Magnesium sulfate is a high-alert medication commonly used in obstetric care, particularly in the management of severe preeclampsia and eclampsia. Because it affects the central nervous system and muscular function, careful monitoring is essential to avoid complications like respiratory depression or loss of reflexes. For nursing students preparing for the NCLEX, understanding the therapeutic range, signs of toxicity, and appropriate nursing interventions is a must. This practice quiz covers the most important points you need to know: dosing, side effects, contraindications, and emergency responses with clear rationales to help reinforce your knowledge and boost your confidence on exam day.
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Magnesium Sulfate Maternity Nursing NCLEX Practice Quiz Questions
Magnesium Sulfate Nursing NCLEX Practice Questions
- What is the main goal in treating a patient with magnesium sulfate during severe preeclampsia?
A. Increased blood pressure
B. Stimulate uterine contractions
C. Prevent seizures
D. Manage fetal heart decelerations
The answer is C. The primary purpose of administering magnesium sulfate during severe preeclampsia is to prevent seizures. Preeclampsia places the patient at risk for progressing to eclampsia, which involves seizures that can be life-threatening to both the mother and fetus. Seizures can cause maternal hypoxia, placental abruption, injury, and preterm labor. Magnesium sulfate acts as a central nervous system depressant and calcium antagonist, helping to calm overexcited nerve cells and reduce the risk of seizure activity. Although magnesium sulfate may have secondary effects such as lowering blood pressure or relaxing (not stimulating) uterine muscles, these are not its main therapeutic goals. Managing blood pressure is typically addressed with antihypertensive medications, and fetal heart decelerations are treated with other interventions such as maternal repositioning or oxyge, not magnesium sulfate.
- Which of the following is an incorrect statement about the action of a magnesium sulfate infusion?
A. Magnesium sulfate decreases seizure risk by depressing the central nervous system.
B. Magnesium sulfate competes with calcium to reduce smooth muscle contractions.
C. Magnesium sulfate enhances the effects of the excitatory neurotransmitter glutamate.
D. Magnesium sulfate helps relax blood vessels, which can lower blood pressure.
The answer is C: The incorrect statement is C. Magnesium sulfate does not enhance glutamate; in fact, it inhibits glutamate release by blocking calcium channels at nerve synapses. Glutamate is an excitatory neurotransmitter, and excessive levels can trigger seizures. By reducing glutamate release, magnesium sulfate helps stabilize the nervous system and prevent seizure activity. Statement A is correct: agnesium depresses CNS excitability to prevent seizures. Statement B is correct: it acts as a calcium antagonist, relaxing smooth muscle and reducing uterine contractions. Statement D is also true: magnesium relaxes vascular smooth muscle, promoting vasodilation and lowering blood pressure, which is beneficial in preeclampsia.
- What is the typical loading dose the nurse would expect for an IV magnesium sulfate infusion for eclampsia management?
A. 1–2 g/hour
B. 4–6 g over 20–30 minutes
C. 6–20 g over 10 minutes
D. 10 g/hour
The answer is B: The standard loading dose of magnesium sulfate for seizure prophylaxis or treatment in eclampsia is 4 to 6 grams given IV over 20 to 30 minutes. This dose rapidly raises serum magnesium levels to the therapeutic range (typically 4–7 mg/dL) to provide quick protection against seizures. Option A (1–2 g/hour) reflects the maintenance dose, not the loading dose. Option C is incorrect because the dose is too high and the infusion time too fast, increasing the risk of serious toxicity. Option D is also incorrect, as a continuous rate of 10 g/hour would far exceed safe maintenance levels and could quickly result in magnesium toxicity.
- After the loading dose of magnesium sulfate, the maintenance is most commonly set at?
A. 25 mL/hr
B. 0.5 g/hr
C. 1–2 g/hr
D. 4 g/hr
The answer is C: After the initial loading dose of magnesium sulfate, the standard maintenance infusion rate is 1 to 2 grams per hour, delivered intravenously. This continuous infusion helps maintain therapeutic serum magnesium levels (4–7 mg/dL) to prevent seizures in patients with preeclampsia or eclampsia. Option A is an inappropriate unit of measure unless the concentration is known. Option B (0.5 g/hr) is too low to sustain effective levels, putting the patient at risk for breakthrough seizures. Option D (4 g/hr) exceeds the typical maintenance rate and increases the risk for toxicity, including respiratory depression and loss of reflexes. Therefore, 1–2 g/hr is the safest and most widely accepted standard for ongoing seizure prophylaxis following the loading dose.
- During the loading dose of a magnesium sulfate infusion for the treatment of eclampsia, the patient states, “It’s so hot in here. My face feels really warm.” Which action by the nurse is most appropriate?
