Association between cumulative duration of deep anesthesia and postoperative acute kidney injury after noncardiac surgeries: a retrospective observational study.

BACKGROUND: Bispectral index (BIS) is a processed electroencephalography monitoring tool and is widely used in anesthetic depth monitoring. Deep anesthesia exposure may be associated with multiple adverse outcomes. However, the relationship between anesthetic depth and postoperative acute kidney injury (AKI) remains unclear. We sought to determine the effect of BIS-based deep anesthesia duration on postoperative AKI following noncardiac surgery. METHODS: This retrospective study used data from the Vital Signs DataBase, including patients undergoing noncardiac surgeries with BIS monitoring. The BIS values were collected every second during anesthesia. Restricted cubic splines and logistic regression were used to assess the association between the cumulative duration of deep anesthesia and postoperative AKI. RESULTS: 4774 patients were eligible, and 129 (2.7%) experienced postoperative AKI. Restricted cubic splines showed that a cumulative duration of BIS < 45 was nonlinearly associated with postoperative AKI (P-overall = 0.033 and P-non-linear = 0.023). Using the group with the duration of BIS < 45 less than 15 min as the reference, ORs of postoperative AKI were 2.59 (95% confidence interval [CI]:0.60 to 11.09, p = 0.200) in the 15-100 min group, and 4.04 (95%CI:0.92 to 17.76, p = 0.064) in the ≥ 100 min group after adjusting for preoperative and intraoperative covariates in multivariable logistic regression. CONCLUSIONS: The cumulative duration of BIS < 45 was independently and nonlinearly associated with the risk of postoperative AKI in patients undergoing noncardiac surgery.

Mechanisms for NH3 decomposition on Si(100)-(2 x 1) surface: a quantum chemical cluster model study.

In this paper, we present a detailed mechanism for the complete decomposition of NH3 to NHx(a) (x = 0-2). Our calculations show that the initial decomposition of NH3 to NH2(a) and H(a) is facile, with a transition-state energy 7.4 kcal mol-1 below the vacuum level. Further decomposition to N(a) or recombination-desorption to NH3(g) is hindered by a large barrier of approximately 46 kcal mol-1. There are two plausible NH2 decomposition pathways: 1) NH2(a) insertion into the surface Si-Si dimer bond, and 2) NH2(a) insertion into the Si-Si backbond. We find that pathway (1) leads to the formation of a surface Si = N unit, similar to a terminal Si = Nt pair in silicon nitride, Si3N4, while pathway (2) leads to the formation of a near-planar, subsurface Si3N unit, in analogy to a central nitrogen atom (Nc) bounded to three silicon atoms in the Si3N4 environment. Based on these results, a plausible microscopic mechanism for the nitridation of the Si(100)-(2 x 1) surface by NH3 is proposed.