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 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

B) Decreased Neuromuscular compliance:

Decreased Drive Muscle Weakness Impaired Transmission

Drug overdose - Electrolyte derangement - Critical illness polyneuropathyBrain-stem lesion - Malnutrition - Neuromuscular blockersSleep deprivation - Myopathy - AminoglycosidesHypothyroidism - Hyperinflation - Guillain–Barré syndromeStarvation/malnutrition - Drugs, corticosteroids - Mysthenia gravisMetabolic alkalosis - Sepsis - Phrenic nerve injuryMyotonic dystrophy

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

DefinitionCourseCausesDiagnosis: - 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