Table 2.

Assessments related to glomerular filtration rate stratified by treatment group

CharacteristicNo Treatment (n = 9,375)Sodium Bicarbonate + NAC (n = 202)NAC Alone (n = 553)Sodium Bicarbonate Alone (n = 244)P Value of Sodium Bicarbonate versus NAC
GFR,b mean (SD), ml/min per 1.73 m273.8 (23.3)55.4 (21.5)58.6 (22.6)68.5 (29.4)<0.001
Stages of kidney diseasea
    Stage 1, n (% total)1831 (20)10 (5)49 (9)46 (19)
        n CN (% stage)293 (16)2 (20)14 (29)23 (50)0.03
    Stage 2, n (% total)4995 (53)62 (31)152 (27)94 (39)
        n CN (% stage)425 (9)10 (16)22 (14)22 (23)0.05
    Stage 3, n (% total)2417 (26)120 (59)334 (60)90 (37)
        n CN (% stage)250 (10)16 (13)44 (13)21 (23)0.03
    Stage 4, n (% total)95 (1)8 (4)17 (3)10 (4)
        n CN (% stage)39 (41)1 (13)3 (18)5 (50)0.16
    Stage 5, n (% total)37 (0.4)2 (1)1 (0.2)4 (2)
        n CN (% stage)14 (38)0 (0)0 (0)2 (50)0.40
CN related to decreased GFR
    ≥60 ml/min per 1.73 m2; OR (95% CI)c1.001.26 (0.59 to 2.45)1.58 (1.02 to 2.39)3.62 (2.38 to 5.41)
    <60 ml/min per 1.73 m2; OR (95% CI)c1.001.27 (0.64 to 2.39)0.98 (0.62 to 1.54)2.64 (1.49 to 4.59)
  • a Stages 1 to 5 correspond to glomerular filtration rates of ≥90, 60 to 89, 30 to 59, 15 to 29, and <15 ml/min per 1.73 m2, respectively (9). CN, contrast nephropathy; OR, odds ratio.

  • b GFR was estimated using the four-variable MDRD equation (9,17,27). This equation uses race (black or not) as a variable. Race was available in 90%, 91%, 90%, and 91% of the no treatment, sodium bicarbonate + NAC, NAC alone, and sodium bicarbonate along groups, respectively. It is for this reason that the number of patients (n) in each group differs from Table 1. Sensitivity analysis vis-à-vis race in the MDRD equation revealed no effect on the significance of the results.

  • c Adjusted for total volume of hydration, β -blocker, diuretic, NSAIDs, ACE inhibitors/ARBs and aspirin therapies, age, gender, contrast iodine load, prior exposure to contrast material, type of imaging study, heart failure, hypertension, renal failure, multiple myeloma, and diabetes mellitus.