Fluid balance and electrolyte distribution in human body.

Fluid balance and electrolyte distribution 

in human body. 

Mass Percent 

• other way of describing the amount of solute in a solution 

• Describes what percentage of a solution by mass is 

comprised by solute. 

mass of solute 

mass of solute 

× 100 % = 

× 100% 

total mass of solution mass of solute + mass of solvent 

• Example 

A student prepares a solution from 5.00 g of sodium fluoride dissolved 

in 95.00 g of water. 

What is the mass percent of sodium fluoride

Using Moles to Describe the Amount of 

Substance in a Solution 

• A number of units may be used to describe the 

concentration of a solute in a solution. 

• The most common unit is molarity (M). 

• The Molarity of a solution is equal to the moles of solute 

divided by the total volume of the solution. 

M 

= 

moles solute 

L solution 

= 

molar 

mass 

mass 

( g) 

solute 

solute x L solution 

• If we know the mass of solute we dissolved in the 

solution, we can convert the mass the solute to moles of 

solute and calculate the molarity. 

• The Molality of a solution is equal to the moles of solute 

per kilogram of solvent 

Total body water and 

its distribution in the body 

compartments. 

The main functions of water in 

the human organism.

Water 

Largest single chemical component of the body: 

45-75% of body mass 

Fat (adipose tissue) is essentially water free, so 

there is relatively more or less water 

in the body depending on % fat composition 

Water is the solvent for most biological 

molecules within the body 

Water also participates in a variety of 

biochemical reactions, both anabolic and 

catabolic 

Body fat measuring 

Skinfold Caliper 

http://www.linear-software.com/online.html

Fluid Compartments 

Body Fluids are separated by semi-permeable membranes into various 

physiological (functional) compartments 

• Two Compartment Model 

- Intracellular = Cytoplasmic (inside cells) 

- Extracellular (outside cells) 

The Two Compartment Model is useful clinically for understanding the 

distribution of many drugs in the body 

• Three Compartment Model 

– [1] Intracellular = Cytoplasmic (inside cells) 

– Extracellular compartment is subdivided into: 

• [2] Interstitial = Intercellular = Lymph (between the cells in the tissues) 

• [3] Plasma (fluid portion of the blood) 

The Three Compartment Model is more useful for understanding 

physiological processes 

Other models with more compartments can sometimes be useful, e.g., consider lymph in the 

lymph vessels, CSF, ocular fluids, synovial and serous fluids as separate compartments 

Fluid Compartments 

• Total Body Water (TBW) - 42L, 

60% of body weight 

– Intracellular Fluid (ICF) - 

28L, 67% of TBW 

– Extracellular Fluid (ECF) - 

14L, 33% of TBW 

• Interstitial Fluid - 11L, 

80% ECF 

• Plasma - 3L, 20% of 

ECF

Water balance 

– Sources for 2500 ml 

- average daily 

intake 

• Metabolic Water 

• Preformed Water 

– Ingested Foods 

– Ingested Liquids 

– Balance achieved if 

daily output also = 

2500 ml 

• GI tract 

• Lungs 

• Skin 

– evaporation 

– perspiration 

• Kidneys 

Water Movement Between the ICF and ECF 

Osmolality – the concentrations of solutes in water 

– solutes will influence the movement of water across membranes 

H 2 

O 

π = iRTc 

Aquaporins- water channel proteins in membranes 

Net filtration (Starling hypothesis) 

= forces favoring filtration – forces opposing filtration 

As fluid flows through capillary it looses water and create greater osmotic 

return of water as it flows toward veinule end of capillary 

Forces favoring filtration 

- Capillary hydrostatic pressure (blood pressure) 

- Interstitial oncotic pressure (water-pulling) 

Forces favoring reabsorption 

- Plasma oncotic pressure (water-pulling) 

- Interstitial hydrostatic pressure 

H 2 

O 

filtration 

H 2 

O 

reabsorption

Oncotic pressure…Colloid osmotic pressure 

• is formed by colloid particles dissolved in solution 

• in plasma the major part forms proteins 65-85 g/l 

Electrophoretic separation of plasma proteins 

(directly proportional to size and charge) 

