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Difficult Weaning

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Title: Difficult Weaning


1
  • Difficult Weaning
  • Dr. Hanaa El Gendy
  • Lecturer Of Anesthesia and Intensive care

2
Learning Objectives
  • 1) The epidemiology of weaning problems.
  • 2) The pathophysiology of weaning failure.
  • 3) The usual process of initial weaning from the
    ventilator.
  • 4) Is there a role for different ventilator modes
    in difficult weaning?
  • 5) How should patients with prolonged weaning
    failure be managed?

3
Definition Of Weaning
  • - Gradual reduction of ventilatory support from
    pts. whose condition is improving.
  • - 80 of patients requiring temporary mechanical
    ventilation do not require a slow withdrawal
    process and can be disconnected within hours or
    days of initial support.
  • - 20 of all initial weaning attempts in
    mechanically ventilated ICU patients failed.
  • - Prolongation of mechanical ventilation is
    associated with weaning failure.

4
Schematic Representation of the Different Stages
Occurring in aMechanically Ventilated Patient
Martin J. Tobin 2001
Definition of the different stages, from initiation to mechanical ventilation to weaning Definition of the different stages, from initiation to mechanical ventilation to weaning
Stages Definitions
Treatment of ARF Period of care and resolution of the disorder that caused respiratory failure and prompted mechanical ventilation
Suspicion The point at which the clinician suspects the patient may be ready to begin the weaning process
Assessing readiness to wean Daily testing of physiological measures of readiness for weaning (NIF, fR/VT) to determine probability of weaning success
Spontaneous breathing trial Assessment of the patients ability to breathe spontaneously
Extubation Removal of the endotracheal tube
Reintubation Replacement of the endotracheal tube for patients who are unable to sustain spontaneous ventilation

5
  • Weaning tends to be delayed
  • -Exposing the patient to unnecessary discomfort
  • -Increased risk of complications
  • -Increasing the cost of care and mortality 12 vs
    27 .
  • Time spent in the weaning process ?4050 of the
    total duration of mechanical ventilation
  • The incidence of unplanned extubation ranges ?
    0.316.
  • In most cases (83), the unplanned extubation is
    initiated by the patient, while 17 are
    accidental
  • Almost half of patients with self-extubation
    during the weaning period do not require
    reintubation

6
Definitions of Weaning Success and Failure
  • Weaning success is defined as
  • Extubation and the absence of ventilatory support
    48 hs following the extubation.
  • Weaning in progress Requirement of NIV after
    extubation
  • Weaning failure is defined as one of the
    following
  • 1)Failed SBT
  • 2) Reintubation and/or resumption of ventilatory
    support 48 hs following successful extubation or
  • 3) Death within 48 hs following extubation.

