Successful Weaning In Patients Research Articles

Blood markers of oxidative stress predict weaning failure from mechanical ventilation.

Patients undergoing mechanical ventilation (MV) often experience respiratory muscle dysfunction, which complicates the weaning process. There is no simple means to predict or diagnose respiratory muscle dysfunction because diagnosis depends on measurements in muscle diaphragmatic fibre. As oxidative stress is a key mechanism contributing to MV-induced respiratory muscle dysfunction, the aim of this study was to determine if differences in blood measures of oxidative stress in patients who had success and failure in a spontaneous breathing trial (SBT) could be used to predict the outcome of MV. This was a prospective analysis of MV-dependent patients (≥72 hrs; n = 34) undergoing a standard weaning protocol. Clinical, laboratory and oxidative stress analyses were performed. Measurements were made on blood samples taken at three time-points: immediately before the trial, 30 min. into the trial in weaning success (WS) patients, or immediately before return to MV in weaning failure (WF) patients, and 6 hrs after the trial. We found that blood measures of oxidative stress distinguished patients who would experience WF from patients who would experience WS. Before SBT, WF patients presented higher oxidative damage in lipids and higher antioxidant levels and decreased nitric oxide concentrations. The observed differences in measures between WF and WS patients persisted throughout and after the weaning trial. In conclusion, WF may be predicted based on higher malondialdehyde, higher vitamin C and lower nitric oxide concentration in plasma.

Effect of noninvasive positive pressure ventilation on weaning success in patients receiving invasive mechanical ventilation: a meta-analysis

Background Noninvasive positive pressure ventilation (NIPPV) has been proposed to shorten the duration of mechanical ventilation in intubated patients, especially those who fail initial weaning from invasive mechanical ventilation (IMV). However, there are also some discrepancies in terms of weaning success or failure, incidence of re-intubation, complications observed during study and patient outcomes. The primary objective of this update was to specifically investigate the role of NIPPV on facilitating weaning and avoiding re-intubation in patients intubated for different etiologies of acute respiratory failure, by comparing with conventional invasive weaning approach. Methods We searched randomized controlled trials (RCTs) comparing noninvasive weaning of early extubation and immediate application of NIPPV with invasive weaning in intubated patients from PubMed, Embase, Cochrane Central Register of Controlled Trials, Web of Knowledge and Springerlink databases. Records from conference proceedings and reference lists of relevant studies were also identified. Results A total of 11 RCTs with 623 patients were available for the present analysis. Compared with IMV, NIPPV significantly increased weaning success rates (odds ratio (OR): 2.50, 95% confidence interval (CI): 1.46-4.30, P=0.0009), decreased mortality (OR: 0.39, 95% CI: 0.20-0.75, P=0.005), and reduced the incidence of ventilator associated pneumonia (VAP) (OR: 0.17, 95% CI: 0.08-0.37, P <0.00001) and complications (OR: 0.22, 95% CI: 0.07-0.72, P=0.01). However, effect of NIPPV on re-intubation did not reach statistical difference (OR: 0.61, 95% CI: 0.33-1.11, P=0.11). Conclusions Early extubation and immediate application of NIPPV is superior to conventional invasive weaning approach in increasing weaning success rates, decreasing the risk of mortality and reducing the incidence of VAP and complications, in patients who need weaning from IMV. However, it should be applied with caution, as there is insufficient beneficial evidence to definitely recommend it in terms of avoiding re-intubation.

Probing with the ventilator

Neurally adjusted ventilatory assist operates through recordings of electrical activity of the diaphragm (EAdi). Barwing and colleagues found increases in EAdi in weaning-failure patients, although the values were not significantly different from weaning-success patients. Future studies will need to carefully control for the considerable biological noise evident in EAdi recordings.

