Obstructive sleep apnoea and perioperative complications in bariatric patients.

BACKGROUND: The objective of this study was to determine the relationship between perioperative complications and the severity of obstructive sleep apnoea (OSA) in patients undergoing bariatric surgery who had undergone preoperative polysomnography (PSG). METHODS: The records of 797 patients, age >18 yr, who underwent bariatric operations (442 open and 355 laparoscopic procedures) at Mayo Clinic and were assessed before operation by PSG, were reviewed retrospectively. OSA was quantified using the apnoea-hypopnoea index (AHI) as none (≤ 4), mild (5-15), moderate (16-30), and severe (≥ 31). Pulmonary, surgical, and 'other' complications within the first 30 postoperative days were analysed according to OSA severity. Logistic regression was used to assess the multivariable association of OSA, age, sex, BMI, and surgical approach with postoperative complications. RESULTS: Most patients with OSA (93%) received perioperative positive airway pressure therapy, and all patients were closely monitored after operation with pulse oximetry on either regular nursing floors or in intensive or intermediate care units. At least one postoperative complication occurred in 259 patients (33%). In a multivariable model, the overall complication rate was increased with open procedures compared with laparoscopic. In addition, increased BMI and age were associated with increased likelihood of pulmonary and other complications. Complication rates were not associated with OSA severity. CONCLUSIONS: In obese patients evaluated before operation by PSG before bariatric surgery and managed accordingly, the severity of OSA, as assessed by the AHI, was not associated with the rate of perioperative complications. These results cannot determine whether unrecognized and untreated OSA increases risk.

Carbon-to-carbon identity proton transfers from propyne, acetimide, thioacetaldehyde, and nitrosomethane to their respective conjugate anions in the gas phase. An ab initio study.

Gas-phase acidities of CH3Y (Y: NO, C identical to CH, CH=NH, and CH=S), barriers to the identity proton-transfer CH3Y + CH2=Y- reversible CH2=Y- + CH3Y, as well as geometries and charge distributions of CH3Y, CH2=Y- and the transition states of the proton transfers were determined by ab initio methods at the MP2/6-311 + G(d,p)//MP2/6-311 + G(d,p), B3LYP/6-311 + G(d,p), and BPW-91/6-311 + G-(d,p) levels of theory. The acidities were also calculated at the CCSD(T)/6-311 + G(2df,2p) level. To make more meaningful comparisons, the same quantities for previously studied systems (Y: H, CH=CH2, CH=O, CN, NO2) were recalculated at the levels used in the present work. The geometric parameters as well as the group charges indicate that the transition states for all the reactions are imbalanced, although there is no correlation between the degree of imbalance and the pi-acceptor strength of the Y group. Based on multi-parameter correlations with the field (sigma F), resonance (sigma R), and polarizability effect (sigma alpha) substituent constants, the contributions of each of these effects to the acidities and barriers were evaluated. For the Y groups whose sigma F, sigma R, and sigma alpha are unknown (CH=NH, CH=S, C identical to CH), a method for estimating these substituent constants is proposed. The barriers for the CH3Y/CH2=Y- systems are all lower than for the CH4/CH3- system; this contrasts with the situation in solution where the Y groups lead to an increase in the barrier. The reasons for this reversal are analyzed. We also make an attempt to clarify the issue as to why the transition states of these reactions are imbalanced, a question which continues to draw attention in the literature.

Carbon-to-carbon identity proton transfer from allene, ketene, ketenimine, and thioketene to their respective conjugate anions in the gas phase. An ab initio study.

Gas-phase acidities of CH2=C=X (X = CH2, NH, O, and S) and barriers for the identity proton transfers (X=C=CH2 + HC triple bond C-X- right harpoon over left harpoon -X-C triple bond CH + CH2=C=X) as well as geometries and charge distributions of CH2=C=X, HC triple bond C-X- and the transition states of the proton transfer were determined by ab initio methods at the MP2/6-311+G(d,p)//MP2/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels of theory. The acidities were also calculated at the CCSD(T)/6-311+G(2df,p) level. A major objective of this study was to examine how the enhanced unsaturation of CH2=C=X compared to that of CH3CH=X may affect acidities, transition state imbalances, and intrinsic barriers of the identity proton transfer. The results show that the acidities are all higher while the barriers are lower than for the corresponding CH3CH=X series. The transition states are all imbalanced but less so than for the reactions of CH3CH=X.