Critical care clinics
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Critical care clinics · Jan 2002
ReviewCytopathic hypoxia. Is oxygen use impaired in sepsis as a result of an acquired intrinsic derangement in cellular respiration?
Several lines of evidence indicate that cellular energetics are deranged in sepsis, not by inadequate tissue perfusion but rather by impaired mitochondrial respiration; that is, organ dysfunction in sepsis may result from cytopathic hypoxia. If this concept is correct, the therapeutic implications are enormous. Efforts to improve outcome in septic patients by monitoring and manipulating cardiac output, systemic oxygen (DO2), and regional blood flow are doomed to failure. Instead, the focus should be on developing pharmacologic strategies (e.g., isoform-selective iNOS or PARP inhibitors) to restore normal mitochondrial function and cellular energetics.
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Critical care clinics · Jan 2002
ReviewNew therapies for adults with acute lung injury. High-frequency oscillatory ventilation.
High-frequency oscillatory ventilation seems theoretically ideal for the treatment of patients with ARDS, allowing adequate oxygenation and ventilation to be maintained without causing further damage to the already injured lung. High-frequency oscillating ventilation also seems a sound strategy for improving oxygenation in patients who are no longer responding to conventional mechanical ventilation. Currently, HFOV should be used in the adult ICU as one of many ancillary therapies available for the treatment of extremely ill, hypoxemic patients with ARDS. Future research may define the role of HFOV as a more routine strategy for preventing VALI in this patient population.
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The role of nitric oxide (NO) in numerous physiologic systems only recently has been discovered. When used as a gas, inhaled NO (iNO) has many unique properties that cause immediate improvements in pulmonary hemodynamics and oxygenation. Acute benefits in physiologic parameters have been demonstrated in numerous studies of iNO in acute respiratory distress syndrome (ARDS), but recent randomized controlled trials have failed to show improvement in outcome. The addition of other treatments that prolong or enhance the affect of iNO or its use with other ventilator modalities such as prone positioning or high-frequency ventilation offer hope that iNO may be beneficial in select groups of patients.
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In general, a rule for corticosteroids in preventing or relieving the acute respiratory distress syndrome (ARDS) has yet to be established, although these drugs are indicated for conditions such as Pneumocystis carinii pneumonia. High-dose corticosteroids have not been shown to reduce mortality through their anti-inflammatory properties when given early to patients with sepsis, septic shock, or ARDS. Corticosteroids have been shown, however, to reduce mortality in patients with late ARDS only in one small, inconclusive study. More recent investigators have focused on the usefulness of low-dose corticosteroids in reducing mortality in patients with sepsis or septic shock who may have relative adrenal insufficiency, but these studies also are inconclusive, and it is unclear that low-dose corticosteroids affect the development of ARDS in these patients.
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A clinically feasible method for assessing regional splanchnic perfusion is still lacking. Methods used for research purposes demonstrate that the effects of current therapies on splanchnic perfusion are not predictable in intensive care patients with and without ARDS. Tonometry, laser Doppler flowmetry, and spectrophotometry have been used to assess splanchnic perfusion. Combining the available methods in different parts of the gastrointestinal tract may help assess splanchnic perfusion more accurately in the near future.