Anesthesia for Premature Rupture of Membranes & Chorioamnionitis

PREMATURE RUPTURE OF MEMBRANES & CHORIOAMNIONITIS

Premature rupture of membranes (PROM) is pres-ent when leakage of amniotic fluid occurs before the onset of labor. The pH of amniotic fluid causes Nitrazine paper to change color from blue to yellow. PROM complicates 10% of all pregnancies and up to 35% of premature deliveries. Predisposing fac-tors include a short cervix, prior history of PROM or preterm delivery, infection, multiple gestations, polyhydramnios, and smoking. Spontaneous labor commences within 24 h of ruptured membranes in 90% of patients. Management of PROM balances the risk of infection with the risk of fetal prematu-rity. Delivery is usually indicated sometime after 34 weeks of gestation. Patients with a gestation of less than 34 weeks can be managed expectantly with prophylactic antibiotics and tocolytics for 5–7 days to allow some additional maturation of fetal organs. The longer the interval between rupture and the onset of labor, the higher the incidence of chorioam-nionitis. PROM also predisposes to placental abrup-tion and postpartum endometritis.

Chorioamnionitis represents infection of the chorionic and amnionic membranes, and may involve the placenta, uterus, umbilical cord, and fetus. It complicates up to 1–2% of pregnancies and is usually but not always associated with ruptured membranes. The contents of the amniotic cavity are normally sterile but become vulnerable to ascending bacterial infection from the vagina when the cervix dilates or the membranes rupture. Intraamniotic infections are less commonly caused by hematog-enous spread of bacteria or retrograde seeding through the fallopian tubes. The principal maternal complications of chorioamnionitis are premature or dysfunctional labor, often leading to cesarean section, intraabdominal infection, septicemia, and postpartum hemorrhage. Fetal complications include acidosis, hypoxia, and septicemia.

Clinical signs of chorioamnionitis include fever (>38°C), maternal and fetal tachycardia, uterine tenderness, and foul-smelling or purulent amniotic fluid. Blood leukocyte count is useful only if mark-edly elevated because it normally increases during labor (normal average 15,000/μL). C-reactive pro-tein levels are usually elevated (>2 mg/dL). Gram stain of amniotic fluid obtained by amniocentesis is helpful in ruling out infection.

The use of regional anesthesia in patients with chorioamnionitis is controversial because of the the-oretical risk of promoting the development of men-ingitis or an epidural abscess. Available evidence suggests that this risk is very low and that concerns may be unjustified. Moreover, antepartum antibiotic therapy appears to reduce maternal and fetal mor-bidity. Nonetheless, concerns over hemodynamic stability following sympathectomy are justified, particularly in patients with chills, high fever, tachy-pnea, changes in mental status, or borderline hypo-tension. In the absence of overt signs of septicemia, thrombocytopenia, or coagulopathy, most clinicians offer regional anesthesia to those patients with cho-rioamnionitis who have received antibiotic therapy.