Terminology and Classification:
The current classification system by ACOG includes four distinct disorders:
I. Gestational Hypertension: New-onset hypertension after 20 weeks without proteinuria or other signs of end-organ damage. It typically resolves by 12 weeks postpartum.
II. Preeclampsia/Superimposed Preeclampsia: The new onset of hypertension after 20 weeks of gestation, accompanied by one or more of the following:
a. Proteinuria
b. Thrombocytopenia (platelet count < 100,000/μL)
c. Impaired liver function (elevated transaminases to twice the normal concentration)
d. Renal insufficiency (serum creatinine > 1.1 mg/dL or a doubling of baseline)
e. Pulmonary edema
f. New onset cerebral or visual disturbances.
III. Eclampsia: The onset of grand mal seizures in a patient with preeclampsia that cannot be attributed to other causes.
IV. Chronic Hypertension: Hypertension present before pregnancy or diagnosed before 20 weeks' gestation.
Pathogenesis:
I. Pathophysiology: The primary pathophysiologic basis is now understood to be placental and endothelial dysfunction, leading to:
a. Generalized Vasospasm (causing hypertension and reduced organ perfusion).
b. Increased Capillary Permeability (causing edema, including pulmonary edema).
c. Activation of the Coagulation System (causing thrombocytopenia).
II. Diagnosis: RollOver Test: This test is obsolete and no longer used in clinical practice. It has been replaced by more reliable clinical monitoring and biomarker research.
Assessment and Diagnostic Criteria
The "mild" vs. "severe" classification of preeclampsia is outdated. The current standard is Preeclampsia vs. Preeclampsia with Severe Features.
Preeclampsia with Severe Features is diagnosed by the presence of any of the following:
i. Systolic BP ≥ 160 mm Hg or Diastolic BP ≥ 110 mm Hg on two occasions at least 4 hours apart (antihypertensive therapy is often initiated sooner).
ii. Thrombocytopenia (Platelets < 100,000/μL).
iii. Impaired Liver Function (Elevated AST/ALT to twice the normal concentration).
iv. Severe Persistent Right Upper Quadrant or Epigastric Pain (This indicates liver involvement, not merely an "aura").
v. Renal Insufficiency (Serum Creatinine > 1.1 mg/dL or a doubling from baseline).
vi. Pulmonary Edema.
vii. New Onset Cerebral or Visual Disturbances (e.g., severe headache, scotomata, blurred vision).
Signs/Symptoms:
I. Proteinuria: Diagnostic threshold is ≥ 0.3 grams in a 24hour urine collection (gold standard),
II. Oliguria: Defined as < 30 mL/hour over 24 hours,
III. Weight Gain/Edema: These are not reliable diagnostic criteria as they are common in normal pregnancy.
IV. Diagnosis is based on BP and evidence of organ dysfunction.
V. HELLP Syndrome: A severe variant of preeclampsia characterized by Hemolysis, Elevated Liver enzymes, and Low Platelets.
Management
A. General and Supportive Care:
I. Bed Rest: Strict bed rest is no longer recommended due to the increased risk of thromboembolism and lack of proven benefit. Activity may be modified, but mobility is encouraged.
II. Diet: Salt restriction and specific high-protein diets are not recommended. A balanced, nutritious diet is advised. Salt restriction can be detrimental.
III. Environment: A calm environment is supportive, but the primary seizure prophylaxis is pharmacological, not environmental.
B. Medication Management (Magnesium Sulfate): Indication: First-line for seizure prophylaxis in preeclampsia with severe features and for treatment of eclampsia.
I. Dosing (Updated):
a. Loading Dose: 4-6 grams IV over 15-20 minutes.
b. Maintenance Dose: 1-2 grams/hour via continuous IV infusion pump.
II. Monitoring for Toxicity (Updated):
a. Respiratory Rate: Must be > 16/minute.
b. Urine Output: Must be > 30 mL/hour.
c. Deep Tendon Reflexes: Must be present (absence is the first sign of toxicity).
d. Serum Magnesium Levels: Therapeutic range is 48 mg/dL.
