Anesthesia for the patient with preeclampsia
Preeclampsia—a syndrome occurring after week 20 of gestation and characterized by hypertension, proteinuria, and generalized edema—becomes eclampsia if a grand mal seizure occurs (see Chapter 184). Preeclampsia/eclampsia abates within 48 h after delivery of the entire placenta.
Manifestations
Preeclampsia is a multisystem disease, affecting the central nervous system and the cardiovascular, respiratory, renal, hepatic, and hematologic systems, as well as the placenta (Table 185-1) (see Chapter 184).
Table 185-1
Manifestations of Preeclampsia
| Body System | Manifestations |
| Central nervous system | Cerebral edema, cerebral hemorrhage, cortical blindness, headache, hyperirritability, hyperreflexia, seizures, vertigo |
| Cardiovascular | Hypoproteinemia; hypovolemia; hemoconcentration; left ventricular hypertrophy; myocardial dysfunction; pulmonary edema; ↑ sensitivity to catecholamines, sympathomimetics, and oxytocics; ↑ systemic vascular resistance |
| Hematologic | DIC,* platelet dysfunction, prolonged bleeding time,† thrombocytopenia |
| Hepatic | Abnormalities on liver function tests, ↓ hepatic blood flow, ↓ plasma cholinesterase levels, periportal hepatic necrosis, subcapsular hemorrhage |
| Placenta | Chronic fetal hypoxia, fetal malnutrition, intrauterine growth retardation, placental abruption, premature birth, premature labor, uteroplacental insufficiency |
| Renal | ↑ Blood urea nitrogen, ↑ creatinine, ↓ glomerular filtration rate, hyperuricemia, proteinuria, ↓ renal blood flow |
| Respiratory | Airway edema, gastric aspiration, interstitial edema, ventilation-perfusion mismatch |
*Disseminated intravascular coagulation (DIC) affects 20% of patients.
Treatment
Intravenous fluid administration should be guided by urine output (goal: >1 mL·kg−1·h−1) and central venous pressure (4-6 cm H2O). In patients manifesting cardiopulmonary dysfunction, some clinicians advocate the use of a pulmonary artery catheter to monitor measures of cardiac function. Intraarterial cannulation allows continual blood pressure monitoring and provides easy access for blood sampling (e.g., clotting parameters, arterial blood gases, and electrolyte and Mg2+ concentrations). Loop diuretics are used to treat pulmonary edema, and mannitol may be given to treat cerebral edema. MgSO4, with its anticonvulsant and antihypertensive properties, reduces CNS irritability, reduces irritability of the neuromuscular junction, and has direct vasodilating action on the smooth muscles of arterioles and the uterus. In excess of therapeutic range, MgSO4 may cause skeletal muscle weakness, respiratory depression, and cardiac arrest. CaCl2 counteracts the adverse effects of MgSO4. Neuromuscular blockade is potentiated by MgSO4, as is the sedative effect of opioids. Other useful antihypertensive agents include labetalol, hydralazine, nitroglycerin, methyldopa, clonidine, prazosin, nifedipine, and trimethaphan. The use of sodium nitroprusside is discouraged by some authors because the fetus is susceptible to cyanide toxicity resulting from continuous sodium nitroprusside infusion. (See Table 184-1 for a summary of the effects of increasing plasma magnesium concentrations.)
