This polyneuropathy (Zochodne.et.al 1987; Le.!iie.D.§D.d..d§...We®rd 1994; Bolton 1996) occurs in 70 per cent of patients who have the systemic inflammatory response syndrome. However, clinical signs are often absent and it remains an occult condition in many ICUs worldwide. Nonetheless, it is important to establish the diagnosis since it is an important cause of difficulty in weaning from the ventilator and problems in rehabilitation after the acute illness has been treated in the ICU.
Only in more severe critical illness polyneuropathy will there be obvious limb weakness and reduced deep tendon reflexes. Signs of sensory impairment are difficult to test in the ICU. Electrophysiological studies are essential to establish the diagnosis. These will reveal a primary axonal degeneration of first motor and then sensory fibers. Phrenic nerve conduction and needle electromyography of the diaphragm will disclose that the difficulty in weaning from the ventilator is due to involvement of the nerves and muscles of respiration (Z,i.fkO a..n,d Ch.e.n 1996). Creatine phosphokinase is either normal or mildly elevated. Muscle biopsy will reveal the presence of both acute and chronic denervation of muscle. Often the muscle is involved directly by the sepsis to varying degrees; this causes muscle necrosis, the severity of which is reflected in the degree of elevation of creatine phosphokinase.
If the sepsis and multiple organ failure can be successfully treated (the mortality remains as high as 50 per cent), recovery from the critical illness polyneuropathy can be expected. This will occur in a matter of weeks in mild cases and in months in more severe cases. Electrophysiological studies will provide valuable information as to the time it may take for successful weaning from the ventilator.
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