A. Reassure the patient that facial flushing is a common side effect
B. Administer calcium gluconate as an antidote
C. Stop the infusion immediately and notify the healthcare provider
D. Apply a cool compress and increase the infusion rate to reduce symptoms
The answer is A: Facial flushing, a sensation of warmth, and mild sweating are expected side effects of magnesium sulfate, especially during the initial loading dose. These symptoms occur due to vasodilation and typically resolve as the body adjusts to the medication. The nurse’s most appropriate response is to reassure the patient that this is a common and temporary reaction, while continuing to monitor for more serious signs of magnesium toxicity. Option A is incorrect because there is no indication to stop the infusion unless toxicity is suspected, such as loss of reflexes or bradypnea. Option B is inappropriate because calcium gluconate is used only in cases of toxicity, not for expected side effects. Option D is unsafe because increasing the infusion rate may worsen side effects or cause toxicity and should never be done without a provider’s order.
- What is the rationale for stopping magnesium sulfate approximately 2 hours before delivery when possible?
A. To prevent overstimulation of the uterus
B. To increase maternal blood pressure
C. To minimize the risk of postpartum hemorrhage
D. To reduce the risk of newborn respiratory depression
The answer is D: Magnesium sulfate crosses the placenta and can suppress the newborn’s central nervous system if delivery occurs while maternal magnesium levels are still elevated. This can lead to respiratory depression, hypotonia (low muscle tone), and decreased reflexes in the neonate. By stopping the infusion approximately 2 hours before birth, magnesium levels have time to decrease slightly, helping to reduce these risks. Option A is incorrect because magnesium actually relaxes the uterus, not overstimulates it. Option B is incorrect because magnesium tends to lower blood pressure due to vasodilation. Option C is incorrect because magnesium sulfate is not associated with an increased or decreased risk of postpartum hemorrhage.
- What strategies can the nurse implement to help decrease the risk of extravasation while infusing magnesium sulfate? Select all that apply.
A. Infuse the medication rapidly
B. Use a small forearm vein
C. Apply a compression dressing on the site during infusion
D. Use a large-bore cannula in the antecubital fossa
E. Assess the site at regular intervals for burning, swelling, and redness
The answers are D and E: To reduce the risk of extravasation while infusing magnesium sulfate, the nurse should use a large-bore cannula in a large vein, such as in the antecubital fossa, to ensure better blood flow and reduce irritation to the vein. Regularly assessing the IV site for early signs of infiltration (such as burning, swelling, or redness)allows for early detection and prompt intervention if needed. Option A is incorrect because rapid infusion increases the risk of vein irritation and toxicity. Option B is incorrect as small or fragile veins (like those in the forearm) are more prone to infiltration. Option C is incorrect because applying a compression dressing can obscure assessment of the IV site and may actually worsen extravasation if it occurs.
- What finding in the patient’s health history would be a contraindication for administering magnesium sulfate?
A. Multiparous
B. Gestational diabetes
C. Hypertension
D. Myasthenia gravis
The correct answer is D: Myasthenia gravis is a serious contraindication to magnesium sulfate administration. Magnesium acts as a calcium antagonist and depresses neuromuscular transmission. In patients with myasthenia gravis, this can result in severe muscle weakness or respiratory failure, as their neuromuscular function is already impaired. Options A (multiparous), B (gestational diabetes), and C (hypertension) are not contraindications to magnesium sulfate. In fact, hypertension related to preeclampsia is one of the main reasons magnesium sulfate is used (to prevent seizures).
- Your patient receiving a magnesium sulfate for the treatment of preclampsia has a magnesium level of 6.4 mg/dL. How do you interpret this level?
A. subtherapeutic
B. therapeutic
C. toxic
The answer is B: The therapeutic range of magnesium sulfate for seizure prevention in preeclampsia is 4 to 7 mg/dL. A level of 6.4 mg/dL falls within this range, indicating that the medication is effectively working to prevent seizures without reaching toxic levels. Option A is incorrect because levels below 4 mg/dL are considered subtherapeutic and may not adequately prevent seizures. Option C is incorrect because toxicity generally occurs when levels exceed 7 mg/dL, often accompanied by clinical signs such as absent reflexes, respiratory depression, bradycardia, or ECG changes.
- Which medication will the nurse ensure is readily available at the bedside in case of magnesium sulfate toxicity?
A. Calcium bicarbonate
B. Calcium gluconate
C. Naloxone
D. Flumazenil
The answer is B: Calcium gluconate is the specific antidote for magnesium sulfate toxicity. It works by counteracting the effects of excess magnesium on the heart and neuromuscular system, helping to restore normal cardiac conduction and muscle function. It is typically given IV in emergency situations when signs of toxicity (such as respiratory depression, bradycardia, or absent reflexes are present). Option A, calcium bicarbonate, is not used as an antidote in this context. Option C, naloxone, is used for opioid overdose. Option D, flumazenil, is used to reverse benzodiazepine effects.
- A patient is 28 weeks pregnant and has developed eclampsia. The patient has received a 4 g loading dose that was infused over 20 minutes. Now, the healthcare provider orders a 1 g/hr maintenance infusion of IV Magnesium Sulfate. You’re supplied with a 20 g/500 mL IV bag of this medication. What is the rate of infusion for the maintenance order?(Required)
A. 50 mL/hr
B. 75 mL/hr
C. 25 mL/hr
D. 100 mL/hr
The answer is C: 25 mL/hr
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