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.
• 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 (Critchley 1978). 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 (Lowry 1994). Research has been impeded by confusion over terminology, with "Gram-negative sepsis," "sepsis syndrome," and "septic shock" all being applied with uncertainty (Bone 1992). 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 (Anonymous 1992). 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" (Anonymous 1992).
Osler observed muscle wasting as a complication of prolonged sepsis (Osler 1996). 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 (Mertens 1961). Henderson and colleagues described a polyneuropathy in patients with burns (Henderson et al 1971). 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 (Bolton et al 1983; Bolton et al 1984). Comprehensive electrophysiologic and morphologic studies established this condition as a primary distal, axonal degeneration of motor and sensory fibers (Bolton et al 1984). Because sepsis and multiple organ failure was designated a critical illness by intensivists, the condition was named critical illness polyneuropathy (Zochodne et al 1987). Similar cases of polyneuropathy have been subsequently reported from the United States (Roelofs et al 1983; Gorson and Ropper 1993), France (Couturier et al 1984; Barat et al 1987; Wijdicks and Fulgham 1994), Holland (Lychlama et al 1987; Leijten and De Weerd 1994), Austria (Berek et al 1996), Germany (Hund et al 1996), and Spain (Lopez Messa and Garcia 1990).
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 (Karpati et al 1972). In 1977, MacFarlane reported an acute quadriplegia that developed in a young man after treatment for asthma with high dose corticosteroids (MacFarlane and Rosenthal 1977). 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 (Bolton 1993). Since these reports, there has been a great deal of interest in elucidating the pathogenesis of what some authors call critical illness myopathy (Latronico et al 1996). Various other names for this entity have also been used including acute quadriplegic myopathy (Hirano 1992), acute myopathy of intensive care (Lacomis et al 1996), critical care myopathy (Faragher et al 1996), acute illness myopathy (Ruff 1996), acute myopathy with selective lyses of myosin filaments (Sher et al 1979), acute necrotizing myopathy of intensive care (Ramsay et al 1993; Zochodne et al 1994), and critical illness neuromuscular disease (Tabarki et al 2002).
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