Electrolyte Derangement

UNDER CONSTRUCTION ...

Management Checklists

Electrolyte Derangements

Hyponatraemia

Normal Reference Range

  • Na 135 – 145 mmol/l

Severity

  • Mild: Na 125 – 134 (HA, N&V, Lethargy)
  • Moderate: Na 120 – 124 (Confusion, Weakness)
  • Severe: Na <120 (Seizures, Coma)

Hypertonic (Translocation)

  • Hyperglycaemia
  • Mannitol
  • Sorbitol
  • Iodinated contrast

Isotonic (Pseudohyponatraemia)

  • Hyperprotienaemia
  • Hyperlipidaemia

Hypotonic

Hypovolaemic

  • Loss of Na and H2O from ECF > ADH secretion > H2O retention
  • Renal loss (UNa >20)
    • Diuretics
    • RTA
    • Salt wasting nephropathy
    • Mineralocorticoid deficiencies
    • Ketonaemia
  • Non-renal loss (UNa <10)
    • Upper GI (Vomiting)
    • Middle GI (Pancreatitis, BO)
    • Lower GI (Diarrhoea, Bowel prep)
    • Other (Sweating, Haemorrhage)

Euvolaemic

  • Increase TBW with minimal change in Na
  • Drugs (Oxytocin, SSRI, MDMA, Carbamazepine)
  • Iatrogenic free water intoxication (MDMA, TURP)
  • Psychogenic polydipsia
  • Non-osmotic ADH secretion (Hypothyroidism, Cortisol deficiency, Thiazides)
  • SIADH

SIADH 

Causes:

  • Malignancy (Breast, Lung, Bladder, Pancreas)
  • CNS (TBI, ICH, Meningitis)
  • Lung (PPV, CAP, TB)

Criteria:

  • Euvolaemic
  • Normal LFTs/EUC/TFTs
  • UNa >40 and Uosm > Sosm

Hypervolaemic

  • Increase TBW and Na (TBW>Na)
  • CCF with oedema
  • Cirrhosis with ascites
  • Nephrotic syndrome
  • Hypothyroidism
  • Pregnancy

Step 1. Determine Hydration Status

  • Hypovolaemic
  • Euvolaemic
  • Hypervolaemic

Step 2. Determine UNa and Urine Osmolality

  • Hypovolaemic
    • UNa <20 = Pre-renal
    • UNa >20 = Renal
  • Euvolaemic
    • Uosm < Sosm = H2O intoxication
    • Uosm > Sosm = SIADH
  • Hypervolaemic
    • UNa <20 = CCF, Cirrhosis, Nephrotic syndrome
    • UNa >20 = CRF, Drugs

Hypernatraemia

Hypokalaemia

Hyperkalaemia

Hypocalcaemia

Hypercalcaemia