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

Difficult WeaningDr. Hanaa El Gendy

Lecturer Of Anesthesia and Intensive care

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?

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.

Schematic Representation of the Different Stages Occurring in aMechanically Ventilated Patient

Definition of the different stages, from initiation to mechanical ventilation to weaning

StagesDefinitions

Treatment of ARFPeriod of care and resolution of the disorder that caused respiratory failure and prompted mechanical ventilation

SuspicionThe point at which the clinician suspects the patient may be ready to begin the weaning process

Assessing readiness to weanDaily testing of physiological measures of readiness for weaning (NIF, fR/VT) to determine probability of weaning success

Spontaneous breathing trialAssessment of the patient’s ability to breathe spontaneously

ExtubationRemoval of the endotracheal tube

ReintubationReplacement of the endotracheal tube for patients who are unable to sustain spontaneous ventilation

Martin J. TobinMartin J. Tobin20012001

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 →40–50% of the total duration of mechanical ventilation

The incidence of unplanned extubation ranges → 0.3–16%. 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

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.

Classification of Patients According to the Weaning Process

GroupDefinitionFrequencyICU

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%

Boles, et al. Eur Respir J 2007

The Pathophysiology of Weaning Failure

Cardiac loadRespiratory load

Neuromuscular causes

DIFFICULT WEANING

Neuropsychological causes

Metabolic

AnaemiaNutrition Thorough & Systematic search for

these potentially reversible

pathologies

Common Pathophysiologies which may Impact on the Ability to Wean a Patient from Mechanical Ventilation

PathophysiologyConsider

Respiratory loadIncreased 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 loadCardiac 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

>712 >== weaning failure

>864 >== reintubation

transthoracic echocardiography (TTE - )detects decreased left ventricular ejection fraction during SBT Schifelbain LM et al 2011

NeuromuscularDepressed 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

NeuropsychologicalDelirium 22-80%

Anxiety, depression 30-75%

MetabolicMetabolic disturbances

Role of corticosteroids

Hyperglycaemia

NutritionOverweight ( body mass index 25 kg/m2)

Malnutrition (body mass index 20 kg/m2) 40% Ventilator-induced diaphragm dysfunction

AnaemiaHb < 8 gm/dl (8-10 gm/dl)

.

Metabolic and endocrine factors

Hypophosphatemia Hypomagensemia

Hypokalemia

Role in difficult weaning needs

further clarification

Hypothyroidism Hypadrenalism

Corticosteroids

Clycemic control

Difficult weaning

Muscle weakness

REINTUBATION VAP WEANING FAILURE

6-8 FOLD INCREASED

RISK

HOW DOES LATENT MYOCARDIAL DYSFUNCTION BECOME MANIFEST DURING WEANING?

PPV SPONTANEOUS

MYOCARDIAL O2 CONSUMPTION

- VE INTRATHORACIC PRESS. VENOUS RETURN

LV AFTERLOAD

Latent ischaemia

Manifest ischaemia

LV Compliance

WOB – Weaning failure

Decreased lung compliance

Pulmonary

edema

SBT

CRITICAL ILLNESS OXIDATIVE STRESS

Loss of diaphragm force-generating capacity that is specifically related to use of controlled mechanical ventilation

Mitochondrial swelling, myofibril damage and increased lipid vacuoles.Oxidative modifications noted within 6 h

Muscle atrophy Structural injury Fibre remodeling

The Usual Process of Initial Weaning from the Ventilator

As EARLY as possible < 72 hs

UnderestimateUnderestimate the ability of patients to be successfully weaned

Discontinuation of sedationsedation is a critical step ( dexmetedomedine might be a good choice)

2 step strategyAssessment readiness for weaning / extubationAssessment readiness for weaning / extubation

Spontaneous breathing trial (SBT)Spontaneous breathing trial (SBT)

Considerations for Assessing Readiness to WeanClinical assessmentAdequate cough Absence of excessive thick tracheobronchial secretion

Resolution of disease acute phase for which the patient was intubated

Objective measurementsClinical stability

Stable cardiovascular status (i.e. fC 140 beats/min, systolic BP 90–160 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 < 350 on FIO2 = 1.0

SvO2 > 60% P(a/A)O2 > .35

Oxygen index = FIO2 x MAP x 100/ PaO2 very good < 5 medium 10 – 20 poor > 25

Adequate pulmonary function

fR 34 breaths/min Vd?Vt < 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 > 65

No significant respiratory acidosis Adequate mentation

No sedation or adequate mentation on sedation (or stable neurologic patient)

