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Skeletal muscle strength in critically ill patients

Measurement of peripheral muscle strength in the Intensive Care Unit (ICU) has been seldom documented. The purpose of the study was to determine whether quadriceps twitch tension (Tw Q) could be measured in a range of critically ill patients in the ICU using a novel non-volitional technique, supramaximal magnetic stimulation of the femoral nerve (Polkey et al.: Muscle Nerve 1996, 19:549–555) and to determine the magnitude of weakness. Measurements were made in 20 patients (12M 8F), mean age 59 (range 24–81) years, with varying diagnoses. Median (95% CI) length of stay (at the time of testing) was 18 (7–29) days. 20 healthy elderly volunteers (12M 8F), mean age 59 (range 25–80) served as controls. Median (95% CI) Tw Q in the patients was 3.5 (2.6–5) kg compared with 9.5 (7.8–11.7) kg in controls (P < 0.01, Mann Whitney U Test) and weakness was not correlated with length of ICU stay. The data demonstrate that profound quadriceps weakness can occur in critically ill patients. This weakness may influence mobilisation and rehabilitation. It is likely that other skeletal muscles are similarly affected, including the muscles of respiration. If so, this would in part, determine weaning outcome.


Supported by NHS Executive Grant No RDF 028

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Harris, M., Hamnegard, CH., Polkey, M. et al. Skeletal muscle strength in critically ill patients. Crit Care 3 (Suppl 1), P204 (2000).

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