A patient at 28 weeks gestation is receiving Labetalol and Magnesium Sulphate for her pre-eclampsia treatment. On checking her BP, you find that it is 86/56 mm Hg. The most likely cause of this finding is?

1. A

   False BP reading

2. B

   Accidental overdose of labetalol

3. C

   Patient is anxious

4. D

   Magnesium toxicity

Appeared in: ISRO 2024

Explanation

• Labetalol is a potent antihypertensive medication used to treat severe hypertension in pre-eclampsia.
• Its primary pharmacological action is to lower blood pressure by blocking alpha and beta-adrenergic receptors.
• An accidental overdose would cause an exaggerated therapeutic effect, leading directly to a significant and dangerous drop in blood pressure (severe hypotension), as seen in the patient's reading of 86/56 mm Hg.
• Hypotension is a known and direct side effect of labetalol, making overdose the most probable cause for this severe reading.

Why Other Options Were Wrong

• Option A: While equipment malfunction can occur, it is clinically unsafe to assume a false reading as the primary cause for a life-threatening vital sign in a high-risk patient receiving potent intravenous medications. The nurse's first action should be to respond as if the reading is a true physiological event.
• Option C: Anxiety triggers a 'fight or flight' response, mediated by the sympathetic nervous system. This leads to the release of catecholamines, which cause vasoconstriction and an increase in heart rate and blood pressure (hypertension), not hypotension.
• Option D: Magnesium sulfate is used as an anticonvulsant, not an antihypertensive. The classic initial sign of magnesium toxicity is the loss of deep tendon reflexes (e.g., patellar reflex). This is followed by respiratory depression (respiratory rate below 12 breaths/min) and then cardiac arrest. Severe hypotension is not the primary or most likely presenting sign.

Related Visual

Clinical Relevance

• Nursing practice connection: Knowing Adverse effects and toxicity of medications used in pre-eclampsia management helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
• Nurses must perform frequent and vigilant monitoring of blood pressure (every 5-10 minutes) during intravenous administration of antihypertensive drugs like Labetalol to detect and manage hypotension promptly.
• Severe maternal hypotension can compromise uteroplacental blood flow, leading to fetal distress. The nurse must be prepared to intervene by stopping the infusion, administering IV fluids, and repositioning the patient.
• It is critical to differentiate between labetalol-induced hypotension and magnesium toxicity. The first assessment for suspected magnesium toxicity is checking the deep tendon reflexes and respiratory rate.

How to Approach the Question

• First, identify the key information in the clinical scenario: a pregnant patient with pre-eclampsia is receiving two medications, Labetalol and Magnesium Sulphate.
• Note the critical clinical finding: a very low blood pressure of 86/56 mm Hg.
• Recall the primary purpose and mechanism of each drug. Labetalol is an antihypertensive (lowers BP). Magnesium Sulphate is an anticonvulsant (prevents seizures).
• Evaluate each option based on the patient's presentation. The patient's primary problem is severe hypotension.
• Connect the clinical finding (hypotension) to the drug whose primary action or overdose effect is to cause hypotension. Labetalol directly lowers BP, so an overdose would cause severe hypotension.
• Rule out the other options. Anxiety causes high BP. Magnesium toxicity presents first with loss of reflexes and respiratory depression. Assuming a false reading is unsafe. Therefore, labetalol overdose is the most logical and direct cause.

Concept Tested & Keywords

• Concept Tested: Adverse effects and toxicity of medications used in pre-eclampsia management.
• Stem keywords: 28 weeks gestation, Labetalol, Magnesium Sulphate, pre-eclampsia, BP 86/56 mm Hg
• Lead-in keywords: most likely cause
• Clinical cues: The patient is receiving a potent antihypertensive (Labetalol) and an anticonvulsant (Magnesium Sulphate).
• Clinical cues: The key clinical finding is severe hypotension (86/56 mm Hg).

Question ID

QgeyW_4gj47vK2YLccHPNa

Copy ID

Reference Book

E6 Obstetrics Williams p. 33-53

E6 Midwifery Obstetrics and Gynecology Nursing Sandeep Kaur p. 14-22