General

Question 1

What is the mechanism of cerebral salt wasting?

Answer 1

• Injured brain releases natriuretic peptide directly to kidneys
• Injured brain increases sympathetic nervous system activity that increases perfusion and dopamine release to the kidneys
• Excessive urinary sodium losses leads to decreased effective circulating volume
• Baroreceptors activated and increase ADH secretion -> water conservation

Question 2

What is cerebral salt wasting?

Answer 2

Extracellular volume depletion due to renal sodium transport abnormality (or loss) in intracranial pathology with normal adrenal and thyroid functions.

• Usually develops in the 1st week following brain insult
• Resolves in 2-4 weeks

Question 3

Conditions leading to cerebral salt wasting?

Answer 3

• Head injury
• Brain tumour
• Stroke
• Intracerebral haemorrhage
• TB meningitis
• Intracranial surgery

Question 4

Difference between cerebral salt wasting and SiADH?

Answer 4

• Extracellular volume status - CSW reduced (signs of hypovolaemia if degree of dehydration is moderate to severe), SiADH normal
• Urine Na secretion and urine volume higher in CSW
• Both can have low uric acid and high FEUA (fractional excretion of uric acid, normal < 10%) -> after Na correction, low uric acid/high FEUA remain in CSW but normalise in SiADH

Question 5

Management approach to cerebral salt wasting?

Answer 5

1. IV hypertonic saline solutions:
   - Correct intravascular volume depletion
   - Correct hyponatraemia
   - Replace ongoing urine Na loss
2. Oral salt supplementation when patients have stabilised
3. Monitor body weight, fluid balance, serum Na level
4. Consider mineralocorticoid (fludrocortisone increase Na reabsorption and K loss from renal distal tubules)

Question 6

Dengue - warning signs?

Answer 6

• Abdominal pain
• Tender liver
• Persistent vomiting/diarrhoea
• Mucosal bleed
• Clinical fluid accumulation
• Altered consciousness level/restlessness
• Increased HCT concurrent with dropping PLT

Question 7

Dengue - clinical evidence of plasma leakage?

Answer 7

• Increasing HCT
• Fluid accumulation in extravascular space
• Haemodynamic instability
• Hypoproteinaemia

Question 8

Severe dengue - criteria?

Answer 8

1. Severe plasma leakage - leading to shock, fluid accumulation with resp distress
2. Severe haemorrhage
3. Severe organ dysfunction
   - AST/ALT > 1000
   - Impaired consciousness
   - Heart/other organs

Question 9

Lactic acidosis - causes?

Answer 9

Pathophysio:
- Lactic acid production > lactic acid clearance
- Impaired tissue oxygenation

Type A (Decreased oxygen delivery)
- Ischaemia e.g. mesenteric
- Shock e.g. hypovolaemic/sepsis
- Cardiac failure
- Resp failure

Type B (Defect in oxygen utilization)
- Renal or hepatic failure
- Alcoholism
- Metformin
- DKA
- Malignancy
- CO or cyanide poisoning
- Thiamine deficiency
- HAART: Didanosine, Stavudine, Zidovudine
- Epilim

Type D
- High carb intake in short bowel syndrome

Question 10

Lactic acidosis - false positives?

Answer 10

• Beta agonists
• Seizures
• Extreme exercise