Preeclampsia, Medications, Magnesium Sulfate

Key Lab Values in Preeclampsia

1. Platelets

   • Commonly less than $100\times 10^3/\mu L$ with preeclampsia and HELLP syndrome.

   • Impacts epidural placement and the ability to clot, necessitating close monitoring.

2. Liver Function Tests (LFTs)

   • Levels (e.g., AST, ALT) increase significantly with preeclampsia and even more so with HELLP syndrome.

   • Indicate impaired liver function.

3. Urine Protein

   • A 24-hour urine collection showing $300 mg$ or more of protein is indicative of preeclampsia.

4. Protein-Creatinine Ratio

   • A ratio greater than $0.3$ is a concern.

Managing Patients with Preeclampsia

1. Environmental Modifications

   • Maintain low lights and decrease external stimuli (e.g., restrict family, minimize staff interruptions, encourage turning off phones/TVs).

   • Raise and pad side rails as a safety measure to protect the patient in case of seizure activity (preeclampsia can progress to eclampsia).

   • Ensure an airway is available at the bedside.

2. Notifications

   • Immediately notify the neonatologist and NICU if the baby is preterm, as delivery may become imminent.

3. Calcium Gluconate Availability

   • Calcium gluconate, the antidote for magnesium toxicity, must be readily available on the unit, not just in the pharmacy.

Medications for Preeclampsia

Antihypertensives

1. Oral Nifedipine

   • Effective for treating preeclampsia.

   • As effective as IV Labetalol and Hydralazine.

   • Useful for newly admitted patients without IV access to initiate blood pressure control.

2. Labetalol

   • Primary IV medication for severe maternal hypertension ($BP\ge 160/110 mmHg$ or $160/105 mmHg$).

   • Algorithm for Severe Elevations (e.g., two severe elevations within 15 minutes):

     • First Dose: $20 mg IV$ push slowly over 2 minutes.

     • Recheck BP in 10 minutes.

     • Second Dose (if BP still high): $40 mg IV$ push slowly over 2 minutes.

     • Recheck BP in 10 minutes.

     • Third Dose (if BP still high): $80 mg IV$ push slowly over 2 minutes.

     • This is known as the "double-double rule" ($20, 40, 80 mg$).

   • Non-response: If blood pressure remains elevated after the third dose, generally switch to an alternative antihypertensive (e.g., Hydralazine or Oral Nifedipine).

   • Cumulative Dose: Maximum IV dose is $300 mg$ in 24 hours.

   • Contraindications: Low pulse, active asthma, heart failure, or heart disease.

3. Hydralazine

   • Another commonly used IV antihypertensive.

Magnesium Sulfate (MgSO4)

• Purpose: Not an antihypertensive; decreases central nervous system (CNS) irritation to prevent and treat seizures (eclampsia).

• Nomenclature: Must not be abbreviated (e.g., "MagSafeit") to avoid confusion with morphine sulfate.

• Preparation and Administration:

  • Typically supplied by pharmacy as $40 grams$ in $1 L$ of Lactated Ringer's (LR) or $20 grams$ in $500 mL LR$ (same concentration).

  • Always administered via an IV pump.

  • Administer as an IV piggyback, connected to the port closest to the IV hub.

• Dosing:

  • Bolus Dose: Commonly $4 grams$ infused over 30 minutes (specific dose and duration may vary per protocol/provider).

  • Maintenance Dose: Commonly $2 grams/hour$ (rate may vary).

• Client and Family Education:

  • Explain the medication's purpose and expected side effects.

  • Instruct about signs and symptoms of toxicity to report.

  • Explain the nature and frequency of continuous assessments during therapy.

• Common Side Effects: Drowsiness, fatigue, flushing, overwhelming warmth, and a burning sensation at the IV site (especially during the bolus).

• Signs of Toxicity: Hypoactive or absent deep tendon reflexes, decreased level of consciousness (drowsiness to unresponsiveness), and decreased respiratory rate.

• Priority Action for Toxicity:

  1. Immediately STOP the magnesium sulfate infusion.

  2. Call for assistance (e.g., charge nurse, rapid response team).

  3. Ensure oxygen is available and obtain a fresh set of vital signs.

  4. Administer Calcium Gluconate (antidote).

• Administration Requirements:

  • Must be administered on a pump, IV piggyback, and connected to the closest port to the hub.

  • Requires a 2-RN review to verify the order and calculations.

Magnesium Sulfate Calculations

Given: Order for a $4 gram$ loading dose, $2 grams/hour$ maintenance, and a total IV fluid limit of $125 mL/hour$. Pharmacy provides a $1 L (1000 mL)$ bag containing $40 grams$ of magnesium sulfate.

1. Loading Dose Rate Calculation

   • Volume to be infused for loading dose: $(4 \text{ g desired} / 40 \text{ g on hand}) \times 1000 \text{ mL} = 100 \text{ mL}$

   • Pump rate for loading dose (over 30 minutes): $100 \text{ mL} / 0.5 \text{ hours} = 200 \text{ mL/hour}$

2. Maintenance Dose Rate Calculation

   • Volume containing 2 grams: $(2 \text{ g desired} / 40 \text{ g on hand}) \times 1000 \text{ mL} = 50 \text{ mL}$

   • Pump rate for maintenance dose: $50 \text{ mL/hour}$ (since it is a $2 grams/hour$ order).

3. Mainline IV Fluid Rate

   • Total desired hourly IV fluid: $125 \text{ mL/hour}$

   • Subtract magnesium maintenance rate: $125 \text{ mL/hour} - 50 \text{ mL/hour (for magnesium)} = 75 \text{ mL/hour}$

   • The mainline IV should be set at $75 \text{ mL/hour}$, and all fluids (except perhaps ice chips) should be on a pump, with strict intake and output (I&O) monitoring.

Nursing Actions for Quality Patient Outcomes

Appropriate nursing actions for patients with preeclampsia to ensure positive outcomes include:

1. Monitoring IV fluids and meticulously assessing intake and output (I&O).

2. Reporting any changes in vital signs, patient behavior, or level of consciousness promptly.

3. Maintaining bed rest, especially for patients on magnesium sulfate, due to its muscle relaxant effects and potential for weakness.