Implantable vascular access devices - past, present, and future

Automated blood sampling in canine telemetry studies: Enabling enhanced assessments of cardiovascular liabilities and safety margins

INTRODUCTION

A successful integration of automated blood sampling (ABS) into the telemetry instrumented canine cardiovascular model is presented in this study. This combined model provides an efficient means to quickly gain understanding of potential effects on key cardiovascular parameters in dog while providing a complete Pharmacokinetic/Pharmacodynamic (PK/PD) profile for discovery compounds without handling artifacts, reducing the need for a separate pharmacokinetic study.

METHODS

Male beagle dogs were chronically implanted with telemetry devices (PhysioTel™ model D70-PCTP) and vascular access ports (SPMID-GRIDAC-5NC). BASi Culex-L automated blood sampling (Bioanalytical Systems, Inc) system was used to collect blood samples at multiple time points. A series of four use cases utilizing four different test compounds and analytical endpoints are described to illustrate some of the potential applications of the technique.

RESULTS

In the four presented use cases, automated blood sampling in telemetry instrumented dogs provides simultaneous cardiovascular (heart rate, arterial blood pressure, and left ventricular pressure), electrophysiological assessment (QTc, PR, and QRS intervals), body temperature, and animal activity, while collecting multiple blood samples for drug analysis.

CONCLUSION

The combination of automated blood sampling with cardiovascular telemetry monitoring is a novel capability designed to support safety pharmacology cardiovascular assessment of discovery molecules. By combining telemetry and high-fidelity ABS, the model provides an enhanced PK/PD understanding of drug-induced hemodynamic and electrocardiographic effects of discovery compounds in conscious beagles in the same experimental session. Importantly, the model can reduce the need for a separate pharmacokinetic study (positive reduction 3R impact), reduces compound syntheses requirements, and shorten development timelines. Furthermore, implementation of this approach has also improved animal welfare by reducing the animal handling during a study, thereby reducing stress and associated data artifacts (positive refinement 3R impact).

Simple thrombin-based method for eliminating fibrinogen interference in serum protein electrophoresis of haemodialysed patients

Introduction

Serum samples of haemodialysed patients collected through vascular access devices, e.g. central venous catheter (CVC) can contain residual heparin, which can cause incomplete clotting and consequently fibrinogen interference in serum protein electrophoresis (SPE). We hypothesized that this problem may be overcome by addition of thrombin and aimed to find a simple thrombin-based method for fibrinogen interference removal.

Materials and methods

Blood samples of 51 haemodialysed patients with CVC were drawn through catheter into Clot Activator Tube (CAT) and Rapid Serum Tube Thrombin (RST) vacutainers (Becton Dickinson, New Jersey, USA) following the routine hospital protocols and analysed with gel-electrophoresis (Sebia, Lisses, France). Samples were redrawn in the CAT tubes and re-analysed after being treated with thrombin using two methods: transferring CAT serum into RST vacutainer and treatment of CAT serum with fibrinogen reagent (Multifibren U, Siemens, Marburg, Germany).

Results

Direct blood collection in RST proved to be slightly more efficient than CAT in removing the interfering band in beta fraction (CAT removed 6/51 and RST removed 12/51, P = 0.031). Transferring CAT serum into the RST vacutainer proved to be more efficient for subsequent removal of interfering band from CAT serum than the addition of fibrinogen reagent (39/45 vs. 0/45 samples with efficiently removed interfering band, P < 0.001).

Conclusion

Fibrinogen interference caused by incomplete clotting because of residual heparin can be overcome by addition of thrombin. Transferring CAT serum into the RST vacutainer was the most efficient method.

Biofunctional catheter coatings based on chitosan-fatty acids derivatives

Multifunctional and biofunctional coatings for medical devices are an attractive strategy towards tailoring the interactions of the device with the body, thereby influencing the host response, and the susceptibility to microbial colonization. Here we describe the development of a coating process to yield amphiphilic, lubricious coatings, resistant to bacterial colonization, based on chitosan. Chitosan-fatty acid derivatives were obtained by simultaneous N,O-acylation of chitosan with either linoleic, α-linolenic, or dilinoleic acid. Chemical characterization of new materials was carried out using ¹H NMR, FTIR, and XPS. Surface properties of coated polyester samples were studied using SEM and contact angle measurements, which indicated that the incorporation of hydrophobic constituents into chitosan macromolecules led to a decrease of both surface roughness and water contact angle. Importantly, tribological testing demonstrated that these new coatings decrease the coefficient of friction due to the self-organization of fatty acid (from 0.53 for the neat chitosan to 0.35 for chitosan-fatty acid derivative). Meanwhile, preliminary bacterial colonization tests indicated significant-over 80%-reduction in E. coli colonization following coating with chitosan-linoleic and chitosan-α-linolenic derivatives. Finally, cytotoxicity and hemocompatibility studies confirmed that all amphiphilic chitosan-fatty acid derivatives were non-toxic and non-hemolytic. Collectively, our results demonstrate the potential of the developed coating strategy, particularly the chitosan-linoleic and chitosan-α-linolenic acid derivatives, for applications as biofunctional catheter coatings.