Context.-Although concern over the risks of red blood cell transfusion has resulted in several practice guidelines for transfusion, lack of data regarding the physiological effects of anemia in humans has caused uncertainty regarding the blood hemoglobin (Hb) concentration requiring treatment.Objective.-To test the hypothesis that acute isovolemic reduction of blood Hb concentration to 50 g/L in healthy resting humans would produce inadequate cardiovascular compensation and result in tissue hypoxia secondary to inadequate oxygen transport.Design.-Before and after interventional study.Setting.-Academic tertiary care medical center.Participants.-Conscious healthy patients (n=11) prior to anesthesia and surgery and volunteers not undergoing surgery (n=21).Interventions.-Aliquots of blood (450-900 mL) were removed to reduce blood Hb concentration from 131 (2) g/L to 50 (1) g/L [mean (SE)]. Isovolemia was maintained with 5% human albumin and/or autologous plasma. Cardiovascular parameters, arterial and mixed venous oxygen content, oxyhemoglobin saturation, and arterial blood lactate were measured before and after removal of each aliquot of blood. Electrocardiogram and, in a subset, Holter monitor were monitored continuously.Main Outcome Measures.-"Critical" oxygen delivery (TO 2 ) as assessed by oxygen consumption (V O 2 ), plasma lactate concentration, and ST changes on electrocardiogram.Results.-Acute, isovolemic reduction of Hb concentration decreased systemic vascular resistance and TO 2 and increased heart rate, stroke volume, and cardiac index (each PϽ.001). We did not find evidence of inadequate oxygenation: V O 2 increased slightly from a mean (SD) of 3.07 (0.44) mL of oxygen per kilogram per minute (mL O 2 •kg −1 •min −1 ) to 3.42 (0.54) mL O 2 •kg −1 •min −1 (PϽ.001) and plasma lactate concentration did not change (0.81 [0.11] mmol/L to 0.62 [0.19] mmol/L; P=.09). Two subjects developed significant ST changes on Holter monitor: one apparently related to body position or activity, the other to an increase in heart rate (at an Hb concentration of 46-53 g/L); both occurred in young women and resolved without sequelae.Conclusions.-Acute isovolemic reduction of blood Hb concentration to 50 g/L in conscious healthy resting humans does not produce evidence of inadequate systemic TO 2 , as assessed by lack of change of V O 2 and plasma lactate concentration. Analysis of Holter readings suggests that at this Hb concentration in this resting healthy population, myocardial ischemia would occur infrequently.

The increased use of allograft tissue for musculoskeletal repair has brought more focus to the safety of allogenic tissue and the efficacy of various sterilization techniques. Gamma irradiation is an effective method for providing terminal sterilization to biological tissue, but it is also reported to have deleterious effects on tissue mechanics in a dose-dependent manner. At irradiation ranges up to 25 kGy, a clear relationship between mechanical strength and dose has yet to be established. The aim of this study was to investigate the mechanical properties of bone and soft tissue allografts, irradiated on dry ice at a low absorbed dose (18.3-21.8 kGy) and a moderate absorbed dose (24.0-28.5 kGy), using conventional compressive and tensile testing, respectively. Bone grafts consisted of Cloward dowels and iliac crest wedges, while soft tissue grafts consisted of patellar tendons, anterior tibialis tendons, semitendinosus tendons, and fascia lata. There were no statistical differences in mechanical strength or modulus of elasticity for any graft irradiated at a low absorbed dose, compared to control groups. Also, bone allografts and two soft tissue allografts (anterior tibialis and semitendinosus tendon) that were irradiated at a moderate dose demonstrated similar strength and modulus of elasticity values to control groups. The results of this study support the use of low dose and moderate dose gamma irradiation of bone grafts. For soft tissue grafts, the results support the use of low dose irradiation.

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Interest in the development of redox-flow batteries (RFBs) for large-scale grid storage is growing, and considerable investments have been made into the research and development of RFBs over the past few decades. Unfortunately, practical implementation has been hampered by various cost and performance issues typical of an immature state of development. One critical factor for the competitiveness of this technology is the installed cost. In this work, we incorporate recent developments in all-vanadium RFB research and present an analysis of the associated cost factors. The major components of a RFB that affect installed cost are identified and used as variables to create a capital cost function. The function is then used to calculate the rate of change of the capital costs with respect to the major components. The capital costs are also calculated for a range of component values and plotted. Key findings include a high sensitivity of system capital cost to purity of vanadium and substantial fractions of the cost associated with perflurorosulfonic acid membranes currently used for proton transport.

This study compared the efficacy and safety of a human acellular dermal matrix (ADM), D-ADM, with a conventional care arm and an active comparator human ADM arm, GJ-ADM, for the treatment of chronic diabetic foot ulcers. The study design was a prospective, randomized controlled trial that enrolled 168 diabetic foot ulcer subjects in 13 centers across 9 states. Subjects in the ADM arms received one application but could receive one additional application of ADM if deemed necessary. Screen failures and early withdrawals left 53 subjects in the D-ADM arm, 56 in the conventional care arm, and 23 in the GJ-ADM arm (2:2:1 ratio). Subjects were followed through 24 weeks with major endpoints at Weeks 12, 16, and 24. Single application D-ADM subjects showed significantly greater wound closure rates than conventional care at all three endpoints while all applications D-ADM displayed a significantly higher healing rate than conventional care at Week 16 and Week 24. GJ-ADM did not show a significantly greater healing rate over conventional care at any of these time points. A blinded, third party adjudicator analyzed healing at Week 12 and expressed "strong" agreement (j 5 0.837). Closed ulcers in the single application D-ADM arm remained healed at a significantly greater rate than the conventional care arm at 4 weeks posttermination (100% vs. 86.7%; p 5 0.0435). There was no significant difference between GJ-ADM and conventional care for healed wounds remaining closed. Single application D-ADM demonstrated significantly greater average percent wound area reduction than conventional care for Weeks 2-24 while single application GJ-ADM showed significantly greater wound area reduction over conventional care for Weeks 4-6, 9, and 11-12. D-ADM demonstrated significantly greater wound healing, larger wound area reduction, and a better capability of keeping healed wounds closed than conventional care in the treatment of chronic DFUs.