Management of Pre-eclampsia
➧ The main therapy for pre-eclampsia is to deliver the baby as soon as he/she is most prudent, to enhance maternal and fetal well-being.
1-Magnesium Sulphate (MgSO₂):
➧ Magnesium sulfate has anti-seizure effects as well as being a vasodilator.
➧ It decreases the pulsatility index in uterine, umbilical, and fetal arteries in women with pre-eclampsia.
➧ It normalizes placental interleukin-6 secretion in a model of pre-eclampsia, which supports the fact that some of its benefits may drive from anti-inflammatory actions.
➧ The use of MgSO₂ in the management of women with severe pre-eclampsia can reduce the development of eclampsia. However, in women with mild pre-eclampsia, the routine use of MgSO₂ for seizure prophylaxis is not recommended.
➧ The two most widely used regimens of magnesium sulfate administration are the IV regimen and the IM regimen.
In the IV regimen: A loading dose of 4 g (usually in 20% solution) is given over 5 min. which is followed by an IV infusion of 1 g/h. for 24 h. after the last seizure.
In the IM regimen: An IV loading dose of 4 g is given over 5 min. followed immediately by 5 g (usually in 50% solution) as a deep IM injection into the upper outer quadrant of each buttock. Maintenance therapy is in the form of a further 5 g IM every 4 h., to be continued for 24 h. after the last fit. If convulsions recur, both regimens advocate a further 2-4 g (depending on the woman’s weight, 2 g if < 70 kg) to be given IV over 5 min.
➧ Parenterally administered magnesium sulfate is cleared almost totally by renal excretion, and magnesium intoxication is avoided by ensuring that urine output is adequate, the patellar or biceps reflex is present, and there is no respiratory depression.
➧ Eclamptic convulsions are almost always prevented by plasma magnesium levels maintained at 4-7 mEq/L (4.8-8.4 mg/dL or 2-3.5 mmol/L). Patellar reflexes disappear when the plasma magnesium level reaches 10 mEq/L. This sign serves to warn of impending magnesium toxicity. When plasma levels rise above 10 mEq/L, respiratory depression develops, and at 12 mEq/L or more, respiratory paralysis and arrest follow.
2-Antihypertensives:
➧ Due to the risk of hemorrhagic stroke in the presence of systolic hypertension, most guidelines recommend lowering non-severe blood pressure to a systolic level of 140-150 mmHg and a diastolic of 90-100 mmHg.
➧ Oral safe agents include methyldopa, labetalol, calcium channel blockers (nifedipine or isradipine), and some β-adrenoceptor blockers (metoprolol, pindolol, propranolol) and low-dose diazoxide.
➧ β-adrenoceptor blockers may cause fetal bradycardia and decrease uteroplacental blood flow.
➧ Atenolol is not recommended due to fetal growth restriction.
➧ Angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II receptor blockers are contraindicated.
➧ Methyldopa is the drug of choice, with well-documented safety after the 1st trimester. It is oral dose is 0.5-3 g/d. in 2 divided doses.
➧ Labetalol oral dose is 200-1200 mg/d. in 2-3 divided doses.
➧ Nifedipine may inhibit labor and has synergistic interaction with MgSO₄. It is oral dose is 30-120 mg/d. of slow-release preparation.
➧ Medical management of blood pressure should be achieved before obstetric or anesthetic interventions if possible. Control of blood pressure with IV hydralazine, labetalol, or infusions of nitroglycerin or nitroprusside should be commenced with arterial and central venous monitoring in severe cases.
Hydralazine:
➧ It is the drug of choice with long experience in safety and efficacy. Its dose is 5 mg IV or IM, then 5-10 mg every 20-40 min.; or a constant infusion of 0.5-10 mg/h.
➧ It is also typically employed in more refractory cases.
➧ The use of hydralazine is often accompanied by maternal tachycardia and cautious administration of up to 500 ml crystalloid is recommended before or at the same time as the initial dose of IV hydralazine to reduce the chance of a precipitous fall in blood pressure.
Labetalol:
➧ It produces less tachycardia and arrhythmia than other vasodilators.
➧ Its dose is 20 mg IV, then 20-80 mg every 20-30 min. up to a maximum of 300 mg; or a constant infusion of 1-2 mg/min.
Glyceryl trinitrate (GTN):
➧ It is the pharmacological agent of choice in women with pre-eclampsia and acute pulmonary edema.
➧ It is administered as an infusion of 5 µg/min., increasing every 3-5 min. to a maximum dose of 100 µg/min.
Sodium nitroprusside (SNP):
➧ Sodium nitroprusside is rarely used in pregnancy and has known maternal adverse effects of hypotension and paradoxical bradycardia in women with severe pre-eclampsia.
➧ Fetal cyanide toxicity is a complication of prolonged treatment. SNP should be used with extreme caution in situations of life-threatening hypertension, immediately before delivery in circumstances where clinicians are familiar with its use.
➧ It is administered as an IV infusion at 0.25–5.0 µg/kg/min.
3-Aspirin:
➧ Since inflammation appears to play a significant role in the pathogenesis of pre-eclampsia, benefits from aspirin in the prevention of pre-eclampsia and its vascular complications may derive not just from an anti-inflammatory action but from its effect of restoring the balance between thromboxane and prostacyclin in the vasculature.
➧ Before using aspirin to prevent pre-eclampsia, consideration must be given to the toxicity in the gastrointestinal tract (GIT) and its effects on renal function.
4-Intravenous fluids:
➧ The use of either crystalloid or colloid solutions has been associated with transient improvements in maternal cardiovascular system parameters.
➧ Fluid management guided by CVP in severe cases has been demonstrated to improve urine output, maintain mean arterial blood pressure, and decrease diastolic blood pressure.
➧ If oliguria persists after normalization of CVP (usually 2-3 cm H₂O) or the physiologic state is complicated by pulmonary edema or cardiovascular decompensation, a pulmonary artery catheter (PAC) may be helpful.
➧ A cardiology consultation and an assessment of cardiopulmonary function with a transthoracic echocardiogram may assist with the diagnosis and management.
➧ The use of IV fluids to increase plasma volume or treat oliguria in a woman with normal renal function and stable serum creatinine levels is not recommended.
➧ Acute pulmonary edema is associated with positive fluid balances of > 5500 mL, which is a frequent cause of admission to intensive care and is a leading cause of death in women with pre-eclampsia.
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