title: Presence of tobramycin in blood and urine during selective decontamination of the digestive tract in critically ill patients, a prospective cohort study.
abstract: BACKGROUND
  Tobramycin is one of the components used for selective decontamination of the digestive tract (SDD), applied to prevent colonization and subsequent infections in critically ill patients. Tobramycin is administered in the oropharynx and gastrointestinal tract and is normally not absorbed. However, critical illness may convey gut barrier failure. The aim of the study was to assess the prevalence and amount of tobramycin leakage from the gut into the blood, to quantify tobramycin excretion in urine, and to determine the association of tobramycin leakage with markers of circulation, kidney function and other organ failure.
  
  
  METHODS
  This was a prospective observational cohort study. The setting was the 20-bed closed format-mixed ICU of a teaching hospital. The study population was critically ill patients with an expected stay of more than two days, receiving SDD with tobramycin, polymyxin-E and amphotericin-B four times daily in the oropharynx and stomach. Tobramycin concentration was measured in serum (sensitive high performance liquid chromatography - mass spectrometry/mass spectrometry (HLPC-MS/MS) assay) and 24-hour urine (conventional immunoassay), in 34 patients, 24 hours after ICU admission, and in 71 patients, once daily for 7 days. Tobramycin leakage was defined as tobramycin detected in serum at least once (> 0.05 mg/L). Ototoxicity was not monitored.
  
  
  RESULTS
  Of the 100 patients with available blood samples, 83 had tobramycin leakage. Median highest serum concentration for each patient was 0.12 mg/L; 99% of the patients had at least one positive urinary sample (> 0.5 mg/L), 49% had a urinary concentration ≥ 1 mg/L. The highest tobramycin serum concentration was significantly associated with vasopressor support, renal and hepatic dysfunction, and C-reactive protein. At binary logistic regression analysis, high dopamine dose and low urinary output on Day 1 were the significant predictors of tobramycin leakage. Nephrotoxicity could not be shown.
  
  
  CONCLUSIONS
  The majority of acute critically ill patients treated with enteral tobramycin as a component of SDD had traces of tobramycin in the blood, especially those with severe shock, inflammation and subsequent acute kidney injury, suggesting loss of gut barrier and decreased renal removal. Unexpectedly, urinary tobramycin was above the therapeutic trough level in half of the patients. Nephrotoxicity could not be demonstrated.
authors: Department of Intensive Care Medicine, Onze Lieve Vrouwe Gasthuis, Oosterpark 9, 1091 AC Amsterdam, The Netherlands. h.m.oudemans-vanstraaten@olvg.nl
authors: Heleen M
authors: HM
authors: Oudemans-van Straaten
authors: Henrik
authors: H
authors: Endeman
authors: Robert J
authors: RJ
authors: Bosman
authors: Milly E
authors: ME
authors: Attema-de Jonge
authors: Marc L
authors: ML
authors: van Ogtrop
authors: Durk F
authors: DF
authors: Zandstra
authors: Eric J F
authors: EJ
authors: Franssen
mesh_terms: D000368:Aged; D000900:Anti-Bacterial Agents / Q000009:adverse effects / Q000097:blood* / Q000652:urine*; D015415:Biomarkers; D016638:Critical Illness; D003666:Decontamination / Q000379:methods*; D005260:Female; D041981:Gastrointestinal Tract; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D008875:Middle Aged; D009102:Multiple Organ Failure / Q000139:chemically induced; D011446:Prospective Studies; D051437:Renal Insufficiency / Q000139:chemically induced; D014031:Tobramycin / Q000009:adverse effects / Q000097:blood* / Q000652:urine*
chemical_list: D000900:Anti-Bacterial Agents; D015415:Biomarkers; D014031:Tobramycin