title: Renal effects of bicarbonate versus saline infusion for iso- and lowosmolar contrast media in rats.
abstract: OBJECTIVE
  Hydration is widely accepted as an effective measure to prevent contrast media (CM)-induced acute kidney injury (AKI). Whether bicarbonate (NaHCO₃) infusion has a greater effect than saline is disputed. Effective prevention of CM-induced AKI by NaHCO₃ has been found by several clinical trials. However, others found either no effect or an enhanced incidence of CM-induced AKI after giving NaHCO₃. Because of their different tubular resorption, NaHCO₃ and saline may have a different capacity to flush the nephron. In this study, we compare the magnitudes by which NaHCO₃ and saline can enhance urinary flow, prevent a decline in glomerular filtration rate (GFR), and limit an increase in urine viscosity, as caused by CM administration.
  
  
  METHODS
  Prewarmed (37°C) CM were administered as 1.5 mL bolus into the thoracic aorta of anesthetized rats. Following 2 CM were studied: iso-osmolar iodixanol (320 mg I/mL) and low-osmolar iopromide (370 mg I/mL). Four protocols (n = 7 rats per protocol) were followed: (1) saline + iodixanol, (2) saline + iopromide, (3) NaHCO₃ + iodixanol, and (4) NaHCO₃ + iopromide. Isotonic saline or NaHCO₃ were infused at a rate of 4 mL/h per kg BM, initiated 60 minutes before CM administration and continued throughout the observation period of 100 minutes. Urine volume was measured gravimetrically, urine viscosity was measured by a microviscometer, and GFR was determined by creatinine clearance.
  
  
  RESULTS
  As compared with saline infusions, NaHCO₃ infusions did not significantly alter the effects that iodixanol and iopromide exerted on urine flow rate, urine viscosity, and GFR. In the iopromide protocols, CM-induced increase in urine flow was about 50% greater than in the respective iodixanol protocols. Conversely, in the iodixanol protocols, urine viscosity was up to 10-fold greater than in the respective iopromide protocol. In the iodixanol protocols, GFR decreased transiently (10-30 min post-CM) by up to 50%, whereas GFR did not decrease in the iopromide protocols.
  
  
  CONCLUSIONS
  Infusing either saline or NaHCO₃ seems to make little difference with regard to urine flow, urine viscosity, and GFR. However, the CM used has a significant effect on these measures. Iopromide enhances urine flow by a greater magnitude than iodixanol, whereas the latter increases urine viscosity to a larger degree than iopromide and transiently decreases GFR.
authors.affiliation: From the Institute of Physiology, Charité-Universitätsmedizin Berlin, CCM, Berlin, Germany.
authors.forename: Mechthild
authors.initials: M
authors.lastname: Ladwig
authors.forename: Bert
authors.initials: B
authors.lastname: Flemming
authors.forename: Erdmann
authors.initials: E
authors.lastname: Seeliger
authors.forename: Lilit
authors.initials: L
authors.lastname: Sargsyan
authors.forename: Pontus B
authors.initials: PB
authors.lastname: Persson
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001639:Bicarbonates / Q000008:administration & dosage* / Q000009:adverse effects*; D003287:Contrast Media / Q000008:administration & dosage* / Q000009:adverse effects*; D004305:Dose-Response Relationship, Drug; D005919:Glomerular Filtration Rate; D007472:Iohexol / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives*; D007674:Kidney Diseases / Q000139:chemically induced* / Q000517:prevention & control*; D008297:Male; D009994:Osmolar Concentration; D051381:Rats; D017208:Rats, Wistar; D012965:Sodium Chloride / Q000008:administration & dosage*; D018709:Statistics, Nonparametric; D014283:Triiodobenzoic Acids / Q000008:administration & dosage / Q000009:adverse effects*; D014556:Urine / Q000737:chemistry; D014783:Viscosity
chemical_list: D001639:Bicarbonates; D003287:Contrast Media; D014283:Triiodobenzoic Acids; D007472:Iohexol; D012965:Sodium Chloride; C038192:iopromide; C044834:iodixanol