OBJECTIVE: This study compared changes in muscle strength after major elective abdominal surgery in young and old patients, and related these changes to body composition and nitrogen balance. SUMMARY BACKGROUND DATA: The breakdown of muscle protein, erosion of lean tissue, and negative nitrogen balance are characteristic metabolic responses to surgical illness. With a substantial loss of muscle mass typical of advancing age, the authors postulated that older patients would be weaker during acute surgical illness and less able to maintain muscle function and meet metabolic demands. METHODS: Active, community-dwelling individuals undergoing major abdominal procedures who were 70 years of age or older or 50 years of age or younger were studied. Total body water (TBW) was determined preoperatively by deuterium oxide dilution. Maximal voluntary handgrip, respiratory muscle strength, and visual analog pain scores were measured preoperatively and on postoperative days 2, 4, and 6. All urine was collected postoperatively for 7 days for determination of total nitrogen, creatinine, and cortisol. RESULTS: The young (age, 36 +/- 9 years [mean +/- standard deviation]; n = 20) and old groups (age, 77 +/- 5 years; n = 20) were similar regarding weight, sex distribution, nutritional status, surgical procedures and anesthesia, and postoperative urine cortisol values. Age group, time after operation, and interaction effects were significant for each strength variable (all p < 0.005 by analysis of variance). Older patients had lower preoperative strength (29% to 41%) and mean 24-hour urine creatinine (27%). Postoperative strength was decreased most markedly on postoperative day 2, with similar proportional changes in the two age groups but lower absolute levels in the older patients. The rate of recovery of strength was substantially less rapid and complete in older patients. Older patients had less postoperative pain and received much less parenteral narcotic than younger patients. Postoperative urine nitrogen was similar in each group. Recovery of strength was not related to malignancy, preoperative strength, muscle mass (urine creatinine), lean body mass (TBW), sex, malignancy, pain, or narcotic administration. CONCLUSIONS: Older patients are weaker preoperatively than younger patients; their strength falls to lower levels after surgery and their postoperative recovery of strength is impaired. The lesser preoperative strength of older patients is due in large part but not totally to diminished muscle mass. Their impaired postoperative recovery appears to be related to more acute factors, such as muscle energetics or substrate availability.
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