Testing the prognostic value of the rapid shallow breathing index in predicting successful weaning in patients requiring prolonged mechanical ventilation

ObjectiveThe study objective was to assess the prognostic value of the rapid shallow breathing index (RSBI) in predicting successful weaning of patients from prolonged mechanical ventilation (PMV) in long-term acute care (LTAC) facilities. The RSBI predicts successful ventilator weaning in acutely ill patients. However, its value in PMV is unclear. MethodsA retrospective cohort study of patients receiving PMV in LTAC facilities was performed. RSBI was measured daily, with weaning per protocol. Initial, mean, and final RSBI; RSBI ≤ 105; rate of change; and variability were assessed. ResultsTwenty-five of 52 patients were weaned from PMV. Only the mean RSBI and the RSBI on the last day of weaning predicted success (78.7 ± 14.2 vs 99.3 ± 30.2, P = .007; 71.7 ± 31.2 vs 123.3 ± 92.5, P = .005, respectively). RSBI variability and rate of change were different between groups (coefficient of variation, .37 ± .12 vs .51 ± .30, P = .02, rate of change: −3.40 ± 9.40 vs 4.40 ± 11.1 RSBI points/day, P = .005, weaned vs failed). ConclusionAlthough isolated RSBI measurements do not predict successful weaning from PMV, RSBI trends may have prognostic value.

The Relationship of 26 Clinical Factors to Weaning Outcome

The Burns Wean Assessment Program (BWAP) assessment checklist is designed to assist clinicians in the systematic evaluation of 26 clinical factors important to weaning. The authors recently described the relationship of the BWAP score (derived from the checklist) to weaning trial outcomes (weaning success or failure) in patients receiving mechanical ventilation for 3 days or longer in 5 adult critical care units. A BWAP score of 50 or higher was significantly associated with weaning success regardless of the specific category of patient (surgical, medical, cardiovascular, etc). This secondary analysis extends the evaluation of the BWAP checklist as it focuses on the importance of each individual BWAP factor to weaning outcomes in 5 different populations of patients. To identify the relative importance of the 26 BWAP factors to weaning success in patients undergoing mechanical ventilation for 3 days or longer in 5 adult critical care units. BWAP checklists were completed within 24 hours of a weaning attempt in surgical-trauma, medical, neurological, thoracic-cardiovascular, and coronary care units in a 5-year period. Advanced practice nurses using a multidisciplinary pathway, the BWAP checklist, protocols for weaning trials, and sedation guidelines managed the patients similarly. A total of 20 BWAP factors were significantly associated with successful weaning in all units combined (P ≤ .02). However, some differences in the importance of the BWAP factors to weaning outcome exist between units, with the neuroscience intensive care unit deviating the most from the other units. Although not all BWAP factors are significantly associated with weaning success, most are predictive. Restructuring the BWAP as a unit-specific weaning checklist and potential predictor may assist clinicians to address factors that may impede weaning more efficiently and effectively.

Predictors of successful extracorporeal membrane oxygenation (ECMO) weaning after assistance for refractory cardiogenic shock

Detailed extracorporeal membrane oxygenation (ECMO) weaning strategies and specific predictors of ECMO weaning success are lacking. This study evaluated a weaning strategy following support for refractory cardiogenic shock to identify clinical, hemodynamic, and Doppler echocardiography parameters associated with successful ECMO removal. Hemodynamically stable patients underwent ECMO flow reduction trials to <1.5 L/min under clinical and Doppler echocardiography monitoring. When a patient had partially or fully recovered from severe cardiac dysfunction, tolerated the weaning trial, and had left ventricular ejection fraction (LVEF) >20-25% and aortic time-velocity integral (VTI) >10 cm under minimal ECMO support, device removal was considered. Among the 51 patients (34 males, aged 54 ± 14 years) who received ECMO for medical (n = 27), postcardiotomy (n = 11), or posttransplantation (n = 5) cardiogenic shock, 38 tolerated at least one ECMO flow reduction trial and 20 were ultimately weaned. Compared with the 13 patients who tolerated the trial but were not deemed weanable, those successfully weaned had, at each ECMO flow level, higher arterial systolic and pulse pressures, VTI, LVEF, and lateral mitral annulus peak systolic velocity (TDSa). All weaned patients had aortic VTI ≥10 cm, LVEF >20-25%, and TDSa ≥6 cm/s at minimal ECMO flow support. These Doppler echocardiography parameters better separated weaned and nonweaned patients than any other parameters tested. Patients who tolerated a full ECMO weaning trial and had aortic VTI ≥10 cm, LVEF >20-25%, and TDSa ≥6 cm/s at minimal ECMO flow were all successfully weaned. However, further studies are needed to validate these simple and easy-to-acquire Doppler echocardiography parameters as predictors of subsequent ECMO weaning success in patients recovering from severe cardiogenic shock.

