Changes in body protein composition following aortic reconstruction.

Major surgery initiates a stress response due to the body's neuroendocrine reaction which leads to a breakdown of muscle protein with an increased urinary nitrogen excretion and a negative nitrogen balance. In vivo neutron activation analysis (IVNAA) is a technique which measures total body nitrogen. A total of 23 IVNAA studies were performed in six patients having aortic reconstruction to assess the effect of this major operation on body nitrogen and to determine the time required for a return to the pre-operative state. Aortic surgery caused a mean decrease of 2.9% in bodyweight (from a mean of 65.4 kg to 63.5 kg) but a much greater decrease of 9.9% in total body nitrogen (from a mean of 1778 g to 1602 g). Only two of six patients had recovered to pre-operative values by the end of the study period which extended for a mean of 92 days.