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Multi-channel electrical bioimpedance: a non-invasive method to simultaneously measure cardiac output and individual arterial limb flow in patients with cardiovascular disease

Cardiac output is the fundamental determinant of peripheral blood flow however; optimal regional tissue perfusion is ultimately dependant on the integrity of the arterial conduits that transport flow. A complete understanding of tissue perfusion requires knowledge of both cardiac and peripheral blood flow. Existing noninvasive devices do not simultaneously assess the cardiac and peripheral circulations. Multi-channel electrical bioimpedance (MEB) measures cardiac output and peripheral flow simultaneously. Assessment of the accuracy of MEB to measure cardiac output in patients with clinical heart failure (group 1) and to measure regional arterial limb flow in patients with exertional leg pain clinically thought to have peripheral arterial disease (group 2). Cardiac output was measured by MEB in 44 patients with moderate to severe clinical heart failure (group 1) and was compared to a cardiac output measured by 2D-Echo Doppler. Peripheral blood flow (regional ankle and arm flow) was measured by MEB in another group of 25 patients with exertional leg pain clinically thought to be claudication (group 2). The MEB ankle/arm flow ratio (AAI index) was then compared to a conventional ankle/brachial pressure ratio (ABI index). There was excellent correlation between the mean cardiac index by MEB (2.01 l/min/m(2)) and by 2D-Echo Doppler (2.06 l/min/m(2)) and bias and precision was 0.05 (2.4%) and +/-0.48 l/min/m(2) (+/-23%), respectively. The correlation was maintained for each measurement over a wide range of cardiac indices. There was good correlation between AAI and ABI measurements (P < 0.05). MEB accurately measures cardiac output in patients with moderate to severe clinical heart failure and accurately measures regional arterial limb flow in patients with peripheral arterial disease.

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Correlation of Vancomycin Dosing to Serum Concentrations in Pediatric Patients: A Retrospective Database Review

Appropriate antimicrobial dosing maximizes therapeutic benefit while minimizing development of antimicrobial resistance. Common pediatric references recommend vancomycin dosing of 40 mg/kg/day divided every 6 to 8 hours for non-central nervous system infections, while some clinicians report utilizing higher initial doses to optimize efficacy. This study compares vancomycin serum concentrations following traditional dosing of 10 mg/kg/dose every 6 to 8 hours versus 15 to 20 mg/kg/dose every 6 to 8 hours. Retrospective database review of vancomycin serum concentrations in pediatric patients. Three hundred fifty-seven patients were analyzed. The mean peak concentration of the 10 mg/kg groups every 6 and every 8 hours were below 25 mg/L, whereas the mean peak concentrations of the 15 mg/ kg groups every 6 and 8 hours were within the 25-40 mg/L range (p < 0.001). The mean trough concentration of the 10 mg/kg group every 6 hours was within the 5-15 mg/L range while the 10 mg/kg group dosed every 8 hours was below target. However, the mean trough concentrations of the 15 mg/kg group dosed every 6 and 8 hours were both within the 5-15 mg/L range (p < 0.001). Vancomycin doses of 15 mg/kg every 6 to 8 hours produce peak and trough serum concentrations within target range more often than 10 mg/kg every 6 to 8 hours.

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Open Access
Health-related quality of life before and after bariatric surgery in adolescents

Background Recent data reaffirm decreased health-related quality of life (HRQL) in obese adults and children. Health-related quality of life is markedly improved after bariatric surgery in adults. Little HRQL data are available in adolescents undergoing bariatric surgery. Methods Sixteen patients (14-20 years old) underwent gastric bypass. Thirteen patients completed a general HRQL measure (Short Form 36 [SF-36]) before surgery. Of these, 9 completed the SF-36 again at various follow-up times, as well as a measure of weight-related quality of life (Impact of Weight on Quality of Life–Lite). Three patients completed postsurgical forms only. Data were analyzed using t test and analysis of variance. Results are reported as mean ± SD. Results Mean age and body mass index at operation were 18.5 ± 1.7 years and 54 ± 7.6 kg/m 2. Postoperatively, patients lost an average of 66% ± 29% excess weight over a mean follow-up of 17 ± 12 (range, 1-39) months. Mean preoperative SF-36 physical component score was 34.7 ± 10 and mental component score was 40.6 ± 13.5 (adult population mean = 50.0 ± 10 for each). At last follow-up, mean physical component score had increased to 55.5 ± 5, and mental component score, to 55.2 ± 8.6 ( P < .0001). Adolescent Impact of Weight on Quality of Life–Lite scores after surgery did not differ from means for normal weight adults (93% ± 7% vs 96% ± 7%, P = .15). Conclusions Health-related quality of life in adolescents and young adults undergoing bariatric surgery improves dramatically in early follow-up. Long-term data are needed to definitively study this surgical therapy for obesity in adolescents.

