4: Potassium handling and electrolytes

Question 1

K range

Question 2

3 ways potassium is regulated

Answer 2

Regulation of potassium:

• Loss through the GI tract
• Renal regulation and secretion:
  
  • Angiotensin II
  • Aldosterone
• Movement from intracellular to extracellular

Question 3

RAAS summary

What releases renin

Answer 3

what releases renin:

• low BP (in renal artery)
• low Na+ in macula dense by JGA
• SNS b1-r activation

Question 4

stimuli for aldosterone secretion

Answer 4

• Angiotensin II
• Potassium (high)

Question 5

Aldosterone binds to MR steroid receptor

Answer 5

(1) ENaC creation (Na resorption)
* Na⁺ resorption occurs through ENaC (Epithelial Sodium Channels) to create a -ve electrical potential in the lumen which drives K⁺ secretion through ROMK (Renal Outer Medullary Potassium) channel
(2) ROMK creation (K excretion)
(3) ­ Sgk1 (Serum Glucocorticoid Kinase 1)
* increased ­ Sgk1 → decreased Nedd4 → decreased degraded sodium channels

Question 6

causes of hyperkalaemia

Answer 6

Question 6

causes of hyperkalaemia

Answer 6

Question 7

ECG Changes associated with hyperkalaemia

Answer 7

1. loss of P waves
2. tall tented T waves
3. widened QRS

Question 7

ECG Changes associated with hyperkalaemia

Answer 7

1. loss of P waves
2. tall tented T waves
3. widened QRS

Question 8

when to manage hyperkalaemia

Answer 8

1. potassium >5.5 with ECG changes
2. potassium >6.5 regardless of ECG changes

Question 9

How to manage hyperkalaemia

Answer 9

Repeat bloods if K+>7 (possible haemolysis)

1. 10mL 10% CaGlu (cardioprotective, does not lover serum K)
2. 100ml 20% dextrose and 10u short-acting insulin, Actrapid (drive K back into cells and dextrose to prevent hypoglycaemia)
3. Nebulised salbutamol as an adjunct
4. in some cases: consider calcium resonium 15g PO or 30g PR (binds K in gut)
5. always treat the cause

Patients on digoxin = take care when IV Ca given as can precipitate arrhythmias, cardiac monitoring should be performed

Question 10

Conn’s or Addison’s

Answer 10

Conns = hypernatraemia, hypokalaemia

Addisons = hyponatraemia, hyperkalaemia

Question 11

S+S of hyperkalaemia

Answer 11

heart palpitations, SoB, CP, N+V

Question 12

Causes of hypokalaemia (GRRR)

Answer 12

Question 13

clinical features of hypokalaemia

Answer 13

Question 13

clinical features of hypokalaemia

Answer 13

Question 14

test for Conn’s

Answer 14

• Screening test for patient with ¯ K⁺ and hypertension  ?Conn’s Syndrome
  
  • Aldosterone: Renin ratio
  • In Conn’s, you expect a HIGH aldosterone: renin ratio because aldosterone supresses renin

Question 15

How do me manage hypokalaemia?

Answer 15

<3 = risk of cardiac arrest

Question 16

RTA types

Answer 16