Sodium and Water Balance Flashcards
What kind of organs are the key organs that control sodium and water?
Endocrine
What does ADH control?
Water balance = makes you pee less by causing water to be reabsorbed from the renal tubules
What does having less ADH cause?
A large volume of dilute urine
How is urine concentration/dilution measured?
By urine osmolarity
What is the link between urine and osmolarity l?
Concentrated urine = high osmolarity
Dilute urine = low osmolarity
How does ADH cause water reabsorption?
By concurrent multiplication
What controls sodium balance?
Steroids from the adrenal gland = mainly aldosterone (sometimes cortisol)
What is the effect of steroids on sodium balance called?
Mineralocorticoid activity = refers to Na+ reabsorption in renal tubules in exchange for K+/H+
What does too much mineralocorticoid activity cause?
Sodium gain
How is sodium concentration measured?
mmolNa+/1L H2O
Reference interval = 135-145mmol/L
What can cause hyponatraemia?
Too much after or too little sodium
What can cause hypernatraemia?
Too little water or too much sodium
Why is water gain/loss from the whole body?
Water can move between all body compartments
Where is sodium confined to?
Extracellular fluid (ECF) = kept there by pump in the plasma membrane (Na+ loss/gain solely to ECF)
What does water movement follow?
Solute movement (ie sodium)
How is having too little water treated?
By giving dextrose = goes through all layers to the intracellular fluid compartment
What can occur if sodium concentration is too high/low?
Patient may have symptoms = altered consciousness, confusion, nausea, vomiting, fitting
Is symptomatic hypo/hypernatraemia a problem?
Yes = is life threatening
When is sodium concentration within the normal reference serious?
If the concentration has fallen or risen rapidly
What are the two kinds of stimuli for ADH release?
Osmotic (in health) or non-osmotic (in disease)
What are some examples on non-osmotic stimuli for ADH release?
Hypovolaemia, hypotension, pain, nausea, vomiting
What does oedema signify?
Effective circulating (vascular) volume depletion = due to altered balance of Starling forces at capillary level
What is the body’s response to oedema?
ADH and aldosterone secretion to try and restore volume
What is the issue in a patient that causes oedema?
They have too much water and sodium
