Incidence and risk factors of nephrotoxicity in patients on colistimethate sodium

Background Colistin is used to treat gram-negative infections but it's highly associated with nephrotoxicity. Objectives To determine the incidence and risk factors as well as mortality in patients on colistin. Setting Sultan Qaboos University Hospital, Muscat, Oman. Methods This was a retrospective cohort study of patients admitted and who received colistin for ≥ 48 h. The exclusion criteria included inhaled colistin therapy, cystic fibrosis, or pregnancy. The study period was from January 2010 to June 2016. Main outcome measures Nephrotoxicity using the Risk, Injury, Failure, Loss and Endstage kidney disease (RIFLE) criteria. The secondary outcomes were incidence, risk factors and mortality in patients on colistin. Results A total of 123 patients were included. Colistin-associated nephrotoxicity (CAN) occurred in 57 (46%) patients after colistin therapy. As per the RIFLE criteria, 22 (18%) patients were classified as 'at risk', 17 (14%) as 'injury', and 18 (15%) as 'failure'. Multivariate analysis indicated that increasing age (adjusted odds ratio (aOR), 1.03; 95% confidence interval (CI) 1.01-1.06; p = 0.004) and higher APACHE II score (aOR 1.08; 95% CI 1.01-1.16; p = 0.040) were significant predictors for the development of nephrotoxicity. Factors associated with mortality included ICU admission (aOR 23.3; 95% CI 5.04-106; p < 0.001), vasopressin use (aOR 5.54; 95% CI 1.56-19.6; p = 0.008) and higher APACHE II score (aOR 1.15; 95% CI 1.03-1.30; p = 0.027). Conclusions The incidence of CAN was 46%. Increasing age and higher APACHE II score were the risk factors for CAN. Factors associated with mortality at 28 days included ICU admission and higher APACHE II score.