Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability

Seabed characterization through a range of high-resolution acoustic systems - a case study offshore Oman

This study uses three acoustic instruments (different in their operating frequencies, 13, 3.5, and 6–10 kHz, and deployment type, hull-mounted, surface-towed and deep-towed) to investigate and characterize the acoustic response of seafloor NE of Oman in a frequency-independent manner. High-resolution control was achieved by having selected areas of our acoustic transects groundtruthed by sampling and/or sea-floor photography. On the regional scale, the greatest degree of change in backscatter amplitude was correlated with major changes of seabed morphology and lithology. However, small-scale roughness had the biggest effect on amplitude on the local scale, i.e. within each area of specific seafloor type. The study also shows that seafloor reflection amplitude changes are far more easily detected by deep-towed instrument than by surface-towed or hull-mounted systems. Whilst there are significant changes in bioturbation types and density along the transects, the suite of instruments deployed was not able to pick up the effect of the bioturbation on acoustic signals

Ice stream motion facilitated by a shallow-deforming and accreting bed

Ice streams drain large portions of ice sheets and play a fundamental role in governing their response to atmospheric and oceanic forcing, with implications for sea-level change. The mechanisms that generate ice stream flow remain elusive. Basal sliding and/or bed deformation have been hypothesized, but ice stream beds are largely inaccessible. Here we present a comprehensive, multi-scale study of the internal structure of mega-scale glacial lineations (MSGLs) formed at the bed of a palaeo ice stream. Analyses were undertaken at macro- and microscales, using multiple techniques including X-ray tomography, thin sections and ground penetrating radar (GPR) acquisitions. Results reveal homogeneity in stratigraphy, kinematics, granulometry and petrography. The consistency of the physical and geological properties demonstrates a continuously accreting, shallow-deforming, bed and invariant basal conditions. This implies that ice stream basal motion on soft sediment beds during MSGL formation is accommodated by plastic deformation, facilitated by continuous sediment supply and an inefficient drainage system

Heat flow in southern Australia and connections with East Antarctica

Viscosity and melt generation at the base of ice sheets are critically dependent upon heat flow. Yet subglacial heat flow is poorly constrained due to the logistical challenges of obtaining boreholes that intersect the bedrock beneath thick ice cover. Currently, continental estimates of Antarctic heat flow are derived from geophysical methods that provide ambiguous constraints of crustal heat sources, despite their demonstrated importance for accurate predictions of future ice sheet behavior. This study pursues an alternative approach by using heat flow measurements from rock units in the Coompana Province of southern Australia, which represent the geological counterparts of those beneath Wilkes Land in East Antarctica. We present nine new surface heat flow estimates from this previously uncharacterized region, ranging from 40 to 70 mW/m² with an average of 57 ± 3 mW/m². These values compare favorably to recent geophysically derived estimates of 50–75 mW/m² for the Totten Glacier catchment of East Antarctica, and to the single in situ measurement of 75 mW/m² from the Law Dome deep ice borehole. However, they are appreciably lower than the range of 56–120 mW/m² (83 ± 13 mW/m² average) for the abnormally enriched Proterozoic terranes of the Central Australian Heat Flow Province. This study provides the first regional heat flow map of geological provinces formerly contiguous with East Antarctica through the application of continent‐scale heat flow data sets tied to a Jurassic plate tectonic reconstruction for Gondwana. Our approach reveals several discrepancies with current heat flow models derived from geophysical methods and provides a more robust analysis of subglacial heat flow using this plate tectonic synthesis as a proxy for East Antarctica.Alicia Pollett, Derrick Hasterok, Tom Raimondo, Jacqueline A. Halpin, Martin Hand, Betina Bendall, and Sandra McLare