Dept. of PathologyDept. of Pathology

Medical CollegeMedical College

Hunan Normal UniversityHunan Normal University

(( 湖南师范大学医学院病理学教研室湖南师范大学医学院病理学教研室 )) 1

Chapter 2Chapter 2

Water and Electrolytes Water and Electrolytes Balance and ImbalanceBalance and Imbalance（水和电解质代谢紊乱）（水和电解质代谢紊乱）

Water Covers 3/4 of the Earth Surface

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Water and Electrolytes Water and Electrolytes Balance and ImbalanceBalance and ImbalanceWater and Electrolytes Water and Electrolytes Balance and ImbalanceBalance and Imbalance

Physiological Basis of Water and Sodium Physiological Basis of Water and Sodium MetabolismMetabolism

Disorder of Other ElectrolytesDisorder of Other Electrolytes

Regulation of Water and Sodium BalanceRegulation of Water and Sodium Balance

Disorder of Water and Sodium MetabolismDisorder of Water and Sodium Metabolism

The maintenance of a relatively constant volume and composition of the body fluids are essential for homeostasis.

A large number of factors can induce dysfunction of homeostasis and result in imbalances of water and electrolyte metabolism.

These are very common and important problems in clinical medicine.

Introduction

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Body Fluid (Body Fluid ( 体液体液 ) ) (50 - 60% of Total Body Weight)(50 - 60% of Total Body Weight)

Water and the solutes in the bodyWater and the solutes in the body

CompositionComposition

WaterWater

ElectrolytesElectrolytes

Organics (low-mol)Organics (low-mol)

ProteinsProteins6

Distribution of Body Fluids

Plasma5%

Interstitial15%

ICF40%

Extracellular fluid, ECF

Intracellular fluid, ICF

Transcellular fluid – secreted fluid(body cavities) (Third space) 1-2％ 7

ECF ICF

Factors Affecting Body Fluid Volume Fat, Sex, Age

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Q: Do fat people have more or less body fluid?

Water and Electrolytes Balance

Volume (容量 )

Composition (成分 )

Osmotic pressure (渗透压 )

Distribution (分布 )

Relative Stable Normally:

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Functions of Body Water

Metabolism of biomoleculesMetabolism of biomolecules

Body temperatureBody temperature

LubricationLubrication

Tissue constituent (bound Tissue constituent (bound HH22O)O)

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Intake

(ml/day)

Output

(ml/day)

Drinking 1000-1500

Food 700

Metabolism 300

Urine 1000-1500

(min: 500)

Lungs 400

Skin 500

Stool 100

Total 2000-2500

(min: 1500)

Total 2000-2500

Daily Balance of Water

11Q: Do infants require more or less water (per kg body weight)?

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ElectrolytesElectrolytes are substances that ionize when dissolved in ionizing solvents such as water.

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Composition of the Body Fluid

ECFICF

0

40

80

120

160

Na+ K+ Cl- HCO3- HPO4

2-

Distribution of Key Electrolytes Between

ECF and ICF

Distribution of Body Fluid ComponentsDistribution of Body Fluid Components

Characteristics：① Composition of electrolytes different between ICF and ECF② Osmotic balance between ICF and ECF③ Electrically neutral in each compartment

Blood Vessel

Cell Membrane

Proteins

Movement of Body Fluids & Electrolytes

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Cell Membrane Blood VesselWater Free Free

Electrolytes Not free FreeProteins Not free Not free

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Osmotic Pressure (OP)

The pressure produced by the solute particles in

the solution.

Depends on the number (not the size) of the

particles.

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Osmotic Pressure (OP) Total plasma osmotic pressure

Sum of osmotic pressure produced by electrolytes and non-electrolytes in the plasma

Normal value: 280 – 310 mOsm/L

Colloid osmotic pressure (oncotic pressure)Produced by proteins (mostly albumin)Normal value: 1.5 mOsm/L (1/200 of total plasma OP)Plays important roles in regulating fluid exchange across blood vessels

Crystalloid osmotic pressureProduced by electrolytes (mostly from Na+ (and Cl-))The majority of plasma OPPlays important roles in regulating fluid exchange

across cell membrane

Physiologic Functions of Electrolytes

Maintenance of osmotic pressureMaintenance of osmotic pressure

Generation of membrane potentialGeneration of membrane potential

- Excitability of nerve and muscle- Excitability of nerve and muscle

Participation in metabolism and Participation in metabolism and

functionfunction

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Intake:5 -10 g/d

Absorption: Almost all by small intestine

Excretion: Kidney (>97%), skin

Sodium Balance

ECF 50%

ICF 10%

Bone40%

ECF: Extracellular fluidICF: Intracellular fluid

Serum [NaSerum [Na++] 130~150 mmol/L] 130~150 mmol/L

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Water and Electrolytes Water and Electrolytes Balance and ImbalanceBalance and ImbalanceWater and Electrolytes Water and Electrolytes Balance and ImbalanceBalance and Imbalance

