Suture Line Response of End-to-Side Anastomosis: A Stress Concentration Methodology.

End-to-side vascular anastomosis has a considerable complexity regarding the suturing of the juncture line between the artery and the graft. The present study proposes a stress-concentration methodology for the prediction of the stress distribution at the juncture line, aiming to provide generic expressions describing the response of an end-to-side anastomosis. The proposed methodology is based on general results obtained from the analysis of pipe connections, a topic that has been investigated in recent years in the field of offshore structural engineering. A key aspect for implementing the stress-concentration-factor approach is the recognition that the axial load due to pressure and flow dynamics exerted along the graft axis controls the "hot spots" on the juncture line, which in turn affects the mechanical response of the sutures. Several parameters, identified to influence the suture line response, are introduced in closed-form expressions for the suture line response calculations. The obtained results compare favorably with finite element results published in the literature. The proposed model predicts analytically the suture line response of end-to-side anastomosis, while capturing the influence of and interdependence among the problem parameters. Lower values of the graft radius, the distance between sequential stitches, and the intersecting angle between the artery and the graft are some of the key parameters that reduce the suture line response. The findings of this study are broad in scope and potentially applicable to improving the end-to-side anastomosis technique through improved functionality of the sutures and optimal selection of materials and anastomosis angle.

Analytical Side-to-Side Related Anastomotic Strategies and Artery Patching.

Suture line stress concentration and intimal hyperplasia are related to the long-term complications of end-toside and side-to-side anastomosis. Several factors, such as hemodynamic effects, biological activities and the mechanical properties of the blood vessels, are identified to influence the problem. Yet, it is not completely clear which are the factors that influence most the long-term complications and in what specific way. This study aims to examine if elastic (compliance) mismatch increases the stress concentration and intimal thickening at the suture line. Better compliance may be obtained by using grafts with similar mechanical properties to the host artery or by anastomosis techniques that utilize vein patches and cuffs (Taylor-patch and Miller-cuff anastomosis). The anastomosis model used in this study is a circular cylindrical system consisting of two semi-cylinders, interconnected by two hinges. The internal blood pressure is applied on the arterial walls. The static and dynamic responses are analytically derived in terms of radial and tangential displacements, internal forces and strains of the two blood vessels and rotation of their cross-section. Results suggest that increased elastic mismatch between the artery and the graft may promote elevated intimal thickening due to large incompatible angles at the junction, whereas there is no correlation between elastic mismatch and elevated stress concentration at the suture line. Another interesting application of the present model is the patching of arteries as applied in carotid endarterectomy.

Prematurity, subclinical intraamniotic infection, and fetal biophysical parameters: is there a correlation?

OBJECTIVE: This prospective study was undertaken to examine the effects of subclinical intraamniotic infection on fetal behavioral patterns. METHODS: Amniotic fluid was obtained from four groups of patients (n = 99): group 1, patients with preterm premature rupture of the fetal membranes (PPROM) without infection; group 2, patients with PPROM and infection; group 3, patients with preterm labor (PTL) and without infection; and group 4, patients with PTL and infection. Fetal biophysical profiles were obtained on admission to the labor suite. Amniotic fluid was analyzed for the presence of microorganisms and endotoxin to confirm intraamniotic infection; cytokines interleukin (IL)-1beta, IL-6, and IL-8 were also assayed. RESULTS: We found no association between low scores for biophysical parameters and subclinical infection in patients with PPROM or PTL. CONCLUSIONS: We could not demonstrate that upon a patient's admission to the labor hall absent fetal breathing and absent fetal movement, as well as reactivity, correlate with subclinical intraamniotic infection. Elevated cytokines, i.e. IL-1beta, IL-6, and IL-8 were associated with subclinical chorioamnionitis.

Cervical pregnancy. A case report.

A cervical pregnancy was treated successfully with systemic methotrexate and folic acid. Serial beta-human chorionic gonadotropin levels, color Doppler velocimetry and hysteroscopy were used to monitor therapy. In view of the substantial morbidity associated with this form of ectopic pregnancy, medical management is an option for treatment.

Preterm premature rupture of membranes: detection of infection.

This prospective study was designed to determine the value of a daily modified biophysical profile in detecting infection in patients with preterm premature rupture of the membranes who were managed expectantly. Ninety-nine patients received daily nonstress tests and biophysical profile scores. Results of the last predelivery study were related to subsequent development of amnionitis or fetal sepsis. Infection was present in 16 patients. When the biophysical profile score was 0/8, infection was uniformly present. When fetal breathing was absent (biophysical profile score, less than or equal to 4/8) and nonstress test was nonreactive, infection was present in 75% of cases (sensitivity, 75%; specificity, 95%). Because a nonreactive nonstress test could be secondary to prematurity instead of infection, these results were analyzed over time. Those who initially had a reactive nonstress test that subsequently became nonreactive were more likely to be infected. We conclude that a daily biophysical profile score and nonstress test can detect infection and propose delivery of patients with a biophysical profile score of 0/8 and nonreactive nonstress test. Patients with absent fetal breathing and a nonstress test that changes from reactive to nonreactive also should be considered for delivery. Absent fetal breathing with a reactive nonstress test or a consistently nonreactive nonstress test should have further testing to rule out infection.

Single-needle insertion in twin amniocentesis.

Amniocentesis in twin gestation is an uncommon event for most medical centers. The current technique used for this procedure includes two or more needle insertions and the introduction of dye into the first sac. A new approach that consists of a single insertion is proposed. The advantages of this alternate technique are that it requires only one insertion, it is a swifter procedure, it does not require the injection of dye, and it offers positive proof of tapping the two gestational sacs. Although this technique may have some potential risks, in our judgment the advantages outweight the potential risks, and this technique should be considered and its feasibility evaluated in cases of twin gestation requiring two-sac tapping.

In utero detection of cardiac failure from an aneurysm of the vein of Galen.

The detection of a vein of Galen aneurysm in a hydrocephalic fetus is presented. The differential diagnosis for the midline cystic structure was made on the basis of the presence of high-velocity flow on Doppler ultrasonographic examination.

Cordocentesis for rapid karyotyping.

Pure fetal blood was obtained by cordocentesis in 101 fetuses of 96 patients at 15 to 38 weeks' gestation. Rapid karyotype was obtained within 2 to 4 days by fetal lymphocyte culture. Chromosomal abnormality was detected in 12 (11.9%) fetuses. Abnormal karyotype was found in 5 of 44 fetuses with structural malformations, 3 of 13 fetuses with intrauterine growth retardation or oligohydramnios, 1 of 3 fetuses with nonimmune hydrops fetalis, 2 (one monozygotic set) of 10 discordant twins, 1 of 12 isoimmunized gestations, none of 8 cases with advanced gestational-maternal age, and none of 6 immune thrombocytopenia cases. This suggests that rapid karyotype should be obtained in all cases of fetal structural malformations, intrauterine growth retardation, and nonimmune fetal hydrops, and may be obtained incidentally in isoimmunized pregnancies and discordant twins to assist in clinical management.