Fluid and Electrolyte Balance Flashcards
Which compartments make up the extracellular fluid?
Plasma Interstitial fluid Synovial CSF Intraocular
What is the total body fluid volume for a 70kg man?
42L
What is the predominant intracellular ion in humans?
Potassium
What are the average total fluid losses per day?
2550ml
What causes gain of fluid?
Food and water intake
Oxidation of food
What causes loss of fluid?
Urine
Faeces
Sweat
Insensible losses
What is insensible losses?
Water that passes through skin and is lost by evaporation
Evaporative loss from the respiratory tract
What are the main differences between sweat and insensible losses?
No solutes in insensible fluid (important when prescribing replacement fluids)
Insensible losses cannot be prevented and is a major sources of heat loss from the body that is not under regulatory control
What sensors detect changes in blood osmolality?
Osmoreceptors
Baroreceptors
What ion is the key driver of total volume?
Sodium
How are levels of sodium in the blood detected?
Volume sensorys
What happens when sodium/ osmolality rises?
Increase in thirst
Increase in release of ADH
Increase in water intake and retention
==> Increased volume
What happens when the blood volume increases?
Increased stretch of vascular system detected by baroreceptors Decrease in renin release Decrease in aldosterone release Increased ANP Decreased sodium and water retention
What is the function of Atrial Natriuretic Peptide?
Counteracts volume overload by increase renal sodium excretion
What happens when there is a decrease in blood volume?
Decrease in stretch of vascular system detected by baroreceptors
If pressure falls, ADH released and thirst centres activated
Increased renin release and subsequently ATII levels
Increased aldosterone release
Decreased release of ANP
Increased sodium and water retention
