Hypernatraemia Flashcards
What is the main cause of this?
Over what level is classed as hypernatraemia? (mol/L)
Dehydration - Sodium is high as it tries to draw as much water back in as possible
> 145 mol/L
Why does dehydration hardly happen in real life?
As body triggers ADH, then thirst to avoid this at all costs
Causes of dehydration:
Extrarenal H2O loss/deficit:
- What 2 group of people is lack of intake likely to happen in?
- What else can water be lost through? - 3
Renal H2O loss:
- What causes the kidneys to lose more water?
- How does diabetes insipidus cause this?
- What medication could cause this?
Excess sodium intake (RARE) - what could cause this?
Elderly
Mentally ill
D&V Burns ====== Glycosuria Urea Mannitol
Either ↓ ADH (central DI) or defective renal ADH receptors (nephrogenic DI) → the impaired ability of the kidneys to concentrate urine (hypotonic collecting ducts) → dilute urine (low urine osmolality)
Diuretics
====
Excess hypertonic fluids - iatrogenic
Seawater ingestion
S+S:
What symptoms do they have?
What are some signs of dehydration?
What are some late, possibly deadly effects?
Tired and weak
Thirsty
Irritable and confused
Reduced skin turgor Dry mouth Oliguria Tachycardia Orthostatic hypotension
Seizures and coma
Investigations:
Urine and serum osmolality can be tested.
What does hypertonic urine suggest?
What does hypotonic urine suggest?
Extrarenal fluid loss - it is hypertonic because there is a loss of water, so the Na conc is higher in the extracellular fluid
DI - there is a high amount of water in the urine and in circulation therefore hypotonic
Management:
Hypotonic fluids have to be given. What fluids are hypotonic?
What type of fluid should be used if they are in shock?
What is given to those with central DI?
Oral water
Dextrose
Saline
Isotonic solution
Desmopressin
ADH release:
How does it lead to increased BP and volume? - 2
Increased reabsorption of water and blood vessel vasoconstriction
