Kidney conditions Flashcards
What are the total body water volumes of men and women?
Men= 60% water, 42 litres
Women= 55% water, 38 litres
How much water a day is lost via sweat and evaporation?
Around 500ml a day- if unwell with a fever can lose upto 1L
How is water pushed in and out of cells?
Drawn due to osmotic pressure, pushed out to hydrostatic pressure
What are the names for patients who are volume deplete, volume overloaded or normal volume?
Volume deplete= hypovolaemic
Volume overloaded= Hypervolaemic
Normal= euvolaemic or normovolaemic
What are the 3 states of hyponatraemia that can occur?
Norvolaemic hyponatraemia
Hypovolaemic hyponatraemia
Hypervolaemic hyponatraemia
What happens when there is a increase of water in all compartments?
No clinical signs- is harder to spot
In what clinical scenarios does fluid loss occur?
Haemorrhage
Burns, water can evaporate
Vomiting- can lose a lot of salt. Same as diarrhoea
Diuretic states e.g. diabetes
Sequestration= pleural space in body is inflammaned and holds water in it
Iatrogenic- diuretics, stroma’s/fistulae and gastric aspiration
In what clinical scenarios does fluid gain occur?
Heart and liver failure
Renal failure- pass a reduced amount of urine
Hypothyroidism; unknown why. Oedema common
Psychogenic polydipsia
ADH excess
Iatrogenic= IV fluids, supplemental nutrition
What are the different ways hyponatraemia can occur?
Pure water gain
When water gain > Na+ gain
When Na+ loss > water loss
Or pure Na+ loss (not possible)
What conditions cause pure water gain?
SIADH, hypothyroidism and iatrogenic causes
Appears as normovolaemic as all compartments swell so hard to detect
What is hypovolaemia and hypervolaemia caused by?
Hypo= when Na+ loss > water loss
Hyper= When water gain > Na+ gain
What are the clinical symptoms of hypovolaemia?
Postural hypotension
Tachycardia
Reduced skin turgor
Organ failure
What are the clinical symptoms of hypervolaemia?
Hypertension
Tachycardia
Peripheral and pulmonary oedema
Organ failure
What type of hyponaetraemia is caused by diahorrea?
Hypovolaemic hyponatraemia
Excessive sodium losses; water losses are insufficient to concentrate sodium back up
What happens in euvolaemic hyponatraemia?
Water is distributed across all compartments
What happens in heart failure?
The pump stops working, and there is a reduced circulatating pressure and reduced organ perfusion.
The coresponding blood pressure mechanisms switch on, even though there is enough volume
There is renin/angiotensin/aldosterone/ADH stimulation, causing more water retetion
What is the vicious cycle of heart failure?
Retaining more water so there is more blood volume
However the weakened left ventricle cannot pump all that volume of water and the blood is very dilute
This causes the osmolaric pressure to pull water into the extracellular space
This leaves the blood volume low- cycle starts again
What is SIADH?
Syndrome of inappropriate ADH secretion- where the body makes too much ADH and there is water retention
What are the causes of SIADH?
Intracranial lesions, infection or inflammation of brain, antipsychotics, sedatives, pain and nausea
What is the treatment of SIADH?
Restrict fluids
Vasopressin antagonists- vaptans
What can cause hypervolaemic hyponatraemia?
- Heart failure
- Liver failure
- Nephrotic syndrome
Where water gains exceed sodium gains
What is the common treatment of hypovolaemia and hypervolaemia?
Hypo= restoration of volume state, blood and saline solution. Cessation of diuretics
Hyper= Diuretics, fluid restriction and treatment of underlying cause
What is the treatment for euvolaemia hyponatraemia?
Treat underlying cause
Stop IV fluids
Fluid restriction
Rarely= demeclocycline
What is the commonest form of malignancy that causes SIADH?
Small cell lung cancer