This document discusses fluid and electrolyte balance. It covers the main electrolytes in the body (sodium, potassium, calcium, magnesium, phosphate, chloride, bicarbonate), their normal ranges and functions. It describes the regulation of total body water and fluid compartments. It then examines causes, symptoms and treatment of various electrolyte imbalances including hypernatremia, hyponatremia, hypokalemia, hyperkalemia, hypercalcemia, hypocalcemia, hyperphosphatemia, hypophosphatemia, hypermagnesemia and hypomagnesemia.

1. FLUID AND ELECTROLYTE BALANCE
ELECTROLYTES:
◦ These are also known as blood electrolytes.
◦ They includes Na+
, K+
, Ca2+
, Mg2+
, PO4, Cl-
, and HCO3
-
◦ Electrolytes are anions or cation.
Functions of the electrolytes:
◦ Maintenance of osmotic pressure and water distribution.
◦ Maintenance of the proper pH.
◦ Helps in nerve conduction.
Regulation of the proper function of the heart and other muscle.
Involvement in oxidation-reduction reactions.
Cofactors for enzymes.
◦ Water constitutes approximately 60% of body weight in men and 55% in
women. Approximately 2/3rd
of body water is found in the intracellular
fluid (ICF) and 1/3rd
in the extracellular fluid (ECF). Of the ECF 80% is
found within interstitial fluid and 20% within serum.
Total body water is regulated by the renal action of Antidiuretic Hormone
(ADH), Aldosterone, Atrial Natriuretic Peptide(ANP), and by thirst
mechanism.
◦ Cell walls function as semipermeable membranes, with water movement
from one compartment to the other being controlled by osmotic pressure
WATER DEPLETION:
◦ Water depletion will occur if intake is inadequate or if there is excessive
loss. Excessive loss of water through the kidney is unusual except in
diabetes insipidus or overuse of diuretics.
◦ Patients with fever will lose water through the skin and ventilated patients
will lose it through the lungs. Diarrhoea also causes water depletion.

2. ◦ Water loss is usually compensated by the thirst mechanism, but this may
not occur in patients who are unconscious, have swallowing difficulties
or are disabled.
◦ Severe water depletion may induce cerebral dehydration causing
confusion, fits, coma and circulatory failure.
◦ The underlying cause for the water depletion should be identified and
treated.
◦ Replacement water should be given orally, where possible, or by
nasogastric tube, intravenously or subcutaneously with 5% dextrose in
water or, in patients with associated sodium deficiency, isotonic saline is
used. Hypotonic saline is sometimes used, where neurologic effects of
hypertonicity are seen.
WATER EXCESS:
◦ Water excess is usually associated with an impaired water excretion, that
is caused by renal failure or the syndrome of inappropriate secretion
of the antidiuretic hormone/arginine vasopressin (SIADH).
◦ This syndrome has several causes including chest infections and some
tumours, particularly small cell carcinoma of the lung.
◦ Excess intake is rarely a cause of water excess since the healthy adult
kidney can excrete water at a rate of up to 2 mL/min.
◦ Patients affected usually present with signs consistent with cerebral
overhydration, although over several days, they may be asymptomatic.
Hyponatremia is usually present.
WATER AND ECF OSMOLALITY:
◦ If the body water content changes independent of the amount of solute,
osmolality will be altered (the normal range is 282–295 mmol/kg of
water).
◦ A loss of water from the ECF will increase its osmolality and result in the
movement of water from the ICF to ECF.
◦ This increase in ECF osmolality will stimulate the hypothalamic thirst
centers to promote a desire to drink while also stimulating the release of

3. vasopressin or ADH. ADH increases the permeability of the renal
collecting ducts to water and promotes water reabsorption with
consequent concentration of urine.
◦ If the osmolality of the ECF falls, there is no desire to drink and no
secretion of ADH. Consequently, a dilute urine is produced which helps
restore ECF osmolality to normal.
SODIUM:
Normal range: 135–145mmol/L.
◦ The body of an average 70 kg man contains approximately 3000 mmol of
sodium. Most of this sodium is freely exchangeable and is extracellular.
◦ In contrast, the ICF concentration of sodium is only about 10 mmol/L.
Each day approximately 1000 mmol of sodium is secreted into the gut
and 25,000 mmol filtered by the kidney. The bulk of this is recovered by
reabsorption from the gut and renal tubules.
◦ The principle role of Na is the regulation of serum osmolality as well as
fluid and acid-base balance.
◦ The kidneys are the primary organs responsible for controlling body Na
and water.
HYPERNATRAEMIA:
◦ Hypernatraemia is an elevated sodium level in blood.
◦ It is defined as serum sodium concentration greater than 145mmol/L.
Causes:
◦ Hypernatremia can result from water loss (most common) or sodium
retention (rare).
Causes of Water Loss:
◦ Inadequate intake of water: This is the most common cause of
hypernatremia. Unable to take in water due to impaired thirst mechanism.

