₂O ( LITRES )

Total 60 42

Intracellular fluid ( ICF ) 40 28

Extracellular fluid ( ECF )* 20* 14*

Interstitial fluid * 15* 10.5*

Plasma* 5* 3.5*

Women & obese have less water .( Higher content of stored fat in an anhydrous form)

Distribution of water in a human body

Distribution of water in a human body (70kg)The body water compartments

Total body water (42L )-60% of body weight

Extracellular fluid ( ECF )-(14L )20% of body weight

Intravascular volume of plasma

2.8L)-4% of body weight

Extravascular or interstitial fluid

11.2L)-16% of body weight

Intracellular fluid ( ICF -28L)-40% of body weight

One third of ECF

two third of ECF

Distribution of Water in the Body

Extra cellular fluid (ECF )

• Plasma ( one third of ECF)

• Lymph (1.5 L )

• Bone

• Cartilage

• Trans- vascular fluid

• Interstial fluid & lymph

Intra cellular fluid (ICF )

• Single compartment –constant composition-two third of total body water

Mixing & exchange of nutrients & metabolites waste between plasma & lymph or Interstial fluid

No exchange between plasma & different structures- bone ,cartilage , connective tissue ( a vascularity )

Distribution of water in the Body

❖Distribution of water between different compartments depends on the concentration gradient of solutes on the either side of the membrane ( osmotic gradient ).

Distribution of Body fluid

Distribution of water in the Body

Comparison of ECF and ICF

Trans vascular fluids (1.5L )

1. CSF

2.Synovial fluid

3.Peritoneal fluids

4. Alimentary secretions(Lumen of Gastro intestinal tract)

5.Pleural fluid

6. Aqueous humor

1. CSF

2.Synovial fluid

Peritoneal fluids -3

Alimentary secretions(Lumen of Gastro intestinal tract) :4

Pleural fluid-5

Aqueous humor -6

Daily intake of Water by the human body in balanced status Sources of water to the human body in balanced status:

1. Exogenous water sources

2. Endogenous water sources

Daily intake of Water by the human body in balanced status

Exogenous Sources of water to the human body in balanced status:

1. Ingested water

2. Water content of solid food

3. Beverages

❖Daily intake of Water by the human body 0.5 – 5 L ( depends on social habits and climates)

Ingestion of water is controlled by a thirst center located in hypothalamus.

Endogenous water sourcesEndogenous water sources = metabolic water produced within

human body by oxidation of food stuff ( 300- 350 ml / day )

Foodstuff (1 gm ) yield of Endogenous water

on oxidation

Carbohydrate 0.6 ml

Protein 0.4 ml

Lipid 1.1 ml

125 ml of Endogenous water is generated for 1000 Cal consumed by the human body.

Metabolic water( endogenous water)

❖Metabolic water due to oxidation of food stuff (1gm )

Carbohydrate

0.6 ml

Protein

0.4ml

Lipid

1.0 ml

Regulation of water content in the human body

Regulation of water content in the human body is achieved by balancing the daily water intake and water output.

• The thirst center located in the third ventricle in hypothalamus , which is stimulated by ECF hyperosmaolality and hypovolemia and inhibited by hypoosmolality and hypervolemia.

• Vasopressin or Antidiuretic hormone (ADH),the anterior pituitary hormone that enhances water reabsorption in response to an increase in ECF osmality or hypovolemia.

• Vasopressin secretion is regulated by hypothalamus which responds to impulses from stretch receptors in left atrium baroreceptors in the aortic arch and carotid sinus .

Thirst center located in the third ventricle in hypothalamus

Control of intake of Water by the human body in balanced status

Increased in osmality of plasma

Stimulation of thirst center of hypothalamus

Increased water intake

Water output from the human body

❖Routes of elimination of water from the human body

1. urine ( major route)

2. Skin

3. Lungs

4. Feces

Water output from the human body

Water output through : 1.Urine❖Urine is a major route of elimination of water from the human

body.

❖Daily output of urine by the human body in balanced status = 1 - 2 L/day

❖Kidney regulates retention and elimination of water from the human body.

❖Water loss by Kidney is highly variable(to get rid of / to retain water).

❖Volume of water as a medium essential to eliminate waste products from the human body = 500 ml / day

❖The human body cannot stop the production of Urine even if water intake is nil.