RSBI = respiratory frequency )fRSBI = respiratory frequency )fRR( / V( / VTT

Predicts successful SBT: sensitivity 0.97 & specificity 0.65Predicts successful SBT: sensitivity 0.97 & specificity 0.65

RSBI = respiratory frequency )fRSBI = respiratory frequency )fRR( / V( / VTT

Predicts successful SBT: sensitivity 0.97 & specificity 0.65Predicts successful SBT: sensitivity 0.97 & specificity 0.65

Spontaneous Breathing TrialSpontaneous Breathing TrialT-tube trial

Low levels of pressure support )PS(

6~8 cmH2O in adults, 10 cmH2O in pediatrics3-14 cmH2O inspiratory pressure is needded to overcome

resistance of endotracheal tube

CPAP

AUTOMATIC TUBE COMPENSATION )ATC(

Designed to reduce work associated with ET resistance

Duration: Esteban et al. AJRCCM, 1999

Patients who fail an SBT do so within first ~20 minSuccess 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 5~7.5 cmH2O CPAP Reissmann et al, ICM, 2000

Passing Passing SBTSBT

Respiratory pattern

Gas exchange

Haemodynamic stability

Subject comfort

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

Repeated frequently )daily( SBTRepeated 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 ventilationNonfatiguing 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%

Failed SBTFailed SBT

Termination of SBTTermination of SBT

-RR > 30 for 5 min

-SpO2 < 90% for 30 sec

-20% change in HR for > 5 min

-P SYS > 180 or < 90 for 1 min

-Anxiety, agitation or diaphoresis

for 5 min

Extubation:Neurological statusAlthough 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. 2001KOH et al. 2005 GCS did NOT predict extubation failure

Excessive secretionsKHAMIEES et al. 2006 Poor cough strengthPoor cough strength and excessive excessive secretionssecretions were common in patients who failed extubation

following a successful SBT .

Airway obstructionPositive leak test is adequate before proceeding with extubation.A successful cuff leak test does not guarantee that post-extubation difficulties will not arise .

Criteria for extubation failureCriteria for extubation failure

-fR >25 breaths/min for 2 h

-HR >140 beats/min or sustained increase or decrease of > 20%

-Clinical signs of respiratory muscle fatigue or increased work of breathing

-SpO2 < 90%; PaO2 <80 mmHg on FiO2 ≥0.50

-Hypercapnia )PaCO2 > 45 mmHg or ≥ 20% from pre-extubation(, pH < 7.33

Weaning ProtocolWeaning Protocol

Standardising process of weaning Protocol-directed daily screening of resp. function & SBTAdvantage:

% ↓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 effectiveMajority of patients are rapidly extubatedPhysicians do not extubate following a successful SBTWhen the quality of critical care is already high

Neil et al. Evidence-Based Guidelines for Weaning and Discontinuing Ventilatory

Support. Chest 2001, 120:S375-395

Is there a role for different ventilator modes in difficult weaning?

DIFFICULT WEANING-MODE OF VENTILATION Maintainence of a favourable balance between respiratory system capacity and load

Attempt to avoid diaphragm muscle atrophy

Aid in the weaning process

Pressure support ventilation

Noninvasive ventilation

Continuous positive airway pressure

Automatic tube compensation

Proportional assist ventilation

Servo-controlled ventilation )ASV/Smartcare(

PSV: should be favoured

-As a weaning mode after initial failed SBT ) )group 2group 2( ( Brochard et al. CCM 1995Brochard et al. CCM 1995

-May be helpful after several failed attempts at SBT ))group 3group 3( ( Vittaca et al. AJRCCM 2000Vittaca et al. AJRCCM 2000

NIV: -Selected patients, esp. hypercapnic respiratory failure (

COPD)-Should NOTNOT be routinely used as in the event of

extubation failure -Its use CANNOTCANNOT be recommended for all patients failing

a SBT Keenan et al, 2002 & Esteban et al, 2004Keenan et al, 2002 & Esteban et al, 2004

-Group 2 & 3: NONO firm recommendations

CPAP: -NoNo clear improvement in outcomes (compared to

T-piece)

-May be effective in preventing hypoxic resp. failure after major surgery Squadrone et al, 2005Squadrone et al, 2005

-Group 1: CPAP may be an alternative modes- Group 2 & 3: NOTNOT been clearly evaluated

ATC :-As successful as simple T-tube or low-level PS

-Lack of trials in groups 2 and 3

PAV:

NOT been investigated thoroughly in weaning trials

ASV:2 non-randomised trials & 1 randomised trial:

