The effects of human factor related issues on assessors during the recruitment process for general and vascular surgery in the UK.

INTRODUCTION: Healthcare professionals increasingly recognise how human factors (HF) can contribute to medical error. An understanding of HF is also important during other high stakes activities such as summative assessments or examinations. National organisations hosting such events need to be aware of potential fatigue, boredom and stress that can occur in interviewers during these often repetitive activities. METHODS: A previously validated questionnaire based around the well known HF analysis and classification system (HFACS) was used to evaluate four factors (care and support, asking questions about the role as an interviewer, working within the rules and boundaries, and stress and pressure) at the 2018 UK general and vascular surgery trainee national selection process. RESULTS: A total of 92 questionnaires were completed and analysed (48% response rate). After recoding for negative phrased questions, no significant differences were found between years of experience in the selection process and mean scores obtained for all four factor items. Interviewers had a positive experience during national selection with mean factor scores ranging from 3.84 to 3.98 (out of a maximum satisfaction score of 5). CONCLUSIONS: Organisations need to plan carefully and recognise the human element to ensure that their interviewers are cared for during any high stakes assessment such as national selection. Our work suggests that a positive assessor experience will further help contribute to a reliable and fair recruitment process.

Impact of performance in a mandatory postgraduate surgical examination on selection into specialty training.

BACKGROUND: The Intercollegiate Membership of the Royal College of Surgeons (MRCS) examination is undertaken by large numbers of trainees in the UK and internationally as a mandatory step within surgical training. Unlike some high-stakes medical examinations, the MRCS is yet to be validated. A quantitative study was undertaken to assess its predictive validity by investigating the relationship between MRCS (Parts A and B) and national selection interview scores for general and vascular surgery in the UK. METHODS: Pearson correlation coefficients were used to examine the linear relationship between each assessment, and linear regression analyses were employed to identify potential independent predictors of the national selection score. All UK medical graduates who attempted the interview in 2011-2015 were included. RESULTS: Some 84·4 per cent of the candidates (1231 of 1458) were matched with MRCS data. There was a significant positive correlation between the first attempt score at Part B of the MRCS examination and the national selection score (r = 0·38, P < 0·001). In multivariable analysis, 17 per cent of variance in the national selection first attempt score was explained by the Part B MRCS score and number of attempts (change in R 2 value of 0·10 and 0·07 respectively; P < 0·001). Candidates who required more than two attempts at Part B were predicted to score 8·1 per cent less than equally matched candidates who passed at their first attempt. CONCLUSION: This study supports validity of the MRCS examination, and indicates its predictive value regarding entry into specialist training.

Widening Participation To The Medical Course At Queens University Belfast.

The United Kingdom Clinical Aptitude Test (UKCAT) was introduced to assist in identification of applicants from all levels of society with the appropriate characteristics to become good doctors. Evidence that the UKCAT has achieved such widened participation (WP) in applicants to medical school remains elusive. One of the limitations to WP investigation has been that data on socioeconomic status of applicants to medical schools has been obtained through voluntary submission on application to UKCAT and up to 30% of applications offered either none or only limited information. In this study of local applicants (451 from Northern Ireland) to Queens University Belfast (QUB) for 2012, socioeconomic data was ascertained through post code analysis. These data were utilized to investigate the relationship between affluence, application to the medical school and UKCAT score. Our study has shown that for NI applicants to QUB medical school, postcode /socioeconomic back ground accounts for only 3 percent of UK CAT score variation. We have also shown that our admissions process is largely independent of socioeconomic background. However we have demonstrated that the socioeconomic profile of applicants from Northern Ireland to QUB medical school is such that even if every applicant to QUB in 2012 were offered a place in the medical school the number of applicants from least affluent areas would increase by only 9. In conclusion efforts to achieve meaningful WP must be directed at raising aspirations for a career in Medicine within the community.

[Ru(phen)2dppz](2+) luminescence reveals nanoscale variation of polarity in the cyclodextrin cavity.

