Elsevier

Critical Care Clinics

Volume 24, Issue 1, January 2008, Pages 165-177
Critical Care Clinics

Mechanisms of Neuromuscular Dysfunction in Critical Illness

https://doi.org/10.1016/j.ccc.2007.10.004Get rights and content

The development of neuromuscular dysfunction (NMD) during critical illness is increasingly recognized as a cause of failure to wean from mechanical ventilation and is associated with significant morbidity and mortality. At times, it is difficult to identify the presence of NMD and distinguish the etiology of the weakness in patients with critical illness, but subtle clinical findings and bedside electrophysiologic testing are helpful in establishing the diagnosis. This article describes the clinical spectrum of acquired neuromuscular weakness in the setting of critical illness, provides an approach to diagnosis, and discusses its pathogenesis. Finally, a defective sodium channel regulation as a unifying mechanism underlying NMD in critically ill patients is proposed.

Section snippets

Incidence of acquired neuromuscular dysfunction in the ICU

Acquired NMD is a comprehensive designation incorporating both CIM and CIP. Alternate terms include ICU-acquired paresis, critical illness neuromyopathy, and critical illness neuromuscular abnormalities. CIM has been reported in at least one third of ICU patients treated for status asthmaticus [7], and studies of critically ill patients suggest incidence rates between 12% and 35% [8], [9], [10], [11]. Prospective studies suggest that CIP may occur in up to 50% to 70% of patients admitted to the

Bedside examination

NMD is typically heralded by difficulty in weaning from mechanical ventilation or by the presence of diffuse weakness in a cooperative patient. Early signs of development of NMD are nonspecific and may simply include a reduction in spontaneous movement of the limbs. In many cases, establishing the presence of NMD in critically ill patients and then distinguishing CIM from CIP are limited by the ability of the clinician to obtain an adequate history and physical examination owing to factors such

Prognosis of ICU-acquired neuromuscular dysfunction

Prospective studies in patients ventilated for more than 7 days have reported increased hospital mortality associated with NMD [12], [14], [24]. In fact, the development of NMD early in the course of critical illness may predict mortality. In a prospective cohort of 48 patients with severe sepsis, it was found that abnormal nerve conduction studies obtained within 72 hours of ICU admission predicted hospital mortality (55% versus 0%, P<.001) [19]. The presence of NMD is also associated with

Mechanisms underlying acquired paresis in critical illness myopathy

There are at least three factors that contribute to weakness in patients with CIM: atrophy of muscle fibers, loss of myosin, and muscle inexcitability [3], [38]. Atrophy and loss of myosin both cause weakness due to loss of force generation following muscle fiber action potentials. The causes of muscle atrophy and loss of myosin are complex and are still poorly understood [5], [39] and, although important, will not be discussed further. The third factor is loss of the ability of muscle fibers

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  • Cited by (0)

    This work was supported by NIH R01 NS040826 (MMR).

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