Critically ill patients frequently undergo contrast enhanced computed tomography (CT) to establish diagnoses and direct management. Contrast agents can disturb kidney function and result in kidney dysfunction. The investigators investigated the effects of high dose N-acetylcysteine (NAC) or placebo, in addition to hydration, in preventing kidney dysfunction following contrast enhanced CT) in critically ill adults in the intensive care units of two teaching hospitals.

Potential participants were identified by staff intensivists or resident physicians following admission to participating ICUs. We included critically ill adult patients at least 18 years of age who consented to participate in the trial, had central venous access and a foley catheter, required a contrast-enhanced CT of any organ system(s), and were considered 'at risk' for the development of CIN. We defined 'at risk' to include patients with at least one of the following at the time of randomization (i) a serum creatinine of > 106 µmol/L and or urea > 6 mmol/L, (ii) urine output of < 0.5 cc/kg over > 4 hrs or (iii) an increase in serum creatinine of > 50 µmol/L in < 24 hours. We stratified based on the presence or absence of diabetes defined as a history of treatment with oral hypoglycemics or insulin.

We excluded patients with a (i) CK > 5,000 or the presence of myoglobinuria, (ii) a known allergy or hypersensitivity reaction to radiographic contrast dye or NAC, (iii) serious illness with imminent threat of dying (low likelihood of survival within 48-hours) or poor prognosis, (iv) pregnancy, (v) patients with cardiogenic shock (NYHA class 3 or 4 symptoms), (vi) known or suspected nephritic, nephrotic or pulmonary-renal syndromes, (vii) a post renal etiology of renal impairment, (viii) previous renal transplant, (ix) known solitary kidney, (x) serum creatinine > 200 µmol/L or (xi) recent exposure to radiographic contrast within 14 days of randomization.

The primary outcome for the study was the development of CIN defined as a rise in serum creatinine of > 50 µmol/L from the time of randomization up to day 5 following contrast exposure.

Secondary outcomes included ICU and hospital length of stay, ICU and hospital mortality and the requirement for renal replacement therapy. We recorded compliance with assigned treatment and assessed for development of severe unexpected adverse events defined as hypotension, bronchospasm and anaphylactic reactions.

Inclusion Criteria:

• The investigators included critically ill adult patients at least 18 years of age who consented to participate in the trial, had central venous access and a foley catheter, required a contrast-enhanced CT of any organ system(s), and were considered 'at risk' for the development of CIN.
• The investigators defined 'at risk' to include patients with at least one of the following at the time of randomization (i) a serum creatinine of > 106 µmol/L and or urea > 6 mmol/L, (ii) urine output of < 0.5 cc/kg over > 4 hrs or (iii) an increase in serum creatinine of > 50 µmol/L in < 24 hours.

Exclusion Criteria:

• The investigators excluded patients with a

  • CK > 5,000 or the presence of myoglobinuria
  • a known allergy or hypersensitivity reaction to radiographic contrast dye or NAC
  • serious illness with imminent threat of dying (low likelihood of survival within 48-hours) or poor prognosis
  • pregnancy
  • patients with cardiogenic shock (NYHA class 3 or 4 symptoms)
  • known or suspected nephritic, nephrotic or pulmonary-renal syndromes
  • a post renal etiology of renal impairment
  • previous renal transplant
  • known solitary kidney
  • serum creatinine > 200 µmol/L or (xi) recent exposure to radiographic contrast within 14 days of randomization.