# Causes - GIT - poor nutrition - malabsorption - renal - alcohol - diuretics - gentamicin - endocirne - [[thyrotoxicosis]] - hyperparathyroidism # features - Mg <0.5 mmol/L - tetany - [[Seizures]] - *arrhythmias* eg [[Torsades de Pointes]] - Mg 0.5-0.7 - neuromuscular irritability - in presence of [[hypokalemia|hypo-k]]: - depression - weakness/lethargy - can cause poorly controled AF in spite of addequate therapy - 50% of patients on diuretic therapy with one of these sx has hypo-mg - in presence of [[Hypocalcemia|hypo-Ca]]: - worsens sx of ↓ Ca when Mg <0.5 ## Cardiac effects - increase SA node automaticity - 2-3 risk of [[Atrial fibrillation]] and SVT following [[ACS|MI]] - does not increase incidence of VT/VF in MI, but may increase risk of R on Ts - no benefit to prophylactic IV Mg after MI - increases the effects of [[Digoxin toxicity]] - prolongs Q-T interval and increase risk of [[Torsades de Pointes]] # Mg Treatment see also [[Magnesium]] - indicated if symptomatic ↓ Mg <0.5 - pre-eclampsia/eclampsia - [[Torsades de Pointes]] - resistant severe asthma - digoxin toxicity with tachyarrhythmia - resistant [[hypokalemia|hypo-k]] - tetanus - [[Box jellyfish]] tox +/- irukandji ## MgSO4 - 1g = 4mmol = ~8meq - 2.47 g = 10 mmol - 2 - 4g/day = 8-16 mmol > [!treatment] Administration dosing > - 10mmol IV over 10-15 min in emergency, or faster if torsades > - pre-eclampsia: 4g IV over 20 min, then 1g/h > - eclampsia: 4g IV over 10 min, then infusion at 1-2g/h > - aim for serum levels of 1.5 - 3.5 mmol/L (4-8 mg/dL) to inhibit seizures ## adverse effects - burning at injection site - hypotension - flushing - bradycardia - *muscular paralysis with repeated doses* - **worsening hypocalcaemia** → may need to administer Ca in addition - may precipitate VF from VT - diarrhoea from oral form