Post-cardiac surgery patient

EarlierEarlier extubation & fewer fewer ventilator adjustments

ReducedReduced 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

Management of patients with prolongedweaning failure

-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 1995VALLVERDU 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

Tracheostomy

Specialized weaning units

Rehabilitation

Home ventilation

Terminal care

No AdvantageNo AdvantageNo AdvantageNo Advantage

Timing of TracheostomyTiming of Tracheostomy

30-day mortality rate Pneumonia

Accidental ExtubationICU length of stay

30-day mortality rate Pneumonia

Accidental ExtubationICU length of stay

Little evidence to guide optimal timing Little evidence to guide optimal timing Need for better predictorsNeed for better predictors

Little evidence to guide optimal timing Little evidence to guide optimal timing Need for better predictorsNeed for better predictors

OutcomeOutcome

Longer durationLonger duration of MV & ICU & hospital stay

Engoren et al, 2004Engoren et al, 2004: poor poor survival & functional outcomes

North Carolina Medicare databaseNorth Carolina Medicare database::Rate of tracheostomy increased

25%25% died in hospital

23%23% discharged to a skilled-nursing facility

35%35% discharged to rehabilitation or long-term care units

8%8% discharged home

Long Term Outcome Long Term Outcome Study? Study? Study Study? Study? Study??

Percutaneous TracheostomyPercutaneous Tracheostomy: : Cost-effective & Fewer complication; NO diff. in outcomeCost-effective & Fewer complication; NO diff. in outcome

Percutaneous TracheostomyPercutaneous Tracheostomy: : Cost-effective & Fewer complication; NO diff. in outcomeCost-effective & Fewer complication; NO diff. in outcome

RehabilitationRehabilitation

Spitzer et al, 1992Spitzer et al, 1992::

62%62% of difficult-to-wean pts had neuromuscular disease severe enough to account for ventilator dependency

Lack of studiesLack 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 Efforts to prevent / treat respiratory muscle weakness might have a role in reducing weaning failurehave a role in reducing weaning failure..

Specialized Weaning UnitsSpecialized 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

34–60% in SWU can be weaned successfullySuccessful weaning can occur up to 3 months after admission

Long-term mortality rate is not adversely affected by transfer

Sucessfully weaned patients in SWU Sucessfully weaned patients in SWU 70% (50~94%) discharged home alive 70% (50~94%) discharged home alive1-YSR 38–53% 1-YSR 38–53% only 5–25% of patients admitted to SWU can be expected to be only 5–25% of patients admitted to SWU can be expected to be ventilator independent and alive at home 1 yr after their initial respiratory failureventilator independent and alive at home 1 yr after their initial respiratory failure

Sucessfully weaned patients in SWU Sucessfully weaned patients in SWU 70% (50~94%) discharged home alive 70% (50~94%) discharged home alive1-YSR 38–53% 1-YSR 38–53% only 5–25% of patients admitted to SWU can be expected to be only 5–25% of patients admitted to SWU can be expected to be ventilator independent and alive at home 1 yr after their initial respiratory failureventilator independent and alive at home 1 yr after their initial respiratory failure

Specialized Weaning Units Specialized Weaning Units )SWU()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 ICUsIn difficult-to-wean patients, the use of clearly defined protocols, independent of the mode used, may result in better outcomes than uncontrolled clinical practice.

Admission criteria:Two documented failed weaning trials

Presence of a tracheostomy tube

Clinical stability & potential to benefit from rehabilitation

Minimum operating standards & staff qualificationsAcceptable nurse/patient ratios (1:2)

Requirement for a supervising pulmonary physician

Qualifications of respiratory therapists

Presence of certain specialised staff members (e.g. nutritionists, psychologists, etc.)

Home VentilationHome Ventilation

Cleveland (OH, USA):ARDS, cardiothoracic surgery or COPD

9% were discharged home with partial ventilatory support1% using NIV & 8% requiring partial MV via tracheostomy

Schönhofer et al: COPD75% discharged home from an SWU

31.5% required home NIV

UK study:35% required further home ventilation, mostly NIV

Terminal care forTerminal care forVentilator-Dependent PatientsVentilator-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.

RecommendationsRecommendations

Evaluate readiness for weaning early

Be aggressive and search for reversible causes in difficult to weanpatients

DIFFICULT TO WEAN PROTOCOL ‐ Most valuable physicians should adhere to standardised weaning guidelines .

PSV – Preferred mode in difficult to wean. T‐ piece trials alsoappropriate. Do not use SIMV.

NIV – Select subgroups. “Weaning in progress”

Thank You