Phosphorylation of ß-cyclodextrin enhances binding with Ru(II)polypyridyl complexes, and promotes selectivity based on chirality and ligand hydrophobicity. For [Ru(phen)2dppz](2+), inclusion of dppz results in a dramatic increase in luminescence with multiple lifetimes. The sensitive response of photophysics to the environment reveals nanoscale variation of polarity.

The use of an acellular porcine dermal collagen implant in the repair of complex abdominal wall defects: a European multicentre retrospective study.

BACKGROUND: The use of biological materials for the repair of complex abdominal wall defects has increased over the years; however, the role of these materials in routine practice remains unclear. The aim of the study was to evaluate clinical outcomes following the use of Permacol™ porcine collagen surgical implant in complex abdominal wall repair. METHODS: This subset analysis of seven European sites from a multicentre retrospective study included patients undergoing open or laparoscopic surgery and treated with Permacol™ surgical implant. Inguinal, parastomal, diaphragmatic, perineal, and hiatal repairs were excluded. Only patients with at least 12 months of follow-up after surgery were included. RESULTS: A total of 109 patients (56 males and 53 females) were included. Patients had a median of two comorbidities (range 0-6). Thirty-three per cent of patients were treated for recurrent hernia. All but one case used an open approach. Sixty-six per cent were Center for Disease Control wound class II-IV at the time of surgery. Fascial closure was achieved in 69%. Median follow-up length was 720 days (range 368-2857). Recurrence rates at 1 and 2 years were 9.2 and 18.3 %, respectively, and were higher in cases without fascial closure. One-year recurrence was higher following use of an onlay technique (P = 0.025). In a multivariate analysis, among 16 comorbidities examined only fascial closure significantly impacted 1-year recurrence (P = 0.049). CONCLUSIONS: Data from this large retrospective multicentre European study strongly suggest the use of Permacol™ porcine collagen surgical implant to be safe and effective for complex abdominal wall repair. The recurrence rate was impacted by fascial closure.

Benzotriazole and 5-methylbenzotriazole in recycled water, surface water and dishwashing detergents from Perth, Western Australia: analytical method development and application.

A simplified and sensitive liquid chromatography mass spectrometry (LC-MS) method without requiring sample pre-concentration was successfully developed for detecting the occurrence of ultra-low (ng L(-1)) concentrations of benzotriazole (BTri), and its derivative 5-methyl benzotriazole (5-MeBT) in various Western Australian environmental water samples. The method detection limit was 2 ng L(-1), providing similar detection limits to other more process intensive methods where pre-concentration using solid phase extraction (SPE) was employed. The method was used to assess the occurrence of BTri and 5-MeBT in wastewater and surface water samples. Over a period of 12 months, BTri and 5-MeBT concentrations in secondary treated wastewater were measured, with the highest BTri and 5-MeBT concentrations observed during winter months at 78 ng L(-1) and 21 ng L(-1), respectively. The method was also used to assess the removal efficiency of BTri and 5-MeBT through an advanced water recycling plant (AWRP). While BTri was more persistent than 5-MeBT, both compounds were removed from the AWRP to <10 ng L(-1) (BTri) and <2 ng L(-1) (5-MeBT), with reverse osmosis (RO) providing the most effective treatment process for their removal.

Fate of benzotriazole and 5-methylbenzotriazole in recycled water recharged into an anaerobic aquifer: column studies.

