Minocycline to Prevent Acute Kidney Injury After Cardiac Surgery

Inclusion Criteria: * Age over 18 years * planned CABG or valvular surgery with cardiopulmonary bypass * Serum creatinine available (within 30 days) * Estimated GFR 15-90ml/min using the abbreviated MDRD formula (CKD stages 2-4) Exclusion Criteria: * Emergent or urgent surgery (to be performed within the next 36 hours) * End stage renal disease, or GFR \< 15ml/min (CKD stage 5) * Estimated GFR\>90ml/min (CKD stage 1 or no CKD) * Ongoing infection by positive blood, urine or sputum cultures or pneumonia on CXR * Allergy to minocycline or tetracyclines * inability to take oral medications * use of preoperative vasopressor agents at therapeutic doses * Pregnant or lactating females * Advanced liver disease by history or exam(cirrhosis, ascitis, jaundice) * Rising creatinine meeting the definition of acute kidney injury prior to surgery * Neurologic signs or symptoms or history of increased intracranial pressure * current participation in another research study involving an investigational drug or device