Potassium + calcium

Question 1

What causes increased secretion of K+?

Answer 1

aldosterone
increased delivery of Na and water
high potassium

Question 2

What value is classed as hypokalaemia?

Answer 2

<3.5mmol/L

Question 3

Clinical features of hypokalaemia

Answer 3

neuromuscular - weakness, constipation, confusion, rhabdo

cardiac - arrhythmias, ECG changes, digoxin toxicity, hypertension

renal - polydipsia/polyuria, metabolic alkalosis

Question 4

Hypokalaemia ECG changes

Answer 4

ST segment depression
flattened T wave
U wave

Question 5

Hypokalaemia aetiology

Answer 5

pseudohypokalaemia
decreased potassium intake/reduced absorption
increased entry into cells
increased GI losses
increased urinary losses

Question 6

What is pseudohypokalaemia?

Answer 6

blood sample with large number of abnormal white cells (eg. AML) - take up extracellular K+ - reduced conc.

Question 7

What causes increased entry of potassium into cells?

Answer 7

insulin - stimulates Na-K ATPase
B2 agonists
alkalosis - metabolic or respiratory
hypokalaemic periodic paralysis

Question 8

What can cause increased urinary loss of potassium?

Answer 8

increased mineralocorticoid activity (primary or secondary hyperaldosteronism)

diuretics - loop + thiazide

renal tubular acidosis

Liddles

Bartters

Gitelmans

Question 9

Mild-moderate hypokalaemia treatment

Answer 9

K3-3.4
oral potassium replacement
(if primary hyperaldosteronism - give aldosterone antagonists)

Question 10

Severe hypokalaemia management

Answer 10

<2.5
IV potassium
10-20mmol per hour via peripheral line
careful ECG monitoring

Question 11

What potassium level is considered hyperkalaemia?

Answer 11

> 5

Question 12

Hyperkalaemia clinical features

Answer 12

asymptomatic
cardiac
weakness - muscle weakness, paralysis of diaphragm

Question 13

ECG changes in hyperkalaemia

Answer 13

mild (5.5-6.5) = peaked T waves, prolonged PR segment

moderate (6.5-8) = loss of P wave, prolonged QRS, ST elevation, ectopic beats

severe (>) = sine wave, VF, asystole, axis deviations, bundle branch blocks, fascicular blocks

Question 14

Hyperkalaemia aetiology

Answer 14

pseudohyperkalaemia
redistribution
reduced renal clearance

Question 15

What causes pseudohyperkalaemia?

Answer 15

movement of K out of cells after specimen taken - eg. fist clenching, mechanical trauma

severe leucocytosis (CLL)

thrombosis (K released from platelet after clotting)

Question 16

What things cause redistribution that causes hyperkalaemia?

Answer 16

increased tissue breakdown - tumour lysis, rhabdo, haemolysis, ischaemia

metabolic acidosis

hyperosmolality and hyperglycaemia

Question 17

What can cause reduced renal clearance leading to hyperkalaemia?

Answer 17

mineralocorticoid deficiency
mineralocorticoid resistance
drugs - K sparing diuretics
acute on chronic kidney disease

Question 18

What drugs can induce hyperkalaemia?

Answer 18

potassium-containing drugs
beta blockers
ACE-i
ARB
aldosterone receptor antagonist
K-sparing diuretics
NSAID, COX-2i
CNI (calcineurin inhibitors eg. cyclosporin, tacrolimus)

Question 19

Hyperkalaemia treatment

Answer 19

monitor if K>6
treat if K>6.5 or ECG changes
calcium gluconate

Question 20

What does calcium gluconate do in hyperkalaemia and how is it given?

Answer 20

antagonises membrane effect of K+ (stabilises cardiac membrane)
20ml of 10% calcium gluconate over 10 mins
effect <1h
repeat - max 40ml until ECG normalises

Question 21

What should be given in hyperkalaemia >6.5 or ECG changes?

Answer 21

calcium gluconate
insulin-glucose (10 units actrapid in 50ml 50% dextrose over 10mins)
monitor BMs

Question 22

How do you reduce total body potassium?

Answer 22

urinary K wasting - diuretics
gut wasting - calcium exchange resins
extracorporeal wasting = haemodialysis or haemofiltration

Question 23

Hypercalcaemia symptoms

Answer 23

abdominal pain
vomiting
constipation
renal stones and failure
polyuria
polydipsia
confusion
depression
cardiac arrest (shortens QT interval)

Question 24

Hypercalcaemia treatment

Answer 24

treat underlying cause
stop exacerbating drugs
ensure good hydration - IV saline
primary hyperparathyroidism - surgery, calcimimetics
malignancy - treat, bisphosphonates
lymphomas/myeloma.granulomatous- - steroids
furosemide - loop diuretics lose calcium
calcitonin - inhibits osteoclasts
dialysis

Question 25

Hypocalcaemia clinical features

Answer 25

paraesthesia
muscle twitching
Trousseau’s sign
Chvostek’s sign
seizures
prolonged QT interval
arrhythmia

Question 26

Hypocalcaemia treatment

Answer 26

based on severity and cause
<1.9, symptoms or signs - IV calcium gluconate
>1,9 - oral calcium

correct hypomagnesaemia
Vit D/hypoparathyroidism - vit D

Question 27

Key calcium regulators

Answer 27

Vit D
PTH
calcitonin

Question 28

What is corrected calcium corrected for?

Answer 28

albumin

Question 29

Calcium functions

Answer 29

bone structure
muscle contraction
cellular metabolism
wound healing
nerve impulse transmission