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Approach to Management of Intussusception in Adults: A New Paradigm in the Computed Tomography Era

Intussusception has been considered an operative indication in adults as a result of the risk of ischemia and the possibility of a malignant lead point. Computed tomographic (CT) scans can reveal unsuspected intussusception. All CT reports from July 1999 to December 2005 were scanned electronically for letter strings to include the keyword intussusception. Identified CT scans were analyzed to characterize the intussusception and associated findings. Clinical, laboratory, pathological, and follow-up variables were gleaned from medical records. Findings were analyzed by treatment and findings at operation. Review of 380,999 CT reports yielded 170 (0.04%) adult patients (mean age, 41 years) with intussusceptions described as enteroenteric in 149 (87.6%), ileocecal in eight (4.7%), colocolonic in 10 (5.9%), and gastroenteric in three (1.8%). Radiological features included mean length of 4.4 cm (range, 0.8-20.5 cm) and diameter of 3.2 cm (range, 1.6-11.5 cm). Twenty-nine (17.1%) had a lead point, and 12 (7.1%) had bowel obstruction. Clinically, 88 (48.2%) patients reported abdominal pain, 52 (30.6%) had nausea and/or vomiting, and 74 (43.5%) had objective findings on abdominal examination. Thirty of 170 (17.6%) patients underwent operation, but only 15 (8.8%) patients had pathologic findings that correlated with CT findings. Seven had,enteroenteric intussusceptions from benign neoplasms (two), adhesions (one), local inflammation (one), previous anastomosis (one), Crohn's disease (one), and idiopathic (one). Three had ileocolic disease, including cecal cancer (one), metastatic melanoma (one) and idiopathic (one; whereas five patients had colocolonic intussusception from colon cancer (three), tubulovillous adenoma (one), and local inflammation (one). Of the 15 without intussusception at exploration, five had pathology related to trauma, four had nonincarcerated internal hernia after Roux-en-Y gastric bypass, four had negative explorations, one had adhesions, and one had appendicitis that did not correlate with CT findings. No patient in the observation group required subsequent operative exploration for intussusception at mean 14.1 months (range, 0.25-67.5 months) follow up. All operative patients demonstrated gastrointestinal symptoms versus 55.3 per cent of the observation group (P < 0.006). Analysis of CT features demonstrated differences among patients observed without operation, those without intussusception at exploration, and confirmed intussusception with regard to mean intussusception length 3.8 versus 3.8 versus 9.6 cm, diameter 3.0 versus 3.2 versus 4.8 cm, lead point 12.1 per cent versus 30 per cent versus 53.3 per cent, and proximal obstruction 3.8 per cent versus 0 per cent versus 46.7 per cent, respectively. Intussusceptions in adults discovered by CT scanning do not always mandate exploration. Most cases can be treated expectantly despite the presence of gastrointestinal symptoms. Close follow up is recommended with imaging and/or endoscopic surveillance. Length and diameter of the intussusception, presence of a lead point, or bowel obstruction on CT are predictive of findings that warrant exploration.

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Multi-Channel Electrical Bioimpedance: A New Noninvasive Method To Simultaneously Measure Cardiac And Peripheral Blood Flow

We sought to assess the ability of a new multi-channel electrical bioimpedance (MEB) methodology to accurately measure both cardiac blood flow and peripheral limb blood flow. Cardiac output is the primary determinant of peripheral blood flow; however, optimal regional tissue perfusion is ultimately dependent on the patency of the arterial conduits that transport that flow. A complete understanding of regional tissue perfusion requires knowledge of both cardiac and peripheral blood flow. Existing noninvasive devices do not simultaneously assess the cardiac and peripheral circulations. Cardiac blood flow (cardiac output) was measured by MEB in 30 healthy volunteers and was compared to a 2D-Echo Doppler cardiac output. Peripheral blood flow (regional ankle and arm flow) was measured by MEB in 15 healthy volunteers. The MEB ankle/arm flow ratio (AAI index) was then compared to a conventional ankle/brachial pressure ratio (ABI index). There was good correlation between the mean cardiac index by MEB (3.08 l/min/m2) and by Echo Doppler (3.13 l/min/m2) and bias and precision was 0.051 (1.6%) and +/-0.52 l/min/m2 (+/-17%), respectively. The close correlation was maintained for each measurement over a wide range of cardiac indices. There was good correlation between AAI and ABI measurements (p < 0.05) with a sensitivity of 100% and specificity of 100%. MEB methodology can precisely measure cardiac output and peripheral limb flow in healthy volunteers.

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Evaluation of Postinjury Hepatocyte Function by Central Amino Acid Clearance

It has been demonstrated by other investigators that central plasma clearance of amino acids accurately predicts hepatocyte function in patients with liver disease and correlates with clinical outcome. This methodology has not heretofore been studied in the trauma patient. It is our hypothesis that central amino acid clearance in trauma patients is more reflective of hepatocyte function than traditional liver function tests. We examined the plasma amino acid clearance rates using L-[1-13C]phenylalanine. Clearance rates were compared to standard liver function tests (LFTs) and the sensitivity and predictability of the technique were determined. The study was conducted on uninjured control subjects and in seriously injured patients, both with and without significant liver injuries. Compared to baseline values in the control group, initial phenylalanine breath scores were reduced in the injured, but exceeded control levels at 7 days postinjury. These changes were statistically significant. There was no difference between those with and without liver trauma. LFTs showed inconsistent and conflicting results. Thus, central amino acid clearance measured by L-[1-13C]phenylalanine oxidation is depressed immediately following injury but reaches supranormal levels at 7 days postinjury. Compared to LFTs, amino acid clearance suggests initial hepatocyte suppression followed by hyperactivity and is a more accurate determinant of hepatocyte function.

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