Hormonal regulation of excretion of Urine

Hormonal regulation of urine production and excretion

Everyday

• 180 L of water filtered by glomeruli into renal tubules

• 178 L of water absorbed by renal tubular cells

• 1-2 L of water excreted as urine (tightly controlled by ADH )


❖Volume of water filtered by glomeruli into renal tubules of Kidney= 180 L/day ( most of this is reabsorbed and 1-2 L /day is excreted as urine )

❖Vasopressin = Antidiuretic Hormone (ADH ) from posterior pituitarygland regulates excretion of water by Kidney.



Increased in osmality of plasma

Increased in secretion of Antidiuretic Hormone (ADH ) from posterior pituitary gland

Increased water reabsorption by the renal tubules

Less urine output till homeostasis is achieved



Decreased in osmality of plasma

Suppression in secretion of Antidiuretic Hormone(ADH ) from posterior pituitary gland

Reduced water reabsorption by the renal tubules

more urine output till homeostasis is achieved

Hormonal regulation of excretion of Urine ❖Diabetes insipidus : deficiency of ADH increased loss of

water from body.

❖Plasma osmality is dependent on the sodium concentration hence sodium indirectly controls the amount of water in the human body.

Water output through :2. skin❖Skin : loss of water (450 ml /day )through perspiration an

unregulated process by the body depends upon atmospheric temperature & humidity

➢↑ atmospheric Temperature ↑ water loss through skin (loss is more in hot climate)

➢For every ↑ body Temperature by 1⁰ C(fever) 15% ↑ water loss through skin

Water output through :3. Lungs❖Water output from Lungs :

Loss of water during Respiration by Lungs about 400 ml /day in expired air

✓ Hot climate

✓ Fever water loss through lungs ↑

➢loss of water via skin through perspiration

➢Loss of water via lung through respiration insensible water loss

Water output through :4 feces ❖Water output through feces : Water entering in GIT most of it

reabsorbed in intestine 150/ml /day loss through feces in healthy individual

Diarrhea increased fecal loss of water

Water balance in the body ( daily intake & output):1

Body H₂O

(4200 ml )

1.Drinking H₂O &

Beverage (1500ml )

2. Food stuff (700ml )

3. Metabolic water (300ml )

Water intake 2500ml

Water output 2500 ml

Intake of water is controlled by thirst Centre (part of Hypothalamus )

Water balance of human body is regulatedpredominantly by controlling water output

(initially by Obligatory loss via skin , lungs and feces followed by urinary output).

Water balance in the body (daily intake & output):2

Body H₂O

(4200 ml )

Kidney Urine

( 1500ml)

/day

Skin

(450 ml )

Insensible & sensible

perspiration

Lungs

( 400ml )

Water vapor in expired

air

Intestine

Feces

( 150ml )

Starvation : obligatory water loss 500 ml/day

Body H₂O

(4200 ml )

2. Food stuff

(700ml )3.

Metabolic water

(300ml )

1.Drinking H₂O &

Beverage (1500ml )

Urine ( 1500ml)

Skin(450 ml )

Feces ( 150ml )

Lungs ( 400ml )

Water balance in the body : daily intake & output :3

Water intake 2500ml

Water output 2500 ml

Abnormalities associated with Water balance

Abnormalities associated with Water balance :

1. Dehydration

2. Overhydration

Disorders of water &Electrolyte balance

❖Water & Electrolyte imbalance lead to

➢Dehydration

➢Over hydration

Causes of Water & Electrolyte imbalance:

1. Imbalance of Water intake & output

2. Imbalance of Sodium intake & output

• Dehydration is the disturbance of water balance in which the output exceeds the intake causing a reduction of body water below the normal level or excessive water loss or both. ( water depletion in the body )

• Dehydration may be as a result of

1.Pure water depletion

( without corresponding loss of electrolytes )

2. Mixed type in which both Water and salt depletion occur

Causes of dehydration

Dehydration may occur as a result of

1. Diarrhea

2. Vomiting

3. Excessive sweating

4. Fluid loss in burns

5. Adreno-corticoid dysfunction

6. Kidney diseases ( e.g. renal insufficiency )

7. Deficiency of ADH ( Diabetes Insipidus )

Pure water depletion( without corresponding loss of electrolytes )

A –Decreased water intake of as in

• Elderly debilitated persons

• Unconscious patients

• Severe dysphagia

• Postoperative patients ,when oral intake has been stopped

B- increased water loss due to

• Sweating ,during fever

• Hyperventilation

• Infantile gastroenteritis

• Diabetes insipidus due to ADH deficiency

• Diabetes Mellitus due to osmotic diuresis

• Nephritis

• Acute renal failure

1.Pure water depletion ( without corresponding loss of electrolytes )occurs under following conditions

