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Muscle wasting in the ICU can be reliably monitored using ultrasound

Introduction

The aim of this study was to establish the intraobserver and interobserver variation of ultrasonographic measurements of the rectus femoris muscle cross-section area (RF-CSA). Muscle wasting is frequent in the ICU, affecting more than one-half of the patients with severe sepsis [1]. Muscle mass reduces rapidly, and 15 to 20% is lost within the first week [1]. To monitor muscle mass, ultrasound has the benefits of being both readily available in the ICU and non-invasive. Ultrasonographic measurement of RF-CSA has an almost perfect correlation with MRI (mean interclass correlation (ICC) = 0.999) [2] and RF-CSA is linearly related to maximum voluntary contraction strength in both healthy subjects and COPD patients (r = 0.78) [3].

Methods

The study had two purposes: to determine the intraobserver variation for RF-CSA by one observer scanning 15 healthy adult volunteers three times each at 2-day intervals; and to determine the interobserver variation for RF-CSA by two observers each scanning 15 adult ICU patients on the same day. Patients were in a supine position, legs in passive extension. The transducer was placed perpendicular to the long axis of the right thigh over the RF, two-thirds of the distance from the anterior superior iliac spine to the superior patellar border [1]. RF-CSA was calculated by planimetry. At each scan, three measurements were made. For intraobserver variation, the 3 × 3 scans were analyzed using the interclass correlation coefficient. For interobserver variation, the three measurements from each observer were averaged and compared using Bland-Altman statistics.

Results

Intraobserver variation: 15 healthy adults, age 39.6 ± 2.4 years, weight 66.8 ± 2.3 kg, sex three male/12 female. ICC: 0.996 (95% CI: 0.990 to 0.998). Interobserver variation: 15 ICU patients, age: 77 ± 8.3 years, weight: 71.3 ± 9.1 kg, sex nine male/six female. Bland-Altman: bias: -0.07 cm2, 95% limits of agreement -0.188 to 0.048 cm2.

Conclusion

Ultrasonographic measurement of RF-CSA is easily learned and quickly performed. It has a very low intraobserver and interobserver variation and can be recommended as a reliable method for monitoring muscle wasting in the ICU.

References

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Correspondence to H Jørgensen.

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Jørgensen, H., Nedergaard, B. & Gilsaa, T. Muscle wasting in the ICU can be reliably monitored using ultrasound. Crit Care 17, P439 (2013). https://doi.org/10.1186/cc12377

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Keywords

  • Maximum Voluntary Contraction
  • Anterior Superior Iliac Spine
  • Healthy Adult Volunteer
  • Interclass Correlation
  • Interobserver Variation