Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 47 Discontinuing Ventilatory Support Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. Learning Objectives Discuss the relationship between ventilatory demand and ventilatory capacity in the context of ventilator discontinuance. List factors associated with ventilator dependence. Explain how to evaluate a patient before attempting ventilator discontinuation or weaning. List acceptable values for specific weaning indices used to predict a patient’s readiness for discontinuation of ventilatory support. Describe factors that should be optimized before an attempt is made at ventilator discontinuation or weaning. Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 2 Learning Objectives (cont.) Describe techniques used in ventilator weaning, including daily spontaneous breathing trials, synchronized intermittent mandatory ventilation, pressure support ventilation, and other newer methods. Contrast the advantages and disadvantages associated with various weaning methods and techniques. Describe how to assess a patient for extubation. List the primary reasons why patients fail a ventilator discontinuance trial. Explain why some patients cannot be successfully weaned from ventilatory support. Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 3 Introduction Ventilatory support sustains life but is not curative Has many complications and hazards Should be withdrawn expeditiously All patients should be evaluated on a daily basis for their ability to wean from ventilatory support Balance desire for early extubation with its exposure to the risks of reintubation. Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 4 Ventilatory Capacity Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 5 All of the following are TRUE about mechanical ventilation, except: A. Ventilatory support sustains life but is not curative. B. It has few complications and hazards. C. It should be withdrawn expeditiously. D. All patients should be evaluated on a daily basis for their ability to wean from ventilatory support Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 6 Methods of Discontinuing Ventilation Three main methods 1. 2. 3. Spontaneous breathing trials (SBT) SIMV PSV Novel modes with no data to support VSV = volume support ventilation, MMV= mandatory minute volume ventilation, ATC = automatic tube compensation, PAV = proportional assist ventilation **Systematic review: 1 SBT per day has shown best results Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 7 Probability of Successful Weaning Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 8 Discontinuing Ventilatory Support In general, patients being considered for removal from ventilatory support fall into one of four categories: 1. 2. 3. 4. removal is quick and routine, normally the vast majority of patients need a more systematic approach, about 15 to 20% of ventilated patients require days to weeks to wean, usually less than 5% of patients ventilator-dependent or “unweanable” patients, less than 1% of patients Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 9 Global Criteria for Discontinuing Ventilatory Support (cont.) Success is tied to Ventilatory work load versus capacity Oxygenation status Cardiovascular status Psychological factors Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 10 Most Important Criteria 1. Reversal of disease state that necessitated ventilatory support 2. Oxygenation status adequate on <0.5 FIO2 3. Medically and hemodynamically stable 4. Patient can breathe spontaneously If the above are all true, then perform a formal evaluation for extubation. Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 11 66 Measurements: 8 Most Consistently Predictive Spontaneous rate Spontaneous VT f/VT (RSBI) – most predictive Minute ventilation MIP P0.1 6 to 30 beats/min >5 ml/kg <105 <10 L/min <20 to 30 mm Hg <6 cm H2O P0.1/MIP <0.3 CROP (CDyn, f, O2, PImax) >13 * No single index has high predictive power, so it is important to consider the total picture. Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 12 Which of the following predictive value is consistent with a patient weaning successfully? A. B. C. D. Spontaneous rate Spontaneous VT f/VT (RSBI) MIP 40 beats/min 4 mL/kg 85 –18 mm Hg Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 13 Preparing the Patient Patient should be rested and stable Maximize bronchodilator and antiinflammatory medications as well as bronchial hygiene Communicate well with patient so as to relieve/minimize anxiety Optimize nutrition, acid/base status, fluid balance, and oxygenation Minimize sedation Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 14 Rapid Ventilator Discontinuance Patients that are likely to wean rapidly Presenting problem corrected in 72 hours Good weaning parameters Good results in SBT of 30 to 120 minutes If the above criteria are met, most patients can be removed from ventilatory support If the patient can protect his or her airway, then extubate at this time Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 15 Progressive Weaning of Ventilatory Support Patients likely to need longer weaning period Ventilated longer then 72 hours Marginal: oxygen, ventilatory, cardiovascular, or medical status Most common methods of weaning: SBT alternating with rest periods on • A/C, SIMV, or significant levels of PSV Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 16 Progressive Weaning: SBT T-tube trial 5 to 30 minutes SBT 1 to 4 hours of rest on A/C, SIMV, or high PSV Gradually, SBT times increase while rest periods diminish Patients rested at night Alternate method is 1 SBT/day and then rest. This can also be done on the ventilator in CPAP mode with PSV or ATC. Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 17 Initial Screening SBT Perform 2–3 minute SBT. If 2 out of 3 of the criteria below are met, start formal wean VT RR MIP-a.k.a (NIF) >5 ml/kg <30–35 beats/min <20 cm H2O Alternate: adequate cough, no vasopressors P/F ratio PEEP f/VT >200 5 <105 Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 18 SBT Termination Termination occurs if any of these criteria met Agitation, anxiety, diaphoresis, altered mental state Respiratory rate > 30 or 35 beats/min SpO2 <90% 20% change in HR or HR > 120 to 140 beats/min Systolic BP > 180 mm Hg or < 90 mm Hg Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 19 Weaning With SIMV Faster weans claimed but contrary to evidence Ease of use is primary reason for use Evidence that at 50% of full ventilatory support, patient WOB approximates that on CPAP In addition, demand flow SIMV imposes considerable WOB Modern ventilators minimize this effect. Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 20 Weaning With SIMV (cont.) Support set below required level; patient makes up the difference. Once precipitating event corrects, support is rapidly reduced. Support is typically reduced in increments of 2 breaths per minute until spontaneous ventilation is achieved Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 21 All of the following are TRUE about SIMV weaning except: A. Faster weans claims are supported by evidence B. Ease of use is primary reason for use C. Evidence that at 50% of full ventilatory support, patient WOB approximates that on CPAP D. Demand flow SIMV imposes considerable WOB Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 22 PSV Weaning Level is set to PSVmax 6 to 10 ml/kg. On resolution of precipitating event PSV reduced increments 2 to 4 cm H2O, usually 1 to 2 times per day Rested at nights 2 strategies for discontinuance of PSV: • Patient tolerates PSV of 5 – 8 cm H2O with no distress • Patient tolerates CPAP with no PSV without distress Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 23 Monitoring During Weaning PaCO2 best index of adequacy of ventilation but only tied to clinical data PaCO2 40 mm Hg with f/VT of 250 shows impending ventilatory failure. PaCO2 40 mm Hg with f/VT of 40 shows ability to breathe spontaneously. SpO2 monitor continuously Cardiovascular status Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 24 Extubation Weaning and extubation separate decisions Extubation requires Ability to protect airway • Gag • Effective cough Airway patency • Minimal edema • Positive “cuff-leak” > 12% volume loss Adequate pulmonary hygiene Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 25 All of the following are required for extubation, except: A. B. C. D. Maximal edema Patients ability to protect airway Airway patency Adequate pulmonary hygiene Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 26 Postextubation Stridor Occurs in 2% to 16% of ICU patients Can result in complete airway obstruction Management includes Cool aerosol mist with oxygen via mask Nebulized racemic epinephrine (0.5 ml 2.25%) Nebulized 1 mg in 4 ml NS dexamethasone HeliOx 60%/40% Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 27 Failure of Extubation Up to 25% of patients require MV again Half of patients with distress following MV discontinuance develop marked hypercapnia Myocardial ischemia associated with failed weaning attempts Failed weans may be undiagnosed NMD or psychological dependence Most common reason: inadequate ventilatory capability which cannot meet ventilatory demand Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 28 Chronically Ventilator-Dependent Patients Prolonged MV occurs in 3% to 7% of ventilated patients, while <1% become dependent Definition: ventilator dependency remains following 3 months of weaning attempts Special long-term acute care facilities specialize in weaning these patients Once dependency established, goal is to restore highest level of independence Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 29 Terminal Weaning Refers to weaning in the face of catastrophic and irreversible illness Weaning occurs despite likely result of patient death Decision made by patient and/or family in consultation with physician. Must meet ethical and legal guidelines May be due to advanced directives, current patient decision, or very poor prognosis Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 30