An updated meta-analysis using only high-quality trials similarly demon- strated no benefit.283 Taken as a whole, these studies do not support any recommendation for the use of N-acetyl-L- cysteine, they do, however, provide sufficient data to con- clude that N-acetyl-L-cysteine does not prevent contrast- induced AKI in patients undergoing angiographic procedures. The correlation between the volume of contrast media and the risk of contrast-induced AKI has been documented in several studies.276,277 Thus, minimization of contrast media volume is important to prevent contrast-induced AKI in patients undergoing angiography. The volume of contrast already administered during diagnostic catheterization is an important factor when considering possible ad hoc PCI. Comparative studies of different contrast media (eg, low- osmolar versus iso-osmolar, one agent versus another agent) have produced variable and sometimes contradictory re- Levine et al 2011 ACCF/AHA/SCAI PCI Guideline e593 sults.334 339 Thus, current data are insufficient to justify specific recommendations about low- and isoosmolar contrast media. This issue is discussed in detail in the 2011 UA/ NSTEMI focused update.340 For a further discussion of contrast media and PCI, the reader is referred to a position statement by the SCAI.284 4.5. Anaphylactoid Reactions: Recommendations Class I 1. Patients with prior evidence of an anaphylactoid reaction to contrast media should receive appropri- ate steroid and antihistamine prophylaxis before repeat contrast administration.252,284 286 (Level of Evidence: B) Class III: NO BENEFIT 1. 