Quantitative neuromuscular ultrasound in the intensive care unit
ABSTRACT Introduction: Intensive care unit acquired weakness (ICU-AW) results from a complex mixture of nerve and muscle pathology, and early identification is challenging. This pilot study was designed to examine the ultrasonographic changes that occur in muscles during ICU hospitalization. Methods: Patients admitted to the ICU for acute respiratory failure were enrolled prospectively and underwent serial muscle ultrasound for thickness and gray-scale assessment of the tibialis anterior, rectus femoris, abductor digiti minimi, biceps, and diaphragm muscles over 14 days. Results: Sixteen participants were enrolled. The tibialis anterior (P = 0.001) and rectus femoris (P = 0.041) had significant decreases in gray-scale standard deviation when analyzed over 14 days. No muscles showed significant changes in thickness. Conclusions: Ultrasound is an informative technique for assessing muscles of patients in the ICU, and lower extremity muscles demonstrated increased homogeneity during ICU stays. This technique should be examined further for diagnosing and tracking those with ICU-AW. Muscle Nerve, 2012.
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ABSTRACT: Introduction: An early diagnosis of Intensive Care Unit–acquired weakness (ICU–AW) using muscle strength assessment is not possible in most critically ill patients. We hypothesized that development of ICU–AW can be predicted reliably two days after ICU admission, using patient characteristics, early available clinical parameters, laboratory results and use of medication as parameters.PLoS ONE 10/2014; 9(10):e111259. DOI:10.1371/journal.pone.0111259 · 3.53 Impact Factor
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ABSTRACT: Intensive care unit-acquired weakness (ICU-AW) is a significant problem. There is currently widespread variability in the methods used for manual muscle testing and handgrip dynamometry (HGD) to diagnose ICU-AW. This study was conducted in two parts. The aims of this study were: to determine the inter-rater reliability and agreement of manual muscle strength testing using both isometric and through-range techniques using the Medical Research Council sum score and a new four-point scale, and to examine the validity of HGD and determine a cutoff score for the diagnosis of ICU-AW for the new four-point scale. Part one involved evaluation of muscle strength by two physical therapists in 29 patients ventilated >48 hours. Manual strength testing was performed by both physical therapists using two techniques: isometric and through range; and two scoring systems: traditional six-point Medical Research Council scale and a new collapsed four-point scale. Part two involved assessment of handgrip strength conducted on 60 patients. A cutoff score for ICU-AW was identified for the new four-point scoring system. The incidence of ICU-AW was 42% (n = 25/60) in this study (based on HGD). In part one the highest reliability and agreement was observed for the isometric technique using the four-point scale (intraclass correlation coefficient = 0.90: kappa = 0.72 respectively). Differences existed between isometric and through-range scores (mean difference = 1.76 points, P = 0.005). In part two, HGD had a sensitivity of 0.88 and specificity of 0.80 for diagnosing ICU-AW. A cutoff score of 24 out of 36 points was identified for the four-point scale. The isometric technique is recommended with reporting on a collapsed four-point scale. Because HGD is easy to perform and sensitive, we recommend a new two-tier approach to diagnosing ICU-AW that first tests handgrip strength with follow-up strength assessment using the isometric technique for muscle strength testing if handgrip strength falls below cutoff scores. Whilst our results for the four-point scale are encouraging, further research is required to confirm the findings of this study and determine the validity of the four-point scoring system and cutoff score developed of less than 24 out of 36 before recommending adoption into clinical practice.Critical Care 02/2015; 19(1). DOI:10.1186/s13054-015-0780-5 · 5.04 Impact Factor
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ABSTRACT: Loss of skeletal muscle strength is a well-recognised feature of ageing and chronic obstructive pulmonary disease (COPD). Reductions in muscle size only partly explain this loss of strength and additional contributory factors remain undetermined. We hypothesised that reductions in skeletal muscle strength, as measured in the ankle dorsiflexor muscles, would be reduced with ageing and COPD as a result of changes in both tibialis anterior muscle size and composition. Twenty healthy, young subjects, 18 healthy, elderly subjects and 17 patients with COPD were studied. Ankle dorsiflexor muscle strength was assessed by maximal voluntary contraction (ADMVC) and 100Hz supramaximal, electrical, peroneal nerve stimulation (100HzAD). Tibialis anterior cross-sectional area (TACSA) and composition, as assessed by echo intensity (TAEI), were measured using ultrasonography. Despite no differences in TACSA between groups, ADMVC and 100HzAD were significantly reduced in COPD patients compared to both healthy elderly and young subjects, when expressed as absolute values and when normalised to TACSA (P < 0.01). TAEI was, however, higher in COPD compared to healthy elderly (P = 0.025) and young (P = 0.0008) subjects suggesting increased levels of non-contractile tissue. Across all participants ADMVC and 100HzAD correlated positively with TACSA (r = 0.78, P < 0.0001) and negatively with TAEI (r = -0.46, P < 0.0005). The variance in 100HzAD was best explained with a regression model incorporating TACSA, TAEI, age and COPD status (r(2) 0.822, P = 0.001). These data demonstrate that the loss of skeletal muscle strength in COPD is related to changes in muscle composition, with infiltration of non-contractile tissue beyond that seen with normal ageing. This article is protected by copyright. All rights reserved.Experimental Physiology 06/2014; 99(8). DOI:10.1113/expphysiol.2014.080093 · 2.87 Impact Factor