Holographic extraction of plane waves from an ultrasound beam for acoustic characterization of an absorbing layer of finite dimensions.

For the acoustic characterization of materials, a method is proposed for interpreting experiments with finite-sized transducers and test samples in terms of the idealized situation in which plane waves are transmitted through an infinite plane-parallel layer. The method uses acoustic holography, which experimentally provides complete knowledge of the wave field by recording pressure waveforms at points on a surface intersected by the acoustic beam. The measured hologram makes it possible to calculate the angular spectrum of the beam to decompose the field into a superposition of plane waves propagating in different directions. Because these waves cancel one another outside the beam, the idealized geometry of an infinite layer can be represented by a sample of finite size if its lateral dimensions exceed the width of the acoustic beam. The proposed method relies on holograms that represent the acoustic beam with and without the test sample in the transmission path. The method is described theoretically, and its capabilities are demonstrated experimentally for silicone rubber samples by measuring their frequency-dependent phase velocities and absorption coefficients in the megahertz frequency range.

Evaluation of nutritional screening tools among patients scheduled for heart valve surgery.

BACKGROUND AND AIM OF THE STUDY: The study aim was to detect the most sensitive nutritional screening tool and to assess its prognostic value with regards to an adverse clinical course in patients with heart valve disease undergoing cardiopulmonary bypass (CPB). METHODS: This prospective cohort study included 441 adult patients who were screened using four nutritional screening tools: Nutritional Risk Screening 2002 (NRS-2002); Malnutrition Universal Screening Tool (MUST); Mini Nutritional Assessment (MNA); and Short Nutritional Assessment Questionnaire (SNAQ). Nutritional assessment was performed using a Subjective Global Assessment (SGA). In-hospital mortality, postoperative complications, and duration of hospital stay were each analyzed. RESULTS: With regards to the detection of malnutrition, the sensitivities of MUST, SNAQ, MNA and NRS-2002 were 100%, 92%, 84.6% and 43.6%, respectively. Malnutrition identified by MUST and MNA were associated with postoperative complications (OR 1.63, p = 0.033 and OR 1.6, p = 0.035) and prolonged hospitalization (OR 1.57, p = 0.048 and OR 1.7, p = 0.02). According to multivariate logistic regression analysis, along with well-known age and duration of CPB, malnutrition identified by MUST and MNA was associated with a risk of development of complications (OR 1.6, p = 0.049 and OR 1.6, p = 0.04, respectively). The sensitivities of SNAQ, MUST, NRS-2002 and MNA with regards to postoperative complications were 26.8%, 28.8%, 10%, and 31.6%, respectively. CONCLUSION: The MUST tool is preferable with regards to the detection of malnutrition. Both, MUST and MNA independently predicted postoperative complications. SNAQ and NRS-2002 proved insensitive with regards to the postoperative course among patients with heart valve disease who were scheduled for cardiothoracic surgery.

Prognostic value of nutritional screening tools for patients scheduled for cardiac surgery.

OBJECTIVES: The aim of this study was to assess the prognostic value of different nutritional screening tools in patients undergoing cardiopulmonary bypass, with regard to adverse clinical outcome. METHODS: This prospective cohort study analysed 1193 adult patients who underwent cardiopulmonary bypass. Patients were screened using five nutritional screening tools: Subjective Global Assessment (SGA), Nutritional Risk Screening 2002 (NRS-2002), Malnutrition Universal Screening Tool (MUST), Mini-Nutritional Assessment (MNA) and Short Nutritional Assessment Questionnaire (SNAQ). In-hospital mortality, postoperative complications, length of stay in intensive care unit and length of hospitalization were analysed. Multivariate backward logistic regression analysis was used to assess the independent predictive value of the studied screening tools. RESULTS: In accordance with univariate analysis, malnutrition detected by SNAQ, MUST, NRS-2002 and MNA was associated with postoperative complications (odds ratio [OR] 1.8, 95% confidence interval [95% CI] 1.3-2.4; OR 1.9, 95% CI 1.4-2.6; OR 1.8, 95% CI 1.2-2.9 and OR 1.9, 95% CI 1.4-2.6). Malnutrition detected by MUST, NRS-2002, MNA and SGA was associated with intensive care unit stay >2 days (OR 1.5, 95% CI 1.1-2.1; OR 2.3, 95% CI 1.5-3.7; OR 1.7, 95% CI 1.2-2.2 and OR 2.7, 95% CI 1.6-4.6). Prolonged hospitalization (>20 days) was predicted by SNAQ, MUST and MNA (OR 1.4, 95% CI 1-1.9; OR 1.6, 95% CI 1.2-2.2 and OR 1.6, 95% CI 1.2-2.2). In accordance with multivariate analysis, only MUST and MNA independently predicted postoperative complications (OR 1.6, 95% CI 1.1-2.3 and OR 1.6, 95% CI 1.1-2.2). Other independent factors influencing postoperative complications were well-known logistic EuroSCORE (OR 1.06, 95% CI 1-1.1) and the duration of cardiopulmonary bypass in minutes (OR 1.01, 95% CI 1-1.01). CONCLUSIONS: MUST and MNA both have independent predictive values with regard to postoperative complications. Taking into account simplicity, MUST is preferable for the cardiac surgical population.

Evaluation of nutritional screening tools for patients scheduled for cardiac surgery.

OBJECTIVE: The aim of this study was to assess the prognostic value of different nutritional screening tools in patients undergoing cardiopulmonary bypass with regard to an adverse clinical course. METHODS: This prospective cohort study analyzed 894 adult patients who underwent cardiopulmonary bypass. Patients were screened using four nutritional screening tools: Nutritional Risk Screening 2002 (NRS-2002), the Malnutrition Universal Screening Tool (MUST), the Mini-Nutritional Assessment (MNA), and the Short Nutritional Assessment Questionnaire (SNAQ). Nutritional status was assessed using the Subjective Global Assessment. In-hospital mortality, postoperative complications, length of stay in the intensive care unit, and length of hospitalization were analyzed. RESULTS: The sensitivities of the SNAQ, MUST, and NRS-2002 to detect the malnutrition confirmed by the Subjective Global Assessment were 91.5%, 97.9%, and 38.3%, respectively, and the MNA showed a sensitivity of 81.8% for the elderly. Malnutrition detected by the SNAQ, MUST, and NRS-2002 was associated with postoperative complications (odds ratios [ORs] 1.75, 1.98, and 1.82, respectively) and a stay in the intensive care unit longer than 2 d (ORs 1.46, 1.56, and 2.8). Malnutrition as detected by the SNAQ and MUST was also associated with prolonged hospitalization (ORs 1.49 and 1.59). According to multivariate logistic regression analysis, postoperative complications were independently predicted by the European System for Cardiac Operative Risk Evaluation (OR 1.1, P < 0.0001), cardiopulmonary bypass time (OR 1.01, P < 0.0001), and malnutrition identified by the MUST (OR 1.2, P = 0.01). CONCLUSION: The MUST independently predicts postoperative complications. The SNAQ and MUST have comparable accuracy in detecting malnutrition. Whether preoperative nutritional therapy would improve the outcome in malnourished patients needs to be studied.