Evidence of Isotopic Fractionation During Vapor Exchange Between the Atmosphere and the Snow Surface in Greenland.

Several recent studies from both Greenland and Antarctica have reported significant changes in the water isotopic composition of near-surface snow between precipitation events. These changes have been linked to isotopic exchange with atmospheric water vapor and sublimation-induced fractionation, but the processes are poorly constrained by observations. Understanding and quantifying these processes are crucial to both the interpretation of ice core climate proxies and the formulation of isotope-enabled general circulation models. Here, we present continuous measurements of the water isotopic composition in surface snow and atmospheric vapor together with near-surface atmospheric turbulence and snow-air latent and sensible heat fluxes, obtained at the East Greenland Ice-Core Project drilling site in summer 2016. For two 4-day-long time periods, significant diurnal variations in atmospheric water isotopologues are observed. A model is developed to explore the impact of this variability on the surface snow isotopic composition. Our model suggests that the snow isotopic composition in the upper subcentimeter of the snow exhibits a diurnal variation with amplitudes in δ18O and δD of ~2.5‰ and ~13‰, respectively. As comparison, such changes correspond to 10-20% of the magnitude of seasonal changes in interior Greenland snow pack isotopes and of the change across a glacial-interglacial transition. Importantly, our observation and model results suggest, that sublimation-induced fractionation needs to be included in simulations of exchanges between the vapor and the snow surface on diurnal timescales during summer cloud-free conditions in northeast Greenland.

Validation of subjective rating scales for assessment of surgical workspace during laparoscopy.

BACKGROUND: Recently, studies have focused on how to optimize laparoscopic surgical workspace by changes in intra-abdominal pressure, level of muscle relaxation or body position, typically evaluated by surgeons using subjective rating scales. We aimed to validate two rating scales by having surgeons assess surgical workspace in video sequences recorded during laparoscopic surgery. METHOD: Video sequences were obtained from laparoscopic procedures. Eight experienced surgeons assessed the video sequences on a categorical 5-point scale and a numerical 10-point rating scale. Intraclass correlations coefficients (ICC) and 95% confidence intervals (CI) were calculated for intra- and inter-rater reliability. RESULTS: The 5-point rating scale had an intra-rater ICC of 0.76 (0.69; 0.83) and an inter-rater ICC of 0.57 (0.45; 0.68), corresponding to excellent and fair reliability, respectively. The 10-point scale had an intra-rater ICC of 0.86 (0.82; 0.89) and an inter-rater ICC of 0.54 (0.39; 0.68), corresponding to excellent and fair as well. All surgeons used the full range of the 5-point scale, but only one surgeon used the full range of the 10-point scale. CONCLUSION: In conclusion, both scales showed excellent intra-rater and fair inter-rater reliability for assessing surgical workspace in laparoscopy. The 5-point surgical rating scale had all categories employed by all surgeons.

Influence of deep neuromuscular block on the surgeons assessment of surgical conditions during laparotomy: a randomized controlled double blinded trial with rocuronium and sugammadex.

BACKGROUND: During laparotomy, surgeons may experience difficult surgical conditions if the patient's abdominal wall or diaphragm is tense. Deep neuromuscular block (NMB), defined as a post-tetanic-count (PTC) between 0-1, paralyses the abdominal wall muscles and the diaphragm. We hypothesized that deep NMB (PTC 0-1) would improve subjective ratings of surgical conditions during upper laparotomy as compared with standard NMB. METHODS: This was a double blinded, randomized study. A total of 128 patients undergoing elective upper laparotomy were randomized to either continuous deep NMB (infusion of rocuronium 2 mg ml -1 ) or standard NMB (bolus of rocuronium 10 mg or increased depth of anaesthesia). Surgical conditions were evaluated using a 5-point subjective rating scale (1: extremely poor, 5: optimal) every 30 min. Primary outcome was the average of scores for a patient's surgical conditions. Other outcomes were surgical rating score during fascial closure, episodes of a need to optimize surgical conditions, occurrence of wound dehiscence, and wound infection. RESULTS: Deep compared with standard NMB resulted in better ratings of surgical conditions; median 4.75 (range 3-5) compared with 4.00 (range 1-5) ( P <0.001), respectively. Deep compared with standard NMB resulted in better ratings of surgical conditions during fascial closure ( P <0.001), fewer episodes of need to optimize surgical conditions ( P <0.001), and fewer incidents with sudden movements ( P <0.001). No differences in operating time, occurrence of wound infection, and wound dehiscence were found. CONCLUSIONS: Deep NMB compared with standard NMB resulted in better subjective ratings of surgical conditions during laparotomy. CLINICAL TRIAL REGISTRATION: NCT02140593.

