2,833 publications from this institution
Clinicaltrials.gov identifier: NCT01203605.
The current outbreak of SARS-CoV-2 has and continues to put huge pressure on intensive care units (ICUs) worldwide. Many patients with COVID-19 require some form of respiratory support and often have prolonged ICU stays, which results in a critical shortage of ICU beds. It is therefore not always physically possible to treat all the patients who require intensive care, raising major ethical dilemmas related to which patients should benefit from the limited resources and which should not. Here we consider some of the approaches to the acute shortages seen during this and other epidemics, including some guidelines for triaging ICU admissions and treatments.
To the Editor: In the article by Schou et al. [1] regarding the effects of acute normovolemic hemodilution on the tolerance of anesthetized pigs to uncompensated blood loss, in their discussion, they state, "we could not confirm the findings of Van der Linden and coworkers that hemodilution increases the tolerance to hemorrhage." We cannot accept the interpretation the authors have placed on our data. Indeed, contrary to their interpretation, we specifically stated in our article [2] "the present data do not imply that the reduced hemoglobin is beneficial at the onset of acute hemorrhage." In our study [2], we tested the hypothesis that hemodilution is associated with an increase in tissue oxygen extraction capabilities, and for this purpose, we used a model of progressive hemorrhage, which has also been used by other groups to evaluate the effects of different conditions on tissue oxygen extraction capabilities in anesthetized animals [3,4]. It was not the purpose of our study to assess the tolerance of hemodiluted animals to hemorrhage, as in the study by Schou et al. [1]. We believe that it is, in fact, a logical assumption that hemodilution will decrease the tolerance to blood loss as the oxygen reserves decrease, and that animals will not tolerate acute blood loss under conditions of extreme hemodilution. Furthermore, at least some of the animals studied by Schou et al. [1] had already developed tissue dysoxia before the hemorrhagic sequence was started, because of the high degree of hemodilution. This is illustrated by the significant increase in serum lactate reported by the authors after the hemodilution procedure and before hemorrhage. In the same animal species, the pig, Trouwborst et al. [5] and Rasanen [6] showed that the critical level of hemodilution below which tissue oxygen delivery did not match oxygen demand, with resultant tissue hypoxia, was reached at a hemoglobin level of 4.0 g/dL, with an oxygen extraction ratio of 56%-57%. Before the hemorrhagic sequence, animals in the study by Schou et al. [1] had a hemoglobin level of 3.3 +/- 0.3 g/dL and an oxygen extraction ratio of 65% +/- 6%. In this situation, the ability of tissue to extract more oxygen to compensate for a further decrease in oxygen delivery due to the decreased blood volume could certainly be expected to be very limited. Philippe Van der Linden, MD, PhD Department of Cardiac Anesthesia; CHU Charleroi; Charleroi, Belgium Jean-Louis Vincent, MD, PhD Department of Intensive Care; CUB Erasme; Brussels, Belgium
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PsCYP15A is a cysteine protease from pea (Pisum sativum L.). It was first recognized as an up-regulated transcript in wilted shoots and subsequently in root nodules containing Rhizobium. Proteolytic activity of PsCYP15A in nodule extracts is now reported following immunopurification with polyclonal antiserum raised against recombinant antigen. Western-blot analysis indicated two forms of PsCYP15A, a pro-form (approximately 38 kD) and a mature form (approximately 30 kD). Both forms were present in most tissue samples, but only the mature form was isolated from cell-fractionated symbiosomes containing nitrogen-fixing bacteroids. Immunolabeling of nodule sections showed localization of PsCYP15A antigen in large vacuolar bodies, cytoplasmic vesicles, and the perisymbiont space. Immunolabeling of tissue sections from wilted shoots also indicated the presence of PsCYP15A in vacuoles and cytoplasmic vesicles. This protease may be involved in the adaptation to changes in cell turgor, both in wilted shoots and in nodule tissue. Additionally, the protease may be involved in protein turnover in the symbiosome compartment.
