15.9 Critical Illness Weakness

Question 1

a) Define critical illness weakness (CIW, 1 mark)

Answer 1

> > Clinically detectable,
symmetrical,
peripheral
(not involving cranial nerves, thus facial sparing)

weakness in critically ill patient
that is not pre-existing.

Question 2

list the types CIW that may occur

Answer 2

(It can affect nerves, muscles or both).
» Critical illness polyneuropathy.

> > Critical illness myopathy.

> > Critical illness neuromyopathy.

Question 3

b) List the risk factors for the development of weakness on the ICU. (6 marks)

Answer 3

Probable risk factors:
» Severe sepsis or septic shock,
increased risk with increasing duration.

> > Multiorgan failure,
increased risk with increasing duration.

> > Prolonged mechanical ventilation
and bed rest.

> > Hyperglycaemia.

Possible risk factors:
» Increasing age.
» Female gender.

> > Severity of illness.

> > Hypoalbuminaemia.

> > Hyperosmolality.

> > Parenteral nutrition.

> > Renal replacement therapy.

> > Vasopressors.

> > Corticosteroids.

> > Neuromuscular blocking agents.

> > Aminoglycosides.

Question 4

c) What are the clinical features of CIW? (4 marks)

Answer 4

> > Weakness that has developed after
onset of critical illness for a week or more,
with exposure to risk factors as detailed earlier.

>> Generalised, symmetrical, 
flaccid weakness, 
usually sparing cranial nerves 
(facial grimacing but no peripheral 
movement in response to painful stimulus).

> > There may be associated sensory loss,
but not autonomic involvement.

> > Other causes excluded.

> > Dependence on mechanical ventilation
OR low muscle strength.

Question 5

d) How may nerve conduction studies determine the type of CIW? (4 marks)

Answer 5

> > Neuropathy:
demonstrated by reduced amplitude of

sensory nerve action potentials (SNAP)
+
compound motor action potentials (CMAP).

Nerve conduction velocity normal/near normal.

>> Myopathy: 
conduction velocity normal, 
SNAP normal, 
CMAP reduced
(low amplitude motor unit potential on EMG).

Question 6

e) What are the options for the management of CIW? (2 marks)

Answer 6

> > Avoidance of risk factors.

> > Blood glucose control.

> > Early mobilisation.

> > Physiotherapy from time of
admission to ICU and during recovery.