Pulmonary infection in intensive care units

Characterisation and evaluation of novel surfactant bacterial anti-adherent coatings for endotracheal tubes designed for the prevention of ventilator-associated pneumonia

It is accepted that ventilator-associated pneumonia is a frequent cause of morbidity and mortality in intensive care patients. This study describes the physicochemical properties of novel surfactant coatings of the endotracheal tube and the resistance to microbial adherence of surfactant coated endotracheal tube polyvinylchloride (PVC). Organic solutions of surfactants containing a range of ratios of cholesterol and lecithin (0:100, 25:75, 50:50, 75:25, dissolved in dichloromethane) were prepared and coated onto endotracheal tube PVC using a multiple dip-coating process. Using modulated temperature differential scanning calorimetry it was confirmed that the binary surfactant systems existed as physical mixtures. The surface properties of both surfactant-coated and uncoated PVC, following treatment with either pooled human saliva or phosphate-buffered saline (PBS), were characterised using dynamic contact angle analysis. Following treatment with saliva, the contact angles of PVC decreased; however, those of the coated biomaterials were unaffected, indicating different rates and extents of macromolecular adsorption from saliva onto the coated and uncoated PVC. The advancing and receding contact angles of the surfactant-coated PVC were unaffected by sonication, thereby providing evidence of the durability of the coatings. The cell surface hydrophobicity and zeta potentials of isolates of Staphylococcus aureus and Pseudomonas aeruginosa, following treatment with either saliva or PBS, and their adherence to uncoated and surfactant-coated PVC (that had been pre-treated with saliva) were examined. Adherence of S. aureus and Ps. aeruginosa to surfactant-coated PVC at each successive time period (0.5, 1, 2, 4, 8 h) was significantly lower than to uncoated PVC, the extent of the reduction frequently exceeding 90%. Interestingly, the microbial anti-adherent properties of the coatings were dependent on the lecithin content. Based on the impressive microbial anti-adherence properties and durability of the surfactant coating on PVC following dip coatings, it is proposed that these systems may usefully reduce the incidence of ventilator-associated pneumonia when employed as luminal coatings of the endotracheal tube.

Physicochemical characterization of hexetidine-impregnated endotracheal tube poly(vinyl chloride) and resistance to adherence of respiratory bacterial pathogens

PURPOSE

Ventilator-associated pneumonia is a frequent cause of mortality in intensive care patients. This study describes the physicochemical properties of hexetidine-impregnated poly(vinyl chloride) (PVC) endotracheal tube (ET) biomaterials and their resistance to microbial adherence (Staphylococcus aureus and Pseudomonas aeruginosa).

METHODS

PVC emulsion was cured in the presence of hexetidine (0-20% w/w) and was characterized in terms of drug release, surface properties (i.e., microrugosity/contact angle), mechanical (tensile) properties, and resistance to microbial adherence.

RESULTS

Under sink conditions, hexetidine release from PVC was diffusion-controlled. Increasing the concentration of hexetidine from 1% to 10% (w/w) (but not from 10% to 20% w/w) increased the subsequent rate of drug release. In general, increasing the concentration of hexetidine decreased both the tensile properties and hydrophobicity, yet increased PVC microrugosity. Following hexetidine release (21 days), the surface properties were similar to those of native PVC. The resistance of hexetidine-containing PVC (1% or 5%) to microbial adherence (following defined periods of drug release) was greater than that of native PVC and was constant over the examined period of hexetidine release.

CONCLUSIONS

ET PVC containing 1% (w/w) hexetidine offered an appropriate balance between suitable physicochemical properties and resistance to microbial adherence. This may offer an approach with which to reduce the incidence of ventilator-associated pneumonia.

Incidence of nosocomial pneumonia in a medical intensive care unit and general medical ward patients in a public hospital in Bombay, India

We prospectively studied the incidence of hospital-acquired pneumonia in 1886 consecutive admissions to an 1800 bed hospital in Bombay; 991 of them to general medical wards and 895 to a 17-bed medical intensive care unit (ICU). The average bed occupancy in the general wards was 56 patients in a ward with 40 beds. Staffing in the general ward was two nurses for 56 patients, and in the ICU three nurses for 17 beds. One hundred and sixty-eight patients developed nosocomial pneumonia: 18 (1.8%) in general wards and 150 (16.7%) in the ICU. Common isolates included Pseudomonas spp (44%) and Klebsiella spp (34%). The most frequently used antibiotics were cefotaxime (34%), amikacin (25%), gentamicin (23%) and ofloxacin (13%). Crude mortality in general ward patients was 88.9 vs 14.6% in patients without pneumonia. The corresponding figures for ICU patients were 67.4 vs 37.1%; 40% of the crude mortality in ICU patients with pneumonia was attributable to the infection. Infected patients stayed an additional 5.8 days in the ICU and 6.7 days in the general ward. Costs of additional stay and antibiotics accounted for 18.6% of the ICU budget. The incidence of nosocomial pneumonia was lower than expected, despite occupancy exceeding bed capacity, low nurse:patient ratios, and extensive reuse of disposable respiratory therapy equipment. Nevertheless, nosocomial pneumonia imposes a significant financial burden on the already scarce resources available for intensive care in developing countries like India.

Evaluation of the protected brush catheter and bronchoalveolar lavage in the diagnosis of nosocomial pneumonia

We assess the sensitivity and specificity of the protected brush catheter (PBC) and bronchoalveolar lavage (BAL) in diagnosing nosocomial pneumonia in nonimmunocompromised critically ill patients. Computerized bibliographic literature searches of MEDLINE were performed, and the reference list of each article selected was reviewed. Of 496 citations, there were 19 articles (describing 18 studies) that proved relevant. Study quality was assessed, and descriptive information concerning study populations, interventions, and clinically relevant outcome measurements was extracted. The sensitivity and specificity of PBC were high (pooled estimates, 89.9 and 94.5%, respectively). Criteria for a positive BAL have varied between studies, and sensitivity ranged from 53.3 to 100%, whereas specificity was 98.6%. Most studies did not report whether antibiotics were withheld on the basis of negative test results. In those that did, the incidence of adverse outcomes consequent on withholding antibiotics was low. BAL and PBC, combined with the use of quantitative cultures, appear to increase accuracy in diagnosing pneumonia. The strength of inference is hampered, however, by the absence of a "gold standard" for the diagnosis of pneumonia. Moreover, the generalizability of these findings is limited by the fact that there are so few methodologically sound studies from so few centers. A randomized trial of PBC is needed.