Early Detection of ICU-Acquired Weakness in Septic Shock Patients Ventilated Longer Than 72 h

Caroline Attwell; Laurent Sauterel; Jane Jöhr; Lise Piquilloud; Thierry Kuntzer; Karin Diserens


BMC Pulm Med. 2022;22(466) 

In This Article

Abstract and Introduction


Purpose: ICU-acquired weakness, comprising Critical Illness Polyneuropathy (CIP) and Myopathy (CIM) is associated with immobilization and prolonged mechanical ventilation. This study aims to assess feasibility of early detection of CIP and CIM by peroneal nerve test (PENT) and sensory sural nerve action potential (SNAP) screening in patients with septic shock and invasively ventilated for more than 72 h.

Methods: We performed repetitive PENT screening from 72 h after intubation until detecting a pathological response. We tested SNAPs in pathological PENT to differentiate CIP from CIM. We performed muscle strength examination in awake patients and recorded time from intubation to first in-bed and out-of-bed mobilization.

Results: Eighteen patients were screened with PENT and 88.9% had abnormal responses. Mean time between intubation and first screening was 94.38 (± 22.41) hours. Seven patients (38.9%) had CIP, two (11.1%) had CIM, one (5.6%) had CIP and CIM, six (33.3%) had a pathological response on PENT associated with ICU-acquired weakness (but no SNAP could be performed to differentiate between CIP and CIM) and two patients had (11.1%) had no peripheral deficit. In patients where it could be performed, muscle strength testing concorded with electrophysiological findings. Twelve patients (66.7%) had out-of-bed mobilization 10.8 (± 7.4) days after admission.

Conclusion: CIP and CIM are frequent in septic shock patients and can be detected before becoming symptomatic with simple bedside tools. Early detection of CIP and CIM opens new possibilities for their timely management through preventive measures such as passive and active mobilization.


Critical illness polyneuropathy (CIP) and critical illness myopathy (CIM) are part of a clinical entity called intensive care unit (ICU) acquired weakness (ICUAW), a frequent complication of critical illnesses[1] shown to delay ventilator weaning and discharge from the ICU, prolong the rehabilitation period and general hospitalization stay and increase risk of death.[2–4] Identified risk factors for CIP and CIM are multiple organ failure (MOF), sepsis and prolonged mechanical ventilation. Incidence of ICU-acquired weakness in patients with severe sepsis was shown to be significantly higher than in other patient groups (64% sepsis vs 30% other).[5] In addition, ICU-acquired weakness was diagnosed in up to 67% of patients with long-term ventilation and seemed to be the cause as well as a consequence of prolonged mechanical ventilation.[3] Indeed, respiratory muscle weakness due to CIP or CIM impaired weaning from mechanical ventilation[6,7] while risk of developing ICU-acquired weakness increased with the duration of exposure to mechanical ventilation.[1,5,8]

An early identification of persons at risk for ICU-acquired weakness would allow timely preventive interventions, such as treating conditions leading to multi organ failure, avoiding unnecessary deep sedation, controlling excessive blood glucose levels and corticosteroid administration and promoting early mobilization as preventive strategy.[9–11] In clinical practice, ICU-acquired weakness is usually diagnosed by muscle strength testing that can only be performed on awake and cooperative patients. Although this tool is necessary to confirm diagnosis, its use for early screening is limited by the need to await patient awakening, especially in subjects remaining in a critical state for days to weeks; thereby, delaying any possible targeted preventive measures to avoid development of ICU-acquired weakness. Electrophysiological studies, on the other hand have the advantage that they do not require patient cooperation and can therefore be pursued systematically on at-risk patients in the early phase of hospitalization.[12,13]

However, complete electrophysiological evaluation is too fastidious for screening critically ill patients.[12,13] Latronico et al. proposed therefore, a simplified screening method using motor peroneal nerve test (PENT) to identify motor conduction loss,[13] allowing early testing on at-risk populations. PENT is a screening method allowing diagnosis of CIP and CIM with a sensitivity of 100% and specificity of 85.2%.[13] It consists of measuring the compound muscle action potential (CMAP) of the common peroneal nerve. Stimulation occurs through an active electrode placed on the belly of the extensor digitorum brevis muscle, and the recording electrode is placed on its distal tendon. In the presence of polyneuropathy or myopathy, the CMAP amplitude is reduced. To differentiate between CIP and CIM, other features must be assessed. For example, a sensory nerve action potential (SNAP) can be recorded at the sural or median nerve and a decreased amplitude of both CMAP and SNAP indicate a polyneuropathy as they testify to injury of both motor and sensory nerves. On the other hand, a delayed muscle contraction with a normal SNAP suggests myopathy.

Earlier identification of ICU-acquired weakness through neurophysiological testing allows gaining several days during which targeted preventive methods could be applied before its obvious clinical manifestation. It would thereby open new perspectives for earlier management of CIP and CIM through preventive measures, like intense passive and active early mobilization. Indeed, early mobilization methods are constantly progressing through the introduction and improvement of robotic devices such as cycloergomatry, MOTOmed-letto® and Erigo®, for example facilitating coma patient rehabilitation by moving the patient into an upright position,[14,15] thereby improving muscle force, endogenous catecholamine production and prevention of complications of bed rest.[14–17] However, mobilization practices seem to be generally lacking, especially in the category of ventilated patients, although they could improve their prognosis.[9]

The aim of this study is to assess the feasibility of the simplified screening method of Latronico et al. for early detection of CIP and CIM in a population known to be at high risk of developing these two conditions: patients admitted to the ICU with septic shock and mechanically ventilated for more than 72 h. This research also aims to describe the current mobilization practices on patients who develop CIP and CIM during their acute ICU stay.