MONTEREY, CALIF. – The rate of severe sepsis among women hospitalized for delivery more than doubled during a recent 10-year period, according to a cohort study reported at the annual meeting of the Society for Obstetric Anesthesia and Perinatology.
In the analysis of more than 9.24 million admissions for delivery from the Nationwide Inpatient Sample, the rate rose from 0.64 to 1.37 per 10,000 deliveries between 1998-2000 and 2007-2008, reported lead investigator Dr. Melissa E.B. Bauer, an obstetric anesthesiologist with the University of Michigan Health System in Ann Arbor.
Dr. Melissa E.B. Bauer
Several comorbidities and obstetric factors independently increased the risk of severe sepsis. For example, women with congestive heart failure had a more than fourfold higher risk, and women undergoing cesarean delivery had a more than fivefold higher risk.
"The etiology of the increase [in severe sepsis] in this population is unknown," she commented. "Possible hypotheses for the increase ... could be the increased cesarean delivery rate. At the start of the study period, the cesarean delivery rate was 21.2%; by 2008, the national rate was 32.3%."
"There’s also a higher-risk patient population. More women today have comorbidities that increase their risk of severe sepsis," she added. "And there’s an increased microbial resistance that could also be contributing."
Dr. Bauer noted that an important related issue is the difficulty of diagnosing sepsis during pregnancy. Some of the physiologic values typically used to establish the presence of the systemic inflammatory response syndrome (SIRS), often seen in sepsis, are actually considered normal for a pregnant woman.
"As the population at risk for severe sepsis continues to increase, unless we also increase our identification of patients with sepsis in this population, the rate of severe sepsis and death will continue to increase," she maintained. "A priority of future research will be to redefine SIRS in pregnant patients."
Session moderator Dr. Alan C. Santos of St. Luke’s Roosevelt Hospital Center in New York said, "I realize there were limitations to this type of study and what data you were able to extract. Could this all just be related to an increase in the background infections, HIV, and substance abuse among our population?"
Dr. Bauer acknowledged that those factors may have contributed and were not captured by administrative data. Factors often went uncoded "unless there was a reason to code a certain factor, basically, if it complicated the delivery and there would be more reimbursement for that type of situation," she said. For example, the investigators found a code for obesity in only about 1% of the sample, when roughly 20% of the population is obese.
"The only risk factor that appears to be at all modifiable is cesarean delivery, and it may add another nail in the coffin of this conversation," commented session attendee Dr. Stephen Pratt of Beth Israel Deaconess Hospital in Boston. "I was just wondering, are you able to look at either indications for cesarean delivery or even at, more broadly, elective versus intrapartum cesarean delivery? My guess is it’s going to be the intrapartum cesarean deliveries that are high risk for sepsis."
"That's an excellent point," Dr. Bauer replied. "The problem is, it’s difficult to determine exactly." However, it may be possible to get a general sense from measures such as the duration of hospitalization before cesarean. "We are certainly going to tease out more of the data," she said.
Previous research has suggested that sepsis of any severity complicates about 1 in every 8,000 deliveries in the United States. But "this has been determined by single-institution, retrospective cohort studies. To date, there has not been a United States population–based study looking at incidence, temporal trends, and risk factors for sepsis," Dr. Bauer noted.
The investigators identified hospital admissions having pregnancy- and delivery-related diagnostic codes, excluding those pertaining to ectopic or molar pregnancy, or abortion. Within this set, they then assessed outcomes of sepsis, severe sepsis (sepsis with organ failure and/or hypotension), and sepsis-related death.
Results showed that the rate of sepsis remained essentially the same during the study period, affecting about 1 in every 3,300 deliveries, according to Dr. Bauer. However, the rate of severe sepsis doubled.
Multivariate analyses showed a variety of comorbidities and demographic and obstetric factors that were independently associated with an elevated risk of severe sepsis: diabetes (odds ratio, 1.4), black race (1.8), delivery before 37 weeks (1.8), cerclage (2.7), hypertensive diseases of pregnancy (4.5), congestive heart failure (4.5), cesarean delivery (5.1), stillbirth (6.5), retained products of conception (6.9), chronic renal disease (16.2), and chronic liver disease (22.3).