Patients were randomly assigned in a 1:1:1:1 ratio to receive hydration with sodium chloride together with 1 of 4 prophylactic regimes ( 1 ) N-acetylcysteine ( NAC ) , ( 2 ) sodium bicarbonate ( NaHCO3 ) infusion , ( 3 ) NAC in combination with NaHCO3 , or ( 4 ) hydration with sodium chloride infusion alone .