Differential contractile response of critically ill patients to neuromuscular electrical stimulation

Abstract

Background Neuromuscular electrical stimulation (NMES) has been investigated as a preventative measure for intensive care unit-acquired weakness. Trial results remain contradictory and therefore inconclusive. As it has been shown that NMES does not necessarily lead to a contractile response, our aim was to characterise the response of critically ill patients to NMES and investigate potential outcome benefits of an adequate contractile response. Methods This is a sub-analysis of a randomised controlled trial investigating early muscle activating measures together with protocol-based physiotherapy in patients with a SOFA score ≥ 9 within the first 72 h after admission. Included patients received protocol-based physiotherapy twice daily for 20 min and NMES once daily for 20 min, bilaterally on eight muscle groups. Electrical current was increased up to 70 mA or until a contraction was detected visually or on palpation. Muscle strength was measured by a blinded assessor at the first adequate awakening and ICU discharge. Results One thousand eight hundred twenty-four neuromuscular electrical stimulations in 21 patients starting on day 3.0 (2.0/6.0) after ICU admission were included in this sub-analysis. Contractile response decreased from 64.4% on day 1 to 25.0% on day 7 with a significantly lower response rate in the lower extremities and proximal muscle groups. The electrical current required to elicit a contraction did not change over time (day 1, 50.2 [31.3/58.8] mA; day 7, 45.3 [38.0/57.5] mA). The electrical current necessary for a contractile response was higher in the lower extremities. At the first awakening, patients presented with significant weakness (3.2 [2.5/3.8] MRC score). When dividing the cohort into responders and non-responders (> 50% vs. ≤ 50% contractile response), we observed a significantly higher SOFA score in non-responders. The electrical current necessary for a muscle contraction in responders was significantly lower (38.0 [32.8/42.9] vs. 54.7 [51.3/56.0] mA, p < 0.001). Muscle strength showed higher values in the upper extremities of responders at ICU discharge (4.4 [4.1/4.6] vs. 3.3 [2.8/3.8] MRC score, p = 0.036). Conclusion Patients show a differential contractile response to NMES, which appears to be dependent on the severity of illness and also relevant for potential outcome benefits. Trial registration ISRCTN ISRCTN19392591, registered 17 February 2011

Breath-synchronized electrical stimulation of the expiratory muscles in mechanically ventilated patients: a randomized controlled feasibility study and pooled analysis

“…Interestingly, our high success rate of contractile activation is not in line with Grunow et al [ 25 ], studying contractile response to FES (verified visually or on palpation) in eight limb muscle groups and reporting that only 64.4% of applied stimulations led to an adequate response on the day of ICU admission; this number declined to 25% after one week. Although the expiratory muscles were not targeted in their study, their maximum stimulation intensity was 70 mA, i.e., our median threshold intensity.…”

“…Over the last decade, inconclusive evidence for the clinical benefits of FES in ICU patients was published [ 15 , 24 ], mainly targeting limb muscles. One reason for these inconsistent results may be the lack of reporting of treatment compliance and contractile response to stimulation [ 25 ]. The effectiveness of FES in activating muscles at an adequate level depends on patient characteristics; factors such as sepsis, edema and vasopressor may play a role [ 26 , 27 ].…”

Upper limb muscle atrophy associated with in-hospital mortality and physical function impairments in mechanically ventilated critically ill adults: a two-center prospective observational study

“…In critically ill patients, lower limb training is predominantly the rehabilitation focus based on the concern for early mobilization [ 35 , 36 ]. However, in recent studies, neuromuscular electrical stimulation has been additionally used for upper limb training [ 37 – 39 ], preventing upper limb muscle atrophy, and the enhanced upper limb training reduced the length of hospitalization [ 39 ]. Our findings suggest that it is worthwhile to monitor upper limb as well as lower limb muscle atrophy and perform early interventions to improve the quality of life in critically ill patients.…”

Long-term outcomes after critical illness: recent insights

“…Electrical muscle stimulation (EMS) exerts beneficial metabolic effects in muscle cells [ 37 , 38 ]. However, illness severity seems to influence the contractile response to EMS and may modulate its benefits [ 39 ]. Novel methods, such as whole-body vibration, are emerging as possible alternatives for muscle activation [ 40 ]; this approach may be particularly suitable for unconscious patients or patients with dressings or wounds that preclude positioning of EMS electrodes.…”