A nurse needs to check the most important parameter if patient is on magnesium sulphate therapy?

RUHS, Jaipur, PB B.Sc Nursing Entrance-2018

Medical & Surgical Nursing

Easy

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2018

Explanation

The presence of the knee-jerk reflex, a deep tendon reflex, is the most critical parameter to monitor during magnesium sulfate therapy.
Disappearance of this reflex is the earliest and most sensitive clinical sign of magnesium toxicity, serving as a crucial warning before more severe complications arise.
According to clinical toxicology, patellar reflexes disappear when the plasma magnesium level reaches approximately 10 mEq/L, which precedes the level that causes respiratory depression.
Therefore, checking this reflex allows for the earliest possible intervention to prevent life-threatening outcomes.

Option A: Monitoring urine output is essential for preventing toxicity, as magnesium is cleared renally. However, it is a measure of clearance capacity, not the earliest clinical sign that toxicity is occurring.
Option C: Respiratory depression (rate less than 12/min) is a critical, life-threatening sign of severe magnesium toxicity, but it occurs after the loss of deep tendon reflexes.
Option D: Magnesium sulfate is used as an anticonvulsant, not primarily as an antihypertensive. While it can cause some vasodilation, blood pressure is not a direct or reliable indicator of magnesium toxicity.

Clinical Relevance

Nursing practice connection: Use the key finding related to Nursing assessment and monitoring for magnesium sulfate toxicity to guide bedside assessment, documentation, and the next nursing action.
Nurses must perform and document hourly checks of deep tendon reflexes, respiratory rate, and urine output for any patient receiving an intravenous magnesium sulfate infusion.
The immediate nursing action for an absent reflex or a respiratory rate below 12/min is to stop the infusion, stay with the patient, call for help, and notify the provider. The antidote, calcium gluconate, must be readily available at the bedside.
What if? If a patient's reflexes are absent but their respiratory rate is still 14/min, the nurse must still stop the infusion immediately. The absence of reflexes is the critical first sign that toxicity is developing, and waiting for respiratory depression would be dangerously negligent.

How to Approach the Question

Identify the core of the question: It asks for the 'most important' parameter to monitor for a specific drug, magnesium sulfate.
Recall or deduce the drug's class and primary risk: Magnesium sulfate is a CNS depressant, and its primary risk is toxicity leading to respiratory and cardiac arrest.
Think about the progression of toxicity. For monitoring purposes, the 'most important' sign is the one that appears earliest, allowing for timely intervention before the condition becomes life-threatening.
Evaluate each option in the context of early versus late signs of toxicity:
Urine output: Relates to drug clearance and risk of accumulation, not a direct sign of current toxicity.
Knee jerk reflex: A neurological sign. Loss of reflexes is a known early indicator of CNS depression from magnesium.

Concept Tested & Keywords

Concept Tested: Nursing assessment and monitoring for magnesium sulfate toxicity.
Stem keywords: magnesium sulphate therapy, most important parameter, check
Lead-in keywords: most important
Negative lead-in flag: false

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