4. ◦ Renal loss: Inappropriate excretion of water, often in the urine, which can
be due to medications like diuretics or lithium or due to diabetes
insipidus.
◦ GI loss: osmotic diarrhea (induced by lactulose, malabsorption).
◦ Insensible losses: excessive sweating may be due to exercise or warm
climate.
◦ Water loss into cells: seizure, severe exercise, rhabdomyolysis.
Causes of Increased Sodium Retention:
◦ Intake of a hypertonic fluid: ingestion of large quantities of sodium,
ingestion of sea water.
◦ Mineralocorticoid excess: such as Conn’s syndrome or Cushing’s
Syndrome.
◦ Secondary hyperaldosteronism associated with, for example, congestive
cardiac failure, nephrotic syndrome, hepatic cirrhosis with ascites, or
renal artery stenosis.
◦ Other causes :
◦ Diarrhea
◦ Vomiting
◦ Inappropriate IV fluids
◦ Renal failure
Diuretics
Examples of drugs known to cause hypernatraemia:
-Lithium and phenytoin
-Adrenocorticotrophic hormone
-Anabolic steroids
-Androgens
-Corticosteroids
-Lactulose
-Estrogens

5. -Oral contraceptives
-Sodium bicarbonate
-Demeclocycline
Symptoms:
-Lethargy
-excessive thirst
-fatigue
-Weakness
-Irritability
-edema.
-Seizures
-Confusion
-coma
HYPONATREMIA:
◦ Hyponatremia is defined as a serum sodium concentration of less than
135mmol/L.
◦ Hyponatremia is classified in adults according to serum sodium
concentration, as follows :
◦ Mild: 130-134 mmol/L
◦ Moderate: 125-129 mmol/L
◦ Profound or severe: < 125 mmol/L
◦ Hyponatremia can be classified according to effective osmolality, as
follows:
◦ Hypertonic hyponatremia: (Serum osmolality : >290 mOsm/kg)
◦ Isotonic hyponatremia: (Serum osmolality : 275-290 mOsm/kg)
◦ Hypotonic hyponatremia – typically considered true hyponatremia.
(Serum osmolality: <275 mOsm/kg)
◦ Hypotonic hyponatremia can be further subclassified according to volume
status, as follows:

6. ◦ Hypervolemic hyponatremia: TBW increases greater than an
increase in total body sodium.
◦ Euvolemic hyponatremia: TBW increase with stable total body
sodium.
◦ Hypovolemic hyponatremia: TBW decreases more than a
decrease in total body sodium.
Causes:
◦ Syndrome of inappropriate anti-diuretic hormone (SIADH).
◦ Heart, kidney and liver problems.
◦ Chronic, severe vomiting or diarrhea.
◦ Hormonal changes.
◦ Drinking too much water.
◦ Intensive physical activities
• Certain drugs also cause hyponatraemia:
Examples of drugs known to cause hyponatraemia:
◦ Amitriptyline and other tricyclic antidepressants
◦ Amphotericin
◦ Angiotensin converting enzyme inhibitors
◦ Carbamazepine
◦ Cisplatin
◦ Clofibrate
◦ Cyclophosphamide
◦ Diuretics
◦ Heparin
◦ Lithium

7. ◦ Miconazole
◦ NSAIDs
◦ Opiates
◦ Tolbutamide
◦ Vasopressin
◦ Vincristine
Symptoms:
-Nausea and vomiting
-Headache
-Confusion
-Loss of energy, drowsiness and fatigue
-Restlessness and irritability
-Muscle weakness, spasms or cramps
-Seizures
-Coma
POTASSIUM:
Normal range: 3.4-5.0mmol/L.
◦ The total amount of potassium in the body is 3000 mmol.
◦ About 10% of the body potassium is bound in red blood cells (RBCs),
bone and brain tissue and is not exchangeable.
◦ The remaining 90% of total body potassium is free and exchangeable,
being pumped in and out by Na/K-ATPase pumps.
◦ The normal daily dietary intake of potassium is of the order of 60–200
mmol.
◦ Major role is regulation of muscle and nerve excitability. Other roles
include control of intracellular volume, protein synthesis, enzymatic
reaction, and carb metabolism.
HYPOKALEMIA: Low levels of potassium in blood usually below
3.4mmol/L is known as Hypokalemia.