7
Classification of Patients According to the
Weaning Process
Group Definition Frequency ICU mortality Hospital mortality
(1)Simple weaning Patients who proceed from initiation of weaning to successful extubation on the first attempt without difficulty 69 5 12
(2) Difficult weaning Patients who fail initial weaning and require up to three SBT or as long as 7 days from the first SBT to achieve successful weaning 16 25
(3) Prolonged weaning Patients who fail at least three weaning attempts or require ? 7 days of weaning after the first SBT 15 25
Boles, et al. Eur Respir J 2007
8
The Pathophysiology of Weaning Failure
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11
Common Pathophysiologies which may Impact on the
Ability to Wean a Patient from Mechanical
Ventilation
Pathophysiology Consider
Respiratory load Increased work of breathing inappropriate ventilator settings Reduced compliance pneumonia (ventilator-acquired) cardiogenic or noncardiogenic oedema pulmonary fibrosis pulmonary haemorrhage diffuse pulmonary infiltrates Airway bronchoconstriction Increased resistive load During SBT endotracheal tube Post-extubation glottic oedema increased airway secretions sputum retention
Cardiac load Cardiac dysfunction prior to critical illness Increased cardiac workload leading to myocardial dysfunction increased metabolic demand unresolved sepsis Brain natriuretic peptide (BNP) -elevation is associated with weaning failure gt712 gt weaning failure gt864 gt reintubation ?transthoracic echocardiography (TTE) - detects decreased left ventricular ejection fraction during SBT Schifelbain LM et al 2011
Neuromuscular Depressed central drive metabolic alkalosis mechanical ventilation sedative/hynotic medications Central ventilatory command failure of the neuromuscular respiratory system Peripheral dysfunction primary causes of neuromuscular weakness CINMA
Neuropsychological Delirium 22-80 Anxiety, depression 30-75
Metabolic Metabolic disturbances Role of corticosteroids Hyperglycaemia
Nutrition Overweight ( body mass index ? 25 kg/m2) Malnutrition (body mass index ? 20 kg/m2) 40 Ventilator-induced diaphragm dysfunction
Anaemia Hb lt 8 gm/dl (8-10 gm/dl)
. .
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14
HOW DOES LATENT MYOCARDIAL DYSFUNCTION BECOME
MANIFEST DURING WEANING ?
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17
The Usual Process of Initial Weaning from the
Ventilator
18
As EARLY as possible lt 72 hsUnderestimate the
ability of patients to be successfully
weanedDiscontinuation of sedation is a critical
step ( dexmetedomedine might be a good
choice)2 step strategyAssessment readiness
for weaning / extubationSpontaneous breathing
trial (SBT)
19
Considerations for Assessing Readiness to Wean
Clinical assessment Adequate cough Absence of excessive thick tracheobronchial secretion Resolution of disease acute phase for which the patient was intubated
Objective measurements Clinical stability Stable cardiovascular status (i.e. fC ? 140 beats/min, systolic BP 90160 mmHg, no or minimal vasopressors) Stable metabolic status Negative fluid balance adequate nutrition Adequate oxygenation SaO2 ? 90 on ? FIO2 0.4 (or PaO2/FIO2 ? 150 mmHg) PEEP ? 5 -8 cmH2O P(A-a)O2 lt 350 on FIO2 1.0 SvO2 gt 60 P(a/A)O2 gt .35 Oxygen index FIO2 x MAP x 100/ PaO2 very good lt 5 medium 10 20 poor gt 25 Adequate pulmonary function fR ? 34 breaths/min Vd?Vt lt 0.6 (0.25-0.4) NIF ? -20 -25 cmH2O VT ? 5 mL/kg CROP weaning index 13 VC ? 10 mL/kg fR/VT 60-105 breaths/min/L Or 130? age gt 65 No significant respiratory acidosis Adequate mentation No sedation or adequate mentation on sedation (or stable neurologic patient)

RSBI respiratory frequency (fR) / VT Predicts
successful SBT sensitivity 0.97 specificity
0.65
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21
Spontaneous Breathing Trial
  • T-tube trial
  • Low levels of pressure support (PS)
  • 68 cmH2O in adults, 10 cmH2O in pediatrics
  • 3-14 cmH2O inspiratory pressure is needded to
    overcome resistance of endotracheal tube
  • CPAP
  • AUTOMATIC TUBE COMPENSATION (ATC)
  • Designed to reduce work associated with ET
    resistance

22
  • Duration Esteban et al. AJRCCM, 1999
  • Patients who fail an SBT do so within first 20
    min
  • Success rate for an initial SBT is similar for a
    30-min compared with a 120-min trial
  • Reintubation rate
  • Passing SBT ? 13 Do not receive SBT ? 40
  • Low levels PEEP
  • 5 cmH2O PEEP during an SBT
  • COPD More likely to pass 30-min SBT with 57.5
    cmH2O CPAP Reissmann et al, ICM, 2000

23
Passing SBT
  • Respiratory pattern
  • Gas exchange
  • Haemodynamic stability
  • Subject comfort

Q2
24
Tobin. Principles and Practice of Mechanical
Ventilation, McGraw-Hill, 1994, s1192
25
Failed SBT
  • Repeated frequently (daily) SBT
  • Unnecessary prolongation of a failed SBT can
    result in muscle fatigue, hemodynamic
    instability, discomfort or worsening gas
    exchange.
  • Nonfatiguing mode of mechanical ventilation (A/C
    or PSV) ?
  • ESTEBAN et al. AJRCCM 2000 Weaning method
  • PS 36, SIMV 5, SIMV PS 28, intermittent SBT
    17 daily SBT 4
  • ESTEBAN et al. JAMA 2002 Weaning trial
  • Once-daily SBT in 89 T-tube 52, CPAP 19, PS
    28

