Influence of muscle relaxants on the mass of intercostal and upper arm muscles in COPD patients during mechanical ventilation

Purpose

The aim of the study is to assess the degree of intercostal and upper arm muscles atrophy in COPD patients requiring ventilatory support and muscular relaxants.

Methods

Twenty-four mechanically ventilated patients hospitalised in the ICU for 18.6 ± 3.6 days, were included in the study. Twelve patients with COPD exacerbation and 12 patients admitted in the ICU for various reasons (control group) received atracurium (0.3–0.6 mg/kg/h) for 2.8 ± 0.4 days. The groups did not differ significantly for age (62.5 ± 6.4 versus 65.6 ± 5.9 years, respectively). Both groups were under the same nutritional schedule. Muscular mass (MM) of intercostals and upper arm muscles were measured in cm by U/S at the 1st and the 5th ICU hospitalisation day. A 10 MHz linear transducer was used and the same intercostal space was scanned in all patients. Measurements were also done at the same position of the right upper-arm. All scans were performed by the same sonographer. The corresponding differences (ΔMM) were compared between the two groups of patients with the aid of the Student t-test (P < 0.05).

Results

Our results concerning measurements of muscle mass (in cm) are presented in the Table as mean values ± standard deviations.

Table 1

Intercostal and upper arm MM was significantly greater in the control group than in the COPD group in the 1st as well as in the 5th hospitalization day. MM thickness was significantly reduced between the 1st and the 5th hospitalization day in both the COPD and the control groups. Nevertheless, the ΔMM difference between COPD and controls was significant for intercostals (P < 0.03) and not significant for upper arm muscles.

Conclusions

MM is significantly lower in COPD mechanically ventilated patients in comparison to other patients under ventilatory support. Muscle relaxants reduce significantly the MM in COPD patients requiring assisted ventilation. Nevertheless, the MM changes are not uniform in various muscles as indicated by the comparison of the COPD to the control group, concerning the intercostals and the upper arm muscles. It seems that a more precise and complete information for the reduction of MM should be estimated at different muscle groups.