Earliest sign of Mg toxicity:
In case of magnesium toxicity ,there can be respirstory depression.In such cases ,infusion should be discontinued,oxygen given and 10ml of 10% calcium gluconate or calcium chloride given IV.Falling oxygen saturation in pulse oxymetry may be an early sign of magnesium toxicity TEXT BOOK OF OBSTETRICS,Sheila Balakrishnan,2nd edition,page no.269
Falling oxygen saturation on pulse oxymetry
Respiratory depression
Cardiac arrest
Anuria
Medical, surgical and gynaecological illness complicating pregnancy