3.2 ICU weakness

Question 1

What may be the causes for difficult weaning?

Answer 1

1. Respiratory causes

• Insufficiently treated pulmonary disease
• Auto-PEEP and hyperinflation

2. Cardiac causes
   * Concomitant cardiac disease
3. others
   * Poor nutrition

• Electrolyte imbalance
• Critical illness neuropathy/ICU weakness
• Poor technique— inadequate rest
  following an exhausting spontaneous breathing trial

Question 2

You mentioned icU weakness.

How can you define it?

Answer 2

ICU-acquired weakness (ICUAW)

is ‘clinically detected weakness in critically ill patients

in whom there is no plausible aetiology other than critical illness’.

The criteria for diagnosing ICUAW are the presence of most of the following
factors:

1. • Weakness developing after the onset of critical illness
2. • Weakness being generalised,
     symmetrical, flaccid,
     and generally sparing
     the cranial nerves
     (e.g. facial grimace is intact)
3. • Muscle power assessed by the
     Medical Research Council (MRC)
     score of < 48
     (or a mean score of < 4 in all testable muscle groups)
     noted on > 2 occasions separated by > 24 hours

• Dependence on mechanical ventilation
• Other causes of weakness having been excluded

Question 3

Can you list the differential diagnosis for icUAW?

Answer 3

• Spinal cord dysfunction
• Critical illness myopathy
• Guillain-Barre syndrome
• Motor neuron disease
• Pre-existing neuropathy
• Myasthenia

Question 4

What can cause ICU weakness?

Answer 4

ICUAW can be classified into those with

1. Critical illness polyneuropathy (CIP),
2. Critical illness myopathy (CIM),
3. Critical illness neuromyopathy (CINM).

The causes are unknown,
though they are thought to be a
possible neurological manifestation of
systemic inflammatory response syndrome.

Question 5

Risk factors for CIP, CIM and CINM include:

Answer 5

1. • Severe sepsis/septic shock with multi-organ failure
2. • Prolonged mechanical ventilation
3. • Prolonged bed rest
4. • Glucose and electrolyte abnormalities
5. • Use of parenteral nutrition,
     renal replacement therapy, steroids, muscle
     relaxants, vasopressors, and aminoglycosides

Question 6

What is the difference between CIP and CIM?

Answer 6

• Similar symptoms and presentations
• Often distinguished largely on the basis of specialised electrophysiological
  testing or muscle and nerve biopsy

Question 7

Can you tell me the details of the electrophysiological investigations required for diagnosis?

Answer 7

1. • Nerve conduction studies

to determine nerve conduction velocities and stimulated amplitudes

compound motor action potentials (CMAPs)
sensory nerve action potentials (SNAPs)

____________________________________

2. • Electromyography to look at muscle electrical activity

motor unit potential (MUP)
amplitudes,
durations
fibre recruitment patterns

both at rest and during activity

Question 8

How may it be treated?

Answer 8

1. • No intervention has been shown in prospective study to improve the
     outcome
2. • Focus on prevention
3. • Optimise rehabilitation

Prevention of ICUAW

1. • Minimisation of the risk factors (as above)
2. • Intensive insulin therapy

Question 9

can you mention a few care bundles you are aware of in the intensive care unit?

Answer 9

1. Ventilator care Bundle
   * Elevation of the head of the bed
   * Peptic ulcer disease prophylaxis
   * Deep venous thrombosis prophylaxis
   * Daily oral care with Chlorhexidine
2. central Line Bundle
   * Appropriate hand hygiene
   * Chlorhexidine skin prep
   * Maximal barriers for central line insertion
   * Subclavian vein placement is preferred site
   * Review lines daily and remove unnecessary catheters
3. Sepsis care Bundle
   Three-hour bundle
   * Measure lactate level
   * Obtain blood cultures prior to administration of antibiotics
   * Administer broad spectrum antibiotics
   * Administer 30 mL/kg crystalloid for hypotension or lactate ≥ 4 mmol/L
4. six-hour bundle
   * Apply vasopressors
   (for hypotension that does not respond to initial fluid resuscitation)
   to maintain a mean arterial pressure (MAP) ≥ 65 mm Hg

• Measure central venous pressure (CVP) and
  central venous oxygen saturation (Scvo2) in refractory hypotension
• Remeasure lactate if initial lactate was elevated

Question 10

can you mention a few care bundles you are aware of in the intensive care unit?

Answer 10

1. Ventilator care Bundle
   * Elevation of the head of the bed
   * Peptic ulcer disease prophylaxis
   * Deep venous thrombosis prophylaxis
   * Daily oral care with Chlorhexidine
2. central Line Bundle
   * Appropriate hand hygiene
   * Chlorhexidine skin prep
   * Maximal barriers for central line insertion
   * Subclavian vein placement is preferred site
   * Review lines daily and remove unnecessary catheters
3. Sepsis care Bundle
   Three-hour bundle
   * Measure lactate level
   * Obtain blood cultures prior to administration of antibiotics
   * Administer broad spectrum antibiotics
   * Administer 30 mL/kg crystalloid for hypotension or lactate ≥ 4 mmol/L
4. six-hour bundle
   * Apply vasopressors
   (for hypotension that does not respond to initial fluid resuscitation)
   to maintain a mean arterial pressure (MAP) ≥ 65 mm Hg

• Measure central venous pressure (CVP) and
  central venous oxygen saturation (Scvo2) in refractory hypotension
• Remeasure lactate if initial lactate was elevated