Possible role of nitric oxide in postoperative ileus: a comparative study

In the present study, the possible involvement of nitric oxide (NO) in the pathogenesis of postoperative ileus was investigated indirectly by measurin g nitrate, a stabile metabolite of NO. Plasma levels and 24-h urinary excretion of nitrate and nitrite were determ ined in the peri-operative period in three different groups of patients und ergoing surgery: group 1 (LT, n=11) underwent a laparotomy, group 2 (LS, n= 12) underwent a laparoscopic procedure, whereas group 3 underwent an extra- abdominal procedure (EA, n=9). Duration of postoperative ileus was assessed clinically using first occurre nce of flatus and defaecation as the end of the period of ileus. Postoperative ileus lasted significantly longer in the LT group (first flat us after 3.0 [3.0-4.0] days) compared with the LS (1.0 [1.0-2.0] days) and EA (1.0 [1.0-3.0] days) groups. Urinary nitrate excretion increased signifi cantly in the LT and EA groups during the first 24 h after surgery (from 79 7.0 [214.0-810.0] and 551.5 [438.3-1215.8] to 2079.0 [889.0-4644.0] and 110 2.5 [315.3-1238.0] mu mol/24 h, median [IQR]), but normalized before the en d of postoperative ileus. Plasma levels of nitrate were unchanged after sur gery, whereas CRP levels were significantly increased in all groups (LT > L S=EA). In the first 24 h following surgery, urinary nitrate excretion is increased , suggesting increased endogeneous synthesis of NO postoperatively. As no c orrelation was found between urinary nitrate excretion and duration of post operative ileus, we conclude that assessment of nitrate has no value in pre dicting clinical outcome after surgery.