Early detection of the covert onset and evolution of critical illness polyneuromyopathy

Abstract

Introduction Critical illness polyneuropathy was first identified by Bolton and colleagues 1 and weakness due to neuropathic and/or myopathic abnormalities is now recognized as a common complication of prolonged critical illness. 2 The presence of abnormally low compound motor action potentials (CMAPs) is considered an important diagnostic criterion. The onset and evolution of this condition following intensive care unit admission has not previously been systematically investigated. Methods A prospective, sequential study of all patients thought likely to require intensive care for 7 days or more was performed over a 12-month period. Admission APACHE II score, daily organ failure score, presence of sepsis, ventilation mode and routine haematology and biochemistry results were recorded. A daily neurological examination and weekly neurophysiological studies were performed for the duration of the patients’ ICU stay. The neurophysiological studies included CMAPs, nerve conduction velocities, sensory action potential amplitudes and electromyography. The Spearman correlation coefficient was used to analyse associations between the recorded physiological data and serial CMAPs. In our institution the lower limits of normal for ulnar and common peroneal nerve CMAPs are 2.5 and 2.8 mV respectively. Results Thirty-two patients were recruited to the study, of whom 23 survived for 7 days or longer. One patient was withdrawn at a relative's request and two patients continued to receive muscle relaxants until death. The median age was 61 yr (range 33–80) and median admission APACHE II score was 20 (9–33). A significant positive correlation was found between serum albumin and CMAPs ( P Conclusions The onset of critical illness motor syndrome may precede by days or weeks clinically detectable weakness, seems to be associated with episodes of sepsis and can occur within days of the onset of sepsis. Recovery in CMAPs may be equally rapid as sepsis subsides.