Postoperative injection of phenylbutazone does not influence fibrinolytic shutdown

Twenty-nine patients undergoing cholecystectomy because of chronic calculous cholecystitis were randomised to receive phenylbutazone 10 mg/kg intramuscularly or a control injection (vehicle-containing local anaesthetic) immediately after completion of surgery. Fibrinogen and plasminogen concentrations in plasma, plasminogen activator inhibitor activity in plasma and fibrinolytic activity in concentrated euglobulins were determined before surgery and on the first, third and seventh postoperative days. Phenylbutazone delayed the postoperative rise of fibrinogen concentration and reduced the plasminogen level on the first day after surgery. Fibrinolytic activity in euglobulins was decreased after the operation in both groups. The great dispersion of the results of plasminogen activator inhibitor activity was the plausible cause of the lack of any significant difference in this variable. The postoperative fibrinolytic shutdown, reflected by the decrease of fibrinolytic activity, was unaffected by phenylbutazone. It can be speculated, however, that the decline of plasminogen concentration after surgery in patients receiving this drug was the result of its stimulatory influence on the conversion of plasminogen into plasmin.