A nurse is assessing a client with severe pre-eclampsia who is receiving magnesium sulfate infusion.
Which finding should alert the nurse to suspect magnesium toxicity?
A.
Respiratory rate of 10 breaths/min
B.
Deep tendon reflexes of 2+
C.
Urine output of 40 mL/hour
D.
Serum magnesium level of 6 mq/L
The Correct answer and Explanation is:
The correct answer is A. Respiratory rate of 10 breaths/min.
Explanation:
Magnesium sulfate is commonly used in the management of severe pre-eclampsia to prevent seizures, but it carries a risk of toxicity. The signs of magnesium toxicity are crucial for timely intervention and include several key symptoms.
1. Respiratory Depression: Magnesium sulfate can cause respiratory depression due to its neuromuscular blocking effects. A respiratory rate of 10 breaths per minute is significantly lower than the normal range (usually between 12-20 breaths per minute for adults). This reduced rate indicates potential respiratory compromise and suggests that the client may be experiencing magnesium toxicity.
2. Deep Tendon Reflexes: Normally, deep tendon reflexes are graded on a scale from 0 to 4+, with 2+ being considered normal. Magnesium toxicity typically presents with diminished or absent reflexes (i.e., 1+ or 0). A 2+ reflex response, as mentioned in option B, is generally within the normal range and does not indicate toxicity.
3. Urine Output: Adequate urine output is essential for the excretion of magnesium sulfate. A urine output of 40 mL/hour is on the lower side of normal but not necessarily indicative of toxicity alone. It is important to monitor urine output, but isolated decreased urine output is not a definitive sign of toxicity without other symptoms.
4. Serum Magnesium Level: The therapeutic range for serum magnesium levels while on magnesium sulfate is generally between 4.8 to 9.6 mg/dL (approximately 2.0 to 4.0 mmol/L). A serum magnesium level of 6 mg/dL, as mentioned in option D, is within the therapeutic range and does not suggest toxicity. Toxic levels are usually above 9.6 mg/dL.
In summary, the respiratory rate of 10 breaths/min is the most alarming finding in this context, as it is indicative of potential respiratory depression due to magnesium toxicity. Immediate assessment and intervention are necessary to manage this serious condition and ensure the safety of the client.