Hypomagnesaemia
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December 11, 2019
Classification
- Normal: 1.1-0.7
- Mild: 0.69-0.5
- Moderate: 0.49-0.4
- Severe: <0.4
Signs/Symps (normally <0.5)
- MSK: Muscle Twitch, Tremor, Tetany, Cramps
- CNS: Apathy, Depression, Hallucination, Agitation, Confusion, Seizure
- CVS: Tachycardia, Hypertension, Arrhythmia, Digoxin Toxicity
- BioChem: Hypokalaemia, Hypocalcaemia, Hypophosphataemia, Hyponatraemia
Causes
- Reduced Intake: Diarrhoea & Vomiting, Small bowel resection Malabsorption states , Alcoholism
- Increased Loss: Chronic renal failure, Drainage from fistula, Refeeding syndrome
- Drugs: Aminoglycosides, Amphotericin, Carboplatin, Ciclosporin, Cisplatin, Diuretics (Loop & Thiazides), Foscarnet, Proton pump inhibitors (PPIs), Salbutamol, Tacrolimus.
Treatment
[Mg] <0.4 or Symptomatic:
- Magnesium Sulfate 5g (20mmol) over 3hrs, in 1000ml 0.9% NaCl or 5% Glucose
- Serious Arrhythmias – 2g (8mmol) can be given over 10-15min
- Actively Seizing – 2-4g (8-16mmol) can be given over 10-15min
- Admit – Patients may require large doses up to 40g (160mmol) over 5 days
[Mg] ≥0.4 and Asymptomatic:
- Oral magnesium replacement should be considered as first choice where possible.
- A rapid raise in [Mg] i.e. IV replacement, reduces the stimulus to retain magnesium.
- Magnesium Aspartate 10-20mmol/day (1-2 sachets/day)
- Diarrhoea/Increased stoma output may occur
- GP to monitor [Mg]
References