Published in:
01-12-2015 | Editorial
Finally, a time and place for electrophysiological testing in critically ill patients?
Published in: Intensive Care Medicine | Issue 12/2015
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ICU-acquired weakness (ICUAW) is a common and debilitating complication of critical illness associated with an increased risk of mortality as well as persistent morbidity in survivors [1‐3]. No clear consensus exists regarding the diagnostic criteria for ICUAW. Recent clinical practice guidelines have emphasized the primacy of the physical examination, using a Medical Research Council (MRC) subscore below 48 (maximum score 60 from six bilateral muscle groups) as the current reference standard that has been widely used in studies of ICUAW albeit with important limitations [4]. However, many critically ill patients are not awake and cooperative during their ICU admission, precluding the ability to complete an MRC-based diagnosis of ICUAW [5, 6]. As such, a number of clinicians and investigators have proposed the use of electrophysiological (EP) studies [i.e., electromyography (EMG) and nerve conduction studies (NCS)] to either complement or replace the need for volitional muscle testing in the diagnosis of ICUAW. However, abnormalities in EMG/NCS performed in critically ill patients are extremely common [7‐9], and their diagnostic utility and prognostic significance remain uncertain [4] (Table 1).
Table 1
Summary of selected studies using electrophysiological testing
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Study
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Diagnostic
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Notes
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|---|---|---|
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Bednarik et al. [9], (N = 46) patients
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EP signs of neuromuscular involvement in 56 % at 30 days
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Guarneri et al. [7], (N = 92) patients
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30 % developed CIP and/or CIM by EP during ICU stay; persistent in 18 patients at ICU discharge
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At 1-year follow up:
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CIM—1 died, 5 recovered completely
CIP/CIM—1 died, 1 recovered, 1 remained tetraplegic
CIP—1 recovered, 2 persisting ICUAW, 1 remained tetraparetic
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Hermans et al. [8], (N = 420) patients
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CIP/CIM diagnosis by EP more frequent in CIT group than IIT group (51 vs. 39 %, p = 0.02)
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CIP/CIM independent risk factor for prolonged mechanical ventilation (OR 1.85, 95 % CI 1.17–2.93)
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Independent risk factors for abnormal EP: prolonged infusion of NMBA (OR 2.01, 95 % CI 1.10–3.99), age (OR 0.98 per year, 95 % CI 0.96–0.99), and days of glucocorticoid treatment (OR 0.97 per day, 95 % CI 0.94–0.99)
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Weber-Carstens et al. [11], (N = 56) patients
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61 % had abnormal dmCMAP indicating a myopathic process within a week after ICU admission
Abnormal dmCMAP predicted ICUAW upon awakening with Sn 83 % and Sp 89 %
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Abnormal dmCMAP significantly associated with subsequent diagnosis of ICUAW (OR 0.47 per mV, 95 % CI 0.28–0.79)
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Wieske et al. [12], (N = 35) patients
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Ulnar SNAP <17.6 µV − Sn 100 % (95 % CI 68–100 %), Sp 79 % (95 % CI 49–95 %)
EDB peroneal CMAP <0.43 mV − Sn 80 % (95 % CI 52–96 %), Sp 75 % (95 % CI 48–93 %)
Both ulnar SNAP and EDB peroneal CMAP abnormal − Sn 77 % (95 % CI 46–95 %), Sp 100 % (70–100 %)
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Diagnostic accuracy for ICUAW may be improved using ICU-based cutoff values (rather than healthy controls)
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