Clinical body composition assessment using in vivo neutron activation analysis (IVNAA)

A prompt gamma IVNAA facility has been developed in Auckland to study body composition in both the depleted surgical patient and the critically ill intensive car patient. The IVNAA method, used in conjunction with the tritium dilution technique, enables total body protein, water and fat to be determined with precision. This paper reviews clinical research on the protein and hydration status of surgical patients requiring nutritional support as are the changes in proteins and fat achieved with nutritional therapy in pre- and post-operative patients. Results are also presented of a clinical trial which examines the efficacy of fat and glucose as hypercalorific energy sources. The IVNAA/tritium dilution method has for the first time been applied to document body composition changes in intensive care patients and results on critically ill post-operative septic intensive care patients are discussed. Data are also presented for patients who have suffered major blunt trauma. Finally, the method is contrasted with skinfold anthropometry as a means of determining total body fat and also with conventional nitrogen balance as a means of monitoring crude protein changes in the clinical situation