By monitoring the brain as the index organ of global oxygen supply–demand balance including major organs, regional cerebral oxygen saturation (rScO2) may indicate adequacy of renal perfusion. The aim of this study was to investigate the relationship between perioperative rScO2 and acute kidney injury (AKI) after off-pump coronary artery bypass (OPCAB). AKI was diagnosed according to the Kidney Disease: Improving Global Outcomes criteria. Collected rScO2 variables were baseline, mean, and lowest value during surgery, maximal percentage decrease from baseline, and areas under the threshold below an absolute value of 50% (AUT50) and of 80% of baseline (AUT80%base). Among 580 patients, AKI developed in 143 (24.7%) patients. Patients with AKI had lower baseline, mean, and lowest rScO2 and higher AUT50 and AUT80%base than those without AKI despite routine efforts to restore the rScO2 values within 20% of the baseline. Among the rScO2 variables, the area under the receiver operating characteristic curve of mean rScO2 was the highest (0.636), which was used for the multivariable logistic regression. Multivariable logistic regression revealed mean rScO2 as an independent predictor of AKI (odds ratio, 0.964; 95% confidence interval, 0.937–0.990; p = 0.008), along with chronic kidney disease and emergency surgery. Low intraoperative mean rScO2 was independently associated with AKI after OPCAB, which may serve as an early marker of renal injury.

Melatonin secretion is stimulated by the dark and inhibited by night. The suprachismatic nuclei (SCN) of the hypothalamus have melatonin receptors and melatonin may have a direct action on SCN to influence “circadian” rhythms. Recent evidence also shows that the circadian system of primate infants is responsive to light at very premature stages and that low‐intensity lighting can regulate the developing clock. After birth of neonatal miniature pigs (mini‐pig), in this study, there is progressive maturation of the circadian system outputs, with pronounced rhythms in sleep‐wake and hormone secretion generally developing after 2 wks of age. Showing the importance of photic regulation of circadian phase in neonatal mini‐pig, exposure of premature neonatal mini‐pig to low‐intensity cycled lighting results in the early establishment of rest‐activity patterns that are in phase with the 24‐hour light‐dark cycle. With the continued elucidation of circadian system development and influences on physiology of mini‐pig and illness, it is anticipated that consideration of circadian biology will become an increasingly important component of neonatal care in animals. [Supported by BioGreen21 Program (Code#20070401034006), Republic of Korea].

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