ASAIO journal : a peer-reviewed journal of the American Society for Artificial Internal Organs
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Between May 1990 and January 1999, 100 patients (68 adult, 32 pediatric) with severe respiratory or cardiac instability were successfully transported to the University of Michigan Medical Center on extracorporeal life support. Diagnoses included adult respiratory distress syndrome (n = 78), cardiac failure (n = 7), sepsis (n = 7), asthma (n = 5), respiratory distress syndrome (of newborn) (n = 2), and airway compromise (n = 1). Of the patients, 53 were supported with venovenous bypass and 47 with venoarterial bypass. ⋯ Complications that occurred during transport included 10 cases of electrical failure, 3 cases of circuit tubing leakage, and 1 case each of circuit rupture, membrane lung thrombosis, and membrane lung leakage. None of the complications occurring during transport had an adverse effect on outcome. We conclude that the long distance transport of patients on extracorporeal life support can be safely accomplished and is an effective option for the unstable patient with severe respiratory or cardiac failure.
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To finalize the design of the next generation of the HeartQuest left ventricular assist device, a suitable impeller had to be designed and tested. The new prototype was based on calculations and test results of previous designs, but required several changes to decrease the size. For most pump designs, this is a simple matter of altering impeller geometry and rotational speed to achieve the desired pressure rise and flow rate. ⋯ This not only saved money, but also sped up the development time for the project. The computer models were developed in TASCflow, a computational fluid dynamics software package from AEA Technologies. This paper analyzes the data from several of the selected models, paying close attention to pumping performance and general trends from specific design changes.
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Previous studies of extracorporeal life support in pediatric patients have identified variables associated with survival. However, none of these studies focused on extracorporeal life support after failure of high frequency ventilation (HFV). In the present study, we determined variables associated with survival for pediatric respiratory failure patients who received HFV prior to extracorporeal life support, using data reported to the Extracorporeal Life Support Organization Registry from 1992 to 1998. ⋯ Venoarterial extracorporeal life support was used in 72% of the patients; venovenous in 28%. The survival rate for the subset of patients with an oxygenation index greater than 42 cm H2O/torr on HFV (n = 122) was not significantly different from the overall sample. We determined that lower mean airway pressure, lower pressure amplitude, decreased oxygenation index, increased PaO2, and increased oxygen saturation on HFV were associated with increased survival in patients who were subsequently treated with extracorporeal life support.
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In hemodialysis patients, volume homeostasis is an important clinical problem. The aim is to have patients at an ideal "dry weight" postdialysis, but current methods for accurately measuring dry weight are disappointing. Krivitski et al. (ASAIO J 1998;44:M535-M540) have described a novel technique whereby extravascular lung water (EVLW) may be measured using blood ultrasound velocity and electrical impedance dilution. ⋯ The normalized EVLW values are almost identical to those obtained in animals (3.1+/-1.4 ml/kg) by Krivitski et al. (see above). We conclude that this new technique can conveniently and noninvasively give an estimate of EVLW in hemodialysis patients. The clinical value of this measurement has now to be determined.
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In hemodialysis (HD) patients, the diameter of the inferior vena cava (IVC) serves for evaluation of the amount of body fluid. IVC measurement is usually performed immediately before and/or after an HD session. In the present study, we examined the validity of IVC diameter in the interdialysis period (interdialytic IVC) for dry weight (DW) optimization. ⋯ After the DW was lowered to obtain an interdialytic IVCe < 16 mm, 25 of the 31 patients had a significant increase in EF, decrease in diastolic left ventricular dimension, and amelioration of hypertension. In conclusion, interdialytic IVCe is considered to be a useful parameter for DW optimization. In hypervolemic patients with IVCe > 16 mm, reduction in DW is expected to improve volume overload and cardiac function.