Hyperkalaemia And Hypokalaemia

Question 1

What is the plasma conc of K+?

Answer 1

3.5-5.5mmol/L-1

Question 2

What is the plasma k+ when someone is hyperkalaemic?

Answer 2

> 5.5mmol/L-1

Question 3

What is the plasma k+ conc when someone is hypokalaemic?

Answer 3

<3.5 mmol/L-1

Question 4

Why are cardiac myocytes so sensitive to change in [k+]?

Answer 4

They have a very low rmp which is very close to the Ek

Question 5

What is the effect of hyperkalaemia on a cardiac action potential?

Answer 5

Depolarises cell

Slows upstroke becuase higher rmp inactivtaes na+ channels

Question 6

What are the risks with hyperkalaemia?

Answer 6

Asystole- depends on the level and speed of it (quicker=more dangerous)

Question 7

What are the classifications of hyperkalaemia?

Answer 7

Mild; 5.5-5.9

Moderate; 6.0-6.4

Severe; >6.5

Question 8

What is a use of hyperkalaemia?

Answer 8

During open heart surgery you can stop the heart by inducing hyperkalaemia

Question 9

What are the treatments for hyperkalaemia? (2)

Answer 9

1. Calcium glauconite (makes the heart less excitable)
2. Insulin and glucose (insulin promotes K+ intake into cells- reduces plasma conc)
   * these wont work if the heart is in asystole

Question 10

What is the effect of hypokalamia?

Answer 10

Lengthens the action potential and delays repolarisation because the low [k+] has an allosteric effect and means the channels cant move k+ as well

Question 11

What are the problems with hypokalaemia?

Answer 11

1. Longer ap can lead to early after depolarisations (EADs)
   =oscillations in membrane potential
   =ventricular fibrillation

• the longer the repolarisation, the more prone the cells is to issues

**any lengthening of the normal wave can lead to fibrillation- the heart is trying to be normal but the contraction is taking too long meaning that there is fibrillations