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Difficulty: MediumPharmacological and Parenteral Therapies

A nurse is evaluating a client who is receiving a continuous intravenous infusion of magnesium sulfate for the management of severe preeclampsia. Which of the following clinical findings indicates severe toxicity and requires the nurse to immediately stop the infusion and prepare the prescribed antidote?

  1. A respiratory rate of 10 breaths per minuteAnswer
  2. B
    Client reports of generalized warmth and facial flushing
  3. C
    Deep tendon reflexes (DTRs) assessed at 2+ bilaterally
  4. D
    A urine output of 45 mL over the past hour

Answer

A respiratory rate of 10 breaths per minute indicates severe magnesium toxicity, requiring immediate cessation of the infusion.
Magnesium sulfate acts as a central nervous system depressant. A respiratory rate below 12 breaths per minute indicates respiratory depression, which is a hallmark sign of severe magnesium toxicity. Because this compromises the client's airway and breathing, the nurse's immediate priority is to stop the infusion and administer the antidote, calcium gluconate, to prevent respiratory arrest.

Step-by-Step Solution

1
Analyze the client's current pharmacological treatment and its mechanism of action.
The client is receiving magnesium sulfate, a central nervous system depressant used to prevent seizures in severe preeclampsia.
Understanding the medication's physiological effects helps differentiate between expected side effects and life-threatening toxicity.
2
Evaluate each clinical finding against the known therapeutic and toxic parameters for magnesium sulfate.
Warmth/flushing and 2+ DTRs are normal or expected findings. A urine output of 45 mL/hr indicates adequate renal clearance. However, a respiratory rate of 10 breaths/min is dangerously low.
Accurate interpretation of assessment data ensures that normal side effects are monitored while true toxicities are aggressively managed.
3
Determine the priority nursing intervention based on the identified toxic finding.
The respiratory depression necessitates immediate discontinuation of the magnesium sulfate infusion and the administration of the antidote (calcium gluconate) to restore respiratory function.
Respiratory depression directly compromises the airway and breathing (ABCs), making it an absolute medical emergency.

Key Concept

Magnesium sulfate toxicity presents with absent deep tendon reflexes, respiratory depression (fewer than 12 breaths/min), hypotension, and decreased level of consciousness. The priority action is to stop the infusion and administer calcium gluconate.
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Topics

Pharmacological and Parenteral Therapies

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