Physiological Basis of Water and Sodium Physiological Basis of Water and Sodium MetabolismMetabolism

Disorder of Other ElectrolytesDisorder of Other Electrolytes

Regulation of Water and Sodium BalanceRegulation of Water and Sodium Balance

Disorder of Water and Sodium MetabolismDisorder of Water and Sodium Metabolism

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Regulation of Body FluidsTwo Levels:

Neural - Thirst

Hormones – Regulation through kidney

Antidiuretic Hormone (ADH)

Aldosterone (ADS)

Atrial Natriuretic Peptide (ANP)

Sensation of Thirst

Thirst CenterThirst Center

ECF Osmotic Pressure

Blood Volume

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Hypothalamus

ECF Osmosis↑

Circulating Volume↓

ADH↑

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Reabsorption of water (>> Na+)

Also called : (Arginine) Vasopressin

Antidiuretic Hormone, ADH (抗利尿激素 )

Hypothalamus

ADH

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Action of ADH:Role of Aquaporins

PK = Protein KinasePKa = Activated Protein Kinase

Renal tubuleEpithelial cell

Effect of ADH

ADH PresentADH Absent

Renin-Angiotensin-Aldosterone System (RAAS)

Angiotensinogen (plasma)

Angiotensin I (plasma)

Angiotensin II (plasma)

Aldosterone (adrenal cortex)

converting enzyme

Reabsorption Na+↑↑ H2O↑

ReninRenin

Plasma Na+ ↓

Plasma K+ ↑

Blood Pressure ↓

↓Na+

JG: Juxtaglomerular

Atrial Natriuretic Peptide (心房钠尿肽 , ANP)

ANP

Excrete Na+ & H2O

Opposing ADS

Opposing ADH

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Circulating Volume ↑

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Regulation of Body Fluids

ADH Osmosis ↑ Distal tubules Reabsorption of H2O>Na+

Blood volume↓ Collecting ducts

ADS Blood volume↓ Distal tubules Reabsorption of Na+>H2O ↓ Na+/↑ K+ Collecting ducts Excretion of potassium

Thirst Osmosis ↑ Thirst center Drinking water Blood volume↓

Regulator Stimulator Site of action Effect

ANP Blood volume ↑ Distal tubules Excretion of sodium Collecting ducts Excretion of water

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Nephron

ADH

ADS

ANP

Regulation of Body Fluids by Hormones

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Water and Electrolytes Balance Water and Electrolytes Balance and Imbalanceand Imbalance

Water and Electrolytes Balance Water and Electrolytes Balance and Imbalanceand Imbalance

Physiological Basis of Water and Sodium Physiological Basis of Water and Sodium MetabolismMetabolism

Disorder of Other ElectrolytesDisorder of Other Electrolytes

Regulation of Water and Sodium BalanceRegulation of Water and Sodium Balance

Disorder of Water and Sodium MetabolismDisorder of Water and Sodium Metabolism

ECF↓

Hypovolemic

ECF ↑

Hypervolemic

ECF N

Serum Na+ ↓

Hyponatremia

Hypovolemichyponatremia

(Hypotonic dehydration)

Hypervolemic hyponatremia

(Water intoxication)

Normovolemic hyponatremia

Serum Na+ ↑

Hypernatremia

Hypovolemic hypernatremia

(Hypertonicdehydration)

Hypervolemic hypernatremia

(Salt intoxication)

Normovolemic hypernatremia

Serum Na+ N Hypovolemia(Isotonic

dehydration)

Hypervolemia(Edema)

Classification of Water and Sodium Metabolic Disorders

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ECF↓

Hypovolemic

ECF ↑

Hypervolemic

ECF N

Serum Na+ ↓

Hyponatremia

Hypovolemichyponatremia

(Hypotonicdehydration)

Hypervolemic hyponatremia

(Water intoxication)

Normovolemic hyponatremia

Serum Na+ ↑

Hypernatremia

Hypovolemic hypernatremia

(Hypertonicdehydration)

Hypervolemic hypernatremia

(Salt intoxication)

Normovolemic hypernatremia

Serum Na+ N Hypovolemia(Isotonic

dehydration)

Hypervolemia(Edema)

Classification of Water and Sodium Metabolic Disorders

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Dehydration refers to total body fluidloss > 2% of TBW.