The fate of benzotriazole (BTri) and 5-methylbenzotriazole (5-MeBT) was investigated under anaerobic conditions at nano gram per litre concentrations in large-scale laboratory columns to mimic a managed aquifer recharge replenishment strategy in Western Australia. Investigations of BTri and 5-MeBT sorption behaviour demonstrated mobility of the compounds with retardation coefficients of 2.0 and 2.2, respectively. Degradation processes over a period of 220 days indicated first order biodegradation of the BTri and 5-MeBT under anaerobic aquifer conditions after a biological lag-time of approximately 30-60 days. Biodegradation half-lives of 29 ± 2 and 26 ± 1 days for BTri and 5-MeBT were respectively observed, with no threshold effect to biodegradation observed at the 200 ng L(-1). The detection of degradation products provided further evidence of BTri and 5-MeBT biodegradation. These results suggested that if BTri and 5-MeBT were present in recycled water recharged to the Leederville aquifer, biodegradation during aquifer passage is likely given sufficient aquifer residence times or travel distances between recycled water injection and groundwater extraction.

Fate of N-nitrosodimethylamine in recycled water after recharge into anaerobic aquifer.

Laboratory and field experiments were undertaken to assess the fate of N-nitrosodimethylamine (NDMA) in aerobic recycled water that was recharged into a deep anaerobic pyritic aquifer, as part of a managed aquifer recharge (MAR) strategy. Laboratory studies demonstrated a high mobility of NDMA in the Leederville aquifer system with a retardation coefficient of 1.1. Anaerobic degradation column and (14)C-NDMA microcosm studies showed that anaerobic conditions of the aquifer provided a suitable environment for the biodegradation of NDMA with first-order kinetics. At microgram per litre concentrations, inhibition of biodegradation was observed with degradation half-lives (260±20 days) up to an order of magnitude greater than at nanogram per litre concentrations (25-150 days), which are more typical of environmental concentrations. No threshold effects were observed at the lower ng L(-1) concentrations with NDMA concentrations reduced from 560 ng L(-1) to <6 ng L(-1) over a 42 day 14C-NDMA aerobic microcosm experiment. Aerobic (14)C-NDMA microcosm studies were also undertaken to assess potential aerobic degradation, likely to occur close to the recharge bore. These microcosm experiments showed a faster degradation rate than anaerobic microcosms, with a degradation half-life of 8±2 days, after a lag period of approximately 10 days. Results from a MAR field trial recharging the Leederville aquifer with aerobic recycled water showed that NDMA concentrations reduced from 2.5±1.0 ng L(-1) to 1.3±0.4 ng L(-1) between the recharge bore and a monitoring location 20 m down gradient (an estimated aquifer residence time of 10 days), consistent with data from the aerobic microcosm experiment. Further down gradient, in the anaerobic zone of the aquifer, NDMA degradation could not be assessed, as NDMA concentrations were too close to their analytical detection limit (<1 ng L(-1)).

Fate of N-nitrosomorpholine in an anaerobic aquifer used for managed aquifer recharge: a column study.

The fate of N-nitrosomorpholine (NMOR) was evaluated at microgram and nanogram per litre concentrations. Experiments were undertaken to simulate the passage of groundwater contaminants through a deep anaerobic pyritic aquifer system, as part of a managed aquifer recharge (MAR) strategy. Sorption studies demonstrated the high mobility of NMOR in the Leederville aquifer system, with retardation coefficients between 1.2 and 1.6. Degradation studies from a 351 day column experiment and a 506 day stop-flow column experiment showed an anaerobic biologically induced reductive degradation process which followed first order kinetics. A biological lag-time of less than 3 months and a transient accumulation of morpholine (MOR) were also noted during the degradation. Comparable half-life degradation rates of 40-45 days were observed over three orders of magnitude in concentration (200 ng L(-1) to 650 µg L(-1)). An inhibitory effect on microorganism responsible to the biodegradation of NMOR at 650 µg L(-1) or a threshold effect at 200 ng L(-1) was not observed during these experiments.

Nurse-led rapid access vascular examination clinic triage reduces inappropriate referrals for peripheral arterial disease.

