Acute Neuromuscular Weakness In The Intensive Care Unit

Bobby Varkey Maramattom, MD, DM; Eelco F. M. Wijdicks, MD Section Editor(s): Dellinger, R. Phillip MD, FCCM

Disclosures

Crit Care Med. 2006;34(11):2835-2841. 

In This Article

Abstract and Introduction

Abstract

Introduction: Patients in the intensive care unit develop generalized weakness due to a number of factors. Neuromuscular weakness is a common cause of failure to wean from the ventilator and decreased limb movements. A rational approach to evaluation of weakness will help to identify most of the common causes of neuromuscular weakness in the intensive care unit.
Aims: This review provides an analysis of neuromuscular weakness and a practical algorithm to assist in diagnostic evaluation.
Conclusions: The most common acquired causes of weakness in the critically ill patient in the intensive care unit are critical illness polyneuropathy and critical illness myopathy. In the intensive care unit setting, electrophysiological studies, biopsies, and imaging studies are often necessary to complement the clinical impression.

Introduction

Sick patients can be weak, but only a proportion of these individuals develop a neurologic disorder causing muscle weakness. However, critically ill patients are exposed to multiple stressors, fluid and electrolyte changes, catabolic stresses, nutritional deficiencies, and medications that act in combination to produce damage to the motor unit. Thus, critically ill patients have a higher likelihood of acquiring neuromuscular weakness in the intensive care unit (ICU). In addition to prolonging hospital stay and increasing morbidity and mortality, these disorders also inflate hospital costs by of thousands of dollars.[1]

The spectrum of neuromuscular disease that is encountered in today's ICU has evolved over the last few decades. Nowadays, weakness acquired in the ICU due to critical illness myopathy (CIM) or polyneuropathy (CIP) is two to three times more common than primary neuromuscular disorders such as Guillain-Barré syndrome (GBS), myopathies, or motor neuron diseases.[2]

Patients in the ICU can develop a variety of mononeuropathies or plexopathies related to ischemia, pressure palsies, prolonged recumbency, compartment syndromes, hematomas, or other causes. They can also develop weakness due to intracranial processes such as ischemic stroke or other diseases. The discussion of these focal or central causes of weakness in ICU patients is also outside the scope of this review. Nevertheless, a brief mention will be made of some of these conditions because a review of weakness in the ICU will be incomplete if these entities are omitted.

To be fair to the title, this review will, however, focus on patients with generalized neuromuscular weakness in the ICU. Two clinical presentations are encountered among this group. One group is those patients who are admitted to the ICU with a nonneurologic illness and subsequently are detected to have generalized weakness in the ICU. The other group of patients is those in whom catastrophic weakness and respiratory failure necessitate emergent admission to the ICU. In these cases, diagnostic tests are usually postponed until the patient is stabilized.

Although a good history and examination help in identifying and localizing the weakness, there are a number of confounding factors. Patients in the ICU are often confused, sedated, or intubated and may find it difficult to communicate with the clinician. Weakness is often detected incidentally or during attempts to wean, and the exact onset of weakness is often unclear. Examination is also hampered by indwelling intravascular catheters, restraints, and sedatives. Nevertheless, important clues can be obtained from the history, examination, scrutiny of medication charts, and investigation reports. Particular attention should be paid to the use of neuromuscular blockers, steroids, antiretroviral agents,[3] statins,[4,5] and fibrates[6] ( Table 1 ). The cumulative drug dosage; adjustment for renal, hepatic, and organ failure; and drug interactions should be analyzed. The identification of the level of pathology will help guide further investigations.

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