8. Causes:
◦ Insufficient consumption of potassium:
◦ Anorexia nervosa, dental problems and dysphagia.
◦ Excessive loss of potassium:
Vomiting, diarrhea and excessive perspiration.
◦ Alcoholism.
◦ Diabetic ketoacidosis
◦ Elevated insulin.
◦ Hypomagnesaemia
◦ Hypothermia
◦ Thyrotoxicosis
Symptoms:
◦ The patient with moderate hypokalemia may be asymptomatic.
◦ Symptoms of severe hypokalemia include:
◦ Muscle weakness
◦ Hypotonia (weak muscle tone)
◦ Paralysis
◦ Depression, confusion
◦ Arrhythmias
◦ Fatigue
◦ Vomiting
◦ Constipation
◦ Hypertension
◦ Hyperglycemia

9. HYPERKALEMIA:
◦ Hyperkalemia is defined as elevated level of potassium greater than
5.0mmol/L in blood.
Causes:
-AKI and chronic renal failure
-Acidosis
-Tumor lysis syndrome
-Cirrhosis
-Diabetic ketoacidosis , Renal tubular acidosis
-High potassium diet, Intravenous potassium supplement
-Malnutrition, fasting, exercise
-Hypoparathyroidism, Addison’s disease
-Blood transfusion.
Drugs causing hyperkalemia:
Angiotensin converting enzyme inhibitors ,Antineoplastic agents
(cyclophosphamide, vincristine) ,Non-steroidal anti-inflammatory drugs ,β-
adrenergic receptor blocking agents ,Cyclosporine, Digoxin (in acute overdose)
Diuretics -potassium sparing (amiloride, triamterene, spironolactone), Heparin
Isoniazid, Lithium ,Penicillins (potassium salt), Potassium supplements,
Tetracycline.
Symptoms:
-Nausea, Vomiting, diarrhea
-Malaise
-Palpitations
-Muscle weakness
-Mild breathlessness
CALCIUM:
Normal range :
Calcium(total): 2.12-2.60 mmol/L
Calcium (ionised): 1.19-1.37 mmol/L

10. ◦ The body of an average man contains about 1 kg of calcium and 99% of
this is bound within bone.
◦ Calcium is present in serum bound mainly to the albumin component of
protein (46%), complexed with citrate and phosphate (7%), and as free
ions (47%). Only the free ions of calcium are physiologically active.
◦ Calcium metabolism is regulated by 1,25- dihydroxycholecalciferol
(vitamin D) and by parathyroid hormone (PTH).
HYPERCALCEMIA:
• Hypercalcemia is an elevated serum calcium levels.
Causes:
◦ Primary hyperparathyroidism
◦ Multiple myeloma and carcinomas
◦ Thyrotoxicosis
◦ vitamins A and D intoxication
◦ acute renal failure , renal transplantation and acromegaly.
◦ Certain drugs like- Thiazide diuretics, lithium, tamoxifen and calcium
supplements.
◦ Hypophosphatemia
Symptoms:
Fatigue
Depression
Confusion
Anorexia
Nausea
Vomiting
Constipation
Pancreatitis
Increased urination
Insulin resistance

11. HYPOCALCEMIA:
◦ Hypocalcemia is defined as low levels of calcium in blood.
Causes:
◦ Severe malnutrition
◦ Hypoalbuminaemia
◦ Hypoparathyroidism
◦ Pancreatitis
◦ Those that cause vitamin D deficiency, for example, malabsorption,
reduced exposure to sunlight, liver disease and renal disease.
◦ Certain drugs like-bisphosphonates, phenytoin, phenobarbital,
aminoglycosides , phosphate enemas, calcitonin, cisplatin, mithramycin
and furosemide.
Symptoms:
◦ Tetany
◦ Paresthesias or Tingling
◦ Muscle spasms: Muscle twitching and cramping
◦ CNS symptoms: Anxiety, Hallucinations , Confusion ,Irritability.
◦ Cardiovascular symptoms: Bradycardia, Ventricular arrhythmias,
Congestive heart failure.
◦ Pulmonary symptoms: Laryngeal or Bronchospasm.
PHOSPHATE :
Normal range: 0.80 – 1.44 mmol/L
◦ About 85% of body phosphate is in bone, 15% in ICF and only 0.1% in
ECF.
◦ Its major function is in energy metabolism. Most phosphate ions are
covalently bound to organic molecules such as lipids(phospholipids),