Dehydration

Classification: Hypotonic dehydration

= Hypovolemic hyponatremia

Hypertonic dehydration

= Hypovolemic hypernatremia

Isotonic dehydration

= Hypovolemia

Definition

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1. Characteristics

Total body fluid loss > 2% of TBW

Na+ loss > water loss

Serum sodium concentration < 130 mmol/L

Plasma osmotic pressure < 280 mOsm/L

Hypovolemic Hyponatremia(Hypotonic Dehydration)

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Pl a

sma

ISF ICF

Normal level

Hypovolemic hyponatremia

2. The changes of Body Fluid Volume

42ECF ↓ ↓ and ICF ↑ (or N)

3. Causes - Renal

Long term use of diuretics Long term use of diuretics (furosemide, mannitol, thiazides)(furosemide, mannitol, thiazides)

inhibits reabsorption of Nainhibits reabsorption of Na++

↓ ↓ ADSADS

Adrenocortical insufficiency (Addison’s Adrenocortical insufficiency (Addison’s disease)disease)

Renal tubular acidosis (RTA)Renal tubular acidosis (RTA)

↑ ↑ NaNa++ excretion excretion

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Causes - Extrarenal

Digestive system: vomiting, diarrhea

Burn (large area)

Accumulation of fluids in the third space

- peritonitis (腹膜炎 )

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4. Clinical Manifestations

Na+ loss > water loss

ECF osmotic pressure ↓

ECF↓

ADS↑(early stage)

H2O reabsorption in kidney: N

Urine: NNa+ in urine ↓

Cell swell in brain

HeadacheLethargy

Blood volume↓↓

Renal Blood Flow ↓

ADS ↑, ADH↑ (late stage)

ISF↓Skin

Elasticity↓

HR↑, BP↓

Hypovolemic Shock

Oliguria (Uria ↓)Na+ in urine ↓

H2O goes into cells

↓

Coma46

Eliminate the causative disease(s)

Fluid therapy:

a) Generally, use 0.9% NaCl and 5% glucose solution (5%

G.S.)

b) NaCl first (salt to glucose is 2 to 1).

c) 3-5% NaCl (hypertonic) could be used for severe patients. Rescue hypovolemic shock (Blood volume↓↓)

5. Principles of Prevention and Treatment

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Hypovolemic Hypernatremia

(Hypertonic Dehydration)

1. Characteristics

Total body fluid loss > 2%

Water loss > Na+ loss

Serum sodium concentration > 150 mmol/L

Plasma osmotic pressure > 310 mOsm/L

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2. Changes of Body Fluid Volume

Pl a

sma

ISF ICF

Normal level

Hypovolemic hypernatremia

49ECF↓ and ICF↓ ↓

3. Causes

Water intake↓No water to drink

Difficulty in eating & drinking

Adipsia (no thirst sensation)

Water loss↑

Water loss only ： Respiratory tract ：

Hyperventilation Skin ： Fever, sweating Kidney ： Polyuria (ADH↓)

Water loss > Na+ loss： Digestive tract ：

Diarrhea, vomiting Skin: Hidrorrhea

(too much sweating) Kidney ： Osmotic diuresis (mannitol)

Hypertonicdehydration

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4. Clinical manifestations

H2O loss > Na+ loss

ECF Osmosis↑

Thirst

ADH↑ Oliguria

Transfusionby self

Dry mouth

CNS dysfunction

Dehydration fever

Cell dehydration

ADH↑ADS↑→ Na+ in urine ↓

Shock and renal failure (late stage)ECF↓↓

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Intracranial Hemorrhage

Eliminate the causative disease(s)

Water loss only:

a) Drinking

b) 2.5～ 3% Glucose infusion.

Water loss > Na+ loss:

a) 0.9% NaCl + 5% Glucose (Glucose infused first).

b) The ratio of NaCl to Glucose is 1 to 2.

5. Principles of prevention and treatment

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Hypervolemic Hyponatremia(Water Intoxication)

1. Characteristics

Water ↑↑ > Na+ ↑

Serum sodium concentration < 130 mmol/L

Plasma osmotic pressure < 280 mOsm/L

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plas

ma

ISF ICF

Normal level

2. Changes of Body Fluid VolumeHypervolemic hyponatremia

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ECF↑↑ and ICF↑

3. Causes

Decreased water loss: Acute renal failure Extensive ADH secretion (after blood loss, shock)

Excessive water gain: Injection of hypotonic solution

(or transfusion of water without salt) Chronic renal failure + Continued water drinking

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4. Clinical manifestations

Water enters cellsWater enters cells

ICFICF ICF osmotic pressureICF osmotic pressure

HeadacheHeadacheNauseaNausea

VomittingVomitting

Cellular swellingCellular swellingIntracranial hypertensionIntracranial hypertension

Blood NaBlood Na++ HemodilutionHemodilution

ECFECFECF osmotic pressure ECF osmotic pressure

Water intoxicationWater intoxication(Water ↑↑ > Na+ ↑)(Water ↑↑ > Na+ ↑)

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Identify and get rid of the causative disease(s).

Restrict water intake.

Provide efficient diuretics and diuretics to excrete the excessive fluid in the body.

In case of emergency, provide 3～ 5% NaCl to elevate plasma osmotic pressure.

5. Principles of prevention and treatment

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