Is deep neuromuscular blockade beneficial in laparoscopic surgery? Yes, probably.

BACKGROUND: Deep neuromuscular blockade during laparoscopic surgery may provide some clinical benefit. We present the 'Pro-' argument in this paired position paper. METHODS: We reviewed recent evidence from a basic database of references which we agreed on with the 'Con-' side, and present this in narrative form. We have shared our analysis and text with the authors of the 'Con-' side of these paired position papers during the preparation of the manuscripts. RESULTS: There are a few low risk of bias studies indicating that use of deep neuromuscular blockade improve surgical conditions and improve patient outcomes such as post-operative pain in laparoscopic surgery. CONCLUSION: Our interpretation of recent findings is that there is reason to believe that there may be some patient benefit of deep neuromuscular blockade in this context, and more detailed study is needed.

Optimising abdominal space with deep neuromuscular blockade in gynaecologic laparoscopy--a randomised, blinded crossover study.

BACKGROUND: Insufflation of the abdomen during laparoscopy improves surgical space, but may cause post-operative shoulder pain. The incidence of shoulder pain is reduced using a lower insufflation pressure, but this may, however, compromise the surgical space. We aimed at investigating whether deep neuromuscular blockade (NMB) would enlarge surgical space, measured as the distance from the sacral promontory to the trocar in patients undergoing gynaecologic laparoscopy. METHODS: Fourteen patients were randomised in an assessor-blinded crossover design. The distance from the sacral promontory to the trocar was measured during deep NMB and without NMB at pneumoperitoneum 8 and 12 mmHg both. Additionally, we assessed surgical conditions while suturing the abdominal fascia using a 4-point subjective rating scale. Deep NMB was established with rocuronium and reversed with sugammadex. RESULTS: At 12 mmHg pneumoperitoneum, deep NMB improved surgical space with a mean of 0.33 cm (95% confidence interval 0.07-0.59) (P=0.01, paired t-test) compared with no NMB. At 8 mmHg pneumoperitoneum deep NMB improved surgical space with a mean of 0.3 cm (95% confidence interval, 0.06-0.54) (P=0.005) compared with no NMB. Deep NMB resulted in significantly better ratings of surgical conditions during suturing of the fascia (P=0.03, Mann-Whitney U-test). CONCLUSION: Deep NMB enlarged surgical space measured as the distance from the sacral promontory to the trocar. The enlargement, however, was minor and the clinical significance is unknown. Moreover, deep NMB improved surgical conditions when suturing the abdominal fascia.

Neuromuscular blockade for optimising surgical conditions during abdominal and gynaecological surgery: a systematic review.

BACKGROUND: The level of neuromuscular blockade (NMB) that provides optimal surgical conditions during abdominal surgery has not been well established. The aim of this systematic review was to evaluate current evidence on the use of neuromuscular blocking agents in order to optimise surgical conditions during laparoscopic procedures and open abdominal surgery. METHODS: A wide search was performed in PubMed, Cochrane library and Embase with systematic approach including PRISMA recommendations. Individual risk of bias was assessed and systematic data extraction were performed. RESULTS: Fifteen studies with data from 998 patients were included. There is good evidence that the use of deep NMB compared with moderate NMB is associated with optimised surgical conditions during laparoscopic cholecystectomy, hysterectomy and nephrectomy/prostatectomy. In laparoscopic cholecystectomy during low pressure pneumoperitoneum, deep NMB marginally improves the surgical conditions. However, to ensure acceptable surgical conditions, it may be necessary to increase the intra-abdominal pressure in up to half of the patients regardless of level of NMB. There is good evidence that moderate NMB improves surgical conditions in some cases during open radical retropubic prostatectomy. However, good and excellent surgical conditions may be achievable even without NMB. There is good evidence to recommend deep NMB in laparoscopic cholecystectomy, nephrectomy and prostatectomy to improve surgical conditions. There is insufficient evidence to recommend an ideal level of NMB creating optimal surgical condition during laparotomy. CONCLUSION: Use of deep NMB in certain laparoscopic procedures may improve surgical conditions. In open abdominal surgery, use of NMB may optimise surgical conditions under certain circumstances.