26
Termination of SBT
  • -RR gt 30 for 5 min
  • -SpO2 lt 90 for 30 sec
  • -20 change in HR for gt 5 min
  • -P SYS gt 180 or lt 90 for 1 min
  • -Anxiety, agitation or diaphoresis
  • for 5 min

27
  • Extubation
  • Neurological status
  • Although depressed mentation is frequently
    considered a contra-indication to extubation, a
    low reintubation rate (9) in stable
    brain-injured patients with a Glasgow coma score
    ?4 COPLIN et al. 2001
  • KOH et al. 2005 GCS did NOT predict extubation
    failure
  • Excessive secretions
  • KHAMIEES et al. 2006 Poor cough strength and
    excessive secretions were common in patients who
    failed extubation following a successful SBT.
  • Airway obstruction
  • Positive leak test is adequate before proceeding
    with extubation.A successful cuff leak test does
    not guarantee that post-extubation difficulties
    will not arise.

28
Criteria for extubation failure
  • -fR gt25 breaths/min for 2 h
  • -HR gt140 beats/min or sustained increase or
    decrease of gt 20
  • -Clinical signs of respiratory muscle fatigue or
    increased work of breathing
  • -SpO2 lt 90 PaO2 lt80 mmHg on FiO2 0.50
  • -Hypercapnia (PaCO2 gt 45 mmHg or 20 from
    pre-extubation), pH lt 7.33

29
Weaning Protocol
  • Standardising process of weaning
  • Protocol-directed daily screening of resp.
    function SBT
  • Advantage
  • ? of patients who required weaning from 80 to
    10
  • ? time required for extubation
  • ? incidence of self-extubation
  • ? incidence of tracheostomy
  • ? ICU costs
  • ? incidence of VAP and death (Dries et al, 2004)
  • No increase or even a decrease in incidence of
    reintubation
  • Less likely effective
  • Majority of patients are rapidly extubated
  • Physicians do not extubate following a successful
    SBT
  • When the quality of critical care is already high

30
Neil et al. Evidence-Based Guidelines for Weaning
and Discontinuing Ventilatory Support. Chest
2001, 120S375-395
31
Is there a role for different ventilator modes in
difficult weaning ?
32
DIFFICULT WEANING-MODE OF VENTILATION
33
  • Pressure support ventilation
  • Noninvasive ventilation
  • Continuous positive airway pressure
  • Automatic tube compensation
  • Proportional assist ventilation
  • Servo-controlled ventilation (ASV/Smartcare)

34
  • PSV should be favoured
  • -As a weaning mode after initial failed SBT
    (group 2) Brochard et al. CCM 1995
  • -May be helpful after several failed attempts at
    SBT (group 3) Vittaca et al. AJRCCM 2000
  • NIV
  • -Selected patients, esp. hypercapnic respiratory
    failure ( COPD)
  • -Should NOT be routinely used as in the event of
    extubation failure
  • -Its use CANNOT be recommended for all patients
    failing a SBT Keenan et al, 2002 Esteban et al,
    2004
  • -Group 2 3 NO firm recommendations

35
  • CPAP
  • - No clear improvement in outcomes (compared to
    T-piece)
  • -May be effective in preventing hypoxic resp.
    failure after major surgery Squadrone et al,
    2005
  • -Group 1 CPAP may be an alternative modes
  • - Group 2 3 NOT been clearly evaluated
  • ATC
  • -As successful as simple T-tube or low-level PS
  • -Lack of trials in groups 2 and 3

36
  • PAV
  • NOT been investigated thoroughly in weaning
    trials
  • ASV
  • 2 non-randomised trials 1 randomised trial
  • Post-cardiac surgery patient
  • Earlier extubation fewer ventilator adjustments
  • Reduced need for ABG high-pressure alarms
  • ASV was compared with SIMV (the worst mode)
  • Smartcare
  • -Maintain a patient in the comfort zone more
    successfully than clinician-directed adjustments
  • -Additional studies needed to evaluate weaning
    efficacy

