Features and markers of nosocomial pneumonia in patients undergoing heart surgery

Background

Nosocomial pneumonia (NP) is probably the most frequent and severe cause of postoperative infection in patients undergoing heart surgery. This group has high incidence (2-20%) of NP.

Objective

Description of the microbiological patterns and markers of NP in patients submitted to heart surgery.

Development and method

An observational and prospective study was conducted between June 2000 and February 2001. All patients submitted to heart surgery and to MV were included. Diagnosis of NP followed NNISS criteria (CDC). We evaluated the results of bronchoalveolar lavage (BAL) and blood cultures collected at the same day of NP diagnosis. Variables analyzed were age, gender, smoking, diabetes, chronic obstructive pulmonary (COPD) disease, body surface, ventricular function, time of extracorporeal circulation (ECC), clamp time, type and length of stay (LOS) in surgery, LOS MV. EPI Info 6.04 from CDC was used to perform univaried analysis.

Results

A total of 211 patients were submitted to heart surgery during this period; 29 NP were observed in 23 (11%) patients. Median age of 66 years, 65% were men. Gender, COPD, diabetes and body surface were not related to increase NP. Smoking patients had increased risk of NP (P < 0.001). Patients with normal ventricular function had a lesser incidence of NP (P = 0.002). LOS in surgery (median 6 h) and clamp time was not related to NP. LOS MV (P < 0.001), duration of ECC (P < 0.001), coronary artery bypass graft (P = 0.04) and emergency (P = 0.01) were related to increase of NP. BAL could not be performed in two cases of NP. Micro-organisms related to these infections were Pseudomonas aeruginosa in five (18%), B cepacia in four (15%), Staphylococcus aureus oxacillin-resistant in three (11%), Haemophillus sp in three (11%), Neisseria sp in one (4%), Enterobacter cloacae in three (11%), E coli in two (7%), Morganella morgani in two (7%), Staphylococcus epidermidis in one (4%), Klebsiella oxytoca in one (4%), Serratia marcenses in one (4%), Proteus mirabilis in one (4%) and Enterobacter aerogenes in one (4%). These data demonstrate high prevalence (11/27) of enterobacteria. We found 18% of positive blood cultures.

Discussion

The initial univariate analysis agrees with the literature information. A multivariate analysis should be performed. Reduction in time of ECC and LOS MV could be associated with decreased infection rate in this group.