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

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

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 →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

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 Boles, et al. Eur Respir J 2007

8. The Pathophysiology of Weaning Failure

10. Respiratory load Cardiac load Neuromuscular causes Neuropsychological causes Metabolic DIFFICULT WEANING Thorough & Systematic search for these potentially reversible pathologies Nutrition Anaemia

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

12. Metabolic and endocrine factors Role in difficult weaning needs further clarification Hypophosphatemia Hypomagensemia Hypokalemia Hypothyroidism Hypadrenalism Muscle weakness Corticosteroids Clycemic control Difficult weaning

13. REINTUBATION VAP WEANING FAILURE 6-8 FOLD INCREASED RISK

14. - VE INTRATHORACIC PRESS.  VENOUS RETURN PPV  SPONTANEOUS  LV AFTERLOAD  MYOCARDIAL O2 CONSUMPTION HOW DOES LATENT MYOCARDIAL DYSFUNCTION BECOME MANIFEST DURING WEANING ?

15. Latent ischaemia Manifest ischaemia  LV Compliance SBT  WOB – Weaning failure Decreased lung compliance Pulmonary edema

16. 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

17. The Usual Process of Initial Weaning from the Ventilator

18. As EARLY as possible < 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 RSBI = respiratory frequency (fR) / VT Predicts successful SBT: sensitivity 0.97 & specificity 0.65

21. Spontaneous Breathing Trial T-tube trial Low levels of pressure support (PS) 6~8 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 5~7.5 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 > 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

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. 2006Poor cough strength and excessive secretions were commonin 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 >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

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, 120:S375-395

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

32. Maintainence of a favourable balance between respiratory system capacity and load • Attempt to avoid diaphragm muscle atrophy • Aid in the weaning process 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: - Noclear improvement in outcomes (compared to T-piece) -May be effective in preventing hypoxic resp. failure after major surgerySquadrone 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 Earlierextubation & 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 1995reported 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. Tracheostomy Specialized weaning units Rehabilitation Home ventilation Terminal care

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 34–60% 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% (50~94%) discharged home alive 1-YSR 38–53%  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 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 (1:2) 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”

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