A comparative analysis of patients with early-onset vs late-onset nosocomial pneumonia in the ICU setting

Study objective: To compare the clinical outcomes of critically ill patient s developing early-onset nosocomial pneumonia (NP; ie, within 96 h of ICU a dmission) and late-onset NP tie, occurring after 96 h of ICU admission). Design: Prospective cohort study. Setting: A medical ICU and a surgical ICU from a university-affiliated urba n teaching hospital. Patients: Between July 1997 and November 1998, 3,668 patients were prospect ively evaluated. Intervention: Prospective patient surveillance and data collection. Results: Four hundred twenty patients (11.5%) developed NP. Early-onset NP was observed ill 235 patients (56.0%), whereas 185 patients (44.0%) develop ed late-onset NP. Among patients with early onset NP, 114 patients (48.5%) spent at least 24 h in the hospital prior to ICU admnission, compared to 57 patients (30.8%) with late-onset NP (p = 0.001). One hundred eighty-three patients (77.9%) with early-onset NP received antibiotics prior to the deve lopment of NP, as compared to 162 patients (87.6%) with late-onset hrp (p = 0.010). The most common pathogens associated with early-onset NP were Pseu domonas aeruginosa (25.1%), oxacillin-sensitive Staphylococcus aurceus (OSS A; 17.9%), oxacillin-resistant S aureus (ORSA; 17.9%), and EnteroLacter spe cies (10.2%). P aeruginosa (38.4%), ORSA (21.1%), Stenotrophomonas maltophi lia (11.4%), OSSA (10.8%), and Enterobacter species (10.3%) were the most c ommon pathogens associated with late-onset NP. The ICU length of stay was s ignificantly longer for patients with early-onset NP (10.3 +/- 8.3 days; p < 0.001) and late-onset NP (21.0 +/- 13.7 days; p < 0.001), as compared to patients without NP (3.5 +/- 3.2 days). Hospital mortality was significantl y greater for patients with early-onset NP (37.9%; p = 0.001) and late-onse t NP (41.1%; p = 0.001) compared to patients without NP (13.1%). Conclusions:: Both early-onset and late-onset NP are associated with increa sed hospital mortality rates and prolonged lengths of stay. The pathogens a ssociated with NP were similar for both groups. This may be due, in part, t o the prior hospitalization and use of antibiotics in many patients develop ing early-onset NP. These data suggest that P aeruginosa and ORSA can be im portant pathogens associated with early-onset NP in the ICU setting. Additi onally, clinicians should be aware of the common microorganisms associated with both early-onset NP and late-onset.