Electrolyte Homeostasis Flashcards Preview

Year 2 EMS MoD > Electrolyte Homeostasis > Flashcards

Flashcards in Electrolyte Homeostasis Deck (80)
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Is serum K a good measure of total body plasma?

No, serum plasma does not reflect total body plasma only a small proportion of total potassium is in the plasma
Total body potassium is determined by total cell mass


How does exchange of ICF -ECF affect plasma K?



Give an example of 4 conditions/states which can lead to ECF-ICF K exchange?

1) Acidosis
2) Insulin/glucose therapy
3) Adrenaline
4) Rapid cellular incorporation - TPN, leukaemia


What is the average potassium intake in a day?



Why does ICF-ECF exchange of K have such a significant effect on plasma [K]?

The ICF [K] is 150mmol/L
This means the total K in cells is 3400mmol
The ECF [K] is 5mmol/L
This means the total K in ECF is 70mmol
A 1% shift of K from the ICF into the ECF causes a 34mmol increase in ECF taking it from 70mmol to 104mmol - a significant increase


Why can changes in pH lead to changes in plasma [K]?

K+ and H+ exchange across membranes
They both bind to negatively charged proteins (eg Hb)
Changes in pH cause shifts in the equilibrium between K+ and H+
Acidosis causes potassium to move out of the cells leading to hyperkalaemia
Alkalosis causes potassium to move into the cells leading to hypokalaemia
Conversely K depletion and excess can affect acid-base status


Does acidosis lead to hyper- or hypokalaemia?

Causes potassium to move out of the cells leading to hyperkalaemia


Does alkalosis lead to hyper- or hypokalaemia?

Causes potassium to move into the cells leading to hypokalaemia


What is a normal glucose reference range?



Give the 5 main causes of hyperkalaemia?

1) Artefactual (delay in sample analysis, haemolysis, drug therapy - excess intake)
2) Renal (acute or chronic renal failure)
3) Acidosis
4) Mineralocorticoid dysfunction (not producing angiotensin) (adrenocortical failure, mineralocorticoid resistance eg. sprionalactone)
5) Cell death - cytotoxic therapy


What are the 5 possible treatments for hyperkalaemia?

1) Correct acidosis if this is the cause
2) Stop unecessary supplements/intake
3) Give glucose and insulin - drives potassium into cells
4) Ion exchange resins - GIT potassium binding
5) Dialysis - short and long-term


What are the 3 causes of potassium depletion?

1) Low intake
2) Increased urine loss (diuretics/osmotic diuresis, tubular dysfunction, mineralocorticoid excess)
3) GIT losses (vomiting, diarrhoea/laxatives, fistulae)


Give 2 causes of hypokalaemia without potassium depletion?

1) Alkalosis
2) Insulin/glucose therapy


With potassium depletion to

Affects the neuromuscular system - lethargy, muscle weakness and cardiac arrhythmias


With potassium depletion to

1) Neuromuscular - lethargy, muscle weakness, heart arrhythmias
2) Kidneys - polyuria, alkalosis - increased renal HCO3 production
3) Vascular
4) Gut


What common things may be found in a history suggesting potassium depletion? 5

1) Diarrhoea
2) Vomiting
3) drugs (diuretics, digoxin)
4) Symptoms of lethargy/weakness
5) Cardiac arrhythmias


What 2 findings are likely to be made in electrolyte investigation in a person with potassium depletion?

1) Hypokalaemia
2) Alkalosis - raised HCO3-


What are the 3 main treatments for potassium depletion?

1) Prevention - adequate supplementation
2) Replacement of deficit
3) Monitor plasma potassium regularly especially if taking diuretics, digoxin, compromised renal function and in support of IV resuscitation


In a replacement of potassium deficit how much should be given orally and how much IV?

1) Oral = 48mmol/day +diet
2) IV =


Describe the steps in aldosterone leading to hypernatraemia?

1) Aldosterone leads to increased urine Na reabsorption and decreased urine K reabsorption, which leads to decreased renal loss of water and increased urine [K] and decreased urine [Na]
2) Decreased renal loss of water causes increased IVV which increases GFR leading to decreased plasma [creatinine] and [urea]
3) Increased IVV also leads to decreased ADH release, which leads to increased water loss which also leads to increased plasma [Na]