Fluid and Electrolyte Balance Disorders (1)

Question 1

Dehydration:
What are its clinical features?

What will be found on investigations?

Answer 1

➊ • ↓JVP
• Tachycardia
• Weak pulse
• ↓Blood pressure and ↓pulse pressure
• ↓Urine output

➋ • ↑Urea, much higher in comparison to creatinine
• ↑Sodium
• ↑Albumin
• ↑Haematocrit

Question 2

Fluid Overload:
What are its clinical features?

What will be found on investigations?

Answer 2

➊ • ↑JVP
• S3 and/or S4 heart sounds
• Signs of pulmonary oedema
• Peripheral oedema

➋ ↓Sodium

Question 3

Hypernatraemia:
What is it?

What are its causes?

How is it managed?

Answer 3

➊ Na > 145 mmol/L

➋ • Excess water loss - DI, Diuretics, DKA, Diarrhoea, Vomiting, Sweating, Burns
• Excessive hypertonic fluid - IV fluids, Enteral feeds
• Decreased thirst - Acute illness, Old age

➌ Fluids

Question 4

Hyponatraemia:
What is it?

What are its causes?

How is it managed?

Which complication should be avoided when managing this?

Answer 4

➊ Na < 135 mmol/L

➋ • Hypovolaemic - Burns, Sweating, Diarrhoea, Vomiting, Addison’s disease
• Euvolaemic - SIADH, Hypothyroidism
• Hypervolaemic - Heart failure, Renal failure, Liver failure, Nephrotic syndrome

➌ • Hypovolaemic - IV 0.9% saline, Treat underlying cause
• Euvoleamic:
‣ SIADH - Fluid restriction, ADH receptor antagonists (e.g. tolvaptan), Furosemide
‣ Hypothyroidism - Levothyroxine
• Hypervolaemic - Fluid restriction, Treat underlying cause

➍ Central pontine myelinolysis

Question 5

Hyperkalaemia:
What is it?

What are its causes?

What needs to be done regularly in these pts?
→ Which changes may be seen?

How is it managed?

Answer 5

➊ K > 5.5 mmol/L

➋ • Impaired excretion - AKI, CKD, ACEi/ARBs, Spironolactone, NSAIDs, LMWH (inhibits ald. release), Addison’s disease
• Increased release - Lactic acidosis, Insulin deficiency, Rhabdomyolysis, Tumour lysis syndrome, Massive haemolysis, Digoxin toxicity, B-blockers

➌ ECG!
→ • Tall tented T-waves
• Flattened P-waves
• Prolonged PR interval (1st degree block)
• Widened QRS complexes

➍ • Insulin + Glucose - insulin to push K into cells, and glucose to prevent hypoglycaemia
• Nebulised Salbutamol - helps push K into cells
• Calcium gluconate (or chloride) over 10 mins - forcardioprotection (This should be given 1st if ECG changes of pt is at high risk of arrhythmia)

Question 6

Hypokalaemia:
What is it?

What ECG changes may be seen?

What are its causes?

When is replacement indicated?

How is it managed if asymptomatic?

How is it managed if symptomatic or ECG changes?

Answer 6

➊ K < 3.5 mmol/L

➋ ‘In hypokalaemia U have no Pot or no T but a long PR and a long QT’

➌ * Renal - Diuretics, Conn’s syndrome, Cushing’s, Hypomagnesaemia
* Extra renal - Inadequate oral intake, Gut losses (e.g. diarrhoea, vomiting), Redistribution into cells (e.g. b-agonists, insulin, theophylline, alkalosis)

➍ * Oral slow release Potassium chloride or Sando-K
* Treat underlying cause

➎ * IV infusion of 1L 0.9% Saline containing 40mmol Potassium chloride
* Avoid glucose solutions (insulin release will worsen hypokalaemia)
* Treat underlying cause
* Check for and treat concomitant hypomagnasaemia as it increases the risk of arrhythmia