A cryogenic ion trap for single molecule vibrational spectroscopy

We report on an ion trapping system for performing a novel form of cryogenic messenger spectroscopy with single molecule sensitivity. The system features a cryogenic radio-frequency ion trap loaded with single analyte molecules via a quadrupole mass filter. We demonstrate the ability to controllably attach inert gas particles to buffer gas cooled, trapped molecular ions. Sympathetic cooling by co-trapped, laser cooled 88Sr+ further reduces the translational temperature of trapped molecules to the millikelvin regime. We verify the presence of cryogenic "tags" via non-destructive optical mass spectrometry and selectively remove these adducts by resonantly driving vibrational transitions in the tagged molecular ions. This enables us to derive the vibrational spectrum of a single analyte molecule from the frequency dependence of the tag detachment rate. We have demonstrated these capabilities by measuring transitions in the C-H stretching region for single cationic fragments of both indole (C8H7N) and 1,3-benzodioxole (C6H4O2CH2). These capabilities are not reliant on a specific molecular level structure and thus constitute a general, non-destructive method for vibrational spectroscopy of individual molecular ions.

Development and evaluation of the General Surgery Objective Structured Assessment of Technical Skill (GOSATS)

Background

Technical skill acquisition is important in surgery specialty training. Despite an emphasis on competency-based training, few tools are currently available for direct technical skills assessment at the completion of training. The aim of this study was to develop and validate a simulated technical skill examination for graduating (postgraduate year (PGY)5) general surgery trainees.

Methods

A simulated eight-station, procedure-based general surgery technical skills examination was developed. Board-certified general surgeons blinded to the level of training rated performance of PGY3 and PGY5 trainees by means of validated scoring. Cronbach's α was used to calculate reliability indices, and a conjunctive model to set a pass score with borderline regression methodology. Subkoviak methodology was employed to assess the reliability of the pass–fail decision. The relationship between passing the examination and PGY level was evaluated using χ2 analysis.

Results

Ten PGY3 and nine PGY5 trainees were included. Interstation reliability was 0·66, and inter-rater reliability for three stations was 0·92, 0·97 and 0·76. A pass score of 176·8 of 280 (63·1 per cent) was set. The pass rate for PGY5 trainees was 78 per cent (7 of 9), compared with 30 per cent (3 of 10) for PGY3 trainees. Reliability of the pass–fail decision had an agreement coefficient of 0·88. Graduating trainees were significantly more likely to pass the examination than PGY3 trainees (χ2 = 4·34, P = 0·037).

Conclusion

A summative general surgery technical skills examination was developed with reliability indices within the range needed for high-stakes assessments. Further evaluation is required before the examination can be used in decisions regarding certification.

Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study

BACKGROUND

Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery.

METHODS

This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy.

RESULTS

Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51-19.97) than planned admissions (OR: 2.32, 95% CI: 1.43-3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8-51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI.

CONCLUSIONS

After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies.

Setting pass scores for assessment of technical performance by surgical trainees

BACKGROUND

One of the major challenges of competency-based training is defining a score representing a competent performance. The objective of this study was to set pass scores for the Objective Structured Assessment of Technical Skill.

METHODS

Pass scores for the examination were set using three standard setting methods applied to data collected prospectively from first-year surgical residents (trainees). General surgery residents were then assigned an overall pass-fail status for each method. Using a compensatory model, residents passed the eight station examinations if they met the overall pass score; using a conjunctive model, residents passed if they met the overall pass score and passed at least 50 per cent of the stations. The consistency of the pass-fail decision across the three methods, and between a compensatory and conjunctive model, were compared.

RESULTS

Pass scores were stable across all three methods using data from 513 residents, 133 of whom were general surgeons. Consistency of the pass-fail decision across the three methods was 95.5 and 93.2 per cent using compensatory and conjunctive models respectively. Consistency of the pass-fail status between compensatory and conjunctive models for all three methods was also very high (91.7, 95.5 and 96.2 per cent).

CONCLUSION

Consistency in pass-fail status between the various methods builds evidence of validity for the set scores. These methods can be applied and studied across a variety of assessment platforms, helping to increase the use of standard setting for competency-based training.

Transatlantic comparison of the competence of surgeons at the start of their professional career

Background

Although the objective in European Union and North American surgical residency programmes is similar—to train competent surgeons—residents' working hours are different. It was hypothesized that practice-ready surgeons with more working hours would perform significantly better than those being educated within shorter working week curricula.

Methods

At each test site, 21 practice-ready candidate surgeons were recruited. Twenty qualified Canadian and 19 qualified Dutch surgeons served as examiners. At both sites, three validated outcome instruments assessing multiple aspects of surgical competency were used.

Results

No significant differences were found in performance on the integrative and cognitive examination (Comprehensive Integrative Puzzle) or the technical skills test (Objective Structured Assessment of Technical Skill; OSATS). A significant difference in outcome was observed only on the Patient Assessment and Management Examination, which focuses on skills needed to manage patients with complex problems (P &lt; 0·001). A significant interaction was observed between examiner and candidate origins for both task-specific OSATS checklist (P = 0·001) and OSATS global rating scale (P &lt; 0·001) scores.

Conclusion

Canadian residents, serving many more working hours, perform equivalently to Dutch residents when assessed on technical skills and cognitive knowledge, but outperformed Dutch residents in skills for patient management. Secondary analyses suggested that cultural differences influence the assessment process significantly.