Albumin 

60% 

α 1 

globulin 1-antitrypsin, 1-acid glycoprotein 

α 2 

globulin haptoglobin, 2-macroglobulin, 

2-antiplasmin, ceruloplasmin 

4% 7% 

β globulin 

transferin, complement, LDL 

10% 

fibrinogen 

γ globulin = Imunoglobulins 

IgA, IgD, IgE, IgG and IgM 

Mr 67x10 3 Mr150x10 3 

Mr340x10 3 

5% 14% 

Water Movement Between the ICF and ECF 

20L/day 

18L/day

Osmotic Equilibrium 

Plasma Osmolarity - Measures ECF Osmolarity 

• Plasma is clinically accessible 

• Dominated by [Na + ] and the associated anions 

• Under normal conditions, ECF osmolarity can be roughly estimated 

as: 

P OSM = 2 [Na + ] p 

……..270-300 mOsm 

{ P OSM = 2[Na + ] + 2[K + ] + [Urea] + [Glucose] }

Edema 

Accumulation of fluid within the 

interstitial spaces 

• Causes: 

– Increase in hydrostatic pressure (blood pressure / hypertension) 

– Losses or diminished production of plasma albumin (hypoproteinemia 

…decrease in oncotic pressure /malnutrition (at insufficient supply of proteins 

…abdominal edema/ insufficient production of proteins at cirrhosis/ large 

losses of proteins by kidney at nephrotic syndrome/) 

- Increases in capillary permeability (at anaphylaxis, allergic 

reaction (release of histamin), inflammation) 

- Lymph obstruction – elephantitus, flibitus 

- Decreased resorption due to raised systemic venous 

pressure – edema due to heart failure 

Edema

Regulating Fluid Intake 

Thirst 

Thirst Quenching 

1. 2. 

Wetting the oral mucosa 

(temporary) 

Stretching of the stomach 

Decreased blood/body 

fluid osmolarity = 

increased hydration 

(dilution) of the blood is 

the most important 

Regulation of Fluid Output 

• Hormonal control 

– 1 Antidiuretic hormone (ADH) [neurohypophysis] 

– 2 Aldosterone [adrenal cortex] 

– 3 Atrial natriuretic peptide (ANP) [heart atrial walls] 

• Causes of physiologic fluid imbalances 

– Dehydration: ↓ blood pressure, ↓ GFR 

– Overhydration: ↑ blood pressure, ↑ GFR 

– Hyperventilation - water loss through lungs 

– Vomiting & Diarrhea - excessive water loss 

– Fever - heavy perspiration 

– exudating Burns, contusion - fluid loss 

– Hemorrhage – if blood loss is severe

Atrial natriuretic peptide (ANP) is a 28-amino acid peptide that is synthesized, stored, and 

released by atrial myocytes in response to atrial distension 

- elevated levels of ANP are found during hypervolemic states (elevated blood volume) and 

congestive heart failure 

A second natriuretic peptide (brain-type natriuretic peptide; BNP) is a 32-amino acid peptide that 

is synthesized within the ventricles (as well as in the brain where it was first identified). Like 

ANP, BNP is released by the same mechanisms that release ANP, and it has similar 

physiological actions, BNP serves as sensitive, diagnostic markers for heart failure in 

patients 

Regulation of Fluid Output

Osm V PB 

ADH 

Factors affecting 

ADH release 

Urine osmolarity regulation by ADH 

ADH

Human angiotensinogen 

is 118 amino acids long 

Pathway of RAAS 

Principal cells & aldosterone

Atrial natriuretic peptide 

28-amino acid peptide 

Distribution of Solutes 

Interstitial fluid is 

essentially an ultrafiltrate 

of plasma, 

water and electrolytes move freely within 

this compartment and between it and the 

intravascular fluid. 

Intravascular fluid has almost the same 

composition as interstitial fluid except 

for its higher protein level.

