Der Anaesthesist
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Preventive strategies aim to reduce gastric acidity (H2-antagonists, antacids), to strengthen mucosal defence mechanisms (sucralfate, antacids, pirenzepine) and to normalize gastric mucosal microcirculation (sucralfate, pirenzepine). Thus, the most important prophylactic measure is an optimized emergency and ICU regime aiming to improve oxygenation and microcirculation. All specific drugs used for stress ulcer prophylaxis have been shown to be effective in prospective controlled studies. ⋯ The most important adverse effect of stress ulcer prophylaxis is nosocomial pneumonia due to gastric alkalinization. This may occur in long-term ventilated patients with a gastric pH > 4 and may account for up to 50% of all nosocomial pneumonias in certain groups of patients. Mortality is not influenced by antacids or H2-antagonists, while sucralfate has been shown to reduce mortality, most probably by inhibition of bacterial translocation.
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Although the attempts to develop an oxygen-carrying alternative to red blood cells (RBC) have spanned the last 100 years, it has proven difficult to develop a clinically useful haemoglobin-based oxygen carrier. Four major problems have been shown to compromise the use of haemoglobin outside the RBC as an oxygen carrier: (1) the increased oxygen affinity due to the loss of 2,3-diphosphoglycerate; (2) dissociation into dimers and monomers with consequent renal and capillary loss of hemoglobin; (3) insufficient concentrations of prepared solutions under iso-oncotic conditions, and thereby reduced oxygen-carrying capacity; and (4) toxicity. Most of these limitations have been overcome by different modifications of haemoglobin, including pyridoxylation, intra- and intermolecular cross-linking, polymerisation, liposome encapsulation, conjugation to inert macromolecules, and genetic engineering. ⋯ Based on promising and reproducible results obtained from animal studies, clinical phase I and II trials with newer haemoglobin solutions have been started in the United States. Substantial knowledge has been gained in the development, production, and evaluation of haemoglobin-based oxygen carriers during the past years. It will probably not take another century before oxygen-carrying RBC substitutes will become available for clinical use.