ASAIO journal : a peer-reviewed journal of the American Society for Artificial Internal Organs
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The implantable pump field is now more than 20 years old. The original goal of developing a totally artificial beta-cell remains unrealized, but programmable insulin pumps that contain all of the elements of the artificial beta-cell except the glucose sensor are involved in clinical trials in the United States and are commercially available in Europe. ⋯ Only a few of the potential applications of implantable pumps have been developed to the stage of commercial availability. This is, in part, because drug companies have traditionally developed parenteral drug applications only as a last resort and, in part, because of the complexity of the regulatory process for implantable pumps, often requiring review by both the drug and device branches of the Food and Drug Administration.
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Most extracorporeal continuous renal replacement therapies (CRRT) require inflow pumping of either dialysate, filtrate replacement solution, or both. Outflow of spent dialysate and ultrafiltrate can be accomplished by gravity drainage or pump. Intravenous infusion pumps have been commonly used for these purposes, although little is known about the accuracy of these pumps. ⋯ The linear peristaltic pumps were most accurate under conditions of low pump inlet pressure, whereas piston pumps were most accurate under conditions of low pump pressure gradient (outlet minus inlet) of 0 or -100 mmHg. The magnitude of error outside these conditions was substantial, reaching 12.5% for the linear peristaltic pump when inlet pressure was -100 mmHg and outlet pressure was 100 mmHg. Error may be minimized in the clinical setting by choosing the pump type best suited for the pressure conditions expected for the renal replacement modality in use.
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Case Reports
Where should the hemofiltration circuit be placed in relation to the extracorporeal membrane oxygenation circuit?
Patients requiring extracorporeal membrane oxygenation (ECMO) frequently experience hypervolemia and metabolic abnormalities that can be effectively managed by hemofiltration. Although several options for hemofiltration circuit placement exist, some may have the disadvantage of recirculation or shunting of poorly oxygenated blood to the patient. ⋯ Despite the absence of pump generated pressure and a low blood flow rate, effective hemofiltration and diafiltration were achieved. This article examines whether placement of the hemofiltration circuit proximal to the ECMO pump has advantages over other hemofiltration circuit placements.
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Severe acute respiratory failure of varying etiology may require the temporary use of artificial gas exchange devices. So far, extracorporeal membrane oxygenation and extracorporeal carbon dioxide removal have been used successfully for this purpose. A totally implantable intravascular oxygenator (IVOX) recently became available. ⋯ The third patient is a long-term survivor 18 months after IVOX therapy. Gas transfer capabilities of IVOX are limited when compared to extracorporeal membrane oxygenation, and this may restrict its clinical applicability in cases of severe adult respiratory distress syndrome. However, IVOX may be used successfully in selected patients with less severe respiratory failure.
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Paired filtration dialysis (PFD) is the only hemodiafiltration (HDF) technique in which the ultrafiltrate is continuously available but not mixed with the dialysate. As is the case during all convective or predominantly convective techniques, use of a replacement fluid is necessary in an amount equal to the difference between the ultrafiltrate and the desired patient weight loss. ⋯ This verified the ultrafiltrate's possible use as replacement fluid. This technique experimentally studied during 24 standard PFD sessions, with a total mean ultrafiltrate of 9,950 +/- 860 ml, allowed a replacement solution to be obtained with the following mean +/- SD composition: pH 7.467 +/- 0.122, HCO3- 27.0 +/- 2.12 mmol/L, Na+ 137.4 +/- 2.6 mmol/L, K+ 4.1 +/- 0.83 mmol/L, Ca++ 1.12 +/- 0.19 mmol/L, urea 68.3 +/- 16.2 mg/dl, creatinine 0.08 +/- 0.02 mg/dl, uric acid 0.05 mg/dl, phosphates 2.77 +/- 0.71 mg/dl, beta-2 microglobulin 0.5 +/- 0.4 mg/L, and atrial natriuretic peptide 4.41 +/- 5.6 pg/ml.(ABSTRACT TRUNCATED AT 250 WORDS)