Urea and electrolyes part 2 Flashcards
Where is sodium mainly absorbed ?
DCT and collecting system.
This happens under aldosterone stimulation.
What is Osmolality ?
Dependent on the number of osmotically active particles in solution
An estimation of the osmolar concentration of plasma and is proportional to the number of particlesper kilogram of solvent
Urine: Important for urine and plasma osmolaity!
Ratio Urine/Plasme should be 3-4 to 1. Urine is 3-4 more concentrated than the plasma.
What does ADH stand for ?
Anti diuretic hormone
What does ADH do when there is an increase in osmorlarity ?
ADH is stimulated when there is high osmorlarity within the collecting tubule. An example of this is when a patient is dehydrated.
The body stimulated ADH to retain water in response, and therefore a patient will only stiumlate SMALL AMOUNTS OF CONCENTRATED URINE.
What does ADH do when there is an decrease in osmorlarity ?
A low serum osmolality will suppress the release of ADH, resulting in decreased water reabsorption and more concentrated plasma
What can cause secretion of ADH.
Hyperosmorlarity
Angiotensin 2 int he RASS system.
Stress
Decreased atrial receprtor firing ( the atria can recognise that there is not enough water going around eg in cases of bleeding, vomiting ect).
What cells in the kidney produce renin ?
Juxtaglomerular Apparatus
Explain RASS SYSTEM.
ATTEMPT TO INCREASE BLOOD VOLUME.
What condition produces too much aldosterone ?
COHNS
What is the regular sodium values?
Serum [Na+]
135-145 mmol/l
What is accounted as severe hypernatremia ?
Anything above >145 mmol/l is high.
Anything above >160 mmol/l is SEVERE.
What is the most likely cause for hypernatremia ?
Net water loss
Causes of this include :
Nasogastric tubes
Diarrhoea and vomiting
Fistulae losses
Diabetes insipidus
Decrease in ADH secretion
ADH resistance
Drugs: Diuretics; Abx; Bicarbonate
Hyperglycaemia
What are the signs of hypernatremia ?
ITS TYPICALLY ASYMPTOMATIC.
- Intense thirst !!
- Muscle weakess
- Insomnia
- lethargy
- Coma
- Fits - This is bevasie water leaves the cells and water will come out of the cells in the brain and the cells will begin to shrink which will have an effect on the brain. equally in hyponatremia the opposite will happen and the brain will swell.
What is Diabtetes insipisus
COMPLETE LACK OF ADH !!!
Therefore they are losing water but not nessessarily losing sodium.
What is evdeice of hypovalemia/ water loss.
Evidence of hypovolaemia:
Decreased skin turgor
Increased heart rate
Decreased JVP
Decreased urine output
Decreased blood pressure
Increased capillary refill time/cool peripheries
Impaired neurological state
What is considered hyponatremia ?
Definition:
< 135 mmol/l
Grade*:
Mild:130–135 mmol/L
Moderate: 120–130 mmol/L
Severe: <120 mmol/L
What is more common hyper or hyponatremia ?
Hyponatremia
What are the symptoms of hyponatremia ?
Coning means that the brain is swelling because water is going into the cells.
Why are alcoholics at risk of hyponatremia ?
Alchol abusers - they are typically malnuritoed because their diet consist mainly of beer.
Secondly ALCHOL SUPRESSES ADH, so we are not going to have retention of sodium and you will lose a lot of water.
High risk groups of hyponatremia ?
Malnourished alcoholics (suppress ADH)
Elderly women on thiazide diuretics
Hypokalaemic patients
Burns patients
However there can be a lot of cross over with hypernatremia.
What examinations are important for assessing for hyponatremia?
Anything that assess for volume of blood.
BP (lying and standing)
Jugular venous pressure
Hydration of mucous membranes
Skin turgor
Any ankle oedema
Any ascites
Respiratory examination
Signs of more severe hyponatraemia
Fluid chart
What would expect with a patient having D+V?
HYPONATREMIA.
Loss of fluid, not absorping electrolytes.
This is different to what you would expect with with a patient with an NG tube, where electrolyes will be getting absored and this will result in hypernatremia.
What are the types of hyponatremia ?
What are Cancer patients at risk of with sodium?
Inaprropriate ADH secretion
What woud you expect if a patient had a urine osmorlarity over 20 ?
SIADH
What can cause SIADH ?
Causes:
Iatrogenic
Hypothyroidism
Exercise (endurance events)
Drugs (e.g. diuretics)
Glucocorticoid deficiency
Addison’s disease
Primary polydipsia
Beer potomania
What do you need to diagnose SIADH ?
