Sodium and Water balance Flashcards
What is the main hormone involved in the control of the bodies water balance?
ADH
Anti-Diuretic Hormone
Where is ADH released from?
The posterior pituitary
What is another word for ADH?
AVP
If there is a high concentration of ADH what happens to the urine?
Small amount of very concentrated urine
If there is a low concentration of ADH what happens to the urine?
Large amount of very dilute urine
How is the concentration of urine measured?
Urine osmolality the more concentrate the higher the osmolarity
How is water reabsorbed?
Via a countercurrent between the vascularised medulla and the collecting duct.
How is the medullas high osmolarity maintained?
Na+ and Cl- is actively transported out of the loop of henle producing a concentration gradient.
What is the importance of this concentration gradient?
Water moves via osmosis from an area of low osmolarity to an area of high, this gradient creates the conditions needed for water to leave the collecting ducts.
Are the walls of the collecting duct permeable?
No, water can only pass through with the aid of Aquaporins.
What are aquaporins?
Specific ion channels which are inserted into the wall of the collecting duct and allow water to leave via osmosis.
What is the function of ADH?
Triggers the insertion of aquaporins into the collecting duct allowing more water to leave the collecting duct and enter the blood via osmosis.
Once inserted do the aquaporins stay in the wall of the collecting duct?
No they have a very short lifespan, must be a continuous stimuli resulting in addition of more aquaporins.
How is the sodium balance controlled?
Steroids
What is the main mineralocorticoid that controls Na+?
Aldosterone
What do steroids do to the sodium balance?
They increase reabsorption of Na+ in exchange for K+
Where about does the Na+ reabsorption take place?
Within the distal tubules
As a result of increased Na+ reabsorption what else happens?
Water follows via osmosis
What is hypernatraemia?
High Na+ concentration
What is hyponatraemia?
Low Na+ concentration
What are the two reasons for being hypernatraemic?
High Na+ levels
Low water volume
What are the two reasons for being hyponaetremic?
Low Na+ levels
High water volume
Where is sodium most concentrated within the bodies fluid?
Within the extracellular fluid
140mmol/L
Where is sodium most diluted within the bodies fluid?
Within the intracellular fluid
4mmol/L
What compartment makes up most of the bodies fluid?
Intracellular around 66%
What does intracellular fluid comprise off?
Fluid contained within the bodies cells
What makes up the extracellular fluid?
Plasma
Interstitial fluid
What happens between the compartments if water is lost?
Water is free to move between all compartments, as a results water loss is shared equally between compartments.
What happens between the compartments if Na+ is lost?
Na+ is only lost from the extracellular fluid
Why is sodium only lost from the extracellular fluid?
As it is confined to the ECF by the Na+/K+ ATPase
Why is fluid also lost from the ECF if Na+ is lost?
As water follows via osmosis
Loss of Na+ is more impactful on the body that simply loss of water?
True, BEWARE can look the same on lab results
List some clinical symptoms that manifest as a result of a high Na+ concentration
Hypertensive
Raised JVP
Oedema
Coughing
List some clinical symptoms that manifest as a result of a low Na+ concentration
Hypotensive
Dry mucous membranes
Decreased skin turgor
Concentrated urine
What is the most common issue surrounding Sodium water balance?
A low Na+ concentration due to a high H2O volume
What are some causes of a high H2O volume leading to low Na+ concentration?
Compulsive drinking
Reduced H2O excretion (SIADH)
What is the treatment for Low Na+ due to high H2O volume?
Fluid restriction
How likely is a low Na+ concentration due to increased Na+ excretion?
Very Rare
What are some causes of a low Na+ concentration due to increased Na+ excretion?
D+V
Excessive sweating
Severe burns
Low sodium intake - V.Rare
What is the treatment for a low Na+ concentration due to increased Na+ excretion?
Give sodium
List some causes of an increased Na+ level
Near drowning
Some IV medication
Increased Na+ intake
Malicious - purposely giving to much
What is the treatment for an increased Na+ concentration?
Remove Na+
Loop diuretics
List some causes of an increased Na+ concentration due low H2O volume
Increased water loss
Reduced rate intake
Give a common cause of increased water loss?
Diabetes mellitus
What is the treatment for too little water resulting in a high Na+ concentration?
IV dextrose 5%
What are the types of IV fluid?
Blood and plasma
0.9% Saline
5% Dextrose
What is blood and plasma used for?
Simple plasma volume replacement
What is 0.9% saline used for?
Extracellular volume increased
Resuscitation fluid
What is 5% dextrose used for?
‘Too little water’
Increases all volumes within all body compartments
What is SIADH
Syndrome of Inappropriate ADH
What does SIADH mean?
ADH is inappropriately released for the bodies osmotic status
What are the two stimuli for ADH release?
Osmotic (healthy)
Non-osmotic ( Disease)
What are common non osmotic stimuli for ADH release?
Hypovalaemia
Hypotension
Pain
Vomiting
What is the pathology behind oedema
Blood volume loss leads to…
Increased ADH and aldosterone release
Increased water retention
However most is retained as interstitial fluid
What are some causes of oedema?
Heart failure
Hypoalbuminaemia
Within the lab what causes Pseudohyponatraemia
An increased concentration of lipids and proteins causes machines to record Na+ Conc as low.
