Hypermagnesaemia

• Definition: Serum Mg above normal range of 1.3-2.2 mEq/L
• Toxic: Mg > 4mEq/L
• Incidence Rare and usually iatrogenic
• Note ↑Magnesium is closely associated with ↑K and ↓Ca

Causes of hypermagnesaemia

1)    Iatrogenic

• Hyperalimentation
• IV and oral magnesium
• Laxatives, enemas, antacids (especially in elderly and renal failure)

2)    Renal Failure

3)    Other

• Perforated viscus with continued oral intake
• Tumour lysis (Increased K, Mg, PO4 and decreased Ca)
• Rhabdomyolysis

Clinical manifestations

• Often asymptomatic
• Serum level >4
  • Muscle weakness, hyporeflexia
  • Nausea and vomiting
  • Hypotension secondary to vasodilation
• Serum level >10
  • Coma
  • Hypoventilation
  • Neuromuscular Paralysis
  • Cardiac arrhythmias, bradycardia and death

Complications

Cardiac arrhythmia and ECG changes

• ECG (as for hyperkalaemia)
  • Increase PR and QTc
  • Prolonged QRS
  • Peaked T waves and flattened p waves
  • Complete AV block and asystole

Correction

• Discontinue magnesium intake
• Antagonising Mg with Calcium
• Removing Magnesium from serum

1. Dialysis – Treatment of choice
2. Calcium chloride 10% in 5-10ml repeated
   • Treats life threatening arrhythmia
3. Forced diuresis
   • IV normal saline and Frusemide
   • Watch for hypocalcemia which can make symptoms worse

CCC Differential Diagnosis Series
NEURO	Anosmia, Ataxia, Blepharospasm, Bulbar and Pseudobulbar palsy, Central Pontine Myelinosis, Cerebellar Disease, Chorea, Cranial nerve lesions, Dementia, Dystonia, Exophthalmos, Eye trauma, Facial twitches, Fixed dilated pupil, Horner syndrome, Loss of vision, Meningism, Movement disorders, Optic disc abnormality, Parkinsonism, Peripheral neuropathy, Radiculopathy, Red eye, Retinal Haemorrhage, Seizures, Sudden severe headache, Tremor, Tunnel vision
RESP	Bronchial breath sounds, Bronchiectasis, High airway pressures, Massive haemoptysis, Sore throat, Tracheal displacement
CVS	Atrial Fibrillation, Bradycardia, Cardiac Failure, Chest Pain, Murmurs, Post-resuscitation syndrome, Pulseless Electrical Activity (PEA), Pulsus Paradoxus, Shock, Supraventricular tachycardia (SVT), Tachycardia, VT and VF, SVC Obstruction
GIT	Abdominal distension, Abdominal mass, Abdominal pain, Asterixis, Dysphagia, Hepatomegaly, Hepatosplenomegaly, Large bowel obstruction, Liver palpation abnormalities, Lower GI haemorrhage, Malabsorption, Medical causes of abdominal pain, Rectal mass, Small bowel obstruction, Upper GI Haemorrhage
GUT	Genital ulcers, Groin lump, Scrotal mass, Urine colour, Urine Odour, Urine transparency,
MSK	Arthritis, Shoulder pain, Wasting of the small muscles of the hand
DERM	Palmar erythema, Serious skin signs in sick patients, Thickened Tethered Skin, Leg ulcers, Skin Tumour, Acanthosis Nigricans
ENDO	Diabetes Insipidus, Diffuse Goitre, Gynaecomastia, Hirsutism, Hypoglycaemia, SIADH, Weight Loss
HAEM	Splenomegaly
PAEDS	Floppy infant
MISC	Anaphylaxis, Autoimmune associated diseases, Clubbing, Parotid Swelling, Splinter haemorrhages, Toxic agents and abnormal vitals, Toxicological causes of cardiac arrest
IMAGING	CHEST: Atelectasis, Hilar adenopathy, Hilar enlargement on CXR, Honeycomb lung, Increased interstitial markings, Mediastinal widening on mobile CXR, Pulmonary fibrosis, Pseudoinfiltrates on CXR, Pulmonary opacities on CXR, ABDO: Gas on abdominal X-ray, Kidney mass, BRAIN: Intracranial calcification, Intracranial structures with contrast, Ventriculomegaly, OTHER: Pseudofracture on X-Ray,
LABS	LOW: Anaemia, Hypocalcaemia, hypochloraemia, Hypomagnesaemia,  HIGH: Bilirubin and Jaundice, Hyperammonaemia, Hypercalcaemia, Hyperchloraemia, Hyperkalaemia, Hypermagnesaemia,  ACID BASE: Acid base disorders, Resp. acidosis, Resp. alkalosis, Creatinine, CRP, Dipstick Urinalysis, Laboratory Urinalysis, Liver function tests (LFTs), Pleural fluid analysis, Urea, Urea Creatinine Ratio, Uric acid, Urinalysis, Urine Electrolytes

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