Electrolyte disturbances and fluid imbalance

Question 1

What does a loop diuretic do?

Answer 1

Inhibits the Na-K-Cl co-transporter in the thick ascending limb of the loop of Henle preventing the reabsorption of NaCl

Question 2

Indications for use of a loop diuretic?

Answer 2

Heart failure (acute and chronic)
Resistant hypertension (esp. in renal impairment)

Question 3

Side effects

Answer 3

Opposite of normal effects e.g. could lead to hypotension, hyponatraemia, hypokalaemia, hypocalcaemia, hypochloraemia causign alkalsosis
Gout
Hyperglycaemia (less common than thiazides)
Renal impairment (dehydration and toxicity)
Ototoxicity

Question 4

What is the effect of activating the RAAS?

Answer 4

Release of renin from kidney due to stretch receptors in kidneys -> angiotensin II
Vasoconstriction
Release of aldosterone from adrenal cortex which increases reabsorption (also K and H excretion)
Release of ANP from the heart which increases the GFR
Release of BNP from the brain which decreases the release of renin and angiotensin II

Question 5

> 3 days on fluids requires what?

Answer 5

Food via oral/enteral/paraenteral route

Question 6

What is colloid?

Answer 6

Fluid that stay in the intravascular space and exert oncotic pressure due to large molecules e.g. blood, human albumin or synthetics like gelafusin

Question 7

What are colloids used for?

Answer 7

Resuscitation

Question 8

What is a crystalloid

Answer 8

A fluid that distributes itself to water compartments in the body and does not remain intravascular (a little) like glucose, NaCl and saline

Question 9

Which compartment does glucose 5% go to?

Answer 9

Mainly intracellular
Interstitial and lymphatic
(a little to intravascular)

Question 10

Which compartment does NaCl 0.18% and glucose 4% go to?

Answer 10

Intracellular
Interstitial and lymphatic
(a little to intravascular)

Question 11

Which compartment does saline 0.8% go to?

Answer 11

Interstitial and lymphatic

a little to intravascular

Question 12

Which compartment does balanced crystalloid go to?

Answer 12

Interstitial and lymphatic

a little to intravascular

Question 13

Which compartment does colloid go to?

Answer 13

Intravascular

Question 14

Daily maintenance fluids:

Answer 14

1L normal saline 0.9% + 2L 5% dextrose with added K

OR 3L dextrose saline with K

Question 15

Who is glucose 5% a good fluid for?

Answer 15

Dehydrated patient who is hypernatraemic

Question 16

Who gets a daily maintenance dose?

Answer 16

Patient who can’t meet fluid/electrolyte needs orally/enterally but has no complex replacement or distribution issues
OR post-successful resuscitation with no signs of shock

Question 17

1st line resuscitation

Answer 17

IV bolus of crystalloid e.g. saline - should raise BP after 15-20 minutes if dehydrated

Question 18

When will an immediate IV bolus of crystalloid not restore blood pressure?

Answer 18

Cardiogenic shock (after immediate bolus you should seek help)

Question 19

After immediate bolus what do you do if there are no signs of shock?

Answer 19

Give boluses up to 2000ml then seek help

Question 20

Protocols for raising serum Na?

Answer 20

Raise by 4-6 mmol/L over a few hours

Raise by no more than 8 mmol/L per day

Question 21

What is the danger of raising Na too quickly?

Answer 21

Can cause central pontine myelinolysis

Question 22

Example of a balanced crystalloid?

Answer 22

Hartmann’s

Question 23

Treatment for chronic hypernatraemia?

Answer 23

Hypotonic fluid given slowly e.g. dextrose 5% lower by no more than 10 mmol/L/day

Question 24

Treatment for acute hypernatraemia?

Answer 24

Lower by 1-2 mmol/L/hour to normalise in 24 hours

Question 25

Treatment for hypervolaemic hyponatraemia?

Answer 25

Treat cause
Fluid restrict
ADH receptor antagonist

Question 26

What is nephrogenic diabetes insipidus?

Answer 26

Renal water loss

Question 27

What is central diabetes insipidus?

Answer 27

Lack of ADH

Question 28

Hormonal cause of hypernatraemia?

Answer 28

Hyperaldosteronism (salt retention)

Question 29

Treatment for hypovolaemic hyponatraemia?

Answer 29

Correct the volume depletion e.g. with IV 0.9% saline

Question 30

ECG of hypokalaemia:

Answer 30

Slightly peaked P wave
Prolonged PR
ST depression
Flat/shallow T wave
U wave
QT interval prolonged

Question 31

Hypokalaemia treatment:

Answer 31

Correct Mg levels
K replacement 10-20mmol/hour + cardiac monitoring
Address cause

Question 32

ECG of hyperkalaemia

Answer 32

Sine wave
Tall tented T wave
Shortened QT
PR lengthened
Widened QRS
No P waves

Question 33

Hyperkalaemia treatment

Answer 33

IV calcium gluconate - antagonises the membrane potential of high K
IV insulin with glucose to drive K into cells
NaCl or beta-agonists to drive K into cells
Loop diuretics, haemodialysis/filtration to remove excess K

Question 34

Endocrine cause of hyperkalaemia?

Answer 34

Addison’s disease (aldosterone insufficiency)

Question 35

What is Addison’s disease?

Answer 35

Auto-immune primary adrenal insufficiency

Deficiencies of cortisol and aldosterone

Question 36

Clinical features of Addison’s disease?

Answer 36

Lethargy, weakness, anorexia, N+V, weight loss, salt craving
Hyperpigmentation esp. in palmar creases, vitiligo
Loss of pubic hair in women
Hypotension
Hypoglycaemia
Crisis: collapse, shock, pyrexia

Question 37

Primary causes of hypoadrenalism:

Answer 37

TB
Metastases (e.g. bronchial carcinoma)
Meningococcal septicaemia (Waterhouse-Friederichson syndrome)
HIV
Anti-phospholipid syndrome

Question 38

Secondary causes of hypoadrenalism:

Answer 38

Pituitary disorders (e.g. tumours, irrigation, infiltration)

Question 39

Other cause of hypoadrenalism

Answer 39

Exogenous glucocorticoid therapy

Question 40

Differential of Addison’s and secondary hypoadrenalism:

Answer 40

Primary Addison’s is associated with hyper pigmentation whereas secondary is not

Question 41

Which drugs cause sexual dysfunction?

Answer 41

Thiazide diuretics