Sodium and Water balance physiology Flashcards
What is water balance controlled by?
ADH
What does high ADH lead to in terms of urine?
small volume of concentrated urine
What does low ADH lead to in terms of urine?
large volume of diluted urine
What is sodium balance controlled by?
mineralocorticoid activity
Which hormones possess mineralocorticoid activtiy?
aldosterone
cortisol
What does high mineralocorticoid activtiy indicate in terms of sodium?
sodium gain
What does low mineralocorticoid activtiy indicate in terms of sodium?
sodium loss
What is mineralcorticoid activtiy?
Na absorption in the renal tubules in exchange for K/H
What is the normal sodium levels?
135-145mmol/L
What can low sodium be due to?
low Na
high H20
What can high sodium be due to?
high Na
low H20
What are dangerous numbers for sodium levels?
<120 or >160
What are the signs of sodium that is too high or low?
nausea altered conciousness confusion vomiting fitting
Where is sodium found?
ECF
What follows sodium by osmosis?
water
What can cause a decreased Na?
SIADH or compulsive water drinking = increasing H20 levels
Sodium loss through skin, kidneys or adrenals
What can cause an increased Na?
H20 loss from diabetes insipious or just low water intake
increased Na from near drowing, some medication, children being force fed salt
What is the management for decreased Na?
give 0.9% saline
What is the management for increased Na?
remove sodium
What is the management for increased H20?
fluid restrict
What is the management for decreased H20?
give water in the form of 0.5% dextrose
What is the benefit of giving 0.5% dextrose?
goes all the way into the ICF, through plasma and ECF
has the same concentration as blood
What is oedema due to?
an altered balance of starlings forces at capillary level between oncotic forces bringing water in and hydrostatic forces pushing it out
Where does water get retained in oedema?
in the ICF
What does SIADH mean?
syndrome of innapropriate ADH release
can lead to hypovoleamia, hypotension, pain, nausea and vomiting
What is pseudohyponatraemia?
extremely low Na levels caused by increased amount of proteins and lipids
the Na:H20 ratio is normal and it will be an incidental finding
What is diabetes insipidus due to?
distruption of the pituitary or pituitary stalk meaning ADH cannot be secreted
lots of pure water lost in the urine
How is diabetes insipidus treated?
desmopressin - exogenous ADH
desmospray, desmopressin oral tables, desmopressin injections
How is diabetes insipidus investigated?
nil by mouth for 8-12 hours
Urine/serum osmol ratio <2 = DI
if improves after desmopressin = cranial DI