Electrolyte Balance 

Electrolytes have 4 important physiological functions in the body 

• essential minerals in certain biochemical reactions 

• control osmosis = control the movement of water between 

compartments 

• maintain acid-base balance 

• conduct electrical currents (depolarization events) 

Regulators: 

Aldosterone ↑ [Na + ] [Cl - ] [H 2 O] ↓ [K + ] 

Atrial Natriuretic Peptide (opposite effect) 

Antidiuretic Hormone ↑ [H 2 O] (↓ [solutes]) 

Parathyroid Hormone ↑ [Ca ++ ] ↓ [HPO 4- ] 

Calcitonin (opposite effect) 

Female sex hormones ↑ [H 2 O] 

Electrolytes 

• Sodium (Na + ) - 136-146 mmol/liter 

– Most abundant cation 

• major ECF cation (90% of cations present) 

• determines osmolarity of ECF 

– Regulation 

• Aldosterone 

• ADH 

• ANP 

– Homeostatic imbalances 

• Hyponatremia 

• Hypernatremia

Hypertonic Alterations - Related to sodium gain or water loss 

• Hypernatremia 

– Serum sodium >146 mmol/L 

– Water movement from the ICF to the ECF 

• Intracellular dehydration 

– Manifestations: 

• Convulsions, pulmonary edema, tachycardia, etc. 

• Water deficit 

- Dehydration 

- Renal free water clearance 

- Manifestations: 

– Tachycardia, weak pulses 

– Elevated hematocrit and serum sodium level 

Hypotonic Alterations - Related to Hyponatremia or free water excess 


- Serum sodium level

Electrolytes 

• Chloride (Cl - ) - 95-103 mmol/L 

– Major ECF anion 

• helps balance osmotic potential and electrostatic equilibrium 

between fluid compartments 

• plasma membranes tend to be leaky to Cl - anions 

– Regulation: aldosterone 


• Hypochloremia - results in muscle spasms, coma (usually 

occurs with hyponatremia) often due to prolonged vomiting 

(elevated sweat chloride diagnostic of Cystic Fibrosis) 

Electrolytes 

• Potassium (K + ) 

– Major ICF cation, concentration maintained by the Na + /K + pump 

• intracellular 120-125 mmol/L 

• plasma 3.5-5.0 mmol/L 

– Very important role in resting membrane potential (RMP) and in 

action potentials = essential for transmission and conduction of nerve 

impulses, normal cardiac rhythms, and skeletal and smooth muscle 

contraction 

• Changes in pH affect K + balance 

– Hydrogen ions accumulate in the ICF during states of acidosis. K + 

shifts out to maintain a balance of cations across the membrane. 

• Aldosterone, insulin, and catecholamines influence serum potassium 

levels 

• Homeostatic imbalances 

• Hypokalemia 

• Hyperkalemia


- Potassium level 5.5 mmol/L 

- Caused by increased intake, shift of K+ from ICF, decreased renal excretion, 

insulin deficiency, or cell trauma 

- Mild attacks 

- Hypopolarized membrane, causing neuromuscular irritability, Tingling of lips 

and fingers, restlessness, intestinal cramping, and diarrhea 

- Severe attacks 

- The cell is not able to repolarize, resulting in muscle weakness, loss or 

muscle tone 

Electrolytes 

• Calcium (Ca 2+ ) 

– Most abundant ion in body 


• most stored in bone (98%) as hydroxyapatite 

- Necessary for structure of bones and teeth, blood clotting, hormone 

secretion, and cell receptor function 

- Regulation: 

• Parathyroid Hormone (PTH) - ↑ blood Ca 2+ 

• Calcitonin (CT) - ↓ blood Ca 2+ 

– Homeostatic imbalances: 

• Hypocalcemia - muscle cramps, convulsions 

• Hypercalcemia - vomiting, cardiovascular symptoms, coma; 

prolonged abnormal calcium deposition, e.g., stone 

formation

Electrolytes 

• Phosphate (H 2 PO 4- , HPO 4 

2- 

, PO 4 

3- 

) 

