Theme 4: Disorders of Metabolism - Part 2 Flashcards
When urea and electrolytes (U&E) measurements are taken, what is measured?
sodium potassium (chloride) (bicarb) urea creatinine
When urea and electrolytes (U&E) measurements are taken, what is estimated?
water - body water is measured by assumption/ estimate as it is too difficult to do via routine process
What could be some causes of disorders of sodium and water concentrations?
- haemorrhage - accidents, surgery
- D&V (diarrhoea and vomiting)
- poor intake - elderly
- increased losses - pyrexia, heat
- diabetes insipidus
- diabetes mellitus
- diuretic therapy
- endocrine disorders - ADH, aldosterone
What is the sodium plasma concentration?
140 mmol/L
What does isotonic mean?
same concentration as blood
What happens if you increase the excretion of a solute (Na)?
will decrease the solute concentration e.g [Na+] now = 136 mmol/L
What is a hypotonic solution?
a solution that has a lower solute concentration compared to another solution.
What is insensible loss?
the amount of fluid lost on a daily basis from the lungs, skin, and respiratory tract, as well as water excreted in the faeces
What would happen to [Na+] if there was a gain of 2L isotonic fluid administered via a saline drip?
- gain would be to ECF
- no change in [Na+]
- no fluid redistribution
What is the function of ADH?
- produced by median eminence
- release increases when osmolality rises
- decreases renal water loss
- causes the kidneys to release less water, decreasing the amount of urine produced
- increases thirst
How do we ascertain ADH status?
- measure plasma and urine osmolality
- urine > plasma suggest ADH is active
What does the renin-angiotensin system do?
- renin–> angiotensin –> aldosterone
- activated by reduced IVV e.g Na depletion or haemorrhage
- causes renal Na retention
How is loss of volume treated?
- with gain of isotonic solution
- if hypotonic solution was used, the solution is diluted which causes oedema and the sodium value will fall as the sodium taken out hasn’t been replaced
What is hyponatraemia?
- too little Na in ECF
- Excess water in ECF
- low blood sodium can be due to little sodium or too much water
What is hyperatraemia?
- too little water in ECF
- too much Na in ECF
what is SIADH?
Syndrome of innapropriate anti-diuretic hormone - too much ADH is produced and can cause hyponatraemia
What is the potassium reference range?
3.6 to 5.0 mmol/L
What do we measure when we think a patient might have a disorder of potassium?
- serum potassium does not reflect body potassium
- small proportion of total potassium in plasma
- total body potassium determined by total cell mass
What happens to [K+] if a patient is acidotic?
- potassium moves out of cells
- hyperkalaemia
What happens to [K+] if a patient is alkalotic?
- potassium moves into cells
- hypokalaemia
What are the causes of hyperkalaemia?
- haemolysis
- drug therapy - excess intake
- acute renal failure
- chronic renal failure
- acidosis
- adrenocortical failure
- cell death - cytotoxic therapy
How do you treat hyperkalaemia?
- correct acidosis if this is the cause
- stop unnecessary supplements/intake
- give glucose and insulin - drives potassium into cells
- ion exchange resins - GIT potassium binding
- dialysis -short and long-term