Question

Which one of the following parameters is NOT necessary for monitoring during magnesium sulphate therapy for eclampsia?

• A. Central venous pressure
• B. Respiratory rate
• C. Patellar reflex
• D. Urinary output

Hint:

Think about what the body needs to clear magnesium and what early toxicity looks like.

Answer 1

The Correct Option is A

Step 1: Know why magnesium sulphate needs close watching.
Magnesium sulphate treats and prevents seizures in eclampsia, but its safe dose range is narrow. As the blood level rises past the therapeutic range, it first dulls the deep tendon reflexes, then slows breathing, and at very high levels it can stop the heart. So every bedside check aims to catch toxicity before it reaches the heart.

Step 2: Check why the patellar reflex matters.
Loss of the knee jerk is the earliest sign of rising magnesium levels. A nurse or doctor checks this reflex before giving each repeat dose, and skips the dose if the reflex is absent.

Step 3: Check why respiratory rate matters.
Respiratory depression follows reflex loss as magnesium rises further. The rate must stay above 12 to 14 breaths a minute; a slower rate is a warning sign to stop the drug and give calcium gluconate as the antidote.

Step 4: Check why urinary output matters.
Magnesium leaves the body through the kidneys. If urine output falls below about 25 to 30 mL an hour (or under 100 mL in four hours), the drug builds up in the blood and toxicity follows even at a normal dose rate. So output must be measured hourly.

Step 5: Check central venous pressure.
Central venous pressure reflects how full the veins and right side of the heart are. It has no role in tracking magnesium levels or toxicity. It is used in other settings, such as guiding fluid therapy in severe preeclampsia with a risk of pulmonary edema, but it is not part of the standard magnesium sulphate monitoring routine.

Final Answer:
The three vital checks for magnesium sulphate therapy are reflexes, breathing rate, and urine output. Central venous pressure is not one of them.
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