Urea and Electrolytes Flashcards
What does a reddish serum indicate in a separated blood sample?
Haemolysis
What are some physiological compensatory mechanisms for fluid loss?
- Thirst
- ADH
- RAAS system
What are some therapeutic compensatory mechanisms for fluid loss?
- IV therapy
- Diuretics
- Dialysis
What is ADH stimulated in response to?
Rise in concentration of osmotically active particles (osmolality)
Since ADH analysis is not readily available how can it be measured?
- Measuring plasma and urine osmolality
- Urine > plasma suggests ADH is active
What levels suggest the RAAS is active?
If urine Na+ is < 10 mmol/l
What do plasma and urine levels of creatinine usually reflect?
Muscle mass
What is elevated urea found in?
- CCF
- Shock
- MI
- Severe burns
- Gastric bleed
How much urea enters the tubular lumen each day?
800 mmol (48g)
What is the normal range of GFR?
90 - 150 ml/min
What is GFR influenced by?
- Renal perfusion pressure
- Renal vascular resistance
- Glomerular damage
- Post-glomerular resistance
What is the best overall measure of kidney function?
GFR
What is eGFR used for?
Used to aid ‘staging’ of kidney disease
What is an AKI flag used for/
Highlights subtle changes in renal function
eGFR and AKI flag values are calculated based on what substance?
Creatinine
What is hyponatraemia caused by?
- Too little Na in ECF (alcoholics usually)
- Excess water in ECF
- Pseudo hyponatraemia due to increased protein or lipid
What is hypernatraemia caused by?
- Too little water in ECF
- Too much in ECF
What is dehydration caused by?
- Water deficiency
- Fluid (Na and water) depletion
What can hypovolaemia plus decreased urine sodium be due to?
- Vomitting
- Diarrhoea
- Skin loss
What can hypovolaemia plus increased urine sodium be due to?
- Diuretics
- Addisons
- Na losing nephritis
What can euvolemia plus normal plasma osmolarity be due to?
Pseudohyponatraemia
What can euvolemia plus low plasma osmolarity plus increased urine Na+ be due to?
- SIADH
- Drugs
- CRF
What can euvolemia plus low plasma osmolarity plus decreased urine Na+ be due to?
- Stress
- Post surgery
- Endocrine: Hypothyroid
What can high plasma osmolarity and euvolemia be due to?
HYpertonic hyponatraemia
What factors can affect plasma potassium?
- Acid-base status
- Insulin / glucose therapy
- Adrenaline
- Rapid cellular incorporation - TPN, leukaemia
What is the effect of an acidosis oh K+?
Potassium moves out of cells (hyperkalaemia)
What is the effect of an alkalosis on K+?
Potassium moves into cells (hypokalaemia)
What can the causes of hyperkalaemia be?
Artefactual - Delay in sample analysis - Haemolysis - Drug therapy - excess intake Renal - Acute + Chronic renal failure Acidosis (intracellular exchange) Mineralocorticoid dysfunction - Adrenocortical failure - Mineralocorticoid resistance - e.g spironalactone Cell death - Cytotoxic therapy
What are the causes of potassium depletion?
- Low intake
- Increased urine loss (diuretics, tubular dysfunction, mineralocorticoid excess)
- GI losses
- Hypokalaemia without depletion (alkalosis, insulin therapy)
What can potassium depletion cause in the kidney?
- Polyuria
- Alkalosis - increase renal HCO3 production
What could you possibly see in a history of someone with potassium depletion?
- Diarrhoea, vomitting, drugs (diuretics, digoxin)
- Symptoms of lethargy / weakness
- Cardiac arrythmias
