mrsa carriage, sepsis, and nicu configuration 1175
Scores ranged from 2 to 4 with higher scores indicating greater level of resources. For each patient, the maximum acuity score throughout his or her stay was used in the analysis.
Clinical Risk Index for Babies–II Score. The Clinical Risk
Index for Babies–II (CRIB-II) score is an aggregation of clinical and laboratory data that is used to provide risk adjustment of mortality and neurologic dysfunction across institutions.16–18 It is a sumof scores for the combination of birthweight, gestational age, and sex; admission temperature; and base excess. Scores range from 0 to 27 with higher scores associated with higher mortality risk. For patients born after more than 32 weeks’ gestation or whose birthweights were in excess of 3,000 grams, only the temperature and base excess portions of the CRIB-II were used.19 CRIB-II scores were available for 1,128 patients. Because this was a subset of patients, multivariate regressions were performedwith and without this variable,which minimally affected the significance of the models.
Mean Colonization Pressure and Average Census Colonization pressure is the ratio of MRSA-positive patient-
days to total patient-days, expressed as a percentage. The mean colonization pressure (MCP) is the arithmetic mean of this ratio over a patient’s hospitalization. TheMCP was calculated for the entire unit and for the patient-specificbed configuration. Average census for the entire unit and the patient-specificbed configuration used the average census of the respective areas during the patient’s admission.
Statistical Analysis
The outcomes of time toMRSA colonization, CLOS, and com- bined CLOS or death were compared between patients in single- patient rooms and those in open-unit rooms. Kaplan-Meier curves yielding log-rank tests as well as univariate, bivariate, and multivariate Cox regressions were used to determine these time- dependent outcomes. Additionally, time-independent inci- dences of these end points were compared using χ2 tests and Fisher exact tests, where appropriate. Analysis of variance was used to determine differences between bed configurations in CRIB-II scores, 5-minute Apgar scores, average daily census, MCP, and hand hygiene compliance upon roomentry and room exit. Pearson χ2 and log-rank testswith alpha values of .05 and 2- sided tests were used for statistical power calculations. Analyses were performed using SAS, version 9.3 (SAS Institute).
results Demographic Characteristics
The 1,823 subjects representing 55,166 patient dayswere included in this analysis. Twenty-seven patients (1.5%) who transferred between single-patient and open-unit layouts were excluded from further analysis. Patients in single-patient and open-unit rooms were similar in terms of birthweight, gestational age at birth, sex,
significantly greater in the single-patient rooms than open- unit rooms (32 vs 31; analysis of variance P<.001). MCP was significantly smaller in the single-patient rooms (2.7% vs 3.6%; analysis of variance P<.001). A median of 48 hand hygiene assessments upon room entry (interquartile range, 37–60) and 53 hand hygiene assessments upon room exit (42–71) per bed configuration per month were available throughout the study period. Hand hygiene com- pliance upon room entry did not differ significantly between staff assigned to the different bed configurations. At room exit, hand hygiene compliance was slightly higher in single-patient rooms at Q1 (100% vs 98.6%) whereas median and Q3 were 100% for both groups (analysis of variance P=.052).
race, insurance type, and illness severity based on CRIB-II score, 5-minute Apgar score, and maximum acuity score (Table 1). The median daily census over the study period was
MRSA
The incidence ofMRSA colonization in single-patient and open- unit rooms was similar (2.1% vs 3.3%; χ2 P=.11). Figure 1 demonstrates the similarity in MRSA-free survival over time between the 2 bed configurations. Univariate Cox regression showed no difference in MRSA colonization rates between bed configurations (χ2 P=.10); this similarity persisted when controlling for demographic (birthweight, gestational age, sex, race, insurance type), patient-driven (CRIB-II score, 5-minute Apgar score, and maximum acuity), and unit-driven (average census,MCP, and hand hygiene adherence) variables (Table 2). Average daily census was the only variable to interact sig- nificantly with bed configuration in the bivariate analyses. Within the subset of patients located in single-patient rooms, each additional one patient in the average census during their hospitalization correlated with 31% greater MRSA colonization rate (hazard ratio, 1.31 [95% CI, 1.02–1.68]; P=.039). This correlation was not seen within the open-unit configuration. A Cox regression model for MRSA colonization using bed configuration and average census was not significant. The only variables to affect MRSA colonization involved
hand hygiene. Lower rates of MRSA colonization of 17% (hazard ratio, 0.834 [95% CI, 0.731–0.951]; P=.0068) and 28% (hazard ratio, 0.719 [95% CI, 0.611–0.846]; P<.0001) were associated with 1% greater hand hygiene compliance on room entry or exit, respectively. This was independent of and similar across bed configurations. A 2-dimensional scatter plot of the MRSA genotypes
(Figure 2) demonstrated that 44 (86%) of the 51 isolates clustered into 2 distinct genotypes. There was no difference in MRSA genotypes between single-patient and open-unit rooms (2-tailed Fisher exact test P=.63) (Table 3).
Late-onset Sepsis
The rates of CLOS in single-patient and open-unit rooms were similar (3.9% vs 4.1%; χ2 P=.89). Coagulase-negative
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