The modifying influence of anaesthesia on postoperative protein catabolism.

We studied two groups of six patients scheduled for gastrointestinal surgery; they were allocated randomly to receive high- or low-dose fentanyl anaesthesia. The confounding effect of protein balance, before the trauma of surgery, on postoperative nitrogen excretion was controlled by standardized protein intake before operation, supplemented by adequate calories. The high-dose group had significantly lower stress levels during surgery, assessed by arterial blood concentrations of cortisone, adrenaline and glucose. After operation, protein catabolism was measured for 7 days. The high-dose group had significantly lower postoperative excretion of ammonia and slightly lower excretion of urea and 3-methylhistidine. Low-stress anaesthesia may thus diminish postoperative catabolism, which could be important in frail patients by reducing mortality, ICU resources, or both.