INTRODUCTION: Peripheral arterial disease causing intermittent claudication (IC) causes decreased quality of life and significant morbidity. We hypothesized that triage of patients referred with suspected IC at a nurse-led rapid access vascular examination (RAVE) clinic would identify those patients requiring vascular surgery assessment. METHODS: A prospective cohort study was performed. Patients referred with suspected IC were assessed using the Edinburgh claudication questionnaire (ECQ) and arterial Doppler assessment with segmental waveform analysis and calculation of ankle brachial pressure index (ABPI). Data were collected regarding cardiovascular risk and its modification. RESULTS: Of 451 consecutive patients, mean age was 65 years (range 30-89). Cardiovascular risk factors included: 173/451 (38%) current smokers (162/451 (36%) were ex-smokers); diabetes, 22%; hypertension, 46%; ischaemic heart disease (angina), 29%; dyslipidaemia, 27%. Therapeutic risk modifications included: antiplatelet therapy, 64.4%; lipid-lowering therapy, 57.8%. abnormal ABPI readings were present in 264/451 (59%), with ratio <0.9 in 209/451 (46.3%), >1.3 in 48/451 (10.6%), and incompressible vessels 7/451 (1.5%). Normal ABPI (ratio >0.9 and <1.3, triphasic Doppler waveforms) were found in 187/451 (41%), these patient were considered inappropriate referrals. Considering those patient with PAD diagnosed on abnormal ABPI (<0.9 or >1.3), Doppler waveform analysis was more sensitive and specific than ECQ. CONCLUSIONS: Diagnosis of IC with clinical history alone is inaccurate in 41 percent of cases, leading to inappropriate referral to vascular surgery. Doppler waveform analysis had excellent sensitivity and specificity for prediction of ABPI <0.9. ABPI measurement in primary care could result in a more efficient use of clinical resources.

Triglyceride to HDL ratio is a reliable predictor of adverse outcomes in risk stratification for candidates undergoing abdominal aortic surgery.

INTRODUCTION: The aim of this study was to establish if an elevated triglyceride to high-density lipoprotein (HDL) ratio (THR) is not only a risk factor for cardiovascular and overall morbidity as the updated evidence shows, but could also be employed as a significant predictor for surgical adverse outcomes and hence be a valid tool for risk stratification of candidates undergoing abdominal aortic surgery. METHODS: This is a single-centre retrospective analysis of 2224 patients who underwent open abdominal aortic surgery between January 1996 and 2009. This cohort was divided into quartiles of THR. A list of covariates has been entered with THR into a multiple logistic model with forwards stepwise selection. The obtained result is an adjusted model, conceived to establish the association between THR and perioperative adverse events. Discrimination of the model so obtained and comparison with vascular-specific risk stratification scoring systems were evaluated using the area under the receiver operating characteristic (AUROC). RESULTS: THR had the highest predictive value for the outcomes of interest. The adjusted odds ratios (ORs) per every 0.1 augmentation of THR were 1.41 (1.08-1.88) for cardiac, 1.38 (1.09-1.84) for respiratory, 1.27 (1.06-1.54) for renal adverse events and 1.02 (0.84-1.23) for mortality. Regarding mortality, either of the scoring systems Vascular Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) and customised probability index (CPI) and the THR ranked as moderate discriminators, with THR performing the worst (AUROC 0.71) compared with Vascular POSSUM (AUROC 0.76) and CPI (AUROC 0.78). THR performed as a very strong predictor of morbidity (AUROC 0.86), ranking above Vascular POSSUM (AUROC 0.72). CONCLUSIONS: THR is a significant predictor of perioperative morbidity and mortality. THR offers a broad outlook on the metabolic state of patients undergoing major abdominal aortic surgery and hence their propensity to adverse events, allowing us to risk-stratify the prognostic outcome of surgical intervention and possibly intervene preoperatively to optimise results.

Do Doppler waveforms at the common femoral artery accurately predict iliac stenosis?

