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The OB/GYN Resident Survival Guide
#17: Diagnose & Manage Intraamniotic Infection (Intrapartum Edition)
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Hello and welcome back for another episode of the OB GYN Resident Survival Guide. Today we're going to be reviewing intra amniotic infection, formerly known as chorioamnionitis. Throughout this episode, I'm going to be using a short form. And so when you hear me say iai, that means intraamniotic infection. So IAI is defined as an infection of the placenta, amniotic fluid membranes, decidua and or of the fetus. Typically, this happens when microorganisms from the lower genital tract ascend into the amniotic cavity, which is normally sterile. However, it can also develop secondary to invasive procedures such as amniocentesis, chorionic villus sampling or sarclage placement, and it can even happen through hematogenous spread in the setting of a systemic maternal infection. Although these infections are relatively uncommon, it's very important to know how to diagnose and manage iai because outcomes for both the mother and the neonate can be much poorer. The maternal patient is at an increased risk of dysfunctional labor, postpartum hemorrhage, endometritis, and then sepsis, which itself can lead to all of the potential sequelae, such as ards, septic shock and even death. Affected neonates are at risk of developing pneumonia, meningitis, cerebral palsy, bronchopulmonary dysplasia, more commonly in preterm infants that are affected, and then of course, sepsis and associated sequelae, including death. Risk factors for developing IAI include prolonged labor, prolonged rupture of membranes, which is generally defined as membrane rupture for 18 hours or greater, as well as nulliparity, use of intrauterine monitors like the FSC and iupc, preexisting lower genital tract infections or sexually transmitted infections, meconium stain fluid and DBS colonization. Historically, we've been taught in training that multiple digital exams could be a risk factor or is a risk factor. However, interestingly, when I was reading this practice bulletin, there was a study done in 2012 that assessed over 2,000 women in labor and and there actually was no association found between exam frequency and intrapartum fever, and that was regardless of membrane rupture status. Of course, this is only one study, but it's relatively recent. It's a pretty good size and the results were surprising to me, so I'll put a link for that in the show notes if you want to read the full paper. So let's talk about the diagnosis and management of iai. The only way to actually confirm an intra amniotic infection is is by running studies on the amniotic fluid or performing a pathologic evaluation of the placenta. Now, you've probably realized that we're not routinely going around and testing the amniotic fluid or obtaining specimens of the placenta for our patients who are laboring, and that's because we can diagnose and treat when there is a clinical suspicion for intra amniotic infection, and in practice we will likely continue doing so until less invasive and faster testing becomes available. So suspected IAI is defined as an isolated temperature of 39 degrees Celsius or greater or 102.2 degrees Fahrenheit, or a temperature of 38 to 38.9 Celsius, which is 100.4 to about 102.1 Fahrenheit, and any of the following maternal leukocytosis, fetal tachycardia and or purulent cervical drainage. But if the temperature is 39 degrees or greater, you should have a high suspicion and treat for IAI even in the absence of those clinical findings. Management primarily focuses on the initiation of antibiotics and the control of a maternal fever with antipyretics like Tylenol. Rapid initiation of antibiotics does reduce the risk of neonatal infection as well as morbidity related to maternal fevers and is associated with an overall lower length of hospital stay in the maternal patient. In addition to the antibiotics and antipyretics, your hospital may have a maternal sepsis protocol that triggers whenever the patient meets criteria. I have this at my institution and it's very similar to the routine adult sepsis protocol that you would have on the med surg floor or in the emergency room. For example, it focuses on IV fluid resuscitation at labs including your CDC with dif, blood cultures, lactate, electrolytes, et cetera and increased frequency of vital sign monitoring. When you are suspecting and initiating treatment for iai, it's also very important to let the pediatric or neonatal ICU team know as they should be present for delivery to assess the infant after birth given the associated potential risks to the neonate. When it comes to antibiotics, the standard is IV ampicillin and IV gentamicin. However, if the patient has a penicillin allergy, depending on the severity you would the gentamicin on, but replace the ampicillin with either cefazolin, clindamycin or vancomycin. There's a great table in The ACOG Committee Opinion 797 Prevention of GBS early onset disease in newborns it's table number two and it reviews for you the differentiation between low, moderate and high risk penicillin allergy symptoms. But generally a high risk penicillin allergy, where you would not want to use cefazolin, but rather clindamycin or vancomycin would be the historic development of hives, flushing, angioedema, anaphylaxis, things like that. The duration of treatment depends on the severity of the infection and risk factors for the patient developing endometritis. So at a minimum, the antibiotics should be continued for the duration of labor. For those that deliver vaginally, antibiotics can be discontinued after delivery and those that deliver by cesarean, one additional dose of antibiotics is recommended in the post op period. The idea here is that the risk of developing endometritis at baseline is much higher after cesarean because of the instrumentation inside of the uterus. So if you combine an already elevated risk of developing endometritis and then add a preexisting infection inside the uterus, we really want to make sure that we're conservative in our treatment to hopefully reduce that risk of persistent infection inside the uterus. Now, all of that being said, if the patient is having persistent fevers after delivery, if they're septic, if there's concern for bacteremia, it's completely acceptable and often necessary to continue antibiotics for a prolonged period of time, regardless of whether or not the patient has delivered. Like with infection in any other scenario, source control is the goal. And in this setting, source control is removal of the fetus and placenta. But in many cases it may take several hours after source control has been achieved before the patient deferves and the sepsis resolves. All right, let's summarize. IAI is an infection of the placenta, amniotic fluid, membranes, decidua and or the fetus itself. Criteria for diagnosis include a maternal temperature of 39 degrees Celsius or greater all by itself, or a temperature of 38 to 38.9 degrees Celsius accompanied by any of the following maternal leukocytosis, fetal tachycardia and or purulent cervical drainage. Treatment focuses on the rapid initiation of IV antibiotics like ampicillin and gentamicin, as well as antipyretics like Tylenol, as well as treating for sepsis when necessary and informing the pediatric team so that they can be present for delivery. That's it for today. As usual, the references are listed in the show notes and I will be here next week with another episode.