Almost without exception-but at times unnoticed-preeclampsia precedes the convulsion onset. Eclampsia is most common in the last trimester and becomes increasingly frequent as term approaches. In more recent years, the incidence of postpartum eclampsia has declined. his is presumably related to improved access to prenatal care, earlier detection of antepartum preeclampsia, and prophylactic use of magnesium sulfate (Chames, 2002). Importantly, other diagnoses should be considered in women with convulsions more than 48 hours postpartum or in women with focal neurological ensue. In severe cases, coma persists from one convulsion to another, and death may result. In rare instances, a single convulsion may be followed by coma from which the woman may never emerge. As a rule, however, death does not occur until after frequent convulsions. Finally and also rarely, convulsions continue unabatedstatus epilepticus-and require deep sedation and even general anesthesia to obviate anoxic encephalopathy.
he respiratory rate ater an eclamptic convulsion is usually increased and may reach 50 or more per minute in response to hypercarbia, lactic acidemia, and transient hypoxia. Cyanosis may be observed in severe cases. High fever is a grave sign as it likely emanates from cerebrovascular hemorrhage.
Proteinuria is usually, but not always, present as discussed earlier (p. 720). Urine output may be diminished appreciably,
FIGURE 40-16 Hematoma of tongue from laceration during an eclamptic convulsion. Thrombocytopenia may have contributed to the bleeding.
:s,
FIGURE 40-19 Serum magnesium concentration in normotensive and preeclamptic women following a 4-g loading dose of magnesium sulfate and 2 g/h infusion. (Data from Brookfield, 2016.)
Maintenance magnesium sulfate therapy has traditionally been continued for 24 hours after delivery. For eclampsia that develops postpartum, magnesium sulfate is administered for 24 hours after the onset of convulsions. A few investigators have truncated this therapy duration to 12 hours and found no seizures (Anjum, 2016; Ehrenberg, 2006; Kashanian, 2016). And more recently, Ludmir and colleagues (2017) described salutary outcomes when magnesium sulfate therapy was stopped after delivery. That said, these studies are small, and the abbreviated magnesium regimen needs further study before being routinely implemented.
Using United States Pharmacopeia (USP) standards, magnesium sulfate USP is MgS04·7H20, and it contains 8.12 mEq magnesium per 1 g. Parenterally administered magnesium is cleared almost totally by renal excretion, and magnesium intoxication is unusual when the glomerular iltration rate is normal or only slightly reduced. Adequate urine output usualy correlates with preserved glomerular iltration rates. That said, magnesium excretion is not urine Row dependent, and urinary volume per unit time does not, per se, predict renal unction. Thus, serum creatinine leves must be mesured to etect a decreased glomeruar iltration rate.