Cutting the legal risks of hypertension in pregnancy

Cerebral tissue perfusion is directly related to mean arterial pressure (MAP), which is calculated from both systolic and diastolic pressures:

In the nonpregnant state, there is a loss of cerebral autoregulation when MAP exceeds 150 mm Hg. This results in cerebrovascular injury leading to hypertensive encephalopathy or hemorrhage. The upper limit of cerebral autoregulation in pregnancy is unknown, and most recommendations for treating blood pressure have focused on diastolic BP values. The maximum duration of sustained hypertension before starting therapy is unknown.

In view of these inconsistencies, and to avoid potential medicolegal claims, the following steps are recommended:

• Antihypertensive treatment should be started in accordance with the information in TABLE 10. The aim of therapy is to keep MAP below 125 mm Hg (but not below 105 mm Hg) and diastolic pressure below 105 mm Hg (but not below 90 mm Hg). This can be achieved with a 5-mg bolus dose of hydralazine, to be repeated as needed every 15 to 20 minutes for a maximum total dose of 20 mg per hour. Blood pressure should be recorded every 15 minutes during therapy and every hour once the desired values are achieved. If hydralazine does not lower BP sufficiently and/or if maternal side effects such as tachycardia or headache develop, another drug such as labetalol (20-mg IV bolus doses) or nifedipine (10-mg oral tablets) can be used.
• If recurrent hypertension (as previously defined) develops, antihypertensive drugs should be repeated as needed. Therefore, it is important to document serial measurements of BP during labor and postpartum in all patients with severe preeclampsia-eclampsia.

These threshold values are empiric. There is no evidence to suggest any correlation between maternal BP values and the likelihood of stroke in women with preeclampsia. Indeed, in the absence of cerebrovascular disease (aneurysms, malformations, or cerebral venous thrombosis) or severe thrombocytopenia, the likelihood of stroke in patients with severe hypertensive disorders of pregnancy was less than 0.1%—even though most of these women were untreated despite a diastolic BP exceeding 110 mm Hg for at least 3 hours.¹⁰ These data fail to suggest that an increment of 5 to 10 mm Hg in diastolic pressure is going to make a difference in the development of stroke.¹⁰

Finally, it is important to obtain arteriography or autopsy in all patients with cerebral hemorrhage in pregnancy or postpartum to rule out the presence of anatomic cerebrovascular malformations.

TABLE 10

Indications for antihypertensive therapy

Fetal distress and mode of delivery

Some of the typical medicolegal claims involving fetal distress and mode of delivery concern the issue of performing a cesarean section to prevent maternal and neonatal complications in patients with preeclampsia, HELLP syndrome, or eclampsia. Vaginal delivery is the best method in these patients. Cesarean section should be reserved for obstetric indications. No limit should be placed on the duration of labor if these patients are progressing normally.

As stated previously, preeclamptic pregnancies may be associated with reduced uteroplacental blood flow and higher than normal rates of fetal growth retardation, oligohydramnios, abruptio placentae, and preterm birth. As a result, these pregnancies are more likely to have abnormal FHR patterns than normotensive pregnancies. Some of these infants will be delivered with low Apgar scores and acidotic blood gases secondary to their antenatal complications rather than labor itself. Thus, it is important to document the presence of these complications before the onset of labor, and to utilize continuous FHR monitoring during labor in all such patients.

Preeclamptic pregnancies are more likely to have abnormal FHR patterns than normotensive pregnancies.

In some patients, the presence of severe abnormal FHR patterns (absent beat-to-beat variability with repetitive late or severe variable decelerations) during labor is evidence of an already compromised fetus that has suffered cerebral injury during the prenatal period or prior to monitoring. This is particularly true when the pregnancy is complicated by severe fetal growth retardation, oligohydramnios, or abruptio placentae. Therefore, delivery of such fetuses by emergency cesarean section does not guarantee that the infant will escape neurologic deficits later in life.