Difficult Weaning

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Difficult Weaning
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Indications for mechanical ventilation

• A) Global pathophysiological indications
• Apnea
• - Acute ventilatory failure
• impending failure
• Refractory hypoxemia
• Signs of respiratory failure

• B) Common clinical conditions when need for
  ventilatory support is high
• ARDS
• Asthma
• COPD
• Chest trauma
• Overdose
• Post cardiac surgery
• Pneumonia
• Sepsis
• Head Trauma

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• Preparing the Patient for Weaning
• Electrolyte Disturbance
• Volume Overload
• Altered Mental status
• Fatigue of the diaphragm
• Adequacy of sleep and sleep deprivation
• Malnutrition

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• Criteria to consider Patients for Weaning
• Reversal of underlying pathology
• Po2, PEEP, FiO2, PH
• ABG
• Vital Data
• CXR

• Parameters Predicting successful Weaning
• Respiratory rate
• Tidal Volume
• Minute Ventilation
• Negative inspiratory force
• Maximal Inspiratory pressure
• RSBI
• RSBI rate

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Algorithm for weaning Protocol
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New Advances in Ventilators to assist Weaning
- Automated tube compensation (ATC)
- Proportional Assisted ventilation (PAV)
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Causes of Difficult Weaning
Imbalance
Respiratory muscle pump
Respiratory muscle load
A) Increased Ventilatory Needs
Increased resistive load
Increased chest Wall Load
Increased parenchyma load

• Bronchospasm
• Airway edema
• Airway obstruction
• Tube kinking
• Sleep Apnea
• Secretions
• Circuit resistance

• Pleural effusion
• Pnumothorax
• Flail chest
• Obesity
• Ascites
• Distension

• Hyperinflation
• Inflammation
• Atelectasis
• Alveolar edema

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B) Decreased Neuromuscular compliance
Muscle Weakness
Impaired Transmission
Decreased Drive
Drug overdose - Electrolyte
derangement - Critical illness
polyneuropathy Brain-stem lesion -
Malnutrition -
Neuromuscular blockers Sleep deprivation
- Myopathy -
Aminoglycosides Hypothyroidism -
Hyperinflation -
GuillainBarré syndrome Starvation/malnutrition
- Drugs, corticosteroids - Mysthenia
gravis Metabolic alkalosis - Sepsis
- Phrenic nerve
injury Myotonic dystrophy
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How to Wean Difficult to Wean Patients
Correction of Causes
Choice of appropriate mode
Tracheostomy
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Neuromuscular Weakness in Critically Ill
Myopathy
Critical illness polyneuropathy (CIP)
Disorders of neuromuscular transmission
Critical illness Polyneuropathy
Definition Course Causes Diagnosis - EPS shows
reduced compound motor and sensory nerve action
potential amplitudes with normal conduction
velocities. - Needle EMG
reveals fibrillation potentials and positive
sharp waves indicating denervation Treatment
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Disorders of neuromuscular transmission

• Prolonged use of neuromuscular blockers
• Decreased Metabolism
• Decremental Response
• Aminoglycosides, Polypeptide antibiotics

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Myopathy
1. Critical illness myopathy

• Histological Pattern
• Normal CPK levels
• Type II myofibres
• IL-1, TNF

2. Thick filament myopathy

• Selective loss of myosin
• Absent neuropathy
• Increased steroid receptors
• Triggering factors NMBA, Denervation
• Diagnosis EPS, CPK , Muscle biopsy

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3. Necrotizing myopathy

• Prominent muscle necrosis
• CPK elevated
• Correlated with NMBA, Steroids
• Diagnosis - difficult to diagnose
• - Direct muscle stimulation
  and calculation of the ratio of nerve and muscle
  evoked compound muscle action potential
  amplitudes.
• - Muscle biopsy is of choice
• No specific treatment is available

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Prevention of neuromuscular weakness in ICU
- Appropriate treatment of sepsis
- Minimize use of NMBA
- Check serum electrolytes
- Avoid Pharmacological agents causing weakness
- Early EPS
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Thank You