Download MBBS Water and Electrolyte Balance Lecture PPT

Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Latest Water and Electrolyte Balance Lecture PPT

WATER AND ELECTROLYTE

BALANCE
Role of water

Water is a medium for a vast number of biochemical

reactions that occur each moment, which form the

basis of life

Water solubilises various biomolecules such as

proteins, nucleic acid and carbohydrates by forming

hydrogen bond with them

Apart from providing an aqueous medium, water act

as strong nucleophile,directly participates as reactant

in various metabolic reaction

Water plays an important role in regulating body

temperature


ELECTROLYTE ? DISTRIBUTION AND

BALANCE

Electrolytes are the substances which readily

dissociate in solution and exist in ionic form i.e.

positively and negatively charged ions

Electrolytes are well distributed in body fluids to

maintain osmotic equilibrium and water balance

Sodium is the principal cation of ECF,while potassium

is the chief cation of ICF

Chloride and bicarbonate are the principal anion of

ECF,while phosphate is the chief anion of ICF
The total concentration of cations and anions in each body

compartment is equal in order to maintain electrical

neutrality

The concentration of molecules in body fluids are mainly

expressed in terms of osmolality and osmolarity

Osmolality : osmotic pressure exerted by number of moles

per kg of solvent

Osmolarity :osmotic pressure exerted by number of moles

per litre of solution

The osmolality of plasma is in the range of 280-

300mosmo/kg

Sodium and its associated anions makes the

largest contribution to plasma osmolality

It is measured by osmometer

osmolality = 2(Na+)+2(K+)+(glucose)+(urea)
Regulation of water and electrolyte

balance

Kidney play a major role in the regulation of

electrolyte and water balance

The regulation is maintained by the hormones

aldosterone,ADH and renin-angiotensin

Aldosterone is a mineralcorticoid produced by the

zona glomerulosa of the adrenal cortex in response to

angiotensin II derived by the action of renin
Renin-Angiotensin system
The secretion of aldosterone is regulated by the renin-

angiotensin system

When there is fall in ECF volume, renal plasma flow

decreases and this would be sensed by the

juxtaglomerular apparatus of the nephron which

secrete renin



Hyponatremia

Hyponatremia is defined as decrease plasma sodium

concentration below 136 meq/l

Hyponatremia typically manifests itself clinically as

nausea,genarlized weakness and mental confusion at

value below 120 meq/l

The central nervous system symptoms are primarily

caused by movement of water in to cells to maintain

osomotic balance and thus swelling of CNS cells

Hyposmotic Hyponatremia
Hyperosmotic Hyponatremia
Isosmotic Hyponatremia
Hyposmotic Hyponatremia

This type of hyponatremia can be result of either

excess loss of sodium (depletional hyponatremia) or

increased ECF volume (dilutional hyponatremia)

Differentiating these initially requires a clinical

assessment of TBW and ECF volume

Depletional hyponatremia is almost accompanied by a

loss of ECF water, but to a lesser extent than sodium

loss

Dilutional hyponatremia is a result

of excess water retention and can

often be detected during physical

examination as presence of weight

gain or edema

Hyperosmotic Hyponatremia

Hyponatremia occurs with an increased amount of

other solutes in the ECF,causing an extracellular shift

of water or intracellular shift of sodium to maintain

osmotic balance between ECF and ICF

The most common cause of this type of hyponatremia

is severe hyperglycemia

As a general rule,the Na+decreases by 1.6 mmoles/l

for every 100 mg/dl increase of glucose above 100

mg/dl

The clinical use of mannitol for osmotic diuresis can

have similar effect
Isosmotic Hyponatremia

If the measured sodium concentration in plasma is

decreased,but measured plasma

osmolality,glucose,urea are normal ,the only

explanation is pseudohyponatremia

This occurs when sodium is measured by an

indirect ion selective electrode in patient with

severe hyperlipidemia or in state of

hyperproteinemia caused due to multiple

myeloma
Hypernatremia

Hypernatremia (plasma Na+>150mmol/l) is always

hyperosmolar

Symptoms of hypernatremia is primarly neurological

and include tremors,irratibility,ataxia,confusion and

coma

Most cases of hypernatremia occurs in patients with

altered mental status or infants,both of whom may

have difficulty in rehydrating themselves despite a

normal thirst reflex


Hypovolemic Hypernatremia

Normovolemic Hypernatremia

Hypervolemic Hypernatremia



Hypokalemia

Plasma potassium level less than 3.5 meq/l is called

hypokalemia

Characterized by muscle weakness,irratibility and

paralysis

Plasma potassium less than 3 meq/l are associated

with serious neuromuscular symptoms

Tachycardia along with flattened T waves is seen in

ECG

Caused due to redistribution of ECF k+ in to ICF or due

to true k+ deficit(loss of potassium rich body fluid or

decreased intake of k+ )
Redistribution
Insulin therapy for diabetic hyperglycemia
Metabolic alkalosis
Acute leukemia

True potassium deficit
Extrarenal loss in diarrhea or excessive sweating
Renal loss in acute tubular necrosis
Mineralcorticoid excess
Cushing syndrome
Hyperkalemia

Plasma potassium greater than 5 mmoles/l is called

hyperkalemia

Characterized by mental

confusion,weakness,tingling,flaccid paralysis of the

extremities

Cardiac effects of hyperkalemia including bradycardia and

conduction defect evident on ECG by prolonged PR and

QRS interval and peaked T waves

Level above 7 mmoles/l leads to cardiac arrest
Pseudohyperkalemia
Hemolysis
Thrombocytosis(>106/l)
Leukocytosis(>105/l)

Redistribution
Metabolic acidosis
Dehydration
Massive tissue hypoxia
Insulin deficiency
Potassium retention
Acute renal disease and end stage renal failure

Addison disease

ACE inhibitors

Potassiun sparing diuretics (spironolactone,Amiloride)