BackgroundProcalcitonin (PCT) is a well-known prognostic marker after elective cardiac surgery. However, the impact of elevated PCT in patients with an initially uneventful postoperative course is still unclear. The aim of this study was to evaluate PCT levels as a prognostic tool for delayed complications after elective cardiac surgery.MethodsA prospective study was performed in 751 patients with an apparently uneventful postoperative course within the first 24 h after elective cardiac surgery. Serum PCT concentration was taken the morning after surgery. All patients were screened for the occurrence of delayed complications. Delayed complications were defined by in-hospital death, intensive care unit readmission, or prolonged length of hospital stay (>12 days). Odds ratios (OR) [with 95% confidence interval (CI)] were calculated by logistic regression analyses and adjusted for confounders. Predictive capacity of PCT for delayed complications was calculated by ROC analyses. The cutoff value of PCT was derived from the Youden Index calculation.ResultsAmong 751 patients with an initially uneventful postoperative course, 117 patients developed delayed complications. Serum PCT levels the first postoperative day were significantly higher in these 117 patients (8.9 ng/ml) compared to the remaining 634 (0.9 ng/ml; p < 0.001). ROC analyses showed that PCT had a high accuracy to predict delayed complications (optimal cutoff value of 2.95 ng/ml, AUC of 0.90, sensitivity 73% and specificity 97%). Patients with PCT levels above 2.95 ng/ml the first postoperative day had a highly increased risk of delayed complications (adjusted OR, 110.2; 95% CI 51.5–235.5; p < 0.001).ConclusionsA single measurement of PCT seems to be a useful tool to identify patients at risk of delayed complications despite an initially uneventful postoperative course.

Technical components produced via sheet metal forming often obtain characteristic crystallographic textures and process induced residual stress distributions. Knowledge of the local residual stress states is essential for the proper components' dimensioning. We report about the expansion of the incremental hole drilling technique for residual stress analysis to highly textured material states. A new evaluation approach using the differential evaluation algorithm is proposed, which bases on the calculation of multiple case specific calibration functions under consideration of the local orientation distribution function of the textured material. Systematic finite element (FE) simulations of incremental hole-drilling experiments are conducted regarding defined ideal nickel single crystal orientations (cube, Goss and brass). Multiple casespecific calibration functions, which consider the materials elastic anisotropy, are calculated and applied for stress calculation. In addition, the influence of a rosette misorientation between stress measurement and FE calibration is investigated. Using this new evaluation strategy a significant improvement of (residual) stress calculation on strongly textured materials is achieved. Finally, the capability of the proposed evaluation approach is experimentally validated for an uniaxially loaded CMSX-4 (nickel base super alloy) single crystal. The investigation clearly proved that in case of strongly anisotropic materials the evaluation using multiple case-specific calibration functions leads to a significant improvement in stress analysis compared to a conventional evaluation.

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