magnesium sulphate in cardiac arrests

[silverdaler]

can anyone please explain for me what is the purpose of using I.V magnesium sulphate in the treatment of cardiac arrests (its for my daughter who is taking her ASL)
thankyou

[Octavius]

magnesium sulfate reduces striated muscle contractions and blocks peripheral neuromuscular transmission by reducing acetylcholine release at the myoneural junction.

Basically it helps to reduce and stop convulsions and aids regulatyion of the heart beat. It is also used to stop pre-eclampsia becoming eclampsia.

http://www.medicinenet.com/magnesium_sulfate-i njection/article.htm

[silverdaler]

thanks octavius - brilliant answer and very useful hyperlink.
could you also tell me, on the PH scale , is above seven acedotic or below ?
cheers !