Hypercapnia Test and Weaning outcome from Mechanical Ventilation in COPD Patients

We evaluated the hypercapnia response test as a weaning outcome predictor from mechanical ventilation in patients with chronic obstructive pulmonary disease (COPD). We studied 44 COPD intubated patients considered ready for a weaning trial. The hypercapnia test was based on the modified method of re-inhalation of expired air Through the hypercapnic test we calculated the ratio of the change in minute volume (V(E)) to the change in PaCO2 (deltaV(E)/deltaPaCO2), the change in airway occlusion pressure at 0.1 second of inspiration (P0.1) to change in PaCO2 (deltaP0.1/deltaPACO2), the ratio of the change in P0.1 to baseline PaCO2 (deltaP0.1/PaCO2) and the ratio of the change in V(E) to baseline PaCO2 (deltaV(E)/PaCO2). Nineteen patients were successfully weaned and 25 patients failed. No differences in baseline clinical characteristics were found between the two groups. Weaning failure COPD patients had lower deltaP0.1/deltaPaCO2 (0.19 +/- 0.11 and 0.34 +/- 0.20 cm H2O/mmHg respectively, P = 0.006) and lower deltaV(E)/deltaPaCO2 (0.21 +/- 0.15 and 0.40 +/- 0.22 l/min/mmHg respectively, P = 0.002) than successfully weaned patients. The area under the receiver operating characteristic curve to discriminate weaning outcome was for the baseline PaCO2 0.81 (95% confidence interval: 0.66 to 0.91), hypercapnic PaCO2 0.76 (0.61 to 0.88), hypercapnic drive response 0.74 (0.59 to 0.86), hypercapnic ventilatory response 0.76 (0.60 to 0.87), deltaP0.1/PaCO2 0.76 (0.60 to 0.87) and for the deltaV(E)/PaCO2 0.81 (0.67 to 0.91). COPD patients with weaning failure have a significantly more blunted response to the hypercapnia response test than weaning success patients. This test could be useful to predict weaning failure patients if the combined values of the hypercapnic drive and hypercapnic ventilatory response were below the threshold values.

Determinants of weaning success in patients with prolonged mechanical ventilation

IntroductionPhysiological determinants of weaning success and failure are usually studied in ventilator-supported patients, comparing those who failed a trial of spontaneous breathing with those who tolerated such a trial and were successfully extubated. A major limitation of these studies was that the two groups may be not comparable concerning the severity of the underlying disease and the presence of comorbidities. In this physiological study, we assessed the determinants of weaning success in patients acting as their own control, once they are eventually liberated from the ventilator.MethodsIn 30 stable tracheotomised ventilator-dependent patients admitted to a weaning center inside a respiratory intensive care unit, we recorded the breathing pattern, respiratory mechanics, inspiratory muscle function, and tension-time index of diaphragm (TTdi = Pdisw/Pdimax [that is, tidal transdiaphragmatic pressure over maximum transdiaphragmatic pressure] × Ti/Ttot [that is, the inspiratory time over the total breath duration]) at the time of weaning failure (T0). The measurements were repeated in all the patients (T1) either during a successful weaning trial (successful weaning [SW] group, n = 16) or 5 weeks later, in the case of repeated weaning failure (failed weaning [FW] group, n = 14).ResultsCompared to T0, in the FW group at T1, significant differences were observed only for a reduction in spontaneous breathing frequency and in TTdi (0.21 ± 0.122 versus 0.14 ± 0.054, P = 0.008). SW patients showed a significant increase in Pdimax (34.9 ± 18.9 cm H2O versus 43.0 ± 20.0, P = 0.02) and decrease in Pdisw/Pdimax (36.0% ± 15.8% versus 23.1% ± 7.9%, P = 0.004).ConclusionsThe recovery of an inadequate inspiratory muscle force could be the major determinant of 'late' weaning success, since this allows the patients to breathe far below the diaphragm fatigue threshold.

