Difficult Weaning

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

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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?

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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.

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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

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• 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

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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.

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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
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The Pathophysiology of Weaning Failure
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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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HOW DOES LATENT MYOCARDIAL DYSFUNCTION BECOME
MANIFEST DURING WEANING ?
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The Usual Process of Initial Weaning from the
Ventilator
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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)
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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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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

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• 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

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Passing SBT

• Respiratory pattern
• Gas exchange
• Haemodynamic stability
• Subject comfort

Q2
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Tobin. Principles and Practice of Mechanical
Ventilation, McGraw-Hill, 1994, s1192
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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

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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

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• 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.

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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

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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

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

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• 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

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• 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

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• 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

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Management of patients with prolongedweaning
failure
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• -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

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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
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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
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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.

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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

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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
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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.

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• 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.)

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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

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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.

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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

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Thank You