Bowel Puncture During Insertion of a Femoral Central Line in the Emergency Department.

BACKGROUND Central venous catheter (CVC) insertion is commonly performed in the emergency department. The femoral vein is often chosen for insertion of CVCs due to its lower risk for complication. We present a rare complication of bowel puncture during insertion of a femoral CVC in the emergency department in a 46-year-old female. CASE REPORT A 46-year-old female with a history of partial gastrectomy and colostomy was transported to the emergency department after being found unconscious. Despite multiple attempts, intravenous access could not be obtained. The emergency physician proceeded to insert a left femoral CVC to obtain venous access. Ultrasound was not used due to perceived urgency, as well as a bedside assessment that the patient's anatomy was straight forward. Stool-like material was aspirated upon inserting the introducer needle, which was quickly removed. An upright x-ray showed no free air, but due to the patient history, an exploratory laparotomy was performed. A single-side perforation in the mid-sigmoid with a small hematoma along the antimesenteric wall was found. The puncture was over sewn, and the patient recovered well; the patient's initial presentation was ultimately considered to be due to medication misuse. CONCLUSIONS This case highlights the importance of using caution in blind attempts at femoral CVC in patients with prior abdominal surgery. It is also important to note the need to avoid insertion of CVCs without the use of ultrasound or when in a rush. If venous access is needed quickly, peripheral or intraosseous venous access can be obtained much more quickly and safely.

Dynamic Bioreactors with Integrated Microfabricated Devices for Mechanobiological Screening.

Biomechanical stimulation is a common strategy to improve the growth, maturation, and function of a variety of engineered tissues. However, identifying optimized biomechanical conditioning protocols is challenging, as cell responses to mechanical stimuli are modulated by other multifactorial microenvironmental cues, including soluble factors and biomaterial properties. Traditional bioreactors lack the throughput necessary for combinatorial testing of cell activity in mechanically stimulated engineered tissues. Microfabricated systems can improve experimental throughput, but often do not provide uniform mechanical loading, are challenging to use, lack robustness, and offer limited amounts of cells and tissue for analysis. To address the need for higher-throughput, combinatorial testing of cell activity in a tissue engineering context, we developed a hybrid approach, in which flexible polydimethylsiloxane microfabricated inserts were designed to simultaneously generate multiple tensile strains when stretched cyclically in a standard dynamic bioreactor. In the embodiment presented in this study, each insert contained an array of 35 dog bone-shaped wells in which cell-seeded microscale hydrogels can be polymerized, with up to eight inserts stretched simultaneously in the bioreactor. Uniformity of the applied strains, both along the length of a microtissue and across multiple microtissues at the same strain level, was confirmed experimentally. In proof-of-principle experiments, the combinatorial effects of dynamic strain, biomaterial stiffness, and transforming growth factor (TGF)-ß1 stimulation on myofibroblast differentiation were tested, revealing both known and novel interaction effects and suggesting tissue engineering strategies to regulate myofibroblast activation. This platform is expected to have wide applicability in systematically probing combinations of mechanobiological tissue engineering parameters for desired effects on cell fate and tissue function. Impact Statement In this study, we introduce a dynamic bioreactor system incorporating microfabricated inserts to enable systematic probing of the effects of combinations of mechanobiological parameters on engineered tissues. This novel platform offers the ease of use, robustness, and well-defined mechanical strain stimuli inherent in traditional dynamic bioreactors, but significantly improves throughput (up to 280 microtissues can be tested simultaneously in the embodiment presented in this study). This platform has wide applicability to systematically probe combinations of dynamic mechanical strain, biomaterial properties, biochemical stimulation, and other parameters for desired effects on cell fate and engineered tissue development.

Microdevice array-based identification of distinct mechanobiological response profiles in layer-specific valve interstitial cells.

Aortic valve homeostasis is mediated by valvular interstitial cells (VICs) found in spatially distinct and mechanically dynamic layers of the valve leaflet. Disease progression is associated with the pathological differentiation of VICs to myofibroblasts, but the mechanobiological response profiles of cells specific to different layers in the leaflet remains undefined. Conventional mechanically dynamic macroscale culture technologies require a large number of cells per set of environmental conditions. However, large scale expansion of primary VICs in vitro does not maintain in vivo phenotypes, and hence conventional macroscale techniques are not well-suited to systematically probe response of these cell types to combinatorially manipulated mechanobiological cues. To address this issue, we developed a microfabricated composite material screening array to determine the combined effects of dynamic substrate stretch, soluble cues and matrix proteins on small populations of primary cells. We applied this system to study VICs isolated from distinct layers of the valve leaflet and determined that (1) mechanical stability and cellular adhesion to the engineered composite materials were significantly improved as compared to conventional stretching technologies; (2) VICs demonstrate layer-specific mechanobiological profiles; and (3) mechanical stimulation, matrix proteins and soluble cues produce integrated and distinct responses in layer-specific VIC populations. Strikingly, myofibroblast differentiation was most significantly influenced by cell origin, despite the presence of potent mechanobiological cues such as applied strain and TGF-ß1. These results demonstrate that spatially-distinct VIC subpopulations respond differentially to microenvironmental cues, with implications for valve tissue engineering and pathobiology. The developed platform enables rapid identification of biological phenomena arising from systematically manipulating the cellular microenvironment, and may be of utility in screening mechanosensitive cell cultures with applications in drug screening, tissue engineering and fundamental cell biology.

Integrating polyurethane culture substrates into poly(dimethylsiloxane) microdevices.

Poly(dimethylsiloxane) (PDMS)-based microdevices have enabled rapid, high-throughput assessment of cellular response to precisely controlled microenvironmental stimuli, including chemical, matrix and mechanical factors. However, the use of PDMS as a culture substrate precludes long-term culture and may significantly impact cell response. Here we describe a method to integrate polyurethane (PU), a well-studied and clinically relevant biomaterial, into the PDMS multilayer microfabrication process, enabling the exploration of long-term cellular response on alternative substrates in microdevices. To demonstrate the utility of these hybrid microdevices for cell culture, we compared initial cell adhesion, cell spreading, and maintenance of protein patterns on PU and PDMS substrates. Initial cell adhesion and cell spreading after three days were comparable between collagen-coated PDMS and PU substrates (with or without collagen coating), but significantly lower on native PDMS substrates. However, for longer culture durations (> or = 6 days), cell spreading and protein adhesion on PU substrates was significantly better than that on PDMS substrates, and comparable to that on tissue culture-treated polystyrene. Thus, the use of a generic polyurethane substrate in microdevices enables longer-term cell culture than is possible with PDMS substrates. More generally, this technique can improve the impact and applicability of microdevice-based research by facilitating the use of alternate, relevant biomaterials while maintaining the advantages of using PDMS for microdevice fabrication.