11.4 Hypertensive Disorders of Pregnancy: Preeclampsia, Eclampsia & MgSO4

11.4 Hypertensive Disorders of Pregnancy: Preeclampsia, Eclampsia & MgSO4

Quick Answer: Hypertensive disorders in pregnancy span chronic hypertension (< 20 weeks), gestational hypertension (> 20 weeks without proteinuria), preeclampsia (> 20 weeks with proteinuria or maternal end-organ failure), and eclampsia (generalized tonic-clonic convulsions). Severe preeclampsia features BP ≥ 160/110 mmHg, intractable headache, visual changes, severe epigastric pain, pulmonary edema, and HELLP syndrome. The definitive anticonvulsant is Magnesium Sulfate (MgSO4) via the Pritchard regimen (14 g loading dose: 4 g IV over 5–10 min + 10 g IM; then 5 g IM 4-hourly for 24 hours). Mandatory pre-dose safety checks require respiratory rate ≥ 16 bpm, active patellar reflexes, and urine output ≥ 30 mL/hr. If toxicity strikes, stop MgSO4 and administer Calcium Gluconate 10% (10 mL slow IV over 10 min).

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Classification and Diagnostic Spectrum of Hypertensive Disorders in Pregnancy

Hypertensive disorders of pregnancy represent one of the most perilous obstetrical challenges in Ghana, contributing substantially to maternal and perinatal morbidity and mortality. Accurate categorization is essential for targeted management.

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Pathophysiology of Preeclampsia and Multi-Organ Dysfunction

Preeclampsia is primarily a disease of the placenta. The cascade begins during early implantation (10–16 weeks):

1. Failed Spiral Artery Remodeling: Normal cytotrophoblast invasion transforms high-resistance, muscular maternal spiral arteries into dilated, flaccid, low-resistance vessels. In preeclampsia, trophoblastic invasion is incomplete; the spiral arteries remain narrow and muscular;
2. Placental Ischemia & Reperfusion Injury: Inadequate placental perfusion generates oxidative stress, causing hypoxic trophoblasts to release circulating toxic anti-angiogenic factors (soluble fms-like tyrosine kinase-1 [sFlt-1] and soluble endoglin) into the maternal circulation;
3. Systemic Endothelial Cell Injury: Circulating factors neutralize Vascular Endothelial Growth Factor (VEGF) and Placental Growth Factor (PlGF), precipitating widespread endothelial cell dysfunction;
4. Widespread Vasospasm & Capillary Leak: Endothelial injury causes loss of nitric oxide, prostacyclin depletion, and intravascular fluid transudation into interstitial spaces (edema), with activation of the coagulation cascade and progressive end-organ hypoperfusion (kidneys, liver, brain, placenta).

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Preeclampsia with Severe Features

Preeclampsia can rapidly escalate into a life-threatening, multi-system crisis. The presence of any one of the following criteria confirms preeclampsia with severe features:

• Severe Blood Pressure Elevation: Systolic BP ≥ 160 mmHg or Diastolic BP ≥ 110 mmHg recorded on two occasions at least 4 hours apart while the client is on bed rest;
• Neurological / Cerebral Symptoms: Persistent, severe frontal or occipital headache unresponsive to standard analgesics; visual disturbances including photophobia, scotomata (blind spots), blurred vision, diplopia, or cortical blindness;
• Hepatic Injury: Severe, persistent epigastric or right upper quadrant abdominal pain refractory to medication (caused by hepatocellular necrosis, subcapsular hematoma, and stretching of Glisson's capsule); elevated serum transaminases (AST or ALT twice the upper limit of normal);
• Hematological Dysfunction (Thrombocytopenia): Platelet count < 100,000/µL;
• Renal Insufficiency: Serum creatinine > 1.1 mg/dL (> 97 µmol/L) or a doubling of baseline serum creatinine in the absence of other renal disease;
• Pulmonary Edema: Sudden onset of severe dyspnea, tachypnea, orthopnea, and coarse crackles on auscultation, driven by high capillary hydrostatic pressure and reduced colloid oncotic pressure.

