Systems approaches to surgical quality and safety: from concept to measurement

OBJECTIVE: This approach provides the basis of our research program, which aims to expand operative assessment beyond patient factors and the technical skills of the surgeon; to extend assessment of surgical skills beyond bench models to the operating theater; to provide a basis for assessing interventions; and to provide a deeper understanding of surgical outcomes. SUMMARY BACKGROUND DATA: Research into surgical outcomes has primarily focused on the role of patient pathophysiological risk factors and on the skills of the individual surgeon. However, this approach neglects a wide range of factors that have been found to be of important in achieving safe, high-quality performance in other high-risk environments. The outcome of surgery is also dependent on the quality of care received throughout the patient's stay in hospital and the performance of a considerable number of health professionals, all of whom are influenced by the environment in which they work. METHODS: Drawing on the wider literature on safety and quality in healthcare, and recent papers on surgery, this article argues for a much wider assessment of factors that may be relevant to surgical outcome. In particular, we suggest the development of an "operation profile" to capture all the salient features of a surgical operation, including such factors as equipment design and use, communication, team coordination, factors affecting individual performance, and the working environment. Methods of assessing such factors are outlined, and ethical issues and other potential concerns are discussed.     

In vivo effects of toxaphene on calmodulin-regulated calcium-pump activity in rat brain

In vivo effect of toxaphene on calcium pump activity in rat brain P2 fraction was studied. Male Sprague-Dawley rats (200-250 g) were dosed with toxaphene at 0, 25, 50, and 100 mg/kg X d for 3 d and sacrificed 24 h after last dose. Ca2+-ATPase activity and 45Ca2+ uptake were determined in brain P2 fraction. Toxaphene decreased both Ca2+-ATPase activity and 45Ca2+ uptake, and the reduction was dose-dependent. Both substrate and Ca2+ activation kinetics of Ca2+-ATPase indicated noncompetitive type of inhibition, as evidenced by decreased catalytic velocity but not enzyme-substrate affinity. The decreased Ca2+-ATPase activity and 45Ca2+ uptake were restored to normal level by exogenously added calmodulin, which increased both velocity and affinity. The inhibition of Ca2+-ATPase activity and 45Ca2+ uptake and restoration by calmodulin suggests that toxaphene may impair active calcium transport mechanisms by decreasing levels of calmodulin.     

Effects of methyl mercury and cadmium on the kinetics of substrate activation of (K+)-paranitrophenyl phosphatase

Previous studies from this laboratory have indicated that methyl mercuric chloride (CH3HgCl) and cadmium chloride (CdCl2) are potent inhibitors of K+-p-nitrophenyl phosphatase (K+-PNPPase). The present studies were undertaken to study the effects of CH3HgCl and CdCl2 on the substrate activation kinetics of K+-PNPPase to understand the mechanism of inhibition of Na+ pump by these heavy metals. Uncompetitive inhibition with regard to activation by PNPP was indicated by altered Vmax and Km values by both the heavy metals. Substrate activation kinetics of heavy metal inhibited K+-PNPPase in the presence of 25 microM dithiothreitol and glutathione indicated mixed type of activation by altering apparent Vmax and Km. Absence of competition between PNPP site and heavy metals appear to indicate absence of reactive-SH groups in the active site. Failure of added iodacetate, in concentrations ranging from 5 X 10(-8) to 5 X 10(-5) M, to inhibit K+-PNPPase further substantiate this conclusion. The results suggest that CH3HgCl and CdCl2 inhibit Na+ pump by inducing conformational changes in the enzyme and thereby decrease catalytic velocity of dephosphorylation of the enzyme-phosphoryl complex. Hydrolysis of PNPP was linear with time with or without either heavy metal and the inhibition exerted by CH3HgCl or CdCl2 on free or heavy metal loaded enzyme indicated absence of heavy metal interaction. The results suggest that CH3HgCl and CdCl2 inhibit K+-PNPPase possibly by binding at two different sites.     

Normal variation in sagittal spinal alignment parameters in adult patients: an EOS study using serial imaging

Purpose

To describe normal variations in sagittal spinal radiographic parameters over an interval period and establish physiological norms and guidelines for which these images should be interpreted.

Methods

Data were prospectively collected from a continuous series of adult patients with first-episode mild low back pain presenting to a single institution. The sagittal parameters of two serial radiographic images taken 6-months apart were obtained with the EOS^® slot scanner. Measured parameters include CL, TK, TL, LL, PI, PT, SS, and end and apical vertebrae. Chi-squared test and Wilcoxon Signed Rank test were used to compare categorical and continuous variables, respectively.

Results

Sixty patients with a total of 120 whole-body sagittal X-rays were analysed. Mean age was 52.1 years (SD 21.2). Mean interval between the first and second X-rays was 126.2 days (SD 47.2). Small variations (< 1°) occur for all except PT (1.2°), CL (1.2°), and SVA (2.9 cm). Pelvic tilt showed significant difference between two images (p = 0.035). Subgroup analysis based on the time interval between X-rays, and between the first and second X-rays, did not show significant differences. Consistent findings were found for end and apical vertebrae of the thoracic and lumbar spine between the first and second X-rays for sagittal curve shapes.

Conclusions

Radiographic sagittal parameters vary between serial images and reflect dynamism in spinal balancing. SVA and PT are predisposed to the widest variation. SVA has the largest variation between individuals of low pelvic tilt. Therefore, interpretation of these parameters should be patient specific and relies on trends rather than a one-time assessment.

     

Performance of diffusion-weighted imaging,perfusion imaging,and texture analysis in predicting tumoral response to neoadjuvant chemoradiotherapy in rectal cancer patients studied with 3T MR: initial experience

Purpose

To determine the performance of texture analysis (TA), diffusion-weighted imaging, and perfusion MR (pMRI) in predicting tumoral response in patients treated with neoadjuvant chemoradiotherapy (CRT).

Methods

12 consecutive patients (8 females, 4 males, 63.2 ± 13.4 years) with rectal cancer were prospectively enrolled, and underwent pre-treatment 3T MRI. Treatment protocol consisted of neoadjuvant CRT with oxaliplatin and 5-fluorouracile. Unenhanced T2-weighted images TA (kurtosis), apparent diffusion coefficient (ADC), and pMRI parameters (Ktrans, Kep, Ve, IAUGC) were quantified by manually delineating a region of interest around the tumor outline. After CRT, all patients underwent complete surgical resection and the surgical specimen served as the gold standard. Receiver operating characteristic (ROC) curve analysis was performed to assess the discriminatory power of each quantitative parameter to predict complete response.

Results

Pathological complete response (pCR) was reported in six patients and partial response (PR) in three patients. Three patients were classified as non-responders (NR). Pre-treatment kurtosis was significantly lower in the pCR sub-group in comparison with PR + NR (p = .01). Among ADC and pMRI parameters, only Ve was significantly lower in the pCR sub-group compared with PR + NR (p = .01). A significant negative correlation between kurtosis and ADC (r = ?0.650, p = .022) was observed. Pre-treatment area under the ROC curves (AUC), to discriminate between pCR and PR + NR, was significantly higher for kurtosis (0.861, p = .001) and Ve (0.861, p = .003) compared to all other parameters. The optimal cutoff value for pre-treatment kurtosis and Ve was ≤0.19 (100% sensitivity, 67% specificity) and ≤0.311 (83% sensitivity, 83% specificity), respectively.

Conclusion

Pre-treatment kurtosis derived from T2w images and Ve from pMRI have the potential to act as imaging biomarkers of rectal cancer response to neoadjuvant CRT.