In patients with preeclampsia and decreased urinary output, which of the following management strategies is false: Monitor for symptoms of magnesium (Mg) toxicity, use caution with fluid management due to an increased risk of pulmonary edema, treat with furosemide (loop diuretic) prior to delivery, or tolerate low urinary output provided that serum creatinine remains stable?

Management of Decreased Urinary Output in Preeclampsia

Treating with furosemide prior to delivery in preeclampsia is FALSE and should be avoided due to the risk of worsening placental perfusion and potentially exacerbating the already compromised intravascular volume. 1

Understanding Fluid Management in Preeclampsia

Preeclampsia is characterized by endothelial dysfunction, capillary leak, and potential alterations in renal function. When decreased urinary output occurs in this setting, several key principles should guide management:

1. Avoid Diuretics Before Delivery

   • Diuretics are contraindicated before delivery in preeclampsia as they:
     • Reduce plasma volume expansion 1
     • Further compromise uteroplacental circulation that is already reduced 1
     • May worsen intravascular volume depletion in "classic" preeclampsia which is often associated with hypovolemia 2

2. Aim for Euvolemia

   • Fluid balance should target euvolemia rather than "running dry" 1
   • Preeclamptic women have capillary leak but may have either reduced or increased cardiac output 1
   • Insensible losses should be replaced (30 mL/h) along with anticipated urinary losses (0.5-1 mL/kg per hour) 1

3. Limit Total Fluid Intake

   • Total fluid intake should be limited to 60-80 mL/h to avoid risks of pulmonary edema 1
   • Careful fluid management is necessary due to increased risk of pulmonary edema in preeclampsia 1

Appropriate Management Strategies

Monitoring for Magnesium Toxicity

• All preeclamptic women receiving magnesium sulfate should be monitored for signs of toxicity 1, 3
• Warning signs include:
  • Loss of patellar reflex at plasma concentrations between 3.5-5 mmol/L 3
  • Respiratory depression at 5-6.5 mmol/L 3
  • Cardiac conduction abnormalities at >7.5 mmol/L 3

Cautious Fluid Management

• Use caution with fluid management due to increased risk of pulmonary edema 1
• Fluid management should be particularly careful in women with oliguria to avoid volume overload 1

Tolerating Low Urinary Output

• Low urinary output (15 mL/h) can be tolerated if creatinine remains stable 1
• This approach recognizes that oliguria may be part of the preeclamptic process rather than indicating acute kidney injury requiring diuretic intervention

Postpartum Considerations

Interestingly, while diuretics are contraindicated before delivery, furosemide may have a role in the postpartum period:

• Furosemide (40 mg/day orally for five days) has been shown to reduce mean daily systolic and diastolic blood pressure in the postpartum period in women with preeclampsia 4
• Postpartum furosemide can reduce the time required until blood pressure is controlled 4

Common Pitfalls to Avoid

1. Administering diuretics before delivery - This can worsen placental perfusion and compromise fetal well-being 1

2. Aggressive fluid restriction - While avoiding excess fluid is important, excessive restriction in a patient with oliguria can lead to acute kidney injury 1

3. Failure to monitor for magnesium toxicity - Especially important in patients with decreased urinary output as magnesium is primarily excreted by the kidneys 3

4. Assuming oliguria always indicates hypovolemia - In preeclampsia, decreased urinary output may reflect the disease process rather than volume depletion 1

By following these principles, clinicians can appropriately manage decreased urinary output in preeclamptic patients while avoiding interventions that may worsen maternal and fetal outcomes.