CRD Summary: This review concluded that N-acetylcysteine did not confer renal protection in patients undergoing cardiac surgery. Overall, the authors' conclusions appear to be supported by the data presented, but some caution is advised given the risk of publication bias and the limited size and number of trials included in the review.

CRD Commentary: This review answered a clearly defined research question. Two databases were searched but no specific attempts were made to locate unpublished information. It was unclear whether language restrictions were applied. Therefore there may be a risk of publication bias and/or language bias. Publication bias was assessed using funnel plots, but given the small number of included trials, this assessment may not be reliable. The authors did not report how trials were selected for inclusion in the review, but two authors extracted the study data and assessed the quality of the trials using standard criteria. This suggested that the risk of reviewer error and bias was reduced. Overall, the sample sizes were described as relatively small, although the data were not reported. The methodological quality of the trials was described as good, so the data are likely to be reliable. Statistical heterogeneity was assessed and found to be low in the majority of cases. The trials were also described as been clinically similar, but there was some variation in surrogate measures of outcome, definitions and local practice. Overall, the authors' conclusions appear to be supported by the data presented, but some caution is advised given the risk of publication bias and the limited size and number of trials included in the review.