ASSESSMENT OF INVOLUNTARY MUSCLE FUNCTION IN PATIENTS AFTER CRITICAL INJURY OR SEVERE SEPSIS

Background: Study of involuntary skeletal muscle function (MFA) has be en well accepted in the area of nutrition assessment and potentially o ffers a means for following progress of the critically ill patient. We report on the application of this technique to intensive care patient s. Methods: MFA was pet-formed by study of the contraction/relaxation characteristics of the adductor pollicis muscle of the thumb after uln ar nerve stimulation. Serial measurements were made in 16 critically i njured patients and 28 patients with severe sepsis and were compared w ith those obtained from 26 control subjects. Extent of loss of total b ody protein (TBP) was quantified with in vivo neutron activation. Resu lts: Significant difficulties exist in applying this technique to inte nsive care patients. In the critically injured, only five acceptable t races could be obtained from a possible 58 measurements. For patients with severe sepsis it was possible to obtain an acceptable trace on 12 of 56 occasions. Neuromuscular block ade and lack of patient cooperat ion were significant impediments to MFA study. Although frequently per ceived as unpleasant by these patients, there was no long-term morbidi ty associated with MFA. No significant differences were seen in maxima l relaxation rate at 30 Hz (MMR30) or force frequency ratios (F10/50 a nd F30/50) between trauma patients and controls. In the sepsis patient group, a significantly higher F10/50 was measured (52% +/- 3% severe sepsis vs 40% +/- 1% control subjects, P < .01). Six patients had MFA measured approximately 21 days after the illness, by which stage they had lost 11% of their initial TBP. Compared.cvith control subjects, no significant differences were observed in MRR30 or F30/50, whereas a h igher value for F10/50 was measured (48% +/- 1% critical illness vs 40 % +/- 1% control subjects, P < .01). Conclusions: The MFA technique is difficult to apply to in tensive care patients. No significant distur bance to MFA is seen after critical injury. Severe sepsis results in a n elevation of F10/50 only. When able to be obtained, MFA results do n ot reflect the extent of proteolysis but are indicative of the state o f cellular energetics.