Difficult Weaning
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
-Preparing the Patient for Weaning:
- Electrolyte
Disturbance
- Volume Overload
- Altered Mental status
- Fatigue of the diaphragm
- Adequacy of sleep and sleep deprivation
- Malnutrition
-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
Algorithm for weaning Protocol
New Advances in Ventilators to assist Weaning:
- Automated tube compensation (ATC)
-
Proportional Assisted ventilation (PAV)
Causes of Difficult Weaning
Imbalance
Respiratory muscle pump
Respiratory muscle load
A) Increased Ventilatory Needs
Increased resistive load
Increased chest Wall Load
-Bronchospasm
- Airway edema
- Airway obstruction
- Tube kinking
- Sleep Apnea
- Secretions
- Circuit resistance
- Pleural effusion
- Pnumothorax
- Flail chest
- Obesity
- Ascites
- Distension
Increased parenchyma load
-Hyperinflation
- Inflammation
- Atelectasis
- Alveolar edema
B) Decreased Neuromuscular compliance:
Decreased Drive
Drug overdose
Brain-stem lesion
Sleep deprivation
Hypothyroidism
Starvation/malnutrition
Metabolic alkalosis
Myotonic dystrophy
Muscle Weakness
- Electrolyte derangement
- Malnutrition
- Myopathy
- Hyperinflation
- Drugs, corticosteroids
- Sepsis
Impaired Transmission
- Critical illness polyneuropathy
- Neuromuscular blockers
- Aminoglycosides
- Guillain–Barré syndrome
- Mysthenia gravis
- Phrenic nerve injury
How to Wean Difficult to Wean Patients
Correction of Causes
Choice of appropriate mode
Tracheostomy
Neuromuscular Weakness in Critically Ill
Critical illness polyneuropathy (CIP):
Disorders of neuromuscular transmission:
Myopathy:
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
Disorders of neuromuscular transmission:
- Prolonged use of neuromuscular blockers
- Decreased Metabolism
- Decremental Response
- Aminoglycosides, Polypeptide antibiotics
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
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
Prevention of neuromuscular weakness in ICU:
- Appropriate treatment of sepsis
- Minimize use of NMBA
- Check serum electrolytes
- Avoid Pharmacological agents causing weakness
- Early EPS
Thank You