Levetiracetam in children with refractory status epilepticus

The objective of this study was to investigate the utility of levetiracetam (LEV) in children with refractory status epilepticus (RSE). Records of children with RSE who received LEV as adjunctive therapy were reviewed. Over a 7-year period, 11 children had received LEV for RSE. Age ranged from 2 days to 9 years (median = 2.5 months). Prior to administration of LEV, the number of anticonvulsants used to treat RSE ranged from 2 to 7 (median = 3). Starting doses of LEV ranged from 15 to 70 mg/kg (median = 30 mg/kg). LEV was felt to be of benefit in 45% (5/11) of cases, resulting in either resolution of RSE or successful weaning of patients off continuous infusions of other anticonvulsants. In 27% (3/11), response to LEV was unclear as other medications were either added or increased concomitantly with LEV use. The median latency to cessation of RSE following LEV initiation was 1.5 days (range = 1-8 days). All responding patients were on LEV doses >or= 30 mg/kg/day (median 40 mg/kg/day). No significant adverse effects of LEV were reported. LEV may be an effective and safe adjuvant therapy in children with RSE.

Sternomastoid, rib cage, and expiratory muscle activity during weaning failure

We hypothesized that patients who fail weaning from mechanical ventilation recruit their inspiratory rib cage muscles sooner than they recruit their expiratory muscles, and that rib cage muscle recruitment is accompanied by recruitment of sternomastoid muscles. Accordingly, we measured sternomastoid electrical activity and changes in esophageal (DeltaPes) and gastric pressure (DeltaPga) in 11 weaning-failure and 8 weaning-success patients. At the start of trial, failure patients exhibited a higher DeltaPga-to-DeltaPes ratio than did success patients (P = 0.05), whereas expiratory rise in Pga was equivalent in the two groups. Between the start and end of the trial, failure patients developed additional increases in DeltaPga-to-DeltaPes ratio (P < 0.0014) and the expiratory rise in Pga also increased (P < 0.004). At the start of trial, sternomastoid activity was present in 8 of 11 failure patients contrasted with 1 of 8 success patients. Over the course of the trial, sternomastoid activity increased by 53.0 +/- 9.3% in the failure patients (P = 0.0005), whereas it did not change in the success patients. Failure patients recruited their respiratory muscles in a sequential manner. The sequence began with activity of diaphragm and greater-than-normal activity of inspiratory rib cage muscles; recruitment of sternomastoids and rib cage muscles approached near maximum within 4 min of trial commencement; expiratory muscles were recruited slowest of all. In conclusion, not only is activity of the inspiratory rib cage muscles increased during a failed weaning trial, but respiratory centers also recruit sternomastoid and expiratory muscles. Extradiaphragmatic muscle recruitment may be a mechanism for offsetting the effects of increased load on a weak diaphragm.

Do Diagnoses and Comorbidities Influence Survival and Weaning Success in Patients Requiring Long-term Ventilator Support?

PURPOSE: To show the effects on outcomes of primary diagnoses and co-morbidities in 157 patients admitted in 2003 to a long-term ventilator support unit with active weaning. Patients were followed until discharge or 3/31/04.

Creatinine Height Index and Nutritional Status as Predictors of Successful Liberation From Prolonged Mechanical Ventilatio

PURPOSE: Malnutrition reduces respiratory muscle mass and can contribute to failure to wean and ventilator dependency in patients on prolonged mechanical ventilation (PMV). Creatinine Height Index (CHI), which reflects lean muscle mass, is regarded as the most accurate indicator of malnutrition. No previous studies have assessed the relation between CHI and weaning. The objective of this study was to determine if CHI can predict successful weaning in patients on PMV in comparison with traditional nutritional indices in a regional weaning center (RWC).

Hemodynamic responses to successful weaning from mechanical ventilation after cardiovascular surgery.

