Critical care : the official journal of the Critical Care Forum
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Methadone, the most widely delivered maintenance therapy for heroin addicts, may be responsible for life-threatening poisonings with respiratory depression. The toxicokinetics and the toxicokinetic/toxicodynamic (TK/TD) relationships of methadone enantiomers have been poorly investigated in acute poisonings. The aim of this study was to describe the relationships between methadone-related respiratory effects and their corresponding concentrations. ⋯ After the ingestion of a toxic dose of a racemic mixture, plasma R- and S-enantiomer concentrations decreased in parallel. Despite large inter-individual variability in methadone toxicokinetics and toxicodynamics, TK/TD relationships would be helpful for providing quantitative data regarding the respiratory response to methadone in poisonings. However, further confirmatory TK/TD data are needed.
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Recent data indicate that transfusion of packed red blood cells (pRBCs) may increase the risk for the development of acute respiratory distress syndrome (ARDS) in critically ill patients. Uncertainty remains regarding the strength of this relationship. ⋯ Development of ARDS after ICU admission is common, occurring in approximately 5% of critically ill patients. Transfusion of pRBCs is independently associated with the development of ARDS in the ICU.
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This report describes the case mix, outcome and activity for admissions to intensive care units (ICUs) of patients who require prior chronic renal dialysis for end-stage renal failure (ESRF), and investigates the effect of case mix factors on outcome. ⋯ Patients with ESRF admitted to UK ICUs are more likely to be male and younger, with a medical cause of admission, and to have greater severity of illness than the non-ESRF population. Outcomes on the ICU were comparable between the two groups, but those patients with ESRF had greater readmission rates, prolonged post-ICU hospital stay and increased post-ICU hospital mortality. This study is by far the largest comparative outcome analysis to date in patients with ESRF admitted to the ICU. It may help to inform clinical decision-making and resource requirements for this patient population.
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Comparative Study
Injurious mechanical ventilation in the normal lung causes a progressive pathologic change in dynamic alveolar mechanics.
Acute respiratory distress syndrome causes a heterogeneous lung injury, and without protective mechanical ventilation a secondary ventilator-induced lung injury can occur. To ventilate noncompliant lung regions, high inflation pressures are required to 'pop open' the injured alveoli. The temporal impact, however, of these elevated pressures on normal alveolar mechanics (that is, the dynamic change in alveolar size and shape during ventilation) is unknown. In the present study we found that ventilating the normal lung with high peak pressure (45 cmH(2)0) and low positive end-expiratory pressure (PEEP of 3 cmH(2)O) did not initially result in altered alveolar mechanics, but alveolar instability developed over time. ⋯ A large change in lung volume with each breath will, in time, lead to unstable alveoli and pulmonary damage. Reducing the change in lung volume by increasing the PEEP, even with high inflation pressure, prevents alveolar instability and reduces injury. We speculate that ventilation with large changes in lung volume over time results in surfactant deactivation, which leads to alveolar instability.
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Comment
Echocardiography and assessing fluid responsiveness: acoustic quantification again into the picture?
Accurate identification of fluid responsiveness has become an important issue in critically ill patients. Pulse pressure and stroke volume variation have been shown to be reliable predictors of fluid responsiveness. ⋯ Acoustic quantification is a high-tech tool for delineating the blood-tissue interface on-screen in real time. Cannesson and coworkers utilized this technique in ventilated patients to assess stroke area changes, with the intention being to predict fluid responsiveness.