Inhibition of prostaglandin synthesis improves post-operative nitrogen balance

The metabolic response to injury includes net breakdown of skeletal muscle protein and negative nitrogen balance. Prostaglandins have been shown to mediate muscle protein breakdown in vitro. To examine the role of prostaglandins in post-operative protein catabolism in vivo, 15 dogs underwent a standard abdominal operation under general anaesthesia during which, catheters were implanted in the aorta and vena cava. Seven of the animals were given Ibuprofen to prevent prostaglandin synthesis during the operation and through the post-operative period, whilst the other eight served as controls. Inhibition of prostaglandin synthesis led to a significant improvement in nitrogen balance due mainly to a decreased excretion of urea (plasma urea levels were unaffected). This may be due to a diminished breakdown of skeletal muscle protein in response to injury, as there was an apparent reduction in efflux of amino-nitrogen and phenyl alanine from hindquarter muscle as compared to post-operative controls. In conjunction with nutritional therapy, inhibition of prostaglandin synthesis may be beneficial in improving nitrogen balance in catabolic patients.