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Maternal-Newborn & Paediatric Nursing · Chapter 8

Reading the Magnesium Ladder

Magnesium toxicity announces itself in a fixed order, and the order is the whole lesson: the reflexes go before the breathing does. Drive the level up the gauge and watch the body report it, decide what to stop and what to give and in which order, then interpret a postpartum preeclampsia panel and build the breathless patient at three weeks.

At the bedside

6.5 mg/dL

Loading dose 4 to 6 g intravenously over 15 to 30 minutes, maintenance 1 to 2 g per hour, always on a pump and always as a secondary line. Therapeutic is approximately 4 to 7 mEq/L, which is 5 to 8 mg/dL — multiply mEq/L by 1.2 to get mg/dL.

Magnesium is cleared renally, so oliguria means accumulation. Urine output is a toxicity parameter here, not just a fluid parameter.

What do you do, and in what order?
Therapeutic rangeFlushing, warmth and drowsiness are expected here
5–8 8–12 12–15 15–25 >25 THERAPEUTIC REFLEXES GO RR < 12 ECG, CONSCIOUSNESS ARREST 6.5
Deep tendon reflexes
Respiratory rate
Urine output
Consciousness
ECG
Therapeutic
Assess before the infusion and hourly during it: deep tendon reflexes, respiratory rate, urine output, level of consciousness, blood pressure and continuous oximetry. Keep calcium gluconate and a bag-valve mask at the bedside of every patient on magnesium.