Critical care : the official journal of the Critical Care Forum
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Mechanically ventilated patients with chronic obstructive pulmonary disease often prove challenging to the clinician due to the complex pathophysiology of the disease and the high risk of patient-ventilator asynchrony. These problems are encountered in both intubated patients and those ventilated with noninvasive ventilation. Much knowledge has been gained over the years in our understanding of the mechanisms underlying the difficult interaction between these patients and the machines used to provide them with the ventilatory support they often require for prolonged periods. This paper attempts to summarize the various key issues of patient-ventilator interaction during pressure support ventilation, the most often used partial ventilatory support mode, and to draw clinicians' attention to the need for sufficient knowledge when setting the ventilator at the bedside, given the often conflicting goals that must be met.
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Review Comparative Study
Drotrecogin alfa (activated): does current evidence support treatment for any patients with severe sepsis?
Two international multicentre randomised controlled trials of drotrecogin alfa (activated) (DrotAA), the Recombinant Human Activated Protein C Worldwide Evaluation of Severe Sepsis (PROWESS) and Administration of Drotrecogin Alfa (Activated) in Early Stage Severe Sepsis (ADDRESS) trials, have produced inconsistent results. When 28-day mortality data from these trials for patients with severe sepsis and at high risk of death are pooled using a standard random-effects meta-analysis technique, there is no statistically significant survival benefit (for patients with Acute Physiology and Chronic Health Evaluation (APACHE II) scores of 25 or more), or a borderline significant benefit (for patients with multi-organ failure). ⋯ These concerns call into question the effectiveness of DrotAA in any patients with severe sepsis. Consequently, further randomised trials of this agent in prospectively defined high-risk patients are required to clarify its role in the management of severe sepsis.
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There is growing acceptance within the medical community of induced (therapeutic) hypothermia as a tool to achieve neuroprotection and/or cardioprotection. Although much work remains to be done in identifying those clinical situations in which hypothermia can be effective, there is now sufficient evidence to regard it as a standard of care, at least for some indications such as selected patients with postanoxic encephalopathy. ⋯ General aspects and advantages/disadvantages of surface versus core cooling are discussed, as are potential side effects, device-specific pros and cons, and cost-effectiveness issues. In addition, the current state of the evidence for use of induced hypothermia for various indications is briefly reviewed.
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Comparative Study
Oxidative stress is increased in critically ill patients according to antioxidant vitamins intake, independent of severity: a cohort study.
Critically ill patients suffer from oxidative stress caused by reactive oxygen species (ROS) and reactive nitrogen species (RNS). Although ROS/RNS are constantly produced under normal circumstances, critical illness can drastically increase their production. These patients have reduced plasma and intracellular levels of antioxidants and free electron scavengers or cofactors, and decreased activity of the enzymatic system involved in ROS detoxification. The pro-oxidant/antioxidant balance is of functional relevance during critical illness because it is involved in the pathogenesis of multiple organ failure. In this study the objective was to evaluate the relation between oxidative stress in critically ill patients and antioxidant vitamin intake and severity of illness. ⋯ The critical condition of patients admitted to the ICU is associated with worsening oxidative stress. Intake of antioxidant vitamins below 66% of RDA and alteration in endogenous levels of substances with antioxidant capacity are related to redox imbalance in critical ill patients. Therefore, intake of antioxidant vitamins should be carefully monitored so that it is as close as possible to RDA.
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Comment Review
Noninvasive ventilation for acute lung injury: how often should we try, how often should we fail?
The selection of patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS) to receive noninvasive ventilation (NIV) is challenging, partly because there are few reliable selection criteria. The study by Rana and colleagues in the previous issue of Critical Care identifies metabolic acidosis and a lower oxygenation index as predictors of NIV failure, although it is unable to identify threshold values. It also demonstrates that treating patients with NIV for ALI/ARDS and shock is an exercise in futility. Future studies need to focus on criteria that will enable selection of patients for whom NIV will have a high likelihood of success.