HELLP Syndrome: A Catastrophic Variant

HELLP syndrome is an acute, life-threatening manifestation of severe microvascular endothelial injury affecting 10–20% of women with severe preeclampsia:

• H (Hemolysis): Microangiopathic hemolytic anemia. Erythrocytes are fragmented as they traverse damaged, fibrin-mesh microvasculature, producing schistocytes on peripheral smear, elevated indirect bilirubin (≥ 1.2 mg/dL), and high lactate dehydrogenase (LDH > 600 U/L);
• EL (Elevated Liver Enzymes): Severe hepatocellular injury causing AST or ALT ≥ 70 U/L or twice the institutional baseline;
• LP (Low Platelets): Consumptive thrombocytopenia with platelet count < 100,000/µL.
• Complications: Disseminated Intravascular Coagulation (DIC), subcapsular liver hematoma rupture, acute renal failure, and placental abruption.

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Emergency Nursing and Medical Care of Eclampsia

Eclampsia constitutes an absolute obstetric emergency. When a convulsion occurs, the nurse must maintain composure and execute immediate life-support protocols.

Step-by-Step Acute Seizure Management (The ABCs)

1. Call for Immediate Help: Summon the emergency obstetric team and resuscitation kit. Never leave the convulsing woman alone;
2. Positioning & Airway: Turn the woman onto her left lateral side with the head tilted slightly downward. This position prevents tongue obstruction, enhances venous return by relieving aortocaval compression, and allows vomitus or saliva to drain freely, preventing fatal aspiration pneumonia;
3. Protect from Injury: Cushion the bed rails with pillows or blankets. Gently guide limbs to avoid physical trauma; never forcibly restrain the client and never force hard mouth gags or spatulas between clenched teeth (which can dislodge teeth, cause tongue trauma, and occlude the airway);
4. Oxygenation: As soon as the convulsion ceases, gently suction secretions from the oropharynx. Administer high-flow oxygen at 8 to 10 L/minute via a non-rebreather face mask to reverse maternal and fetal hypoxia;
5. Intravenous Access & Monitoring: Establish wide-bore IV access; connect pulse oximeter, blood pressure cuff, and continuous fetal heart rate monitoring.

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Anticonvulsant Therapy: Magnesium Sulfate (MgSO4) Protocol

Magnesium Sulfate (MgSO4) is the uncontested, evidence-based gold standard for both the prevention of seizures in severe preeclampsia and the treatment of eclamptic convulsions. The landmark international Collaborative Eclampsia Trial confirmed MgSO4 is dramatically superior to diazepam and phenytoin in halving recurrent convulsions and reducing maternal mortality.

Mechanism of Action

Magnesium Sulfate acts as a potent central and peripheral neuroprotective agent:

• Antagonizes central N-methyl-D-aspartate (NMDA) glutamate receptors, suppressing neuronal excitability and seizure discharge;
• Induces potent cerebral arterial vasodilation, reversing cerebral ischemia and vasospasm;
• Protects blood-brain barrier integrity, reducing vasogenic cerebral edema;
• Blocks presynaptic release of acetylcholine at the neuromuscular junction, attenuating peripheral muscle twitching.

The Standard Pritchard Regimen (IV + IM)

The Pritchard regimen is the preferred protocol across Ghana Health Service facilities due to its proven efficacy, safety profile, and feasibility in settings without electronic syringe pumps:

+-----------------------------------------------------------------------------------------+
|                              PRITCHARD REGIMEN PROTOCOL                                 |
|                                                                                         |
| LOADING DOSE:                                                                           |
| - IV: 4 g of 20% solution slow IV push over 5-10 minutes                                |
| - IM: 10 g of 50% solution (5 g in each buttock deep IM with 1 mL 2% lidocaine)         |
|                                                                                         |
| MAINTENANCE DOSE:                                                                       |
| - 5 g of 50% solution deep IM in alternating buttocks every 4 hours                     |
|                                                                                         |
| DURATION: Continue for 24 hours after delivery OR 24 hours after last convulsion        |
+-----------------------------------------------------------------------------------------+

1. Loading Dose (Total 14 g):
   • Intravenous Component: 4 g IV administered as a 20% solution over 5 to 10 minutes (prepared by drawing 8 mL of 50% MgSO4 [4 g] and diluting with 12 mL sterile water to make 20 mL of 20% solution);
   • Intramuscular Component: 10 g IM administered immediately following the IV bolus—inject 5 g (10 mL of 50% MgSO4) deep IM into the upper outer quadrant of each buttock (total 10 g in two buttocks) using a long 20G/21G needle. Add 1 mL of 2% lidocaine to each syringe to mitigate intense local injection pain;
2. Maintenance Dose (5 g IM Every 4 Hours):
   • Administer 5 g (10 mL of 50% solution) deep IM in alternating buttocks every 4 hours;
3. Duration of Maintenance:
   • Continued uninterrupted for 24 hours following delivery or 24 hours following the last convulsion, whichever occurs later;
4. Managing Recurrent Seizures:
   • If a seizure recurs after 15 minutes of the loading dose, administer an additional 2 g of 20% MgSO4 IV slowly over 5 minutes.