OBJECTIVE: Evaluate whether common femoral artery (CFA) Doppler waveform assessment predicted the presence of significant iliac artery stenosis as visualised on magnetic resonance angiography (MRA). METHOD: Three-year retrospective study of patients investigated using CFA Doppler waveforms and MRA. The patients were identified from vascular/radiology databases. Waveforms were reported real time as monophasic, biphasic or triphasic. Results were compared with MRA findings. RESULTS: In 76 patients, 119 waveforms were assessed. MRA demonstrated 37 iliac vessels with significant stenosis. 32 (86%) had abnormal waveforms (monophasic/biphasic), 5 were triphasic. In 82 cases where MRA showed no significant stenosis, waveforms were abnormal in 35 (43%). Abnormal CFA waveforms have sensitivity of 86% and specificity of 57%. Monophasic waveforms alone were more specific (88%) but less sensitive (57%) for predicting iliac lesions. CONCLUSION: Whilst CFA waveform morphology is a useful adjunct in detection of iliac disease, normal triphasic waveforms do not exclude iliac stenosis.

Successful delayed secondary open conversion after endovascular repair using partial explantation technique: a single-center experience.

BACKGROUND: Endovascular aneurysm repair (EVAR) reduces the morbidity and mortality associated with abdominal aortic aneurysm repair, but in some patients endoleak or aneurysm expansion may necessitate secondary open conversion (SOC). We reviewed the outcomes after delayed SOC following EVAR in consecutive patients at a single center. METHODS: We retrospectively reviewed all patients undergoing EVAR to identify a cohort undergoing delayed SOC in a single center between 1998 and 2008. We analyzed delayed SOC patients for operative indications, technique, and early outcomes. We made specific comment on the surgical techniques used, with respect to partial or total endograft explantation. RESULTS: Delayed SOC was carried out in 10/285 (3.5%) consecutive patients implanted with the Zenith endograft; during this period, two further patients had SOC after initial EVAR in another center. Graft types were Zenith (n = 10), Talent (n = 1), and AneuRx (n = 1). Indications for open conversion were infected graft (n = 3), sac expansion (n = 3), type 1 endoleak (n = 2), type 2 endoleak (n = 2), juxtarenal aneurysm (n = 1), and rupture (n = 1). Explantation techniques were partial explantation with in situ replacement (n = 7), full explantation with axillobifemoral bypass (n = 3), in situ replacement (n = 1), and suturing (n = 1)Complete stent explantation was required in 4 patients with axillo-bifemoral bypass in three of them. 7 patients had partial stent explantation and one patient stent was left insitu. Postoperative morbidities included myocardial infarction (n = 1), renal dialysis (n = 1), and chest infection (n = 3). No 30-day mortality was noted, and all patients were discharged from hospital and remain well with median follow-up of 5 months (interquartile range 1.7-26.7). CONCLUSION: SOC after EVAR is feasible in selected patients with low morbidity and mortality. Partial explantation with in situ replacement, in the absence of sepsis, may be the preferred revascularization option but may require long-term follow-up.

The role of transthoracic echocardiography in embolic acute limb ischaemia.

INTRODUCTION: Embolic acute limb ischaemia (ALI) is commonly treated by re-vascularization and long-term anticoagulant therapy. Transthoracic echocardiography (TTE) is commonly used to screen for cardiac embolic source, but may not affect management. REPORT: We reviewed 115 consecutive patients with embolic ALI, 61% underwent TTE, with cardiac thrombus identified in only 3%. Incidental severe abnormalities requiring further cardiological investigation were detected in 19% of patients. Inpatient TTE did not affect mortality, morbidity, amputation rate, or anticoagulation. DISCUSSION: Transthoracic echocardiography seldom identifies a cardiac embolic source, but identifies many patients with severe incidental cardiac abnormalities, suggesting cardiology screening of these patients remains important.

Positive fluid balance is associated with complications after elective open infrarenal abdominal aortic aneurysm repair.

