Contradictory effects of uncomplicated versus complicated abdominal surgery on the hepatic capacity for urea synthesis in rats

Female Wistar rats weighing 217 g were subjected to two types of surgical stress: uncomplicated (hysterectomy) and complicated (spleen and uterus ligated, crushed, and left in situ). Liver function as assessed by amino-N conversion was measured as the capacity for urea-N synthesis preoperatively (control animals) and on Days 1, 3, and 6 postoperatively. Uncomplicated surgery transiently increased the capacity for urea-N synthesis by 30% the first postoperative day (P less than 0.001). Complicated surgery decreased the capacity for urea-N synthesis to 55% throughout the investigation period (P less than 0.001). This was not due to a general change in liver mass since galactose elimination capacity remained constant. The increase in the capacity for urea-N synthesis after uncomplicated surgery is probably due to glucagon since plasma glucagon increased whereas plasma insulin and blood glucose remained unchanged after amino acid loading. The persistent decrease in the capacity for urea-N synthesis in complicated surgery is not due to changes in these regulators: glucagon increased, insulin decreased, and the rats were hypoglycemic. All changes are expected to increase the capacity for urea-N synthesis. The mechanism for the emergence of these two distinct metabolic patterns is not known. The phenomenon is probably important for interpretation of metabolic data on clinical stress.

The influence of abdominal surgical trauma on the exchange of blood-borne amino acids in the human leg

Associated with surgical trauma is an increased release of gluconeogenic substrates from the periphery. The present study was undertaken to investigate the peripheral exchange of blood and plasma amino acids as well as some other gluconeogenic substrates (lactate and glycerol) in connection with abdominal surgery. Measurements of leg blood flow and femoral arterio-venous substrate differences were made before, during and immediately after elective cholecystectomy. Blood and plasma concentrations of most amino acids except alanine decreased during and immediately after surgery. Simultaneously there was an increased release of several of the amino acids as well as lactate and glycerol from the leg. The total release of plasma amino acids from one leg in the immediate postoperative period was about 2.5 times as high as before surgery. The turnover rates of amino acids as well as the changes in turnover rates were comparable whether the calculations were made from plasma or whole blood concentrations. At the end of surgery there was a high peripheral uptake of 3-hydroxybutyrate concomitant with a low release of amino acids.

Parenteral nutrition of injured patients: Effect of manipulation of aminoacid infusion (increasing branched chain while decreasing aromatic and sulphurated aminoacids)

Sixteen critically ill injured patients received parenteral nutrition providing nitrogen (0.34 g kg(-1) day(-1)) and glucose (32 kcal kg(-1) day(-1)) for 5 days. They were randomly divided into two groups with respect to aminoacid supply: an essential aminoacid solution vs the same solution enriched in branched chain amino acid (BCAA) content and decreased in phenylalanine and methionine content (mean BCAA intake, 0.55 vs 0.69 g kg(-1) day(-1)). Basal values of nitrogen metabolism without treatment showed no difference between the two groups. Nitrogen losses and 3 methylhistidine (3-MEH) excretion were elevated; the plasma aminoacid pattern was altered by the trauma and except for phenylalanine, aspartate and glutamate, plasma aminoacid concentrations were decreased below normal values. Net muscular aminoacid output was demonstrated by femoral arterio-venous (av) differences that were all negative except for glutamate and citrulline TPN with both solutions improved the nitrogen balance and reduced the negative aminoacid balance across the leg. Adjusting a TPN regimen to increase the BCAA content without altering the total nitrogen infused, had no effect on overall nitrogen balance, but exerted a beneficial effect on body protein catabolism, as assessed by the urinary 3-MEH excretion rate, and a transient improvement in the aminoacid balance across the leg at the peak of the infusion. The short-lived effect of BCAA suggest a metabolic effect of these aminoacids which deserves further study.