Objective
Multiple scoring systems exist to identify inpatients who are at risk for clinical deterioration. None of these systems have been evaluated in an obstetric population. We examined the Systemic Inflammatory Response syndrome (SIRS) and Modified Early Warning score (MEWS) criteria in pregnant women with chorioamnionitis.
Study Design
This was an 18-month retrospective analysis of patients with chorioamnionitis. SIRS and MEWS scores were calculated; clinical outcomes were ascertained, and test characteristics were calculated for the primary outcome of sepsis, intensive care unit transfer, or death.
Results
Nine hundred thirteen women with chorioamnionitis were identified. Five women experienced sepsis; there was 1 death. Five hundred seventy-five of the 913 women (63%) met SIRS criteria (95% confidence interval, 59.8–66.2%; positive predictive value, 0.9%). Ninety-two of the 913 women (10.3%) had a MEWS score of ≥5 (95% confidence interval, 8.3–12.2%; positive predictive value, 0.05%).
Conclusion
SIRS and MEWS criteria do not identify accurately patients who are at risk for intensive care unit transfer, sepsis, or death among pregnant women with intrauterine infection and should not be used in an obstetric setting.
In 1992, the American College of Chest Physicians and the Society of Critical Care Medicine (ACCP/SCCM) convened a consensus panel to standardize the definition of sepsis. From this conference arose the concept of a continuum of sepsis with 4 phases—the Systemic Inflammatory Response syndrome (SIRS), sepsis, severe sepsis, and septic shock. SIRS incorporates temperature, heart rate, respiratory rate, and white blood cell count ( Table 1 ); at least 2 of these items must be abnormal. In sepsis, the criteria for SIRS are met and result from documented infection (culture-proven or visible). Severe sepsis is associated with organ dysfunction or hypoperfusion; septic shock is a subset with hypotension that necessitates inotropic or vasopressive agents.
| Variable | Measure |
|---|---|
| Temperature, °C | >38 or <36 |
| Heart rate, beats/min | >90 |
| Respiratory rate, breaths/min | >20 or Pa co 2 <32 torr |
| White blood cell count, cells/mm 3 | >12,000 or <4000 or >10% immature (band) forms |
Since the adoption of these definitions, prospective trials have confirmed the prognostic importance of the 4 phases of the sepsis syndrome. One large prospective study of patients in an intensive care unit (ICU) noted that 48% of patients with SIRS progressed to sepsis, severe sepsis, or septic shock. Additionally, there was a stepwise increase in mortality rates from SIRS (7%) to sepsis (16%), severe sepsis (20%), and septic shock (46%). Recently, the Modified Early Warning system (MEWS) was developed as a tool to identify inpatients who are at risk for catastrophic decompensation. This system is based on 5 physiologic parameters and has predicted ICU transfer, evaluation for cardiopulmonary emergency, or death at 60 days.
Febrile morbidity affects 15-20% of women during labor or the immediate postpartum period. Thus, the potential utility of a scoring system that could predict accurately which obstetric patients will deteriorate clinically is great. However, because of the demographic and physiologic differences between an obstetric population and the general population in which SIRS and MEWS were developed, it is not certain that these scoring systems are applicable to obstetric patients. If these systems are not generalizable to obstetric patients, their adoption could result in either over-utilization of resources or under-identification of women who are at greatest risk. We examined SIRS and MEWS among pregnant women with intrauterine infection and assessed whether these prognostic tools accurately predicted clinical decompensation.
Materials and Methods
The study was approved by the Northwestern University Institutional Review Board before initiation, and a waiver of informed consent was granted for chart reviews. We conducted an analysis of all patients with chorioamnionitis during an 18-month period (June 2006-November 2007) at a single tertiary care center. Multiple search strategies were used to ensure that all patients with puerperal infection would be identified. First, a perinatal database that includes information on all obstetric admissions and deliveries was searched using the following terms: febrile in labor , chorioamnionitis , therapeutic antibiotics , or maternal ICU transfer . These terms are present as defined fields in the electronic delivery record. A second query of a billing database was conducted by the identification of all obstetric patients with ICD-9 codes for endomyometritis, chorioamnionitis, or sepsis. Also, the Quality Management database, which includes data on obstetric patients who have been transferred to the ICU, was used to identify additional obstetric patients with febrile morbidity. The records of all patients from these sources were then reviewed in detail by 1 of 4 investigators (J.R.L., D.R.G., M.K., M.L.) to verify the diagnosis of chorioamnionitis. Chorioamnionitis was defined as maternal fever in labor to at least 100.4°F with associated uterine tenderness, maternal or fetal tachycardia, or purulent or foul-smelling amniotic fluid. All patients who were determined to have chorioamnionitis were included in the study.
Maternal demographic information and obstetric data including age, race, gravity, parity, gestational age at presentation, Group B streptococcus (GBS) status, route of delivery, and presence of medical comorbidities were abstracted from the medical record. Each set of vital signs (temperature, heart rate, blood pressure, and respiratory rate) that was recorded during labor was abstracted, with the exception of those taken within 40 minutes of epidural placement, given the transient changes in blood pressure and heart rate that may be associated with this procedure. Intrapartum characteristics (duration of labor and duration of rupture of membranes) and laboratory results were abstracted as well.
After all data were collected, SIRS and MEWS scores were generated for each patient in the study cohort. The standard ACCP/SCCM criteria for SIRS were used as shown in Table 1 . MEWS scores were calculated based on the parameters outlined in Table 2 . The single MEWS score that was highest was selected for further analysis. We calculated the percentage of women who met SIRS criteria or who had a MEWS score of ≥5, with 95% CIs. Test characteristics (sensitivity, specificity, positive predictive value, negative predictive value) of both the SIRS and MEWS scoring systems in the prediction of the primary outcome (ICU transfer, sepsis, or death) were determined. SIRS scores were either positive (≥2 criteria met) or negative. MEWS scores were considered “positive” at ≥5, as defined in a previous study. Because each woman did not have all vital sign data elements available that would allow SIRS or MEWS scores to be calculated, we initially calculated the test characteristics (sensitivity, specificity, positive predictive value, negative predictive value) for the cohort of patients with complete data. We then chose to assume that all missing data were normal and recalculated the test characteristics. We recognized that much of the missing data was likely to be abnormal; however, we made this conservative assumption to ensure that the predictive value of the scoring systems would not be underestimated. Statistical analyses were performed in Minitab 13 software (Minitab Inc., State College, PA).