BACKGROUND: Open abdominal aortic aneurysm (AAA) repair is associated with cardiac and respiratory complications and an overall mortality rate of 2 to 8%. We hypothesised that excessive fluid administration during the perioperative period contributes to complications and poor outcome after AAA repair. METHODS: This was a retrospective cohort study. Medical records were analysed for fluid balance and complications in 100 consecutive patients treated by open AAA repair at a single centre between 2002-2005. Mortality and all major adverse events (MAE) such as myocardial infarction (MI), cardiac arrhythmia (Arr), pulmonary oedema (PO), pulmonary infection (PI), and acute renal failure (ARF) were included in the analysis. Level of care and hospital stay, were also recorded. RESULTS: There were no in-hospital deaths. MAE occurred in 40/100 (40%): MI (6%); Arr (14%); PO (14%); PI (25%); ARF (8%). Complications were not predicted by preoperative cardiovascular risk factors, operative and clamp time, or blood loss. Patients with complications had significantly greater cumulative positive fluid balance on postoperative day 0 (p<0.01), day 1 (p<0.05), day 2 (p<0.03) and day 3 (p<0.04). This relationship also existed for individual complications such as MI, and pulmonary oedema. These patients had significantly longer ICU/HDU (p<0.002) and hospital stay (p<0.0001). CONCLUSIONS: Serious complications are common after elective open AAA repair, and we have shown that positive fluid balance is predictive of major adverse events increased HDU/ICU and overall hospital stay.

Validity of the Hardman index to predict outcome in ruptured abdominal aortic aneurysm.

This study assessed the validity of the Hardman index in predicting outcome following open repair of ruptured abdominal aortic aneurysm and whether this scoring system can be used reliably to select patients for surgical repair. Patients undergoing open repair of ruptured abdominal aortic aneurysm in two university teaching hospitals over a 5-year period were identified from a computerized hospital database. Thirty-day mortality was the main outcome measure. Five Hardman index factors were calculated and related to outcome retrospectively. There were 178 patients with a mean age of 73.9 years (range 51-94) and a male to female ratio of 5.4:1. The overall in-hospital mortality was 57.3% (102/178). Univariate analysis of risk factors showed that age >76 years (P = 0.007, odds ratio [OR] 2.34, 95% confidence interval [CI] 1.26-4.37) and electrocardiograghic evidence of ischemia on admission (P = 0.002, OR 3.75, 95% CI 1.57-8.93) were associated with high mortality. However, loss of consciousness (P = 0.155, OR 1.56, 95% CI 0.85-2.86), hemoglobin <9 g/dL (P = 0.118, OR 1.89, 95% CI 0.85-4.22), and serum creatinine >0.19 mmol/L (P = 0.691, OR 1.25, 95% CI 0.42-3.70) were not significant predictors of mortality. Using a multivariate analysis, age >76 years (P = 0.043, OR 2.29, 95% CI 1.03-5.11) and myocardial ischemia (P = 0.029, OR 2.93, 95% CI 1.12-7.67) were again found to be the significant predictors of mortality. The operative mortality was 44%, 46%, 68%, 79%, and 100% for Hardman scores of 0, 1, 2, 3, and 4, respectively. No patient had a score of 5. The Hardman index is not a reliable predictor of outcome following repair of ruptured abdominal aortic aneurysm. High-risk patients may still survive and should not be denied surgical repair based on the scoring system alone. Further evaluation of the risk factors is required to reliably and justifiably exclude those patients in whom the intervention is inappropriate.

Clinical effectiveness and cost-effectiveness of laparoscopic surgery for colorectal cancer: systematic reviews and economic evaluation.