III. Antidote: Calcium Gluconate 1 gram (10% solution) IV over 10 minutes must be available at the bedside.
C. Blood Pressure Management: Antihypertensive medications (e.g., Labetalol, Nifedipine) are used to manage severe hypertension (≥ 160/110 mm Hg) to prevent maternal stroke.
D. Delivery:
Delivery is the only definitive cure for preeclampsia. The timing is based on gestational age and disease severity. Vaginal delivery is preferred, but cesarean section is performed for standard obstetric indications.
Nursing Problem Priorities:
I. Seizure Prophylaxis & Neurologic Monitoring: Administer MgSO₄ and monitor for signs of toxicity and CNS irritability.
II. Severe Hypertension Management: Administer antihypertensive medications as ordered to prevent cerebral vascular accident (stroke).
III. Maternal-Fetal Surveillance: Continuous fetal monitoring; frequent maternal vital signs, strict I&O, and assessment for symptoms of severe features (headache, epigastric pain, visual changes).
IV. Fluid Balance Management: Monitor for pulmonary edema; avoid fluid overload.
V. Prevention of Complications: Monitor for progression to HELLP syndrome, eclampsia, placental abruption, and pulmonary edema.
VI. Patient & Family Education: Educate on signs/symptoms of worsening condition, emphasizing that the risk persists up to 46 weeks postpartum.
Dosing Details: First-Line Antihypertensive Medications in Pregnancy:
The following table provides specific dosing for both acute/severe hypertension and ongoing maintenance therapy.
|
Medication |
Route |
Indication |
Dosing Protocol |
Key Monitoring & Nursing Considerations |
|
Labetalol |
IV |
Acute Severe Hypertension |
• Initial Dose: 20 mg IV push over 2 minutes. |
• Contraindicated in patients with asthma, heart
failure, or bradycardia. |
|
Nifedipine |
Oral (Capsule) |
Acute Severe Hypertension |
• Dose: 10 mg orally. |
• Avoid sublingual administration due to risk of
precipitous BP drop. |
|
Hydralazine |
IV |
Acute Severe Hypertension |
• Initial Dose: 5 mg IV push over 2 minutes. |
• Onset of action can be slower (10-20 minutes). |
|
Labetalol |
Oral |
Maintenance Therapy |
• Starting Dose: 100 mg twice daily. |
• Monitor heart rate and BP. |
|
Nifedipine |
Oral (ER) |
Maintenance Therapy |
• Starting Dose: 30 mg once daily (extended-release
formulation). |
• Use extended-release (ER/XL) for maintenance. |
|
Methyldopa |
Oral |
Maintenance Therapy |
• Starting Dose: 250 mg two or three times daily. |
• Safest for long-term use in pregnancy (extensive
safety data). |
Clinical Protocol for Acute Severe Hypertension (≥160/110 mm Hg)
This is often managed using a standardized algorithm or "severe hypertension pathway" to ensure timely treatment.
- Confirm Reading: Re-check BP after 15 minutes with an appropriate-sized cuff.
- Administer First-Line Agent: Choose one (e.g., Labetalol 20 mg IV).
- Re-assess BP: Check BP every 10-20 minutes.
- Escalate if Needed:
- If BP remains ≥160/110 mm Hg after 10-20 minutes, administer the next dose in the sequence (e.g., Labetalol 40 mg IV).
- Switch Agents if Goal Not Met: If the maximum dose of the first agent is ineffective (e.g., BP still severe after Labetalol 80 mg), switch to a second-line agent (e.g., Nifedipine 10 mg orally).
- Target: The goal is to achieve a BP below 160/110 mm Hg within 30-60 minutes and then maintain it in a safer range (e.g., 140-150/90-100 mm Hg).
- Notify Physician: If the BP does not respond to two first-line agents, this is considered refractory hypertension and requires immediate physician consultation, as it may signal impending crisis.
Important Note: These protocols are for educational purposes. All medication administration must follow specific, written physician orders and the official protocols of the treating institution.