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Monitoring for Magnesium Toxicity & Antidote Protocol

[!CAUTION] Critical Nursing Concept: Renal Excretion & Toxic Accumulation Magnesium Sulfate is excreted exclusively by the kidneys via glomerular filtration. Preeclamptic women frequently exhibit renal impairment and oliguria; if glomerular filtration falls, magnesium accumulates rapidly in maternal serum, progressing from loss of reflexes to lethal respiratory arrest and asystole!

The Three Mandatory Pre-Requisites Before Every Maintenance Dose

Before administering each 4-hourly intramuscular maintenance dose, the nurse must assess, verify, and document the following three clinical parameters:

1. Patellar / Knee-Jerk Reflex: Must be clearly present. Loss of deep tendon reflexes is the earliest and most sensitive clinical sign of magnesium toxicity (occurring at serum levels of 8–10 mEq/L);
2. Respiratory Rate: Must be ≥ 16 breaths per minute. Magnesium-induced neuromuscular blockade paralyzes respiratory musculature, causing respiratory depression (< 12 breaths/min) at levels of 12–15 mEq/L;
3. Hourly Urine Output: Must be ≥ 30 mL/hour over the preceding 4 hours (or ≥ 100 mL accumulated over 4 hours). If urine output is < 30 mL/hr, magnesium cannot be excreted and will rapidly reach toxic concentrations.

Action if ANY parameter is abnormal: Withhold the maintenance dose immediately and alert the obstetrician.

Emergency Protocol for Magnesium Toxicity

If the client exhibits loss of patellar reflexes, respiratory depression (< 16 breaths/min), or cardiac arrhythmia:

1. Stop Magnesium Sulfate immediately;
2. Administer the Specific Antidote:
   • Give Calcium Gluconate 10%;
   • Dose: 1 g (10 mL of 10% solution) by slow IV push over 10 minutes;
   • Calcium directly antagonizes the neuromuscular and cardiac blocking actions of magnesium;
3. Support Resuscitation: Provide bag-valve-mask assisted ventilation or endotracheal intubation with 100% oxygen if respiratory failure is present.

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Antihypertensive Therapy for Severe Hypertension

Antihypertensive therapy is indicated immediately for severe hypertension (Systolic BP ≥ 160 mmHg or Diastolic BP ≥ 110 mmHg) to prevent intracranial hemorrhage (maternal stroke), encephalopathy, and placental abruption.

• Treatment Target: Lower blood pressure smoothly to a target diastolic range of 90 to 100 mmHg (and systolic 135–145 mmHg). Never drop blood pressure precipitously, as sudden maternal hypotension impairs uteroplacental perfusion, causing acute fetal bradycardia and distress.
• First-Line Pharmacological Agents in Ghana:
  • Hydralazine: 5 to 10 mg slow IV over 2 minutes; repeat 5–10 mg every 20–30 minutes until target BP is achieved (maximum cumulative dose: 20–30 mg);
  • Labetalol: 20 mg IV bolus over 2 minutes; if response is inadequate after 10 minutes, escalate to 40 mg, then 80 mg every 10 minutes (maximum dose: 300 mg). Contraindicated in asthma, congestive heart failure, and second/third-degree heart block;
  • Oral Immediate-Release Nifedipine: 10 mg capsule swallowed whole (do NOT chew, bite, or administer sublingually); repeat in 30 minutes if needed.

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Definitive Management: Timely Delivery

Delivery of the fetus and placenta is the only definitive cure for preeclampsia and eclampsia. Once maternal stabilization is accomplished—seizures controlled with MgSO4, hypoxia corrected, and severe hypertension mitigated—the obstetric team plans definitive delivery regardless of gestational age in eclampsia or severe refractory preeclampsia. Vaginal delivery with cervical ripening is favored when feasible, reserving emergency Cesarean section for obstetric indications or fetal decompensation.