P Pu ur rp po os se e: : This systematic review is aimed at answering the following questions: 1) Is near-infrared spectroscopy (NIRS) clinically effective in detecting cerebral desaturation during heart surgery? 2) Are these results based on studies with solid methodology?S So ou ur rc ce es s: : MEDLINE, internet, and hand searches up to February 2004 for English and French papers on NIRS.P Pr ri in nc ci ip pa al l f fi in nd di in ng gs s: : Forty-eight papers were retrieved, with a total of 5,931 cardiac surgery patients monitored by NIRS. More than 83% of patients underwent coronary artery bypass graft surgery. The majority of studies were prospective for the monitored group. Clinically, NIRS monitoring appears to detect brain desaturation episodes encountered during surgery. However, the majority of studies retrieved suffered from major methodological limitations and a low level of evidence. NIRS validity vs jugular bulb oximetry is questioned together with its predictive value in identifying those who will suffer postoperatively from neurological deficits. The sole randomized controlled trial appears to have recorded negative results in this respect.C Co on nc cl lu us si io on n: : The clinical application of NIRS in heart surgery as a brain-monitoring device seems interesting. However, NIRS has to be investigated more rigorously to prove its clinical utility in cardiac surgery. EUROLOGICAL complications and cognitive deficits are preoccupations in cardiac surgery because of their frequency, variety and long-term impact. [1][2][3] Disparities between prevalence and incidence can be explained by patient characteristics (age and comorbidities), 2,4-6 type of surgery, 4 differences in definitions of deficits, and how and when deficits are measured. Objectif