Weaning from mechanical ventilation is usually associated with an increase in oxygen consumption (VO2), which may stress the cardiovascular system. We studied relative changes in the cardiac index and oxygen extraction ratio (EO2) during successful weaning in patients after cardiac surgery (n = 52), cardiac transplantation (n = 17), or abdominal aortic surgery (n = 11). Cardiac index was determined by the thermodilution technique and arterial and mixed venous blood gases were obtained before and 30 min after the start of weaning through a T-piece. The cardiovascular changes were evaluated in 42 patients in whom VO2 (calculated by Fick's equation) increased by more than 10%. Cardiac index increased more after abdominal aortic surgery (from 3.27 +/- 0.77 to 4.44 +/- 0.581 min(-1) m(-2), p < 0.01) than after cardiac surgery (from 2.53 +/- 0.59 to 2.87 +/- 0.46 1 min(-1) m(-2), p < 0.01) or cardiac transplantation (from 2.99 +/- 0.64 to 3.33 +/- 0.741 min(-1) m(-2), p < 0.05). EO2 remained stable in patients after aortic surgery (from 25.9 +/- 7.1 to 25.2 +/- 5.6 %, NS) but increased slightly after cardiac surgery (from 33.3 +/- 6.1 to 37.3 +/- 6.4%, NS) and significantly after cardiac transplantation (from 25.8 +/- 4.1 to 28.2 +/- 4.0%, p < 0.05). Hence the cardiovascular response to weaning from mechanical ventilation may vary according to the type of surgery.

Changes in breathing pattern and respiratory muscle performance parameters during difficult weaning.

This study examined, using noninvasive means, the changes in breathing pattern and inspiratory muscle pressure-time indices during difficult progressive withdrawal of pressure-support ventilation. A prospective analysis of the temporal evolution of several respiratory variables in difficult-to-wean patients. A university hospital intensive care unit. A heterogeneous group of 17 patients receiving prolonged mechanical ventilation. Daily measurements of breathing pattern and respiratory muscle performance parameters in difficult-to-wean patients. We examined breathing pattern variables, rapid shallow breathing (respiratory rate/tidal volume), tracheal occlusion pressure, maximal inspiratory pressure (P(I)max), and the tension-time index of the inspiratory muscles (TTmus = P(I)/P(I)max x Ti/Ttot) (where Ti/Ttot is inspiratory fraction of the cycle). All measurements were repeated at 24-hr intervals throughout the difficult weaning period. The patients were extubated on satisfying ten of 12 classical weaning criteria. Eleven patients were successfully weaned from mechanical ventilation while six patients were not. Weaning failure was associated with the following: a) longer periods of mechanical ventilation before weaning; b) high values of tracheal occlusion pressure, respiratory rate, minute ventilation, and effective impedance maintained throughout the difficult weaning period; and c) persistent high PaCO2 and intrinsic positive end-expiratory pressure values. As the weaning failure patients' inspiratory muscles confronted an increasing inspiratory load, values of the tension-time index of the inspiratory muscles entered or remained in the fatigue zone. In contrast, weaning success patients normalized their breathing pattern and decreased their tracheal occlusion pressure, effective impedance, and tension-time index values. Breathing pattern alterations and respiratory muscle performance impairments lead to ventilator dependency after prolonged mechanical ventilation. The measurement of variables such as the noninvasive tracheal occlusion pressure, inspiratory power of breathing, and tension-time index of the inspiratory muscles facilitate the management of difficult-to-wean patients.

Comparison of Standard Weaning Parameters and the Mechanical Work of Breathing in Mechanically Ventilated Patients

Standard bedside criteria of respiratory mechanical capability and the mechanical work of spontaneous breathing were measured in 17 mechanically ventilated patients. Eleven patients were extubated within 24 hs of study and required only a brief period of mechanical ventilation (group 1). Group 2 consisted of six patients requiring more prolonged ventilator support. Group 1 patients met three of four bedside criteria; seven patients met all four. Five of six patients in group 2 also satisfied three of four standard criteria while ventilator-dependent, whereas only two patients satisfied all four when successfully weaning. As group 2 patients progressed from unsuccessful to successful weaning there was no consistent improvement in bedside criteria; however, measures of work did significantly improve. Hence, satisfaction of bedside mechanical weaning criteria is associated with weaning success in patients requiring brief mechanical ventilation. In patients requiring prolonged ventilation, work may be a better indicator of successful weaning.