– Important ICF anions; plasma 1.7-2.6 mmol/L 

• most (85%) is stored in bone as calcium salts 

• also combined with lipids, proteins, carbohydrates, nucleic acids (DNA 

and RNA), and high energy phosphate transport compound 

• important acid-base buffer in body fluids 

– Regulation - regulated in an inverse relationship with Ca 2+ by PTH and 

calcitonin and Vitamin D (If the concentration of one increases, that of the other 

decreases) 

– Parathyroid hormone (PTH) - Increases plasma calcium levels 

– Vitamin D = Fat-soluble steroid - Increases calcium absorption from the GI tract 

– Calcitonin - Decreases plasma calcium levels 


• Phosphate concentrations shift oppositely from calcium concentrations 

and symptoms are usually due to the related calcium excess or deficit 

Hypophosphatemia and Hyperphosphatemia 

• Hypophosphatemia 

– Osteomalacia (soft bones) 

– Muscle weakness 

– Bleeding disorders (platelet impairment) 

– Anemia 

– Leukocyte alterations 

• Hyperphosphatemia 

– High phosphate levels are related to the low calcium levels 

- Increased neuromuscular excitability (partial depolarization) 

- Muscle cramps

Electrolytes 

• Magnesium (Mg 2+ ) 

– 2 nd most abundant intracellular electrolyte, 0.8-1.3 mmol/L in plasma 

• more than half is stored in bone, most of the rest in ICF 

(cytoplasm) 

• important enzyme cofactor; involved in neuromuscular activity, 

nerve transmission in CNS, and myocardial functioning 

– Homeostatic imbalance 

• Hypomagnesemia - Associated with hypocalcemia and 

hypokalemia, Neuromuscular irritability,Tetany, Convulsions, 

Hyperactive reflexes vomiting, cardiac arrhythmias 

• Hypermagnesemia - Muscle weakness, Hypotension, 

Respiratory depression, Lethargy, drowsiness, Bradycardia 

Acid-Base Balance 

• Normal metabolism produces H + (acidity) 

• Three Homeostatic mechanisms: 

– Buffer systems - instantaneous; temporary 

– Exhalation of CO 2 - operates within minutes; cannot 

completely correct serious imbalances 

– Kidney excretion - can completely correct any imbalance 

(eventually) 

• Buffer Systems 

– Consists of a weak acid and the salt of that acid which 

functions as a weak base


• Carbonic Acid - Bicarbonate Buffer 

– A weak base (carbonic anhydrase) 

H + + HCO 3- ⇔ H 2 CO 3 ⇔ H 2 O + CO 2 

• Phosphate Buffer 

NaOH + NaH 2 PO 4 ⇔ H 2 O + Na 2 HPO 4 

HCl + Na 2 HPO 4 ⇔ NaCl + NaH 2 PO 4 

• Protein Buffer (resp. hemoglobin & albumin) 

Most abundant buffer in body cells and plasma 

Amino acids have amine group (proton 

acceptor = weak base) and a carboxyl group 

(proton donor = weak acid) 


• CNS and peripheral 

chemoreceptors control 

changes in blood pH 

• Increased [H + ] causes 

immediate hyperventilation 

and later increased renal 

secretion of [H + ] and [NH 4+ ] 

• Decreased [H + ] causes 

immediate hypoventilation 

and later decreased renal 

secretion of [H + ] and [NH 4+ ]

• Acidosis 

– High blood [H + ] 

– Low blood pH, 7.45 

Acid-Base Imbalances 

• Acid-Base imbalances may be due to problems with ventilation or due to a 

variety of metabolic problems 

– Respiratory Acidosis (pCO 2 

> 45 mm Hg) 

– Respiratory Alkalosis (pCO 2 

< 35 mm Hg) 

– Metabolic Acidosis (HCO 3- 

< 23 mmol/l) 

– Metabolic Alkalosis (HCO 3- 

> 26 mmol/l) 

