Prolonged peripheral arteriovenous perfusion with a membrane oxygenator

The authors have developed the optimal method of performing prolonged veno-arterial perfusion and studied its influence on the animal organism. In 22 experiments a membrane oxygenator on the national film "Sigma" was used. It has been established that for successful performing of prolonged veno-arterial perfusion it is necessary to strictly maintain the circulating blood volume and take measures to prevent disorders in the microcirculation. The blood trauma in the membrane oxygenator with the "Sigma" film is inimal.     

Comparative evaluation of a new disposable rotating membrane oxygenator with bubble oxygenator.

The comparative in vivo performance of adult-size bubble and rotating membrane oxygenators was evaluated during closed-chest cardiopulmonary bypass for six hours in two groups of dogs. The results show that the rotating membrane oxygenator is efficient in oxygen and carbon dioxide transfer with minimal trauma to blood, while platelet destruction and hemolysis were marked with the bubble oxygenator. Cerebral, cardiac, and respiratory complications were frequent with the bubble oxygenator and absent with the membrane oxygenator.     

Haematological characteristics of a new membrane oxygenator: the Cobe CML

The new Cobe CML membrane oxygenator is more compact than other membrane oxygenators and has a combined venous and cardiotomy suction reservoir. Its size makes it as easy to use as a bubble oxygenator. The studies reported here were designed to show whether the excellent haemocompatibility found with other types of membrane oxygenators had ben compromised by the changes introduced in the Cobe CML oxygenator. Platelet number and function (ADP induced aggregation) plasma betathromboglobulin concentration and plasma haemoglobulin concentration were studied in nine patients where the Cobe CML oxygenator had been used and these were compared with ten patients managed with a Shiley S-100 bubble oxygenator. We conclude that the constructional changes of the Cobe CML oxygenator do not affect the haemocompatibility of this type of membrane oxygenator and that it remains significantly better than the Shiley S-100 bubble oxygenator.     

Laboratory evaluation of a new membrane oxygenator with a built-in hemoconcentrator

In order to facilitate the handling of cardiopulmonary bypass (CPB) and simplify the circuit, we have developed a new membrane oxygenator with a hemofiltration function. The hollow fiber units for gas exchange and hemofiltration were combined in concentric circles in a cylindrical housing. The total priming volume was 190 ml. Because we used a silicon-coated hollow fiber membrane for gas exchange, this oxygenator was completely resistant to serum leakage. The gas exchange and hemofiltration sections both have a blood-outside flow configuration. All blood flows in a radial direction from around the central core to the surrounding hollow fiber units, first to the hemofiltration portion and then to the gas exchange section. Filtered fluid was easily collected through a stopcock mechanism. The oxygen transfer rate was 312 ml/min at a blood flow rate of 6 L/min, and the ultrafiltration rate was 3.5 L/hour at a blood flow rate of 4 L/min with 25% hematocrit and 200 mmHg transmembrane pressure in an in vitro study. The pressure drop was 62 mmHg at a blood flow rate of 4 L/min. We found no adverse effects in an in vivo study using a mongrel dog. In conclusion, this durable combined device could achieve excellent and simplified hemoconcentration by having all the blood in the unit flow through the hemofiltration portion, and may be useful not only in CPB during open heart surgery, but also in extracorporeal membrane oxygenation.     

A multi-center trial with a modified design of the Sarns membrane oxygenator

A redesigned hollow fiber bundle was incorporated into an existing oxygenator that underwent clinical trials at seven cardiovascular surgery centers. Clinical investigators were asked to assess gas transfer performance under clinical conditions that could be considered challenging to any microporous membrane oxygenator, i.e., with large body weight patients, long bypass times, or normothermic bypass and surgery. Sixty-six patients, ranging in weight from 54.5 kg to 143 kg, constituted the initial evaluation population. Enhanced oxygen transfer was noted by all of the investigators. Fi0 2 requirements for patients weighing 100 kg or more never exceeded .85, despite oxygen consumption levels reaching as high as 396 mL/min. Two centers documented a 15% to 18% reduction in Fi0 2 requirements compared to their standard oxygenator.     