37
Management of patients with prolongedweaning
failure
38
  • -31.2 of ICU admissions
  • -Significant amount of the overall ICU
    patient-days and 50 of financial resources
  • -20 of MICU patients remained dependent on MV
    after 21 days
  • VALLVERDU et al 1995 reported that weaning
    failure occurred in as many as 61 of COPD
    patients, in 41 of neurological patients and in
    38 of hypoxaemic patients
  • Reversible factors?
  • Neuromuscular and chest wall disorders
  • Less likely to be weaned completely but also less
    mortality
  • COPD highest mortality

39
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40
30-day mortality rate Pneumonia Accidental
Extubation ICU length of stay
No Advantage
Little evidence to guide optimal timing Need for
better predictors
Timing of Tracheostomy
41
Outcome
  • Longer duration of MV ICU hospital stay
  • Engoren et al, 2004 poor survival functional
    outcomes
  • North Carolina Medicare database
  • Rate of tracheostomy increased
  • 25 died in hospital
  • 23 discharged to a skilled-nursing facility
  • 35 discharged to rehabilitation or long-term
    care units
  • 8 discharged home
  • Long Term Outcome ? Study? Study? Study?

Percutaneous Tracheostomy Cost-effective
Fewer complication NO diff. in outcome
42
Rehabilitation
  • Spitzer et al, 1992
  • 62 of difficult-to-wean pts had neuromuscular
    disease severe enough to account for ventilator
    dependency
  • Lack of studies demonstrating an impact of
    rehabilitation on the prevention or reversal of
    weaning failure or other outcomes.
  • Efforts to prevent / treat respiratory muscle
    weakness might have a role in reducing weaning
    failure.

43
Specialized Weaning Units
  • Bridge to home
  • Relieve pressure on ICU beds
  • 2 types
  • Step-down / respiratory care units in acute care
    hospitals
  • Regional weaning centres that serve acute care
    hospitals
  • 3460 in SWU can be weaned successfully
  • Successful weaning can occur up to 3 months after
    admission
  • Long-term mortality rate is not adversely
    affected by transfer

44
Sucessfully weaned patients in SWU ? 70 (5094)
discharged home alive 1-YSR 3853 ? only 525
of patients admitted to SWU can be expected to be
ventilator independent and alive at home 1 yr
after their initial respiratory failure
45
Specialized Weaning Units (SWU)
  • Weaning successful rate
  • Post-operative patients (58)
  • Acute lung injury (57)
  • COPD or neuromuscular disease (22)
  • Outcomes of care between SWUs ICUs Few studies
  • SWUs may be cost-effective alternatives to acute
    ICUs
  • In difficult-to-wean patients, the use of clearly
    defined protocols, independent of the mode used,
    may result in better outcomes than uncontrolled
    clinical practice.

46
  • Admission criteria
  • Two documented failed weaning trials
  • Presence of a tracheostomy tube
  • Clinical stability potential to benefit from
    rehabilitation
  • Minimum operating standards staff
    qualifications
  • Acceptable nurse/patient ratios (12)
  • Requirement for a supervising pulmonary physician
  • Qualifications of respiratory therapists
  • Presence of certain specialised staff members
    (e.g. nutritionists, psychologists, etc.)

47
Home Ventilation
  • Cleveland (OH, USA)
  • ARDS, cardiothoracic surgery or COPD
  • 9 were discharged home with partial ventilatory
    support
  • 1 using NIV 8 requiring partial MV via
    tracheostomy
  • Schönhofer et al COPD
  • 75 discharged home from an SWU
  • 31.5 required home NIV
  • UK study
  • 35 required further home ventilation, mostly NIV

48
Terminal care forVentilator-Dependent Patients
  • -Poor Quality of Life Low survival rates
  • -Withdrawal of mechanical ventilation ?
  • -Full disclosure of prognostic data
  • -Routine palliative care or ethics consultation
    can improve the quality of decision making in the
    acute ICU setting.

49
Recommendations
  • Evaluate readiness for weaning early
  • Be aggressive and search for reversible causes in
    difficult to wean
  • patients
  • DIFFICULT TO WEAN PROTOCOL - Most valuable
    physicians should adhere to standardised weaning
    guidelines.
  • PSV Preferred mode in difficult to wean. T-
    piece trials also
  • appropriate. Do not use SIMV.
  • NIV Select subgroups. Weaning in progress

50
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