Fatigue and muscle amino acids during surgical convalescence.

Muscle and plasma amino acids, subjective fatigue and body weight were studied in 16 patients before and 20 days after uncomplicated elective abdominal surgery. Fatigue increased from a mean (+/- SEM) preoperative level of 2.4 +/- 0.4 arbitrary units to 4.4 +/- 0.5 on postoperative day 20, while body weight fell from 67.3 +/- 2.5 to 64.7 +/- 2.9 kg (both differences p less than 0.001). Correlation was found between increase in fatigue and fall in body weight (r = 0.56, p less than 0.05). Plasma amino acids showed little change after surgery. In muscle, the nonessential amino group taurine, asparagine, glutamate and glycine increased and histidine and arginine decreased (both p less than 0.05) postoperatively. No correlation was found between postoperative fatigue and weight loss versus changes in muscle amino acids. Some of the well-defined immediate postoperative changes in muscle amino acids thus persisted into late, otherwise uncomplicated convalescence, but postoperative fatigue was related only to weight loss--not to changes in muscle or plasma amino acids.