You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Emergent Renal Dysfunction with Colistin Pharmacotherapy. STUDY OBJECTIVE: To evaluate the association between the administration of intravenous (IV) colistin and the emergence of renal dysfunction. DESIGN: A retrospective medical record review. SETTING: A tertiary care academic medical center. PATIENTS: A total of 174 critically ill patients who received at least one dose of IV colistin between 2004 and 2007. MEASUREMENTS AND MAIN RESULTS: The primary outcome was development of renal dysfunction, defined as an increase in serum creatinine of 50% or more during therapy or the initiation of renal replacement therapy (RRT), in patients who received at least one dose of colistin and were not already on RRT. The severity of renal dysfunction was further categorized by the RIFLE criteria. Demographic and clinical characteristics were analyzed by logistic regression for association with new renal dysfunction. A total of 174 patients were evaluated for renal dysfunction. Of these patients, 84 (48%) experienced renal dysfunction on colistin. On multivariate analysis, age in years (odds ratio [OR] 1.03, 95% confidence interval [CI] 1.01-1.05) and receipt of concurrent nephrotoxin(s) (OR 3.35, 95% CI 1.34-8.36) significantly increased the risk of developing renal dysfunction. CONCLUSION: In this critically ill population, renal dysfunction occurred frequently and was associated with older age and receipt of nephrotoxins.
{"Chemical": ["Colistin", "creatinine", "colistin"]}