• Compensation: the physiological response to an acid-base imbalance 

begins with adjustments by the system less involved 

Causes of Acid-Base Imbalances 

• Respiratory Acidosis 

– Chronic Obstructive Pulmonary Diseases e.g., emphysema, 

pulmonary fibrosis 

– Pneumonia 

• Respiratory Alkalosis 

– Hysteria 

– Fever 

– Asthma

Causes of Acid-Base Imbalances 

• Metabolic Acidosis 

– Diabetic ketoacidosis, Lactic acidosis 

– Salicylate poisoning (children) 

– Methanol, ethylene glycol poisoning 

– Renal failure 

– Diarrhea 

• Metabolic Alkalosis 

– Prolonged vomiting 

– Diuretic therapy 

– Hyperadrenocortical disease 

– Exogenous base (antacids, bicarbonate IV, citrate toxicity after 

massive blood transfusions) 

Metabolic Acidosis

Metabolic Alkalosis 

Respiratory Acidosis

Respiratory Alkalosis 

Electrolyte Balance 

Electrolytes have 4 important physiological functions in the body 

• essential minerals in certain biochemical reactions 

• control osmosis = control the movement of water between 

compartments 

• maintain acid-base balance 

• conduct electrical currents (depolarization events) 

Regulators: 

Aldosterone ↑ [Na + ] [Cl - ] [H 2 O] ↓ [K + ] 

Atrial Natriuretic Peptide (opposite effect) 

Antidiuretic Hormone ↑ [H 2 O] (↓ [solutes]) 

Parathyroid Hormone ↑ [Ca ++ ] ↓ [HPO 4- ] 

Calcitonin (opposite effect) 

Female sex hormones ↑ [H 2 O]

Electrolytes 

• Sodium (Na + ) - 136-146 mmol/liter 

– Most abundant cation 

• major ECF cation (90% of cations present) 

• determines osmolarity of ECF 

Plasma OSM = 2[Na + ] + 2[K + ] + [Urea] + [Glucose] 

– Regulation 

• Aldosterone 

• ADH 

• ANP 




Hypertonic Alterations - Related to sodium gain or water loss 


– Serum sodium >146 mmol/L 

– Intake of hypertonic salt solution 

– Water movement from the ICF to the ECF 

• Intracellular dehydration 

– Manifestations: in consequence of cell dehydration 

• Excitability, convulsions, or on the other hand drowsiness 

accompanying with pulmonary edema, tachycardia, etc. 

• Water deficit 

- Dehydration (osmotic diuresis at glycosuria (diabetes), 

gastrointestinal losses-osmotic diarrhea, infectious enteritis, high 

fever, burn injury, elevated perspiration) 

- Renal free water clearance 

- Manifestations: 

– Tachycardia, weak pulses 

– Elevated hematocrit and serum sodium level

Hypernatremia 

Serum sodium >160 mmol/L in 60 % lethal 

Therapy: 

at water deficit – isotonic solutions (physiological saline 

solution) or slightly hypotonic (2/3 F) 

at normovolemia or hypervolemia – thiazide diuretics 

(hydrochlorothiazide, decreasing of electrolytes reabsorption in 

renal tubules) and 5% glucose 

frequent monitoring of electrolyte plasma level during the 

treatment, avoid to fast reestablishment of the electrolyte level 

(max 1-2 mmol/L/h and 12 mmol/L/day 

Hypotonic Alterations - Related to Hyponatremia or free water excess 


- Serum sodium level

Hyponatremia 

! 

- water moves into cells based on osmolarity difference, brain cells (neurons) 

decrease water uptake by compensatory mechanisms decreasing the intracellular 

osmolarity by elevation of K + efflux (during 24h), and organic substances metabolism 

(during 48h, e.g. elimination of polyalcohols, aminoacids, cholin derivates) 

! 

Therapy: 

the major risk is to fast reestablish the normal level of Na + ions. The lower 

osmolarity of neurons due to compensatory mechanisms causes water efflux from 

the neurons, the neurons will shrink and released from myelin sheath!!! 

