Lecture 7 - Hypo And Hypernatremia Flashcards
What is considered hypernatremia?
Na+ > 146mmol/L
What is the major cause of hypernatraemia, fluid loss or Na+ gain?
Change in fluid levels
What are some causes of hypernatremia?
Uncontrolled diabetes
Fluid loss without replacement (sweating, burns and vomiting)
Diabetes Insipidus (large vol of dilute urine)
Incorrect IV fluid replacement
Primary aldosterone
What is considered hyponatremia?
Na+ <135mmol/L
Where is hyponatremia very common?
Hosptial patients
What are the symptoms of Hyponatremia?
Agitation
Nausea
Focal neurology (affects nerves in brain)
Coma
Lose consciousness
Seizures
Feeling weak
What are some causes of Hyponatremia leading to water loss?
Diuretics (thiazides)
Water overload or retention
Inc ADH levels
Inc plasma Osmolality (mannitol, glucose)
What are some causes of hyponatremia that lead to True Na+ loss?
Diarrhoea and vomitting
Diuretics/renal failure
Peritonitis
Burns
How do you approach treating a patient with low Na+? (Hyponatraemia)
Always look at the Osmolality of the blood first
What is the normal range of serum osmolality?
275 - 295mosm/kg
How do you calculate osmolality?
Osmolarity = (2 x Na conc) + glucose conc + urea conc (sometimes add K+)
In the osmolarity equation why do you multiply the sodium conc by 2?
Since Na always accompanied by Cl-
If a patients serum osmolarity is hyper osmotic when they have hyponatraemia what does this indicate?
Its not a kidney related issue
usually due to mannitol , hyperglycaemia
If someone is hyponatraemic what do you need to asses?
Their extracellular fluid volume
Are they fluid depleted or oedematous?
What is indicated if a patient is oedematous with hyponatremia with the serum being Hypoosmotic?
Blood not filtered properly
What is indicated in hyponatraemia oedematous patients with a low urine conc of Na+?
Acute/chronic renal failure
What is indicated in hyponatraemia oedematous patients with a high urine conc of Na+?
Nephrotic syndrome
Cirrhosis
Cardiac failure
What is nephrotic syndrome?
Patients lose albumin into the urine from the blood
This leads to oncotic pressure decreasing so less water drawn from interstitium back into blood
If a hyponatraemic patient is fluid depleted what is indicated by the urine conc of Na+ being low?
Sodium is not being lost from the kidneys
So could be a bleed from the Gi tract or skin
If a hyponatraemic patient is fluid depleted what is indicated by the urine conc of Na+ being high?
Losing too much sodium in urine
(Cerebral salt wasting)
What is cerebral salt wasting syndrome?
When a traumatic brain injury leads to losing salt from body
What could be the cause of hyponatraemia in a patient that has normal extracellular fluid volume with a low sodium conc in urine?
Severe Polydipsia
What could be the cause of hyponatraemia in a patient that has normal extracellular fluid volume with a high sodium conc in urine?
SIADH
Glucocorticoid deficiency
Acute/chronic renal failure
Generally how do treat hyponatraemia?
What about hypernatraemia?
Hyponatraemia = restrict water intake
Hypernatraemia = give fluids
What potential complication can occur with rapid developing hyponatraemia?
Pontine demyelination
What is pontine demyelination?
Myelin cells around nerves swell which can damage nerves
This is due to lots of water being present
How can hyponatremia be specifically treated?
Infuse hypertonic saline
Furosemide
A hyponatraemic patient has:
-decreased serum osmolarity
-increased urine osmolarity
-high urine Na+ conc
What is this condition potentially indicative of?
They are Hypoosmotic so have taken on to much fluid (low serum osmolarity)
Lots of water gone into blood instead of urine (high urine osmolarity)
Body tries eliminating more Na+ to get rid of as much water
Likely have SIADH
How can valproate and carbamazepine lead to SIADH?
Can cause excess ADH release
What are Valproate and carbamazepine often used to treat?
Epilepsy
What is the main ion in the Intracellular fluid compartment?
What is the main ion in the Extracellular fluid compartment?
ICF = K+
ECF = Na+ and Cl-
What body fluid compartmen is being diluted in dilutional hyponatremia?
Often the ECF
Which organ is of major concern in dilutional hyponatremia?
Brain
