Critical care : the official journal of the Critical Care Forum
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Key questions remain unresolved regarding the advantages and limitations of colloids for fluid resuscitation despite extensive investigation. Elucidation of these questions has been slowed, in part, by uncertainty as to the optimal endpoints that should be monitored in assessing patient response to administered fluid. Colloids and crystalloids do not appear to differ notably in their effects on preload recruitable stroke volume or oxygen delivery. ⋯ Colloids can be considered in patients with severe or acute shock or hypovolaemia resulting from sudden plasma loss. Colloids may be combined with crystalloids to obviate administration of large crystalloid volumes. Further clinical trials are needed to define the optimal role for colloids in critically ill patients.
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Greater understanding of the pathophysiology of carbon dioxide kinetics during steady and nonsteady state should improve, we believe, clinical care during intensive care treatment. Capnography and the measurement of end-tidal partial pressure of carbon dioxide (PETCO2) will gradually be augmented by relatively new measurement methodology, including the volume of carbon dioxide exhaled per breath (VCO2,br) and average alveolar expired PCO2. Future directions include the study of oxygen kinetics.
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Review
Fluid balance and colloid osmotic pressure in acute respiratory failure: emerging clinical evidence.
Available evidence suggests that both hydrostatic and osmotic forces are important in the development of acute respiratory distress syndrome (ARDS) or, more broadly, acute lung injury (ALI). More than 80% of ARDS patients in a large-scale randomized controlled trial (RCT) exhibited, at least intermittently, pulmonary artery wedge pressures (PAWP) above 18 mmHg. Retrospective analyses have shown that PAWP elevation is associated with increased mortality. ⋯ These results provide evidence that combined therapy with furosemide and albumin is effective in augmenting serum albumin and STP levels, promoting weight loss, and improving oxygenation and longer-term hemodynamic stability. Although mortality did not differ between groups, the RCT showed a trend toward reduced duration of mechanical ventilation and length of stay in the intensive care unit in patients receiving furosemide + albumin. The findings of the RCT further highlight the importance of both hydrostatic and osmotic forces in hypoxemic respiratory failure, a subject that requires further investigation.
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An advanced understanding of acid-base physiology is as central to the practice of critical care medicine, as are an understanding of cardiac and pulmonary physiology. Intensivists spend much of their time managing problems related to fluids, electrolytes, and blood pH. Recent advances in the understanding of acid-base physiology have occurred as the result of the application of basic physical-chemical principles of aqueous solutions to blood plasma. ⋯ These variables are carbon dioxide, relative electrolyte concentrations, and total weak acid concentrations. All changes in blood pH, in health and in disease, occur through changes in these three variables. Clinical implications for these findings are also discussed.
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Extracorporeal membrane oxygenation (ECMO) is a technique for providing life support, in case the natural lungs are failing and are not able to maintain a sufficient oxygenation of the body's organ systems. ECMO technique was an adaptation of conventional cardiopulmonary bypass techniques and introduced into treatment of severe acute respiratory distress syndrome (ARDS) in the 1970s. The initial reports of the use of ECMO in ARDS patients were quite enthusiastic, however, in the following years it became clear that ECMO was only of benefit in newborns with acute respiratory failure. ⋯ In conventional treatment lung-protective ventilation strategies were introduced and ECMO was made safer by applying heparin-coated equipment, membranes and tubings. Many ECMO centres now use these advanced ECMO technology and report survival rates in excess of 50% in uncontrolled data collections. The question, however, of whether the improved ECMO can really challenge the advanced conventional treatment of adult ARDS is unanswered and will need evaluation by a future RCT.