Application of machine perfusion preservation as a viability test for marginal kidney graft

BACKGROUND: This study evaluated the usefulness of machine perfusion preservation parameters as indicators of kidney graft viability. METHODS: Eighty-eight cadaveric kidneys were analyzed in this study. Of these, 74 kidneys (84.1%) were procured from nonheartbeating donors. The criteria for an acceptable kidney for transplantation were a perfusion flow of more than 0.4 mL/min/g with a concurrent decreasing perfusion pressure. The average perfusion pressure was 30-50 mmHg. We divided the kidneys into three groups: group 1 (n=35), 0.45-0.65 mL/min/g machine perfusion flow (MPF); group 2 (n=30), 0.65-0.90 mL/min/g MPF; and group 3 (n=23), more than 0.9 mL/min/g MPF. RESULTS: A higher rate of primary nonfunction (PNF; 25.7%) was found in group 1, compared with 6.7% in group 2 and 0% in group 3. A higher rate of 30.4% immediate function was found in group 3, compared with 16.7% in group and 8.6% in group 1. However, a longer period of acute tubular necrosis (ATN; 12.0 days) was found in group 1 compared with 8.6 days in group 2 and 8.7 days in group 3. PNF was detected in 7 (77.8%) cases with more than 16 hr of total ischemic time (TIT) in group 1. In contrast, all of nine cases with more than 16 hr of TIT in group 3 were functional. CONCLUSIONS: MPF is a reliable indicator of graft viability based on the rate of PNF and immediate renal allograft function, especially in marginal donors.     

Predictor parameters of liver viability during porcine normothermic ex situ liver perfusion in a model of liver transplantation with marginal grafts

Normothermic ex situ liver perfusion (NEsLP) offers the opportunity to assess biomarkers of graft function and injury. We investigated NEsLP parameters (biomarkers and markers) for the assessment of liver viability in a porcine transplantation model. Grafts from heart‐beating donors (HBD), and from donors with 30 minutes (donation after cardiac death [DCD]30′), 70 minutes (DCD70′), and 120 minutes (DCD120′) of warm ischemia were studied. The HBD, DCD30′, and DCD70′‐groups had 100% survival. In contrast, 70% developed primary nonfunction (PNF) and died in the DCD120′‐group. Hepatocellular function during NEsLP showed low lactate (≤1.1 mmol/L) in all the groups except the DCD120′‐group (>2 mmol/L) at 4 hours of perfusion (P = .04). The fold‐urea increase was significantly lower in the DCD120′‐group (≤0.4) compared to the other groups (≥0.65) (P = .01). As for cholangiocyte function, bile/perfusate glucose ratio was significantly lower (<0.6) in all the groups except the DCD120′‐group (≥0.9) after 3 hours of perfusion (<0.01). Bile/perfusate Na+ ratio was significantly higher (≥1.2) after 3 hours of perfusion in all the groups except for the DCD120′‐group (≤1) (P < .01). Three hours after transplantation, the DCD120′‐group had a significantly higher international normalized ratio (>5) compared to the rest of the groups (≤1.9) (P = .02). Rocuronium levels were higher at all the time‐points in the animals that developed PNF during NEsLP and after transplantation. This study demonstrates that biomarkers and markers of hepatocellular and cholangiocyte function during NEsLP correlate with the degree of ischemic injury and posttransplant function.     

Complement activation by extracorporeal circulation: effects of precoating a membrane oxygenator circuit with human whole blood

In an in vitro study of extracorporeal circulation (ECC), uncoated oxygenators (UC), oxygenators precoated with whole human blood (CN) and oxygenators precoated with blood and then rinsed with Ringer's acetate (CR) all significantly (p less than 0.001) activated the initial and terminal parts of the complement cascade. After 60 min C3 activation had increased by 692% (UC), 750% (CN) and 393% (CR), and terminal complement complex (TCC) concentrations by 194% (UC), 215% (CN) and 273% (CR). C3 activation was significantly (p less than 0.05) less in the CR than in the other groups. There was no statistical intergroup difference in increase of TCC concentration. Complement activation was accompanied by a significant drop in neutrophil counts, which was uninfluenced by coating or rinsing. The observed dissociation of the complement cascade shows that assessment of activation products from both parts is necessary for evaluation of total complement activation. The study suggests that protein precoating may improve biocompatibility of ECC.