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Sodium balance

Sodium

  • Daily requirement: 1mmol/kg/day (cf 0.5mmol/kg/day for Potassium) 

 

Distribution of Sodium in body

  1. 50% extracellular
  2. 45% in bone
  3. 5% intracellular

Physiological role

  1. Osmotic effects: internal water balance
  2. Generates action potential

 

  Hypontraemia Hypernatraemia 
Classification
  1. Water gain
    • Increased intake: polydipsia, binge drinking, TURP syndrome
    • Increased retention: SIADH (lung, brain), cardiac failure, hepatic failure
  2. Sodium loss (water loss)
    • Renal loss: Diuretics, addisons
    • Gut loss: diarrhoea, vomiting
    • Other: Burns, DKA
  3. Pseudohyponatraemia
    • Due to measurement peculiarities in presence of hyperlipidaemia

 
  1. Water loss
    • Reduced intake:
    • Increased loss: Diabetes insipidus (lack of vasopressin - cranial lack or nephrogenic insensitivity), osmotic diuresis
  2. Sodium gain (over water)
    • Conn's / cushings
    • Hypertonic saline
Clinical features
  • Features of brain oedema - confusion, agitation, fits, reduced level of consciousness
  •  
Management
  1. Overload - restrict
  2. Losses - replace
 

 

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