In vivo evaluation of an implantable portal pump system for augmenting liver perfusion

FIRST-PASS EFFECTS OF VERAPAMIL ON THE INTESTINAL ABSORPTION AND LIVER DISPOSITION OF FEXOFENADINE IN THE PORCINE MODEL

The aim of this study in pigs was to investigate the local pharmacokinetics of fexofenadine in the intestine and liver by using the pig as a model for drug transport in the entero-hepatobiliary system. A parallel group design included seven pigs (10-12 weeks, 22.2-29.5 kg) in three groups (G1, G2, G3), and a jejunal single-pass perfusion combined with sampling from the bile duct and the portal, hepatic, and superior caval veins was performed. Fexofenadine was perfused through the jejunal segment alone (G1: 120 mg/l, total dose 24 mg) or with two different verapamil doses (G2: 175 mg/l, total dose 35 mg; and G3: 1000 mg/l, total dose 200 mg). The animals were fully anesthetized and monitored throughout the experiment. Fexofenadine had a low liver extraction (E(H); mean +/- S.E.M.), and the given doses of verapamil did not affect the E(H) (0.13 +/- 0.04, 0.16 +/- 0.03, and 0.12 +/- 0.02 for G1, G2, and G3, respectively) or biliary clearance. The E(H) for verapamil and antipyrine agreed well with human in vivo data. Verapamil did not increase the intestinal absorption of fexofenadine, even though the jejunal permeability of fexofenadine, verapamil, and antipyrine showed a tendency to increase in G2. This combined perfusion and hepatobiliary sampling method showed that verapamil did not affect the transport of fexofenadine in the intestine or liver. In this model the E(H) values for both verapamil and antipyrine were similar to the corresponding values in vivo in humans.

Investigation of materials for blood-immersed bearings in a microaxial blood pump

Rotary blood pumps are gaining popularity among cardiothoracic surgeons. This article presents an in vitro investigation for choosing a suitable mechanical bearing system in a medium-long term microaxial pump. Different metallic, polymeric, and ceramic components are introduced. Polymers displayed mechanical insufficiency for the application, whereas certain ceramics displayed an inconsistent pattern of failure. We are in search of a compromise in properties that would favor a durable material combination.

Intravascular micropump for augmented liver perfusion: first in vivo experience

The aim of this study was to assess the in vivo performance of a new microaxial rotary blood pump developed for long-term intraportal implantation. The pump, measuring 7 mm in diameter, has a single stage impeller and is powered by a microelectric motor. The pump was implanted into the portal vein in 13 large white pigs under general anesthesia. All animals recovered after the portal pump implantation, and they were observed until the pump failed. The 2 longest running pumps performed for 40 and 36 h, respectively. Either thrombus formation or technical problems, especially in the bearings, were the main causes of pump failure during the experiment. No local or systemic adverse effects were observed during the portal pumping period. Full recovery of the animals following intraportal pump implantation was achieved. However, further technical improvements to the pump are required to maintain a longer performance in vivo.