The International Journal of Artificial Organs

The purpose of this study was to determine the changes in calcium and potassium content in the red blood cells (RBC) of uremic patients during a hemodialysis (HD) session and a 6/hrs CAPD exchange. RBC calcium and potassium were determined in 20 patients on HD in three blood samples collected at 0′-HD (pre-HD), 45′-HD and 240′-HD (end-HD), in 20 patients on CAPD, in two blood samples, collected at 0′ time (pre-inflow) and 120′, (solution in peritoneal cavity) during a 6/hrs exchange (4 exchanges / 24 h) and in 20 normal subjects. The mean value (±SD) of RBC calcium in controls was 15.6 ± 3.75 μmol/L, in hemodialysed patients at 0′-HD, 45′-HD and 240′-HD 51.5 ± 8.5, 70.4 ± 12.5 and 51.1 ± 10 μmol/L respectively and CAPD patients at time 0′ and 120 of an exchange 53.6 ± 23.4 and 70.6 ± 9.2 respectively. These values show that RBC calcium in hemodialysed patients is generally significantly higher (p < 0.0001) than in controls. The value at 45′-HD is also significantly higher (p < 0.0001) than at 0′ or 240′-HD. In CAPD patients, at 0′ and 120′ of a 6/hrs exchange, it is significantly higher (p < 0.0001) than in controls, as is the value at 120′ (p < 0.001) in comparison to 0′. The mean value (±SD) of RBC potassium at the aforementioned time measurements were 95.9 ± 3.34, 92.5 ± 4.32 and 93.85 ± 3.89 mmol/L respectively for patients on HD, 95 ± 3.3 and 94.6 ± 5.28 mmol/L respectively for patients on CAPD and 99.1 ± 3.70 mmol/L in controls. These values show that RBC potassium of hemodialysed patients is significantly lower in comparison to that of controls (0′-HD: p < 0.01, 45′-HD and 240′-HD: p < 0.001); also the value at 45′-HD and 240′-HD is significantly lower (p < 0.001, p < 0.01 respectively) when compared to that at 0′-HD. In patients on CAPD, at 0′ time and 120′ during 6/hrs exchange, potassium is significantly lower (p < 0.001) in comparison to that of controls.

In conclusion, uremic patients present high erythrocyte calcium and low potassium with fluctuations during HD-sessions and CAPD 6/hrs exchange.

This study was designed to compare the efficacy and potential protective or injurious effects of tidal liquid ventilation (TLV), liquid-assisted high-frequency oscillatory ventilation (LA-HFOV), and high PEEP conventional mechanical ventilation (CMV) in neonatal respiratory distress syndrome. Preterm lambs (124–126 days gestation), prophylactically treated with natural surfactant, were allocated to one of the treatment modalities or to an untreated fetal control group (F), euthanised after tracheal ligation. LA-HFOV animals received an intratracheal loading dose of 5 mL.kg^-1 followed by a continuous intrapulmonary instillation of 12 mL.kg^-1;h^-1 FC-75 perfluorocarbon liquid. The ventilation strategies aimed at keeping clinically appropriate arterial blood gases for a study period of 5 hours. A histological lung injury score was calculated and semiquantitative morphometry was performed on lung tissue fixed by vascular perfusion.

The alveolar-arterial pressure difference for O₂ was significantly lower throughout the study in TLV compared to CMV lambs; at 1, 2, and 5 hours, oxygenation was better in TLV when compared to LA-HFOV. Total lung injury scores in TLV lambs were significantly lower than in either CMV or LA-HFOV animals, but higher when compared to F. CMV and LA-HFOV induced an excess of collapsed and overdistended alveoli, whereas in TLV alveolar expansion was normally distributed around predominantly normal alveoli. CMV and LA-HFOV, but not TLV, were associated with an excess of dilated airways.

Thus, in the ovine neonatal RDS model, TLV compared favourably to either gas ventilation strategy by its more uniform ventilation, reduced lung injury, and improved gas exchange.

The PUCA (pulsatile catheter) pump is a left ventricular assist device (LVAD) capable of unloading the left ventricle (LV) and improving coronary flow by providing a counterpulsation effect. It consists of an extracorporeal located membrane pump, coupled to a transarterial catheter that enters the body via a superficial artery and ends in the LV. Blood is aspirated from the LV and pumped in the ascending aorta through the same catheter guided by a valve system. Timing and frequency of the PUCA pump influence its efficacy. To study the influence of several pump parameters a numerical model of the device and the circulatory system has been developed. Results of animal experiments were used to validate the model.

Optimization studies resulted in a pump configuration with a stroke volume of 50 cc and pump:heart frequency mode of 1:2 that starts ejection at the beginning of diastole.

Extracellular matrix (ECM) in the liver affects the phenotype of both hepatocytes and non-parenchymal cells. To be able to mimic in vivo liver function for extracorporeal hepatic support using human cell lines, a necessary step is to upregulate the function normally seen in monolayer culture. 3-D spheroid colonies were formed by culturing single HepG2 cells encapsulated in alginate beads. ECM expression in these cultures was compared to monolayer Hep G2 cultures. The following ECM proteins were detected immunohistochemically:- collagens I, III, V and VI, the glycoproteins fibronectin, tenascin and vitronectin, and the basement membrane protein laminin. In 3-D cultures, all proteins except tenascin were strongly expressed, as compared with weak or undetectable expression in monolayer cultures, even with 10-fold increases in the antibody concentration used. In conclusion, we have demonstrated that the 3-D environment created by alginate encapsulation of cell lines leads to cell behaviour mimicking that in vivo.

Most types of medical technology assessment are performed only after the technology has been developed. Consequently, they have only minor effects on changes in clinical practice. Our study introduces a new method of constructive medical technology assessment that can change the development and diffusion of a medical device to improve its later clinical effectiveness. The method, based on Saaty's Analytic Hierarchy Process, quantitatively supports discussions between various parties involved in technological development and diffusion. We applied this method in comparing a new blood pump with two competitors based on technical, medical and social requirements. These discussions changed the evaluators’ perspectives, reduced diasagreements, and ended in a reliable evaluation of the pump's performance. On the basis of these results, adaptations were derived which improved the design and diffusion of the blood pump. This application shows the adequate potential of our method to steer technological development and diffusion of artificial organs.