Preeclampsia
This is a review of types of hypertension during pregnancy, pathophysiology of preeclampsia, natural progression and complications, and treatment options.
Hypertensive disorders happen in about 7% of all pregnancy and can be a major cause of maternal mortality. Chronic hypertension is an elevated blood pressure (SBP > 140 or DBP > 90) in a pregnant patient prior to 20 weeks gestation. Gestational hypertension is an elevated BP after 20 weeks gestation. Preeclampsia use to be defined as hypertension with proteinuria, however that definition has changed to solely requiring an elevated BP of SBP > 160 or DPB > 100.
The underlying issue with preeclampsia is decreased perfusion to the placenta creating ischemia. Spiral arteries that would typically supply the uterine wall do not reach the myometrium, leading to superficial placental implantation. This leads to uterine release of renin which increases angiotensin activity, and ultimately leads to systemic arterial vasoconstriction. This creates hypertension, tissue hypoxia, and endothelial damage. With endothelial damage comes platelet aggregation that can result in coagulapathies such as disseminated intravascular coagulation. Endothelial damage also causes the release of vasoactive substances such as cytokines, peroxides, and free radicals. Increased sodium and fluid retention results from increase aldosterone. Many of the symptoms associated with preeclampsia are also related to an imbalance of thromboxane and prostacyclin, which normally are produced in equal amounts. However, in preeclampsia, thromboxane is 7x greater than prostacyclin.
With the high degrees of endothelial damage and capillary leakage, you should be on the look out for proteinuria, cerebral edema, intracranial hemorrhage, heart failure, and pulmonary edema.
Patients can be classified as preeclampsia with severe features if they have an elevated blood pressure with any of the following signs/symptoms: thrombocytopenia, increase in LFTs greater than 2x the upper limit of normal, epigastric or RUQ abdominal pain, renal insufficiency, pulmonary edema, new-onset headaches, visual disturbances. These are a result of widespread vasoconstriction. Neurologic symptoms are especially concerning as cerebral hemorrhage/edema account for 50% of deaths related to preeclampsia.
The goals of treatment for preeclampsia are normalizing blood pressure and preventing seizures. The most common medications used to treat blood pressure in this scenario are labetolol, hydralazine, and nifedipine. Seizure prophylaxis is more commonly achieved with magnesium sulfate - a 4g bolus followed by a continuous infusion of 1-2 g/hr until 24 hours postpartum. If you have to break a seizure, common anticonvulsants include lorazepam, diazepam, phenytoin, and keppra.
