Expectant management of preeclampsia
How to maintain the precarious balance between fetal benefit and maternal health according to disease severity and gestational age.
Choosing antihypertensive drugs. Calcium-channel blockers are preferred to control blood pressure during pregnancy in women with diabetes. Outside of pregnancy, angiotensin-converting enzyme (ACE) inhibitors are best to avert long-term complications, but avoid these drugs in pregnancy (along with angiotensin-receptor blockers), particularly beyond 16 weeks.
Delivery is indicated in all women with vascular diabetes mellitus beyond 34 weeks when preeclampsia is present.
Intrapartum management
Close fetal heart rate and maternal blood pressure monitoring are mainstays, along with magnesium sulfate and antihypertensive therapy.
All women with preeclampsia should receive continuous monitoring of fetal heart rate and uterine activity, with special vigilance for hyperstimulation and onset of vaginal bleeding during labor. (For a description of potential maternal complications, see TABLE 1; fetal complications are described in FIGURE 3.)
Uterine irritability, recurrent variable or late decelerations, and the development of vaginal bleeding may be the first signs of abruptio placentae.
I recommend recording maternal blood pressure at least hourly to detect progression from mild to severe hypertension and to determine the need for antihypertensive therapy.
TABLE 1
Likelihood of maternal complications
| Disease progresses during labor (from mild to severe) | 10% |
| Eclampsia | |
| • Mild disease | <0.5% |
| • Severe preeclampsia | 1–2% |
| Stroke (encephalopathy or hemorrhage) | <1% |
| Mainly with severe or early onset disease | |
| Pulmonary edema | 1–2% |
| Usually associated with fluid overload or long-standing chronic hypertension | |
Prevent progression to eclampsia
Magnesium sulfate is the drug of choice in women with preeclampsia. Recent reviews indicate that it reduces the rate of convulsions from 2% to 0.6% in women with severe preeclampsia. In women with mild preeclampsia, the benefit of magnesium sulfate remains unclear.
I recommend IV magnesium sulfate during labor and postpartum when a woman has the indications listed in TABLE 2.
The dose of magnesium sulfate is 6 g IV loading over 20 minutes, followed by a maintenance dose of 2 g/hour.
Magnesium sulfate should be started before surgery (elective cesarean delivery) and continued for at least 12 hours postpartum (I prefer 24 hours).
TABLE 2
When to give prophylactic magnesium sulfate
| Use intrapartum and for at least 12 hours postpartum |
|---|
When the patient has:
|
When treating hypertension in labor, avoid “hypotensive overshoot”
The goal of intrapartum treatment is to lower maternal blood pressure without causing precipitous hypotensive overshoot that may lead to reduced maternal organ perfusion, particularly uteroplacental blood flow. Such acute lowering of maternal blood pressure is a common cause of nonreassuring fetal heart rate patterns during labor.
What blood pressure necessitates treatment? There is no doubt that severe levels of hypertension should be treated to avoid potential cerebrovascular and cardiovascular complications in healthy women. However, there is disagreement about what constitutes severe hypertension.
In previously healthy women, I recommend antihypertensive therapy for systolic pressures of 170 mm Hg or above and/or for diastolic pressures of 110 mm Hg or above.
For women with thrombocytopenia, disseminated intravascular coagulation, or pulmonary edema, I recommend treatment for systolic pressures of 160 mm Hg or above and diastolic pressures of 105 mm Hg or above. This latter group should also be given IV furosemide (20 to 40 mg) to promote diuresis. I also recommend treatment at these levels in the postpartum period.
For women with diabetes, renal disease, or left ventricular cardiac disease, antihypertensive medications should be used to keep systolic pressure below 140 mm Hg and diastolic pressure below 90 mm Hg during labor and postpartum. Further, patients in congestive heart failure or with left ventricular diastolic dysfunction should receive furosemide in addition to antihypertensive drugs.
Choosing a drug. My drugs of choice are IV labetalol and oral nifedipine. These 2 drugs, along with IV hydralazine, are the most commonly recommended medications for severe hypertension in pregnancy (TABLE 3).
Although many authorities prefer hydralazine, recent data indicate that, compared with IV labetalol and oral nifedipine, IV hydralazine is associated with more maternal side effects and worse perinatal outcomes (more fetal distress in labor).
TABLE 3
Drug profiles: Dosing and side effects of antihypertensives used in pregnancy
| MEDICATION | ONSET OF ACTION | DOSE | SIDE EFFECTS |
|---|---|---|---|
| Hydralazine | 10-20 minutes | 5-10 mg intravenously every 20 minutes up to maximum dose of 30 mg | More maternal side effects and worse perinatal outcomes than labetalol or nifedipine. |
| Skin blisters; chest pain; general feeling of discomfort, illness, or weakness; joint or muscle pain; sore throat and fever; swollen lymph glands | |||
| Labetalol* | 10-15 minutes | 10-20 mg intravenously, then 40-80 mg every 10 minutes up to maximum dose of 220 mg/hour or continuous infusion of 1-2 mg/minute | Breathing difficulty and/or wheezing, cold hands and feet, mental depression, shortness of breath, slow heartbeat, swelling of lower extremities, back or joint pain, chest pain, confusion, fever and sore throat, hallucinations, irregular heartbeat, unusual bleeding and bruising, yellow eyes or skin |
| Nifedipine | 5-10 minutes | 10-20 mg orally, repeated in 30 minutes, up to maximum dose of 50 mg/hour | Breathing difficulty, coughing, or wheezing; irregular or fast, poundingheartbeat; skin rash; swelling of lower extremities; chest pain; fainting; painful, swollen joints; vision impairment |
| Sodium nitroprusside† | 0.5-5 minutes | 0.25-5 μg/kg/minute by intravenous infusion | Risk of fetal cyanide poisoning with prolonged treatment. |
| Maternal effects include symptoms of hypothyroidism, headache, abdominal pain, drowsiness, nausea, involuntary muscle movements, perspiration, restlessness, paraesthesia, palpitations, dizziness, retching, tachycardia | |||
| *In women with asthma and congestive heart failure | |||
| †Rarely needed except in hypertensive encephalopathy or cerebral hemorrhage | |||