12. proteins, carbohydrates (DNA,RNA),and ATP. Mineralization of bone
and teeth.
◦ Serum phosphate levels are regulated by vitamin D and Parathyroid
hormone (PTH).
◦ HYPERPHOSPHATAEMIA:
◦ Hyperphosphatemia is abnormally elevated level of phosphate in blood.
Causes:
◦ Hypoparathyroidism, Chronic renal failure, Tumour lysis, severe
haemolysis.
Symptoms:
◦ Ectopic calcification, Secondary hyperparathyroidism, renal
osteodystrophy, Azotemia.
◦ Anorexia, nausea, vomiting, muscular weakness, hyperactive reflexes,
tetany, and tachycardia.
HYPOPHOSPHATEMIA:
◦ Hypophosphatemia is low level of phosphate in blood.
Causes:
◦ Refeeding syndrome.
◦ Respiratory alkalosis
◦ Alcohol abuse
◦ Malabsorption
◦ Hyperexcretion of phosphate in the urine (phosphaturia).
Symptoms:
◦ General debility, anorexia, anaemia, muscle weakness and wasting and
some bone pain and skeletal wasting.
◦ Confusion, delirium and coma

13. MAGNESIUM:
Normal range: 0.7–1.00 mmol/L
◦ Magnesium is an essential cation, found primarily in bone, muscle and
soft tissue.
◦ About 1% of the total body content is in the ECF.
◦ As an important cofactor for numerous enzymes and ATP.
◦ It is critical in energy requiring metabolic processes, protein synthesis,
membrane integrity, nervous tissue conduction, muscle contraction,
hormone secretion.
◦ Regulates heart contractility, Relaxes skeletal and smooth muscle,
Regulates blood pressure, Regulates calcium, and cleans the bowel.
HYPERMAGNESEMIA:
◦ Hypermagnesemia is elevated level of magnesium in blood.
Causes:
◦ Renal insufficiency and excess magnesium administration, such as
magnesium containing laxatives, antacids.
◦ Hemolysis
◦ Diabetic ketoacidosis, adrenal insufficiency, hyperparathyroidism and
lithium intoxication.
Symptoms:
◦ Weakness
◦ Hypotension
◦ Vomiting, nausea
◦ Altered mental functioning.
HYPOMAGNESAEMIA:
◦ Hypomagnesaemia is low level of magnesium in blood.

14. Causes:
◦ Excessive gastro-intestinal losses, renal losses, surgery, trauma, infection,
malnutrition and sepsis.
◦ Alcoholism, Diuretic use.
◦ Antibiotics (i.e. aminoglycosides, amphotericin, pentamidine, gentamicin,
tobramycin)
◦ Certain drugs like – Cisplatin, amphotericin B and ciclosporin
◦ Excess calcium, Increased levels of stress, Excess saturated fats, Excess
coffee or tea intake, Insufficient water consumption, Excess salt, Excess
sugar intake.
Symptoms:
◦ Weakness
◦ Irritability
◦ Tetany, delirium
◦ Convulsions
◦ Confusion
◦ Anorexia
◦ Nausea, vomiting
◦ Paresthesia
◦ Cardiac arrhythmias.
CHLORIDE:
Normal range: 96-106 mmol/L.
◦ Most abundant anion in the ECF and is important in maintenance of acid-
base balance.
◦ Its absorption is coupled with bicarbonate secretion.
Hypochloremia is caused due to metabolic alkalosis or acidosis caused by

15. organic or other acids, CRF, fasting, prolonged diarrhea or vomiting, and
diuretic therapy.
◦ Hyperchloremia can be due to Na water retention, ARF, dehydration,
excess Cl administration.
CHLORIDE:
Normal range: 96-106 mmol/L.
◦ Most abundant anion in the ECF and is important in maintenance of acid-
base balance.
◦ Its absorption is coupled with bicarbonate secretion.
Hypochloremia is caused due to metabolic alkalosis or acidosis caused by
organic or other acids, CRF, fasting, prolonged diarrhea or vomiting, and
diuretic therapy.
◦ Hyperchloremia can be due to Na water retention, ARF, dehydration,
excess Cl administration.