The Diagnosis and Incidence of Critical Illness Polyneuromyopathy in Medical and Neurosurgical ICU Patients

This study plans to learn more about whether simpler diagnostic tests can be used to identify the development of acute neuromuscular loss of function in patients with critical illness and respiratory failure receiving mechanical ventilation. ICU patients admitted to the University of Colorado Hospital will be screened for eligibility and enrollment in the study to receive weekly measurements of nerve and muscle function through nerve conduction studies (NCS), muscle ultrasound tests, and concentric needle electromyography (EMG) tests. Collected data includes the subject's age, gender, race, ethnicity, length of stay in ICU, time on mechanical ventilation and pertinent medical history that could indicate baseline neuromyopathy (CNS disease, diabetes, HIV, alcohol use disorder). Baseline neurological examination will be performed within 48 hours of meeting the inclusion criteria. This examination will include the level of consciousness, muscle tone, motor strength using the Medical Research Council (MRC) Scale, sensory function, muscle stretch reflexes, and plantar responses. For MRC testing, six muscle groups will be tested bilaterally: shoulder abduction, elbow flexion, wrist extension, hip flexion, knee extension, and foot dorsiflexion. Clinical weakness on examination (which is necessary to make the diagnosis of CIPNM (Critical Illness Polyneuropathy and Myopathy)) is defined as an MRC score equal to or less than 48 (maximum score is 60). If a subject cannot participate in any MRC strength testing (e.g. due to sedation or encephalopathy) they will be coded at the lowest level (most severe clinical weakness). Nerve conduction studies (NCS) and concentric needle electromyography (EMG) will be performed (as described below) on the same day as the initial neurological examination. The neurological examination and NCS/EMG will be repeated on a weekly basis until CIPNM is diagnosed or the subject is discharged from the ICU. SPECIFIC AIM #1: Aim 1.1: To determine whether amplitude reductions in the peroneal and sural nerve action potentials on NCS can serve as accurate screening tests for CIPNM in patients with acute respiratory failure. Aim 1.2: To determine whether increased duration of the CMAP on NCS can serve as an accurate screening test for CIPNM in patients with acute respiratory failure. Aim 1.3: To determine whether changes in muscle ultrasound echogenicity and/or thickness can serve as accurate screening tests for CIPNM in patients with acute respiratory failure. Aim 1.4: To determine the incidence of CIPNM in patients with neurological critical illness (such as intraparenchymal and subarachnoid hemorrhage), which requires prolonged length of stay in a neurosurgical intensive care unit.