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  • Updated 01.04.2021
  • Released 03.29.1999
  • Expires For CME 01.04.2024

Critical illness myopathy and polyneuropathy

Introduction

Overview

This article describes the neuromuscular complications of critical illness. The author discusses a large study that links intensive glucose control in critically ill patients to an increased risk of moderate and severe hypoglycemia, both of which are associated with an increased risk of death. Furthermore, he reviews the American Diabetes Association current recommendations for a target blood glucose in order to reduce the risk of hypoglycemia in critically ill patients.

Key points

• After intensive neurorehabilitation, most critical illness neuropathy or myopathy patients recover within 1 to 2 years.

• The presence of additional central nervous system lesions is associated with poor prognosis for recovery.

Historical note and terminology

Critical illness polyneuropathy is most often described in patients in the critical care unit with sepsis. Sepsis originally meant putrefaction, a decomposition of organic matter by bacteria and fungi (23). Over time, it has been increasingly associated with a severe systemic response to infection, usually resulting in early death. With improvements in medical and surgical care, survival of many critically ill patients is now prolonged, but the mortality rate may still be greater than 30%, and approximately half a million patients are reported each year with sepsis in the United States (74). Research has been impeded by confusion over terminology, with "Gram-negative sepsis," "sepsis syndrome," and "septic shock" all being applied with uncertainty (18). In attempts to resolve this confusion, The Society of Critical Care Medicine and The American College of Chest Physicians convened a consensus conference in 1992 to standardize definitions (05). Recognizing that a severe systemic response can be evoked in the absence of infection (eg, trauma and burns), the panel coined the term "systemic inflammatory response syndrome" (05).

Systemic inflammatory response syndrome
This diagram shows the various factors associated with the development of the systemic inflammatory response syndrome and its nervous system complications. (Reproduced with permission from: Bolton CF. Sepsis and the systemic infla...

When systemic inflammatory response syndrome was associated with a documented infection, the term "sepsis" could be applied. Furthermore, the terms "severe sepsis" and "septic shock" were reserved for those patients with organ dysfunction and hypoperfusion or hypotension, despite adequate fluid replacement.

Osler observed muscle wasting as a complication of prolonged sepsis (89). In 1961, Mertens described "coma-polyneuropathies" in patients who had circulatory shock associated with acute intoxication and severe metabolic crises, seemingly due to metabolic and ischemic lesions of the peripheral nervous system (80). Henderson and colleagues described a polyneuropathy in patients with burns (46). Between 1977 and 1981, Bolton and colleagues observed 5 unusual patients in the critical care unit who showed difficulty in weaning from the ventilator and who had severe weakness in the limbs (16; 17). Comprehensive electrophysiologic and morphologic studies established this condition as a primary distal, axonal degeneration of motor and sensory fibers (17). Because sepsis and multiple organ failure was designated a critical illness by intensivists, the condition was named critical illness polyneuropathy (127). Similar cases of polyneuropathy have been subsequently reported from the United States (97; 40), France (21; 07; 116), Holland (75; 70), Austria (09), Germany (53), and Spain (72).

During the 1990s researchers began to find, on review of muscle and nerve pathology as well as electrophysiologic studies, that there was a significant component of primary myopathic disease in patients with critical illness. As early as 1972, Karpati and colleagues described in animal models a corticosteroid-induced thick filament myopathy after nerve transection (55). In 1977, MacFarlane reported an acute quadriplegia that developed in a young man after treatment for asthma with high dose corticosteroids (76). This clinical pattern was recognized in a number of other patients, who were then postulated to have a “functional denervation” due to sepsis and neuromuscular blockade, then later developed a thick filament myopathy with exposure to corticosteroids (11). Since these reports, there has been a great deal of interest in elucidating the pathogenesis of what some authors call critical illness myopathy (68). Various other names for this entity have also been used including acute quadriplegic myopathy (50), acute myopathy of intensive care (62), critical care myopathy (33), acute illness myopathy (99), acute myopathy with selective lyses of myosin filaments (102), acute necrotizing myopathy of intensive care (93; 128), and critical illness neuromuscular disease (108).

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