Na, K, H20 and electrolyte disorders

Question 1

What is measured in U and Es?

Answer 1

Na
K
Cl
Bicarbonate (HCO3)
Urea
Creatinine

Question 2

What is estimated in U and Es?

Answer 2

Water

Question 3

What is electrolyte balance important?

Answer 3

Maintenance of cellular homeostasis
Cardiovascular electrophysiology
renal physiology

Question 4

Clinical examples of poor electrolyte balance

Answer 4

haemorrhage 
poor intake - food and water 
diuretic therapy 
Diabetes
endocrine disorders- ADH, aldoesterone etc.

Question 5

What are the concepts looked for in U and Es?

Answer 5

Concentrations, compartments, contents, volume, rates of gain and loss

Question 6

What happens to a cell if you decrease the volume?

Answer 6

Will decrease the concentration of any solute

Question 7

What happens to a cell if you increase the excretion of a solute?

Answer 7

The solute concentration will decrease

Question 8

What is the normal Na level within cells?

Answer 8

10 mmol/L

Question 9

what is the normal Na level within ECF?

Answer 9

140 mmol/L

Question 10

What is the normal K level within cells?

Answer 10

150

Question 11

What is the normal K level in the ECF?

Answer 11

5

Question 12

What is isotonic solution?

Answer 12

similar to blood or blood

Question 13

What happens during a loss of isotonic solution?

Answer 13

Loss in ECF
No change in Na
No fluid redistribution

Question 14

What is hypotonic solution?

Answer 14

water

Question 15

What happens during a loss of hypotonic solution?

Answer 15

Greater loss from ICF than ECF (not sure why need to check)
No change in Na
No fluid redistribution

Question 16

What happens during a gain of hypotonic solution?

Answer 16

Greater gain to ICF than ECF
Small decrease in Na
Fluid redistribution between ECF an ICF

Question 17

What does ADH do? Where is it produced and how do we test for it?

Answer 17

Anti- diuretic hormones
Produced by eminence and release increases with rising osmolity, decreases renal water loss
Induced thirst
Test ADH status via plasma and urine osmolity

Question 18

What does the RAAS system do? How do we test for it?

Answer 18

Activated by Intravascular volume (decrease such as haemorrhage)
Test using measurement of plasma and urine Na
If urine

Question 19

What would happen if you replaced an isotonic fluid loss with

a. Isotonic fluid
b. hypotonic fluid

Answer 19

a. No change in Na or fluid redistribution- this is the correct one to do
b. Fall in Na and a fluid redistribution- this would dry out the patient

Question 20

What would happen is you replaced a hypotonic fluid loss with

a. isotonic fluid
b. hypotonic fluid

Answer 20

a. Na slightly increased but no fluid redistribution- this would over hydrate the patient
b. Na is restored and there is no fluid redistribution, this is the correct one to do

Question 21

What is hyponatraemia?

Answer 21

Too much H20, too little Na both in ECF

Question 22

What is hypernatremia?

Answer 22

Too much Na and too little H20 both in ECF

Question 23

What values within the ECF for K are potentially dangerous? What problems would it cause?

Answer 23

6

Cardiac conduction defects, abnormal neuromuscular

Question 24

What are the problems with measuring serum K? How would you determine total body K?

Answer 24

Most K is within the ICF therefore is not an accurate representation
Total body potassium determined by total cell mass

Question 25

What sort of things cause ECF-ICF exchanges in K?

Answer 25

Acidosis or alkalosis
Insulin/glucose therapy
adrenaline
Rapid cellular incorporation e.g TPN, leukaemia

Question 26

What is the usual total mmol of K within the plasma?

Answer 26

70

Question 27

What is the usual total mmol of K within the ICF?

Answer 27

3400

Question 28

What do K and H both bind to?

Answer 28

negatively charged proteins e.g. Hb

Question 29

What does Acidosis and Alkalosis do in terms of K concentration in the ECF?

Answer 29

Acidosis- H+ ions move into cell and displace K+ therefore it moves into ECF = HYPERKALCAEMIA

Alkalosis - Less H+ therefore K moves into cell and there is less in ECF = HYPOKALCAEMIA

Question 30

What are the artefactual, renal, mineralocorticoid, cell death and intercellular exchange causes of hypercalcaemia?

Answer 30

Artefactual- delay in sample testing, haemolysis (breakage of cells during sample taking releases K) and drug therapy

Renal- ARfailure can increase K as it is not filtered out and chronic Rfailure

Intracellular exchange- acidosis

Mineralocorticoid - adrenocortical failure, use of spironolactone

Cell death- chemo, large release of dead cell component s

Question 31

How can we treat hyperkalaemia?

Answer 31

Correct acidosis- but be careful not to decrease it too much
stop unnecessary supplements
Give glucose and insulin- drives K back into cells
Ion exchange resins- helps GIT K binding
Dialysis- short term solution

Question 32

What are the causes of K depletion?

Answer 32

Low intake
increased urine loss - diuretics, tubular defects, mineralocorticoid excess (steroid therapy)
GIT losses-vomiting, fistulae etc.
Hypokalaemia without depletion-alkalosis, insulin/glucose therapy

Question 33

Effects of K depletion? Acute and chronic

Answer 33

Acute-Neuromuscular- lethargy, weakness, heart arthymias

Chronic- same neuromuscular as acute
Kidney -polyuria and alkalosis due to increase in renal bicarbonate (due to damage of the kidneys)
Gut can seize up
Vascular

Question 34

How do you treat a depletion is K? Prevention, replacement and who would you monitor closely?

Answer 34

Prevention- by using K sparing diuretics, adequate supplementation

Replacement deficit-
Oral 48mmol/day + diet
IV