Muscle wasting and energy balance in critical illness.

BACKGROUND

In nine patients with multiple organ failure ultrasound was able to identify muscle wasting despite the presence of oedema (Campbell et al., J Clin Nutr 62 (1995) 533).

AIMS

The purpose of the present study was twofold: one was to determine whether this technique was applicable to a much larger ICU population, many of whom were not as ill as the original subjects. The second reason was to determine whether a relationship could be identified between rates of wasting and energy balance.

METHODS

Serial measurements of both mid-upper arm circumference (MAC) and muscle thickness, using ultrasound, were made at 1-3 day intervals between 5 and 39 (median 7) days in 50 critically ill patients.

RESULTS

Muscle thickness decreased in 48 of the 50 patients at a median rate of 1.6%/day with a range of 0.2-5.7%/day. In 33 patients, in whom MAC did not change significantly with time, muscle thickness decreased by between 0.3 and 4.2 (median 1.6)%/day. In three patients MAC increased significantly with time but muscle thickness decreased by between 1.3 and 5.7 (median 2.6)%/day. Twelve patients showed a significant decrease in MAC with time and muscle thickness in this group decreased by between 0.2 and 4.0 (median 1.3)%/day. The percentage decrease in muscle thickness between the groups, in whom MAC decreased or did not change, was not significantly different (P = 0.475).

CONCLUSION

We have demonstrated that an ultrasound technique devised to identify muscle wasting in the presence of severe fluid retention works in the majority (48/50) of patients when applied to a wider ICU population. Energy balance made no difference to the rate of wasting.