Erasme Hospital, University of Brussels, Brussels, Belgium (Vincent) Eli Lilly and Company, Indianapolis, IN (Williams, Nelson)
Levy, Mitchell M. MD; Vincent, Jean-Louis MD, PhD; Jaeschke, Roman MD, PhD; Parker, Margaret M. MD; Rivers, Emanuel MD, MPH; Beale, Richard MD; Hollenberg, Steven M. MD; Dellinger, R Phillip MD Author Information
Reply: We thank Drs Loukili and Liaudet for their interest in our article "A large-bolus injection, but not a continuous infusion of sodium selenite improves outcome in peritonitis" (1) and for providing some further insight into the underlying molecular mechanisms that may account for the beneficial anti-inflammatory effects of the selenocompound, selenite, that were demonstrated in our study. Clinical studies using selenocompounds in critically ill patients have generally not taken into consideration the possibility of a pro-oxidative action of the selenocompound, especially when administered as a bolus. The effects of a large dose of selenite, especially as a bolus administration, should be separated from the effects of a moderate (below the low adverse effect level) dose of selenite, which may have a nutritionally beneficial effect based on the induction of anti-oxidant selenoenzymes by selenium (2). Failure to do this may explain, in part, why the results of different studies have been inconsistent, notably the discrepant results of two recent large, multicenter randomized clinical trials (3, 4). We therefore wanted to test the hypothesis that a controlled use of the pro-oxidant effects of sodium selenite could be beneficial in this setting. One of the many observations that may support a seemingly paradoxical therapeutic use of a pro-oxidative dose of selenite in septic shock is the in vitro observation that selenite, at a concentration greater than 5 μmol/L (comparable with those achieved in our study), inhibits the DNA-binding activity of transcription factors, like nuclear factor κB and activator protein 1, by direct modification of essential thiol groups (5, 6). Moreover, in a preliminary study using a rat LPS model, Dr Forceville et al. (7) observed that an intraperitoneal injection of a large dose of selenite improved survival. Indeed, we found that a bolus administration of sodium selenite was associated with amelioration of microcirculatory perfusion and cardiac function, lower plasma IL-6 levels, and improved survival in our ovine experimental model of sepsis. Importantly, these beneficial effects were not the result of the anti-oxidant effects of selenium-containing selenoproteins because they were not observed in animals that received a continuous infusion of a similar dose of sodium selenite. Our study was not designed to explore the mechanisms involved in the observed effects of selenite. It would, for example, have been interesting to have determined the difference between modulation of redox potential involving paired electrons with high energy and modulation of free radicals involving one electron with high energy (5). However, this may have made the message more complex. The modification of redox potential conduct to interact with many pathophysiological cascades, including nuclear factor κB, especially in circulating cells should certainly be studied further. In addition to the possible mechanism on IKK mentioned by Drs Loukili and Liaudet, another potential mechanism is the ADMA/DDAH system, an important intracellular regulator of NOS activity (8). Inhibition of DDAH enzyme activity may be of therapeutic significance in the treatment of septic shock because excessive iNOS activity and NO overproduction play a central role in sepsis-induced vasodilatation and microcirculatory dysfunction. Intriguingly, oxidant compounds have been observed to abrogate DDAH activity because a crucial cysteine residue held in its active center is susceptible to oxidation (8). A study is under way to investigate whether DDAH inhibition plays a part in the observed beneficial effects elicited by the pro-oxidant doses and blood concentrations of sodium selenite in our recent study. Unraveling the complex effects of oxidative stress in sepsis and inflammation and assessing the potential effects of pro-oxidant and anti-oxidant agents will clearly be an exciting field of research for some years to come. Zhen WangM Réanimation Polyvalente CH Meaux Hôpital Saint Faron France Jean-Louis Vincent Erasme Hospital Université Libre de Bruxelles Belgium
Cardiovascular alterations in sepsis include a decrease in vascular tone and an impairment in myocardial contractility, and occur largely as the result of the release and action of mediators of the sepsis cascade. Many mediators are involved including cytokines, particularly tumour necrosis factor and interleukin-1, and secondary mediators such as nitric oxide and oxygen free radicals. The degree of reduced vascular tone and myocardial depression have both been related to the severity of sepsis. In this article we will review current knowledge on the factors involved in the cardiovascular alterations of sepsis, the clinical implications of these alterations, and the possibilities for future treatments.