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      Failed Weaning from Mechanical Ventilation and Cardiac Dysfunction

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          Abstract

          Failure to transition patient from controlled mechanical ventilation to spontaneous breathing trials (SBTs) in a timely fashion is associated with significant morbidity and mortality in the intensive care unit. In addition, weaning failures are common in patients with limited cardiac reserves. Recent advances in cardiac echocardiography and laboratory measurement of serum biomarkers to assess hemodynamic response to SBT may provide additional information to guide clinicians to predict weaning outcome.

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          Most cited references56

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          Weaning from mechanical ventilation.

          Weaning covers the entire process of liberating the patient from mechanical support and from the endotracheal tube. Many controversial questions remain concerning the best methods for conducting this process. An International Consensus Conference was held in April 2005 to provide recommendations regarding the management of this process. An 11-member international jury answered five pre-defined questions. 1) What is known about the epidemiology of weaning problems? 2) What is the pathophysiology of weaning failure? 3) What is the usual process of initial weaning from the ventilator? 4) Is there a role for different ventilator modes in more difficult weaning? 5) How should patients with prolonged weaning failure be managed? The main recommendations were as follows. 1) Patients should be categorised into three groups based on the difficulty and duration of the weaning process. 2) Weaning should be considered as early as possible. 3) A spontaneous breathing trial is the major diagnostic test to determine whether patients can be successfully extubated. 4) The initial trial should last 30 min and consist of either T-tube breathing or low levels of pressure support. 5) Pressure support or assist-control ventilation modes should be favoured in patients failing an initial trial/trials. 6) Noninvasive ventilation techniques should be considered in selected patients to shorten the duration of intubation but should not be routinely used as a tool for extubation failure.
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            Cardiovascular effects of continuous positive airway pressure in patients with heart failure and obstructive sleep apnea.

            Obstructive sleep apnea subjects the failing heart to adverse hemodynamic and adrenergic loads and may thereby contribute to the progression of heart failure. We hypothesized that treatment of obstructive sleep apnea by continuous positive airway pressure in patients with heart failure would improve left ventricular systolic function. Twenty-four patients with a depressed left ventricular ejection fraction (45 percent or less) and obstructive sleep apnea who were receiving optimal medical treatment for heart failure underwent polysomnography. On the following morning, their blood pressure and heart rate were measured by digital photoplethysmography, and left ventricular dimensions and left ventricular ejection fraction were assessed by echocardiography. The subjects were then randomly assigned to receive medical therapy either alone (12 patients) or with the addition of continuous positive airway pressure (12 patients) for one month. The assessment protocol was then repeated. In the control group of patients who received only medical therapy, there were no significant changes in the severity of obstructive sleep apnea, daytime blood pressure, heart rate, left ventricular end-systolic dimension, or left ventricular ejection fraction during the study. In contrast, continuous positive airway pressure markedly reduced obstructive sleep apnea, reduced the daytime systolic blood pressure from a mean (+/-SE) of 126+/-6 mm Hg to 116+/-5 mm Hg (P=0.02), reduced the heart rate from 68+/-3 to 64+/-3 beats per minute (P=0.007), reduced the left ventricular end-systolic dimension from 54.5+/-1.8 to 51.7+/-1.2 mm (P=0.009), and improved the left ventricular ejection fraction from 25.0+/-2.8 to 33.8+/-2.4 percent (P<0.001). In medically treated patients with heart failure, treatment of coexisting obstructive sleep apnea by continuous positive airway pressure reduces systolic blood pressure and improves left ventricular systolic function. Obstructive sleep apnea may thus have an adverse effect in heart failure that can be addressed by targeted therapy.
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              Acute left ventricular dysfunction during unsuccessful weaning from mechanical ventilation.

              The authors studied the hemodynamic effects of rapidly weaning from mechanical ventilation (MV) 15 patients with severe chronic obstructive pulmonary disease (COPD) and cardiovascular disease who were recovering from acute cardiopulmonary decompensation. In each patient, 10 min of spontaneous ventilation (SV) with supplemental oxygen resulted in reducing the mean esophageal pressure (X +/- SD, + 5 +/- 3 to -2 +/- 2.5 mmHg, P less than .01) and increasing cardiac index (CI) 3.2 +/- 0.9 to 4.3 +/- 1.3 1/min/M2, P less than .001), systemic blood pressure (BP 77 +/- 12 to 90 +/- 11 mmHg, P less than .001), heart rate (HR 97 +/- 12 to 112 +/- 16 beats/min, P less than .001), and, most importantly, transmural pulmonary artery occlusion pressure markedly increased (PAOPtm 8 +/- 5 to 25 +/- 13 mmHg, P less than .001), mandating a reinstitution of MV. In four patients with left ventricular (LV) catheters, the PAOP correlated with the LV end-diastolic pressure during both MV and SV. Gated blood pool imaging showed SV increased the LV end-diastolic volume index (65 +/- 24 to 83 +/- 32/M2, P less than .002) with LV ejection fraction unchanged. Patients were treated for a mean of 10 days with diuretics, resulting in a reduction of blood volume (4.55 +/- 0.9 1 to 3.56 +/- 0.55 1) and body weight (-5 kg, P less than .001). Subsequently, nine of the 15 patients were weaned successfully from mechanical ventilation with unchanged PAOP.
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                Author and article information

                Journal
                Crit Care Res Pract
                Crit Care Res Pract
                CCRP
                Critical Care Research and Practice
                Hindawi Publishing Corporation
                2090-1305
                2090-1313
                2012
                6 September 2012
                : 2012
                : 173527
                Affiliations
                1VA Western New York Healthcare System, Division of Critical Care Medicine, Department of Anesthesiology and Medicine, Buffalo School of Medicine and Biomedical Sciences, The State University of New York, Buffalo, NY 14215, USA
                2Strong Memorial Hospital, University of Rochester, Rochester, NY 14642, USA
                3VA Western New York Healthcare System, Division of Cardiothoracic Anesthesia and Pain Medicine, Department of Anesthesiology, Buffalo School of Medicine and Biomedical Sciences, The State University of New York, Buffalo, NY 14215, USA
                Author notes
                *Jahan Porhomayon: jahanpor@ 123456buffalo.edu

                Academic Editor: Zsolt Molnar

                Article
                10.1155/2012/173527
                3443576
                22991658
                64f0e772-ef4a-46b5-a491-128f649784a5
                Copyright © 2012 Jahan Porhomayon et al.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 20 June 2012
                : 3 August 2012
                Categories
                Review Article

                Emergency medicine & Trauma
                Emergency medicine & Trauma

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