International anesthesiology clinics
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Int Anesthesiol Clin · Jan 1999
ReviewThe role of the gut in major surgical postoperative morbidity.
Gut mucosal hypoperfusion has been termed the motor of multiple organ failure. While a large proportion of high-risk surgery proceeds unremarkably, the insult to the inflammatory system during perioperative periods of regional hypoperfusion may manifest themselves over the subsequent few days, leading to microvascular thrombi, organ dysfunction, and failure. Several approaches have been made to prevent this, including systemic optimization of the cardiovascular system and specific targeting of the splanchnic circulation with monitoring techniques such as tonometry or metabolic markers of hepatic function to guide fluid and drug therapies. ⋯ Techniques that may help us identify at-risk patients may include in-depth cardiovascular assessment, possibly with echocardiography or a noninvasive cardiac output monitor such as the suprasternal adaptation of the ODM esophageal Doppler. The measurement of baseline endotoxin immune status (EndoCAb) may select those patients in advance who are most at-risk from gut mucosal hypoperfusion, thus allowing a more rational use of tonometry. Conventional risk scoring systems used in conjunction with knowledge of the type of surgery to be undertaken and whether large fluid shifts are likely along with the less conventional techniques discussed above may enable perioperative therapy to be closer to optimal.
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In this review, traditional weaning parameters, integrative indexes, and experimental methods of predicting weaning outcomes have been reviewed. All have limitations; however, judicious application of these parameters may guide clinical decisions regarding timing of weaning trials. Of the parameters reviewed, the RSBI has several advantages and may identify patients who are candidates for weaning. ⋯ Most patients will be successfully extubated after a single SBT, and weaning methods that focus on sequential decrements in ventilator support appear to needlessly prolong ventilation. However, for patients who fail, identification of potential causes of continued ventilator dependence should focus on the various pathophysiological causes outlined. Although a number of patients will require prolonged ventilator support beyond the critical care setting, the growing experience with this population demonstrates that a large percentage have favorable outcomes.