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