Uncomplicated surgery, but not general anesthesia, decreases muscle protein synthesis.

The impact of anesthesia and surgery on protein metabolism is not well characterized. The single effect of general anesthesia and the combined effects of surgery and general anesthesia on protein synthesis in skeletal muscle were studied in metabolically healthy patients (n = 14) undergoing elective abdominal surgery. The rate of muscle protein synthesis was calculated from the increase in enrichment of [1-13C]leucine in protein during 90 min after an intravenous infusion of [1-13C]leucine (0.05 g/kg, 20 atom percent excess). The 1-13C enrichments of plasma leucine and plasma alpha-ketoisocaproate were used to indicate the enrichment of muscle free leucine. The protein synthesis rate was unaffected by general anesthesia; however, at the end of surgery, a 31.5% decline was seen from 2.19(2.13,2.33)%/24 h before anesthesia to 1.50(1.21,1.77)%/24 h (P less than 0.05) immediately after cholecystectomy while the patients were still under general anesthesia.