OBJECTIVE: The aim of this study was to determine the clinical effectiveness and cost-effectiveness of laparoscopic, laparoscopically assisted (hereafter together described as laparoscopic surgery) and hand-assisted laparoscopic surgery (HALS) in comparison with open surgery for the treatment of colorectal cancer. DATA SOURCES: Electronic databases were searched from 2000 to May 2005. A review of economic evaluations was undertaken by the National Institute for Health and Clinical Excellence in 2001. This review was updated from 2000 until July 2005. REVIEW METHODS: Data from selected studies were extracted and assessed. Dichotomous outcome data from individual trials were combined using the relative risk method and continuous outcomes were combined using the Mantel-Haenszel weighted mean difference method. Summaries of the results from individual patient data (IPD) meta-analyses were also presented. An economic evaluation was also carried out using a Markov model incorporating the data from the systematic review. The results were first presented as a balance sheet for comparison of the surgical techniques. It was then used to estimate cost-effectiveness measured in terms of incremental cost per life-year gained and incremental cost per quality-adjusted life-year (QALY) for a time horizon up to 25 years. RESULTS: Forty-six reports on 20 studies [19 randomised controlled trials (RCTs) and one IPD meta-analysis] were included in the review of clinical effectiveness. The RCTs were of generally moderate quality with the number of participants varying between 16 and 1082, with 10 having less than 100 participants. The total numbers of trial participants who underwent laparoscopic or open surgery were 2429 and 2139, respectively. A systematic review of four papers suggested that laparoscopic surgery is more costly than open surgery. However, the data they provided on effectiveness was poorer than the evidence from the review of effectiveness. The estimates from the systematic review of clinical effectiveness were incorporated into a Markov model used to estimate cost-effectiveness for a time horizon of up to 25 years. In terms of incremental cost per life-year, laparoscopic surgery was found to be more costly and no more effective than open surgery. With respect to incremental cost per QALY, few data were available to differentiate between laparoscopic and open surgery. The results of the base-case analysis indicate that there is an approximately 40% chance that laparoscopic surgery is the more cost-effective intervention at a threshold willingness to pay for a QALY of pound 30,000. A second analysis assuming equal mortality and disease-free survival found that there was an approximately 50% likelihood at a similar threshold value. Broadly similar results were found in the sensitivity analyses. A threshold analysis was performed to investigate the magnitude of QALY gain associated with quicker recovery following laparoscopic surgery required to provide an incremental cost per QALY of pound 30,000. The implied number of additional QALYs required would be 0.009-0.010 compared with open surgery. CONCLUSIONS: Laparoscopic resection is associated with a quicker recovery (shorter time to return to usual activities and length of hospitalisation) and no evidence of a difference in mortality or disease-free survival up to 3 years following surgery. However, operation times are longer and a significant number of procedures initiated laparoscopically may need to be converted to open surgery. The rate of conversion may be dependent on experience in terms of both patient selection and performing the technique. Laparoscopic resection appears more costly to the health service than open resection, with an estimated extra total cost of between pound 250 and pound 300 per patient. In terms of relative cost-effectiveness, laparoscopic resection is associated with a modest additional cost, short-term benefits associated with more rapid recovery and similar long-term outcomes in terms of survival and cure rates up to 3 years. Assuming equivalence of long-term outcomes, a judgement is required as to whether the benefits associated with earlier recovery are worth this extra cost. The long-term follow-up of the RCT cohorts would be very useful further research and ideally these data should be incorporated into a wider IPD meta-analysis. Data on the long-term complications of surgery such as incisional hernias and differences in outcomes such as persisting pain would also be valuable. Once available, further data on both costs and utilities should be included in an updated model. At this point, further consideration should then be given as to whether additional data should be collected within ongoing trials. Few data were available to assess the relative merits of HALS. Ideally, there should be more data from methodologically sound RCTs. Further research is needed on whether the balance of advantages and disadvantages of laparoscopic surgery varies within subgroups based on the different stages and locations of disease. Research relating to the effect of experience on performance is also required.

Use of polymer mats in series for sequential reactive barrier remediation of ammonium-contaminated groundwater: field evaluation.

