Is there a hydrogen bond radius? Evidence from microwave spectroscopy, neutron scattering and X-ray diffraction results

Intermol. distances in $D-H\cdot\cdot\cdot A$ hydrogen bonded systems have usually been interpreted in terms of the van der Waals radii of D and A. In this work, X-ray and neutron diffraction data from the Cambridge Crystal Structure Database (CSD) and the electrostatic potential of A, have been used to define hydrogen bond radii for OH, NH and CH groups. For OH, X-ray and neutron diffraction both give comparable results, validating the X-ray data for defining a hydrogen bond radius. The hydrogen bond radii determined for $C \equiv CH$ and OH groups from CSD anal. are comparable to those detd. from the gas phase rotational spectroscopic data for HCCH and $H_2O$ complexes. For NH as a proton donor, gas phase structural data are scarce and a hydrogen bond radius has been detd. by using X-ray diffraction data only. For the CH group, the histogram of hydrogen bond distances shows a peak recognizable as a hydrogen bond only if it is acidic such as $CCl_3H$, OCH (aldehydic) or CCH (acetylenic). The hydrogen bond radii for OH, NH and acidic CH groups are $0.60 \hspace {2mm} \pm \hspace {2mm} 0.15, \hspace {5mm} 0.76 \hspace {2mm} \pm \hspace {2mm} 0.15 \hspace {5mm} and \hspace {5mm} 1.10 \hspace {2mm} \pm \hspace {2mm} 0.20 \hspace {2mm}\AA$, respectively. For $C-CH_3$ and $CH_2CH_3$, though a peak in the histogram of distances is not found, the distribution of hydrogen bond angles unambiguously shows that the preferred geometry is linear. It appears that a CH group without any electronegative substituents could have a radius larger than $1.2 \AA$ when involved in hydrogen bonding

Pancreatic surgery outcomes: multicentre prospective snapshot study in 67 countries

Background: Pancreatic surgery remains associated with high morbidity rates. Although postoperative mortality appears to have improved with specialization, the outcomes reported in the literature reflect the activity of highly specialized centres. The aim of this study was to evaluate the outcomes following pancreatic surgery worldwide.Methods: This was an international, prospective, multicentre, cross-sectional snapshot study of consecutive patients undergoing pancreatic operations worldwide in a 3-month interval in 2021. The primary outcome was postoperative mortality within 90 days of surgery. Multivariable logistic regression was used to explore relationships with Human Development Index (HDI) and other parameters.Results: A total of 4223 patients from 67 countries were analysed. A complication of any severity was detected in 68.7 percent of patients (2901 of 4223). Major complication rates (Clavien-Dindo grade at least IIIa) were 24, 18, and 27 percent, and mortality rates were 10, 5, and 5 per cent in low-to-middle-, high-, and very high-HDI countries respectively. The 90-day postoperative mortality rate was 5.4 per cent (229 of 4223) overall, but was significantly higher in the low-to-middle-HDI group (adjusted OR 2.88, 95 per cent c.i. 1.80 to 4.48). The overall failure-to-rescue rate was 21 percent; however, it was 41 per cent in low-to-middle-compared with 19 per cent in very high-HDI countries.Conclusion: Excess mortality in low-to-middle-HDI countries could be attributable to failure to rescue of patients from severe complications. The authors call for a collaborative response from international and regional associations of pancreatic surgeons to address management related to death from postoperative complications to tackle the global disparities in the outcomes of pancreatic surgery (NCT04652271; ISRCTN95140761)