Biochemical findings in dehydration❖Biochemical findings in dehydration include

1. Volume of the ECF ( e.g. plasma )decreases with concomitant rise in electrolyte concentration ( increased ECF osmolality) and osmotic pressure

2. Water is drawn from intracellular fluid shrunken cells and disturbed metabolism( e.g. increased protein breakdown )

3. Increased ADH secretion increased water retention decreased urinary output (decreased urine volume )

4. Decreased urine sodium

5. Increased concentration of plasma sodium ,protein ( Normal or slight increased ) and blood urea ( mild)

6. Water depletion often accompanied by loss of electrolytes from body (Na⁺ ,K⁺ etc.)

Dehydration of muscles and nerveCells leading to weakness and confusion .

- Oliguria

( and tongue )thirst

Hemoconcentration

Consequences of dehydration

❖Consequences of dehydration include :

• increased in plasma sodium and osmality

• Deceased renal flow which stimulates Aldosterone secretion with increased reabsorption of sodium that aggravates hypernatremia

• Increased in ECF osmolality ,resulting in diffusion of water from the cells to the ECF

Dehydration( vicious cycle )

Sodium depletion

Anorexia

VomitingLoss of NaCl in vomitus

Salt depletion

Homeostatic mechanisms in dehydration ❖Homeostatic mechanisms in dehydration that compensate

dehydration include:

• Stimulation of thirst center with increased intake of water

• ADH secretion with increased water reabsorption ( except Diabetes insipidus )

Management of Dehydration

• Treatment of choice of dehydration : Intake of plenty of water

• Intravenous administration of isotonic solution (usually 5% glucose ) to patient who cannot take orally (and should be monitored carefully )

• if dehydration is accompanied by loss of electrolytes : oral/intravenous administration of isotonic solution (usually 5% glucose ) until urine volume exceeds 1500ml

Management of Dehydration

Management of Dehydration in children

Osmotic imbalance and dehydration in Cholera

• Cholera is transmitted through water and food contaminated by the bacterium Vibrio Cholerae.

• Vibrio Cholerae produces a toxin which stimulate intestinal cells to secrete various ions ( Cl - , Na+ ,K +,HCO3 - ) into intestinal lumen.

Vibrio Cholera

Osmotic imbalance and dehydration in Cholera Vibrio Cholerae produces a toxin which stimulate intestinal cells to secrete various ions

( Cl-

, Na+,K+,HCO3-) into intestinal lumen

These ions collectively raise the osmotic pressure and suck water into lumen

Diarrhea (heavy loss of water 5-10 L /day )

Loss of dissolved salts and severe dehydration

Death if not treated with oral rehydration therapy (ORT)

Overhydration ( water intoxication )

Definition of Overhydration : state of pure water excess or water intoxication• Retention of large quantity of water deleterious effects • excretion large volume of dilute urine ( when water without electrolyte

given )❖Causes of Overhydration : a) Excessive intake of large volumes of salt free fluids b) Renal failure c) Excessive administration of fluids parenterally d) Hyper secretion of ADH ( syndrome of inappropriate ADH secretion –

SIADH )This lead to decrease plasma electrolytes(dilution of ECF &ICF)

↓Decreased osmolarity

Syndrome of inappropriate ADH secretion –SIADH

Biochemical tests for Diagnosis of SIADH

Clinical Symptoms of Overhydration ( water intoxication )

1 . Nausea

2. Vomiting

3. Head ache

4.Muscular weakness /lethargy

5. Confusion

7 convulsion

8. Coma

9. Death

Biochemical findings in water excess

❖Biochemical findings in water excess include:

• Decrease in plasma sodium

• Increase in ECF volume

• Decrease in plasma proteins

• Decrease in ECF osmolality

• Increase in urine volume

• Decrease in urine sodium: in Addison’s disease

• Increase in urine sodium: other conditions

Management in water excess

Management in water excess include :

➢Restriction of water intake

➢Infusion of hypertonic saline if water intoxication occurs

Rabies

Clinical symptom of Rabies

Hydrophobia is One of the diagnostic symptom of

Rabies

Consequences of viral infection in Rabies

Management of Rabies

Comparison of Overhydration ( water intoxication ) and Dehydration

Management of Dehydration and Overhydration ( water intoxication )

Cushing's syndrome is associated with Water and sodium retention

metabolism of water and its clinical significance

Health & Medicine