Effect of Nebulized Colistin on the Ventilator Circuit: a Prospective Pilot Case- Control Study from a Single Cancer Center

Nebulized colistin (NC) is used for the treatment of pneumonia due to multidrug- resistant Gram-negative bacteria. In this one-year case-control study, our objective was to evaluate the effect of NC on the ventilator circuit (VC) components. The case group consisted of 25 mechanically-ventilated patients who received NC for the treatment of nosocomial pneumonia while the control group was 25 mechanically-ventilated patients who did not receive NC. Respiratory therapists inspected the VC every 4 hrs and whenever a ventilator alarm was reported. The VC component was changed if the alarm did not subside after necessary measures were performed. Patients from both groups were treated at the adult medical/surgical intensive care unit at King Hussein Cancer Center. In the case group, 22 (88%) patients required changing at least one of the circuit components (flow sensor, exhalation membrane, or nebulizer kit). The median number of changes (range) per patient of the flow sensor, exhalation membrane, and nebulizer kit were: 2 (1-3), 2 (1-6), and 1 (1-2), respectively. Large amounts of white crystals, which resembled the colistin powder, were reported on the replaced VC components. The flow sensor was changed in 2 control patients, but white crystals were absent. Crystals obtained from one case subject were confirmed to be colistin by chromatographic mass spectroscopy. Further studies are needed to evaluate the effect of crystal formation on the efficacy of NC and clinical outcomes.