1. if the disnatremia was developed during the last 48hrs, than fast correction 

could be made (1-2mmol/L/h) 

2. if plasma [Na + ] is 105-120 mmol/L and neurological symptoms are present make 

the correction by 1-2mmol/L/h 

without neurological symptoms the speed of correction could be only 

0.5mmol/L/h 

3. if plasma [Na + ] is less than 105 mmol/L, first 20 mmol/L at 1-2mmol/L/h, and then 

slowly 

Hyponatremia 

Calculation of total need of Na + 

mmol Na + = mass (kg) x f x (targeted Na + - determined Na + ) 

f = 0.6 for man 

f = 0.55 for woman 

Example: 70 kg weighted man has plasma [Na + ] 115 mmol/L, we would like to 

increase the [Na + ] to 127 mmol/L/day (i.e. by 12 mmol/L) 

mmol Na + = 70 x 0.6 x (12) = 504 

concentrations of available salt solutions: 

0.9% NaCl (physiological saline solution)…1ml = 0.15 mmol Na + and Cl - 

10% NaCl ….1ml = 1.7 mmol Na + and Cl - 

5.8% NaCl …1ml = 1 mmol Na + and Cl - 

4.2% NaHCO 3 

….1ml = 0.5 mmol Na + and HCO 3 

-

• Chloride (Cl - ) - 95-108 mmol/L 

– Major ECF anion 

• helps balance osmotic potential and electrostatic equilibrium 

between fluid compartments 

• plasma membranes tend to be leaky to Cl - anions 

– Regulation: aldosterone 


• Hypochloremia - results in muscle spasms, coma (usually 

occurs with hyponatremia) often due to prolonged vomiting 

(elevated sweat chloride diagnostic of Cystic Fibrosis) 

Hypochloremia with normonatremia results in metabolic 

hypochloremic alkalosis 

Heperchloremia with normonatremia results in metabolic 

hyperchloremic acidosis 

Combined disbalances are treated based on the plasma [Na + ] 

Hypochloremia with normonatremia or hypernatremia (e.g. due to 

administration of drugs with Na + , such as NaHCO 3 

, Na-lactate, Na-acetate, 

..), vomiting at hyperaldosteronism (e.g. at activation of JG cells due to 

stenosis of renal artery) 

1. treatment of the cause, e.g. antiemetics at vomiting 

2. solution NaCl, KCl at hypokalemia, 4.2% Argininhydrochloride at significant 

alkalosis 

Calculation of total need of Cl - 

mmol Cl - = mass (kg) x 0.3 x BE 

where BE is base excess…. is in the normal range from -2.5 to +2.5 mmol/L, is equal to 

amount of strong acid (or base) which is needed to titrate 1L of plasma to pH 7.4 at normal 

pCO 2 (5.3 kPa and temp. 37 °C) 

in the case, where respiratory compensatory mechanism is involved in regulation of pH (at 

the alkalosis is pCO 2 due to hypoventilation), then use Nejedly’s formula: 

mmol Cl - = mass (kg) x 0.3 x BE x 

pH determined 

-pH targeted 

pH determined 

-pH X 

7.248 

pCO 2 

2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 

pH X 

7.67 7.61 7.567 7.517 7.487 7.457 7.427 7.397 7.377 7.35 7.332 7.314 7.298 7.28 7.263

Hyperchloremia with normonatreia 

1. treatment of the cause, obstruction of urinary tract (accompanied with 

hypernatremia and hyperkalemia), hypoaldosteronism, drug 

administration e.g. HCl, NH4Cl, lysine-HCl, arginine-HCl), acute 

diarrhea (accompanied with hypokalemia) 

2. treatment of acidosis by NaHCO 3 

if pH of artery blood is


- Potassium level

Calcium (Ca 2+ ) 

– Most abundant ion in body 


• most stored in bone (98%) as hydroxyapatite 

- Necessary for structure of bones and teeth, blood clotting, hormone 

secretion, and cell receptor function 

- Regulation: 

• Parathyroid Hormone (PTH) - ↑ blood Ca 2+ 

• Calcitonin (CT) - ↓ blood Ca 2+ 

- Homeostatic imbalances: 

