Electrolyte Disorders Flashcards
Function of water
• Solvent for all body processes
• Transport nutrients to cells
• Regulates cell volume
• Removes waste products -> urine
• Body coolant -> sweating
Water balance in healthy individuals
Water intake from things such as fluid intake,moist food and metabolic processes=2500ml
Water loss in things such as urine,faeces,insensible loss(breath,perspiration)=2500ml
Functions of electrolytes
Maintenance of body pH
Cofactors in enzyme reactions
Oxidation-reduction reactions
Correct functioning of muscles and nerves
Water balance by maintaining osmotic pressure
Osmolality
-measure of solute in a solution
-indicator of fluid balance
-285 – 295 mOsm/kg in both ECF and ICF
-Water moves from a region of low osmolality to a region of high osmolality
Ecf
-Extra cellular fluid divided into 2 sub categories:intertidal fluid,blood plasma
-na2+ most important ion
Icf
-intracellualr fluid
-k+ Most important ion
How is fluid distribution regulated
-through osmosis and maintaining electrolyte balance preventing cells from bursting
-maintenance of electrical neutrality due to the ionic gradient (sodium potassium pump)
Distribution of water in the body compartmented
1)1/3 in extra cellular fluid
-within that there is water movement through glomerular filtration,trans cellular fluid and secretions
2) 2/3 in the intracellualr fluid
Loss of water from ecf
-during dehydration water is lost from ecf increasing ecf osmolality
-ions can’t be exchanged to maintain the balance so water moved from the icf
-normal osmolality is 290
What will be the immediate effect when there is a rise in plasma osmolality due to a rise in blood glucose as in diabetes mellitus?
Cells dehydrate
Regulation of blood volume
Water deprivation results in rising plasma osmolality causing osmoreceptors in the brain to detect Low water volume and either to :
A)increase thirst which will increase liquid consumption and therefore increase total body volume resulting in correct osmolality
B)release adh which will cause water retention and reduced urinalysis output and result in correct osmolality
Adh
Vasopressin that helps blood vessels construct and helps the kidneys to control the amount of water and salt in the body causing eater retention
Macula dense cells
Salt sensors that generate signals that control vital kidney functions including renal blood floe,glomerular filtration and renin release
Role of the affront arteriole in the juxtaglomerular apparatus
Detect low blood pressure which will results in release of renin
Granular cells
Control blood volume
Synthesise store and secrete the enzyme renin
Reninangiotensin aldosterone system
-low blood pressure sensed by afferent arteriole
-granular cells in the jga complex secrete renin which then joins with a protein called angiotensionogen produced in the liver
-Angiotensin 1 (10aa) is then converted using ace(angiotensin converting enzyme) to angiotensin 2 (8aa)
-angiotensin 2 then either a)causes increased blood vessel tone which increases blood pressure inhibiting jga cells from secreting further renin
B)causes the release of adh from posterior pituitary gland increasing blood volume and blood pressure therefore inhibiting jga cells from secreting further renin or c)binds to the adrenal cortex and leads to the production of aldosterone ,this results in incartesed na+ reabsorption
Clinical features of dehydration
-increased pulse
-decreased blood pressure
-decreased skin turgor
-soft/sunken eyeballs
-dry mucous membranes
-decreased ursine output
-creased consciousness
Clinical features of over hydration
-normal pulse
-Normal or increased blood pressure
-increased skin turgor
-Normal eyeballs
-Normal mucous membranes
-Normal or decreased urine output
-decreased consciousness
Conns syndrome
-Also primary hyperaldosteronism
-Adrenal adenoma Adrenal hyperplasia
-Aldosterone ↑
-Renin ↓
-Hypokalaemia
Addison’s disease
-Also primary hyperaldosteronism
-Adrenal adenoma Adrenal hyperplasia
-Aldosterone ↑
-Renin ↓
-Hypokalaemia
-hyponatreamia
Cushing disease
-Pituitary tumour ACTH ↑
-Cortisol ↑
-Hypernatraemia
-hypokalemia
Clinical symptoms of hyponatreamia
• Mild confusion
• Fatigue
• Muscle cramps
• Brain oedema, seizures • Respiratory arrest
• Death
Sodium levels in plasma
Average adult man: 3700mmol Sodium
Normal plasma sodium concentration (135 –145 mmol/L)
• Renal regulation to maintain sodium balance
Below reference range: hyponatraemia Above reference range: hypernatraemia
Hypo-and hypernatraemia are primarily problems of water, rather than Na+ balance
Parameter for hydration status:
• Concentration of urea in plasma
• Changes in body weight
Clinical symptoms of hypernatremia
• Thirst
• Drymucousmembranes • Decreasedtissueturgor • Disorientation,confusion • Muscleweakness
• Convulsions
• Coma
• Severbrainshrinkage
Types of hyponatreamia
Hypolovemic
Euvolemic
Hypervolemic
Hypovolemic hyponatreamia
-Na2+ and water deficit
-Caused by gastrointestinal loss,diuretics,burns
-Treatment:isotonic saline
Euvolemin hyponatreamia
-Water excess,normal body na2+
-caused by siadh,water overload,post surgery,hypothyroidism
-treatment:water restriction
Hypervolemic hyponatreamia
-na 2+and water excess
-caused by:congestive heart failure,liver ,renal failure
-na and water restriction
Hypernatreamia
Predominantly Deficit of water relative to sodium rather than excess of sodium
• Diabetes Insipidus
• Gastrointestinal loss
• Accidental or deliberate salt ingestion
• Inadequate water intake