A pilot-scale field trial was undertaken to evaluate the potential of in situ polymer mats (installed in series) as permeable reactive barriers within a treatment wall remediation system to induce sequential bioremediation of ammonium-contaminated groundwater. The treatment wall consisted of 10 m wide impermeable wings on either side of a 0.75 m wide permeable reactive zone flow-through box. Two polymer mats were positioned in the flow-through box. The upgradient polymer mat within the flow-through box was used to deliver oxygen to induce bacterial nitrification of the ammonium to nitrite/nitrate as the groundwater moved past. The downgradient polymer mat delivered ethanol to induce bacterial denitrification of the nitrite/nitrate to produce nitrogen gas. The field trial was carried out at a near-shore location. Initially the flow-through box was left open; however, this resulted in substantial groundwater mixing, which inhibited sequential remediation. Once the flow-through box was in-filled with gravel, groundwater mixing was reduced, achieving a greater than 90% reduction in total N. Estimated first-order half-lives for nitrification and denitrification rates were 1.2 and 0.4 d, respectively. Field nitrification half-lives were approximately an order of magnitude greater than rates determined in large-scale columns using soil and groundwater from the site, while denitrification half-lives were similar. The results of this pilot-scale field trial indicate that sequential bioremediation of ammonium-contaminated groundwater at field scale is feasible using in situ polymer mats as permeable reactive barriers, although hydraulic conditions can be complex in such barrier systems.

The production of oxidants in Europa's surface.

The oxidants produced by radiolysis and photolysis in the icy surface of Europa may be necessary to sustain carbon-based biochemistry in Europa's putative subsurface ocean. Because the subduction of oxidants to the ocean presents considerable thermodynamic challenges, we examine the formation of oxygen and related species in Europa's surface ice with the goal of characterizing the chemical state of the irradiated material. Relevant spectral observations of Europa and the laboratory data on the production of oxygen and related species are first summarized. Since the laboratory data are incomplete, we examine the rate equations for formation of oxygen and its chemical precursors by radiolysis and photolysis. Measurements and simple rate equations are suggested that can be used to characterize the production of oxidants in Europa's surface material and the chemical environment produced by radiolysis. Possible precursor molecules and the role of radical trapping are examined. The possibility of oxygen reactions on grain surfaces in Europa's regolith is discussed, and the earlier estimates of the supply of O(2) to the atmosphere are increased.

Use of polymer mats in series for sequential reactive barrier remediation of ammonium-contaminated groundwater: laboratory column evaluation.

Large-scale column experiments were undertaken to evaluate the potential of in situ polymer mats (installed in series) to be used as permeable reactive barriers for delivery of oxidants and reductants to induce sequential bioremediation of ammonium-contaminated groundwater (approximately 120mg L(-1) NH4+-N), without bioaugmentation. The strategy was for the first group of polymer mats to deliver oxygen to induce bacterial nitrification of the ammonium to nitrite/ nitrate as the groundwater moved past and for the second group of polymer mats to deliver hydrogen or ethanol, to induce bacterial denitrification of the nitrite/nitrate to produce nitrogen gas. Once purging of the first polymer mat commenced, ammonium concentrations decreased downgradient from the polymer mats. Nitrification rates increased and stabilized over the 6-month experiment, with stable nitrification half-lives in the range 0.07-0.25 days. Nitrification most likely occurred in a biologically active zone at the polymer wall/aqueous interface. With hydrogen delivery via the polymer mats, a denitrification half-life (nitrate plus nitrite removal) of 3.5 days was induced. Denitrification rates were significantly enhanced when ethanol was delivered via a polymer mat, with denitrification half-lives in the range of 0.12-0.34 days. Nitrification/ denitrification rates were maintained for groundwater flow rates up to 300 m yr(-1), suggesting oxygen and ethanol delivery rates via the polymer mats were sufficient not to limit nitrification or denitrification. In soil columns, the polymer mat delivery system provided an effective and reliable technique for delivery of oxygen and hydrogen or ethanol for sequential nitrification/denitrification of ammonium-contaminated groundwater. Scale-up of this concept to a field pilot-scale is currently underway.