Hypocalcemia (necrotic pancreatitis, malabsorption, hypoparathyreosis, 

vitamin D deficit (osteomalacia)) - muscle cramps, convulsions 

Therapy: 1. cause, 2. 10% Ca-gluconicum (10ml ampules, 1ml = 

0.25mmol) 

Hypercalcemia (hyperparathyreosis, hypervitaminosis D, osteolytic tumor 

metastasis)- vomiting, cardiovascular symptoms, coma (critical [Ca+] is 

above 3.75 mmol/l); prolonged abnormal calcium deposition, e.g., 

stone formation 

Therapy: 1.cause, 2. increase of diuresis by furosemide (at 3L/day), 

glucocorticoids decreasing Ca+ absorption by intestine, calcitonin 

Phosphate (H 2 PO 4- , HPO 4 

2- 

, PO 4 

3- 

) 

– Important ICF anions; plasma 0.7-1.5 mmol/L 

• most (85%) is stored in bone as calcium salts 

• also combined with lipids, proteins, carbohydrates, nucleic acids 

(DNA and RNA), and high energy phosphate transport compound 

• important acid-base buffer in body fluids 

– Regulation - regulated in an inverse relationship with Ca 2+ by PTH and 

calcitonin and Vitamin D (If the concentration of one increases, that of 

the other decreases) 

– Parathyroid hormone (PTH) - Increases plasma calcium levels 

– Vitamin D (fat-soluble steroid) - Increases calcium absorption from the 

GI tract 

– Calcitonin - Decreases plasma calcium levels 


• Phosphate concentrations shift oppositely from calcium 

concentrations and symptoms are usually due to the related 

calcium excess or deficit

Hypophosphatemia and Hyperphosphatemia 

• Hypophosphatemia 

(abrosia, malnutrition, renal losses, hyperparathyreosis) 

– Osteomalacia (soft bones) 

– Muscle weakness 

– Bleeding disorders (platelet impairment) 

– Anemia 

– Leukocyte alterations 

Therapy: significant decrease


• Normal metabolism produces H + (acidity) 

• Three Homeostatic mechanisms: 

– Buffer systems - instantaneous; temporary 

– Exhalation of CO 2 - operates within minutes; cannot 

completely correct serious imbalances 

– Kidney excretion - can completely correct any imbalance 

(eventually) 

• Buffer Systems 

– Consists of a weak acid and the salt of that acid which 

functions as a weak base 


• Carbonic Acid - Bicarbonate Buffer 

– A weak base (carbonic anhydrase) 

H + + HCO 3- ⇔ H 2 CO 3 ⇔ H 2 O + CO 2 

• Phosphate Buffer 

NaOH + NaH 2 PO 4 ⇔ H 2 O + Na 2 HPO 4 

HCl + Na 2 HPO 4 ⇔ NaCl + NaH 2 PO 4 

- mainly intracellularly, during acidemia proton is bound, during alkalemia proton is 

released via cell membrane K + /H + antiporter 

• Protein Buffer (resp. albumin & hemoglobin ) 

Amino acids have amine group (proton 

acceptor = weak base) and a carboxyl group 

(proton donor = weak acid) 

hemoglobin- oxyhemoglobin systém, where 

oxyhemoglobin is stronger acid than 

hemoglobin (proton is more simply released)

Acid-Base balance systems in blood 

1. Carbonic Acid - Bicarbonate Buffer 53 % 

2. Hemoglobin-oxyhemoglobin 35 % 

3. Plasma proteins 7 % 

4. Phosphate buffers 5 % 

plasma pH 7.37-7.43 

Examples: 

Prescribe infusion therapy for mineral blood alteration: 

a) 70 kg man with polyuria 3.5 L/d, plasma [K + ] = 2.8 mmol/L, urine 

[K + ] = 13 mmol/L and with normal levels of other minerals and 

normal blood pH 

b) 60 kg woman with plasma [Cl - ] = 78 mmol/L with normal levels of 

other minerals and blood pH 7.52, pCO 2 6.5 kPa, BE +4.2 and 

normal renal function

Fluid balance and electrolyte distribution in human body.

Create successful ePaper yourself

Delete template?

Save as template?