High-dose colistin for microbiologically documented serious respiratory infections associated with carbapenem-resistant Acinetobacter baummannii in critically ill cancer patients: a retrospective cohort study

Background: Recent studies suggested that high doses of colistin are necessary in the treatment of serious infections. However, few studies have evaluated such treatment. The objective of this study was to evaluate the effectiveness and nephrotoxicity of high-dose colistin in critically ill patients with respiratory infections associated with carbapenem-resistant Acinetobacter baumannii (CRAB). Methods: This was a retrospective cohort study of critically ill cancer patients who received high-dose intravenous colistin for treatment of CRAB-related respiratory infections. Patients received colistimethate sodium 9 million IU/day or an equivalent dose, adjusted for renal function. Treatment effectiveness was evaluated by determining the microbiological clearance, recurrent and new CRAB-related infections, and mortality in the intensive care unit (ICU). Nephrotoxicity was defined according to the RIFLE (risk, injury, failure, loss, and end-stage kidney disease) criteria. Results: A total of 89 patients met the inclusion criteria. Microbiological clearance was observed in 51 (66.2%) subjects who had at least 2 follow-up cultures (n = 77). In patients who achieved microbiological clearance, recurrent and new CRAB-related infections occurred in 3 (5.9%) and 9 (17.6%) subjects, respectively. Fifty-seven patients (64%) died in the ICU. Thirty-five (39.3%) subjects developed nephrotoxicity according to the RIFLE criteria, which was classified as risk in 4 (11.4%) subjects, injury in 8 (22.8%) subjects, and failure in 21 (60%) subjects. Conclusions: In critically ill cancer patients, high-dose colistin was associated with microbiological clearance in about two-thirds of the subjects with CRAB-related respiratory infections but mortality was high. A significant portion of patients developed nephrotoxicity while receiving colistin therapy.