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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)
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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
Water and Electrolytes Balance
Volume (容量 )
Composition (成分 )
Osmotic pressure (渗透压 )
Distribution (分布 )
Relative Stable Normally:
9
Functions of Body Water
Metabolism of biomoleculesMetabolism of biomolecules
Body temperatureBody temperature
LubricationLubrication
Tissue constituent (bound Tissue constituent (bound HH22O)O)
10
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)?
13
ElectrolytesElectrolytes are substances that ionize when dissolved in ionizing solvents such as water.
15
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
17
Cell Membrane Blood VesselWater Free Free
Electrolytes Not free FreeProteins Not free Not free
18
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)
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
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 ↑
35
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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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
38
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
39
Dehydration refers to total body fluidloss > 2% of TBW.
Dehydration
Classification: Hypotonic dehydration
= Hypovolemic hyponatremia
Hypertonic dehydration
= Hypovolemic hypernatremia
Isotonic dehydration
= Hypovolemia
Definition
40
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)
41
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
43
Causes - Extrarenal
Digestive system: vomiting, diarrhea
Burn (large area)
Accumulation of fluids in the third space
- peritonitis (腹膜炎 )
44
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
47
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↓↓
51
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
52
Hypervolemic Hyponatremia(Water Intoxication)
1. Characteristics
Water ↑↑ > Na+ ↑
Serum sodium concentration < 130 mmol/L
Plasma osmotic pressure < 280 mOsm/L
53
plas
ma
ISF ICF
Normal level
2. Changes of Body Fluid VolumeHypervolemic hyponatremia
54
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+ ↑)
56